974 results on '"Propriété mécanique"'
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2. Heat treatment of poplar plywood: Modifications in physical, mechanical and durability properties
- Abstract
Plywood made of poplar are limited to indoor usages since poplar exhibits a rather low natural durability. Recently, wood heat treatments have been applied to improve properties such as decay susceptibility and dimensional stability. This study examines the potential of exposing poplar plywood to heat treatment to extend the potential of applications of this engineered wood product to outdoor end uses, and new markets accordingly. Plywood panels were glued with two different adhesive formulations based on the same melamine-urea-formaldehyde (MUF) resin to compare their respective ability to resist to the heat treatment. These different plywoods were thermally modified in saturated steam conditions at 215 °C for 2 hours following the ThermoWood® process, up to reach 14% in mass loss. The durability improvement brought by the heat treatment was assessed in order to evaluate any possible outdoor uses for such plywood. After all the conducted analyses, the potential to use heat treated poplar plywoods in humid interior and protected exterior service conditions was confirmed.
- Published
- 2023
3. Heat treatment of poplar plywood: modifications in physical, mechanical and durability properties
- Author
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B Marcon, J Viguier, K Candelier, MF Thevenon, JC Butaud, L Pignolet, A Gartili, L Denaud, and R Collet
- Subjects
K50 - Technologie des produits forestiers ,fungal durability ,module d'élasticité ,Mathématique ,bond quality ,Mécanique: Mécanique des matériaux [Sciences de l'ingénieur] ,bending modulus of elasticity ,Nature and Landscape Conservation ,Traitement thermique ,termite resistance ,Ecology ,heat treatment ,Forestry ,Contreplaqué ,Populus ,poplar ,Propriété mécanique ,plywood ,bending strength ,Technologie du bois ,Propriété du bois - Abstract
Plywood made of poplar are limited to indoor usages since poplar exhibits a rather low natural durability. Recently, wood heat treatments have been applied to improve properties such as decay susceptibility and dimensional stability. This study examines the potential of exposing poplar plywood to heat treatment to extend the potential of applications of this engineered wood product to outdoor end uses, and new markets accordingly. Plywood panels were glued with two different adhesive formulations based on the same melamine-urea-formaldehyde (MUF) resin to compare their respective ability to resist to the heat treatment. These different plywoods were thermally modified in saturated steam conditions at 215 °C for 2 hours following the ThermoWood® process, up to reach 14% in mass loss. The durability improvement brought by the heat treatment was assessed in order to evaluate any possible outdoor uses for such plywood. After all the conducted analyses, the potential to use heat treated poplar plywoods in humid interior and protected exterior service conditions was confirmed. ANR-10-EQPX-16 XYLOFOREST laboratoire Mixte Public/privé qui associe les Arts et Métiers (campus de Cluny) et l’entreprise Brugère
- Published
- 2023
4. Effet du Facteur de Forme et de la Fraction Massique des Fibres Courtes d’Alfa sur le Comportement Mécanique d’un Bio-composite Alfa/Greenpoxy.
- Author
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Amrane, Aboubakr, Sereir, Zouaoui, Poilâne, Christophe, and Vivet, Alexandre
- Subjects
- *
GEOMETRIC shapes , *SURFACE states , *BEND testing , *SIEVES , *FIBERS , *LASER beam cutting - Abstract
This experimental study highlights the effect of the geometric form factor (λ=length/diameter) and the fiber mass fraction on the mechanical behavior of an Alfa/Greenpoxy bio-composite. The Alfa stalks, collected in the Djelfa region in the Algeria highlands, were cut into pieces with length of 7 to 10 cm, washed and dried for two days at 70 °C. Using a knife mill coupled to three sieves (1.6, 2 or 2.5 mm), three categories of short fibers, according to their form factor λ, were obtained. Depending on the incorporated mass fraction (5, 10, 15 or 20 %) and the three form factors λ of the fibers, twelve types of plates were manufactured by hand molding followed by a curing cycle to accelerate the polymerization, reduce porosity and improve the final surface state. The main mechanical characteristics were determined with tensile, bending and shock tests on ISO 3167-type A samples, obtained by laser cutting. The results revealed that the increase of the form factor and the mass fraction gives rise to a significant improvement of the mechanical properties. We conclude that optimal processing conditions will maximize the mechanical properties of Alfa/Greenpoxy bio-composites. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
5. Influence of Sahelian and Sudanian provenances on the physical and mechanical properties of Faidherbia albida wood from Chad
- Abstract
Faidherbia albida is a typical emblematic species of African dryland areas. In Chad, it is used for many purposes, but very little is known about the technological properties of its wood, which sometimes leads to inappropriate uses. This work consisted to study the physical and mechanical properties of this wood, collected in the Sahelian and Sudanian chadian zone. As well as the impact study of the sampling areas of these properties. The result obtained shows that, the density, infradensity; modulus of elasticity, compression strength were significantly higher in the Sahelian zone than in the Sudanian zone, i.e. 508 and 409 kg·m−3; 5555 and 23.7 MPa, compared to 444 and 359 kg·m−3; 4150 and 19.6 MPa. The total tangential shrinkage, total volumetric shrinkage, fibre saturation point; static bending strength were significantly lower in wood from the Sahelian zone compared to the Sudanian zone, i.e. 4.6%, 7.7%, 23.7%; 42.5 MPa, compared to 6.6%, 9.5%, 28.9%; 52.6 MPa. The total radial shrinkage values obtained were not significantly different between the two provenances (mean: 3.1%).
- Published
- 2022
6. Variations des caractéristiques physiques et mécaniques du bois de Balanites aegyptiaca en fonction de trois provenances
- Author
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Jean Gérard, Dao Dougabka, Rémy Marchal, Alban Guyot, Daniel Guibal, Tikri Bianzeube, Caroline Vincke, Morgane Dendoncker, and UCL - SST/ELI/ELIE - Environmental Sciences
- Subjects
K50 - Technologie des produits forestiers ,Matériaux [Sciences de l'ingénieur] ,Ecology ,Evolution ,Forestry ,Behavior and Systematics ,Propriété mécanique ,Provenance ,Propriété technologique ,Balanites aegyptiaca ,Ecology, Evolution, Behavior and Systematics ,Propriété du bois ,Propriété physicochimique - Abstract
Balanites aegyptiaca est une espèce caractéristique et emblématique des zones sèches d’Afrique et d’Asie. Elle revêt une grande importance socio-économique dans toute sa zone naturelle de répartition du fait de ses multiples usages. Toutefois, les propriétés technologiques de son bois sont mal connues, d’où des utilisations parfois inappropriées mais qui pourraient être élargies. Afin de mieux adapter ses applications à ses caractéristiques, nous avons déterminé les indicateurs de stabilité physique (masse volumique, infradensité, retrait radial total, retrait tangentiel total, retrait volumique total et point de saturation des fibres) et les indicateurs de comportement mécanique (module d’élasticité longitudinal, contrainte de rupture en flexion et compression) de ce bois. Quatre-vingt-treize éprouvettes prélevées dans 13 arbres provenant des zones sahélienne et soudanienne tchadiennes, et de la zone sahélienne sénégalaise ont été testées. Les résultats obtenus montrent que, pour les trois provenances, le bois de B. aegyptiaca est mi-lourd (797 kg/m3) avec une stabilité dimensionnelle moyenne : l’anisotropie de retrait est supérieure à 2 (2,2), le retrait radial total et le retrait tangentiel total sont moyens, respectivement égaux à 4 % et 8,5 %. Ses caractéristiques mécaniques sont moyennes (contraintes de rupture en compression et flexion statique respectivement égales à 49,4 MPa et 104,5 MPa) à faible (module d’élasticité longitudinal de 10 473 MPa). Une comparaison des résultats obtenus en fonction des zones de prélèvement a mis en évidence des tendances variables selon les caractéristiques étudiées. Ces variations entre les trois provenances restent cependant limitées. Les résultats de l’étude montrent que le bois de B. aegyptiaca pourrait être utilisé de façon appropriée sous forme de matériau pour une plus large gamme d’emplois, sous réserve de la mise en place d’une gestion adaptée permettant sa restauration par plantation.
- Published
- 2021
7. Influence of Sahelian and Sudanian provenances on the physical and mechanical properties of Faidherbia albida wood from Chad
- Author
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Dao Dougabka, Jean Gérard, Tikri Bianzeube, Daniel Guibal, Rémy Marchal, and Alban Guyot
- Subjects
K50 - Technologie des produits forestiers ,Static bending ,Impact study ,Young's modulus ,symbols.namesake ,Faidherbia albida ,General Materials Science ,Propriété physicochimique ,Shrinkage ,Volumetric shrinkage ,biology ,biology.organism_classification ,Compressive strength ,Agronomy ,Propriété mécanique ,Provenance ,symbols ,Geology ,Propriété du bois - Abstract
Faidherbia albida is a typical emblematic species of African dryland areas. In Chad, it is used for many purposes, but very little is known about the technological properties of its wood, which sometimes leads to inappropriate uses. This work consisted to study the physical and mechanical properties of this wood, collected in the Sahelian and Sudanian chadian zone. As well as the impact study of the sampling areas of these properties. The result obtained shows that, the density, infradensity; modulus of elasticity, compression strength were significantly higher in the Sahelian zone than in the Sudanian zone, i.e. 508 and 409 kg·m−3; 5555 and 23.7 MPa, compared to 444 and 359 kg·m−3; 4150 and 19.6 MPa. The total tangential shrinkage, total volumetric shrinkage, fibre saturation point; static bending strength were significantly lower in wood from the Sahelian zone compared to the Sudanian zone, i.e. 4.6%, 7.7%, 23.7%; 42.5 MPa, compared to 6.6%, 9.5%, 28.9%; 52.6 MPa. The total radial shrinkage values obtained were not significantly different between the two provenances (mean: 3.1%).
- Published
- 2021
8. Influence des variations climatiques sur la croissance et la qualité du bois de deux essences des zones semi-arides tchadiennes : Faidherbia albida (Del.) A. Chev. et Balanites aegyptiaca (L.) Delile
- Author
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Dougabka, Dao
- Subjects
P40 - Météorologie et climatologie ,Conditions météorologiques ,Facteur climatique ,K10 - Production forestière ,Faidherbia albida ,Propriété mécanique ,Accroissement du diamètre ,Balanites aegyptiaca ,Zone semi-aride ,Propriété du bois ,Propriété physicochimique - Abstract
Faidherbia albida et Balanites aegyptiaca sont deux espèces caractéristiques et emblématiques de la zone semi-aride tchadienne. Elles revêtent une grande importance socio-économique dans toutes leurs zones naturelles de répartition du fait de leurs multiples usages. La présente étude de nature exploratoire a consisté à comprendre le déterminisme des variations des caractéristiques du bois des deux espèces en relation avec leurs variations de conditions de croissance. Sa finalité est de mieux connaitre l'hétérogénéité de comportement technologique des bois de ces deux espèces afin de mieux les valoriser dans les processus de reboisement et d'élargir leur domaine d'utilisation locale. L'étude a été réalisée selon deux approches. La première a consisté à déterminer par des méthodes conventionnelles et normalisées une sélection de caractéristiques physiques, mécaniques et chimiques des bois prélevés dans deux zones climatiques tchadiennes (zone sahélienne et zone soudanienne) et une zone climatique sénégalaise (zone sahélienne), et à étudier leurs variations en fonction des conditions de croissance liées essentiellement aux différences climatiques. La seconde a consisté à étudier les variations radiales de caractéristiques physiques, mécaniques, et de la composition isotopique de carbone 13 (δ13C), ceci en fonction de la croissance des arbres, par des mesures réalisées sur des micro-échantillons prélevés au niveau des cernes. Les résultats du premier volet de l'étude ont mis en évidence pour les deux espèces des tendances variables pour toutes les caractéristiques étudiées. Pour Faidherbia albida, l'infradensité, la masse volumique, les retraits de séchage et les trois caractéristiques mécaniques étudiées sont significativement plus élevés dans la zone sahélienne sénégalaise que dans les deux provenances tchadiennes. Cette même tendance est observée pour les taux d'extractibles et de lignine, mais les taux de cellulose et d'hémicellulose sont significativement plus élevés dans la zone sahélienne tchadienne. Pour Balanites aegyptiaca, les tendances sont variables suivant les propriétés, avec un effet inverse des provenances pour le retrait tangentiel et le retrait radial, et aucune tendance marquée pour le retrait volumique. Le point de saturation des fibres est faible pour les trois provenances (inférieur à 25 %). En zone soudanienne tchadienne, la masse volumique est significativement plus élevée que dans les deux autres zones, alors que la contrainte de rupture en compression et le module d'élasticité longitudinal sont moins élevés. Les taux de lignine et d'hémicellulose sont plus élevés en zone sahélienne tchadienne. Une analyse des extractibles par GC-MS a mis en évidence des différences marquées entre les deux espèces d'une part et les trois provenances d'autre part. Ces différences pourraient être mises en relation avec celles observées entre provenances et espèces pour certaines propriétés physiques et mécaniques du bois telles que les retraits de séchage, le PSF, la masse volumique et le module d'élasticité. L'effet de chaque extractible sur ces propriétés resterait cependant à établir, en tenant compte des probables impacts conjugués de ces différents composés. Le second volet de l'étude a montré que l'accroissement moyen était légèrement supérieur en zone soudanienne qu'en zone sahélienne ce qui reflète les différences de conditions climatiques qui impactent la croissance des arbres. Pour Faidherbia albida, l'absence de différence significative de δ13C entre les deux provenances peut s'expliquer par le fait que cette espèce est une phréatophyte. Pour Balanites aegyptiaca, le δ13C moyen dans la zone sahélienne est significativement inférieur à celui de la zone soudanienne, tendance inverse à celle à laquelle on pouvait s'attendre. Ce résultat tend à montrer que cette espèce présente une bonne efficacité et une bonne stratégie opportuniste d'utilisation de l'eau. L'étude des relations entre les variables prises deux à deux a donné des résultats contrastés. L'absence de relation entre la largeur de cerne et la pluviométrie peut être liée à plusieurs causes : pluviométrie sur les sites de prélèvement des bois différente de celle de la station météorologique éloignée de ces sites, comportement phréatophile avéré de Faidherbia albida et possible pour Balanites aegyptiaca, et délimitation incertaine des cernes liée à leur structure. Les perspectives de recherche à venir sur les deux espèces sont multiples, et concernent aussi bien le protocole d'échantillonnage (utilisation de branches au lieu de troncs), l'étude des rythmes de croissance afin de comprendre le phénomène de disparition/fusion partielle des cernes, que l'élargissement de l'étude à d'autres provenances.
- Published
- 2022
9. Modélisation numérique de l'expérience élastographie par IRM : Excitation et tissu hétérogénéité
- Author
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Du, Quanshangze and STAR, ABES
- Subjects
Propagation des ondes ,Elastographie par résonance magnétique ,Méthode des éléments finis étendue (X-FEM) ,Continuum mechanics ,Parametric study ,Viscoelasticity ,Mechanical properties ,Imagerie par résonance magnétique - IRM ,Modélisation rhéologique ,Etude paramétrique ,[SPI.MECA] Engineering Sciences [physics]/Mechanics [physics.med-ph] ,MRI Imaging ,Wave conversion ,Steady-State ,Etat stationnaire ,Conversion des ondes ,Magnetic resonance elastography ,Inhomogénéité du contact ,Propriété mécanique ,Rheological model ,Mécanique des milieux continus ,Inhomogeneity interface ,Extended finite element method (XFEM) ,Wave Propagation ,Viscoélasticité - Abstract
The diagnosis of various pathologies, including some cancers, has long been based on palpation, since a tumor is significantly stiffer than healthy tissue. More advanced and quantitative methods have been developed over the last decades, especially the Magnetic Resonance Elastography (MRE). This method uses magnetic resonance imaging (MRI) on mechanically stressed tissue to estimate the mechanical properties of soft tissue. The reconstruction of the elasticity modulus of the tissue in MRE is often based on a model with simple behavior laws of the imaged tissue (linear elasticity, isotropy, homogeneity), which could be extended to more complex cases thanks to modeling by the Finite Element Method (FEM) in particular. FEM has been used in MRE to simulate the propagation of mechanical waves in a tissue, to better understand the effects of different parameters on MRE measurements, to reconstruct stiffness, to evaluate novel MRE inversion methods, etc. However, in inhomogeneous cases with complex interfaces, FEM modeling can be particularly costly as it requires an explicit mesh of these interfaces. In this work, we explored, using an explicit dynamic FE solver developed in this thesis, the behavior of mechanical waves propagating in a linear, isotropic, viscoelastic and inhomogeneous medium, in order to better control the parameters of a MRE experiment. In the solver, the eXtended Finite Element Method (XFEM) has been implemented; this formulation of FEM originates from fracture mechanics and has been widely used over the last two decades to model discontinuities such as cracks and inclusions. Using the developed numerical tool, we studied the behavior of waves in the vicinity of an interface (oblique or complex), in particular the phenomena of wave reflection and wave conversion. It has been shown that the use of the XFEM method significantly reduces the computation time while ensuring an equivalent accuracy, in terms of displacement fields and reconstructed stiffness. Furthermore, we have addressed, by simulation, the criterion of establishing the steady state of the waves which must be reached to ensure correct recording by MRI. Today, this criterion is still empirical and can influence the quality of MRE data. We have thus proposed a metric to quantify the achievement of the steady state of wave propagation in a tissue with or without inclusion. Finally, these methods were implemented on a practical case of breast MRE. Based on breast models, we evaluated the influence of experimental parameters (size and position of the inclusion, polarization of the excitation, boundary conditions, etc.) on the achievement of steady state., Le diagnostic de différentes pathologies, dont certains cancers, a longtemps été basé sur la palpation, puisqu'une tumeur est sensiblement plus rigide qu'un tissu sain. Des méthodes plus avancées et quantitatives ont été développées au cours des dernières décennies, notamment l'Elastographie par Résonance Magnétique (ERM). Cette méthode utilise l'imagerie par résonance magnétique (IRM) sur un tissu sollicité mécaniquement pour estimer les propriétés mécaniques des tissus mous. La reconstruction du module d'élasticité du tissu en ERM est souvent basée sur un modèle avec des lois de comportement simples du tissu imagé (élasticité linéaire, isotropie, homogénéité), qui pourrait être étendu à des cas plus complexes grâce à la modélisation par la Méthode des Eléments Finis (MEF) notamment. La MEF a été utilisée en ERM pour simuler la propagation des ondes mécaniques dans un tissu, pour mieux comprendre les effets de différents paramètres sur les mesures d’ERM, reconstruire la rigidité, évaluer de nouvelles méthodes d’inversion d’ERM, etc. Cependant, dans des cas inhomogènes avec interfaces complexes, la modélisation par MEF peut être particulièrement coûteuse car elle nécessite un maillage explicite de ces interfaces. Dans ce travail, nous avons exploré, à l'aide d'un solveur EF en dynamique explicite développé dans cette thèse, le comportement d'ondes mécaniques se propageant dans un milieu linéaire, isotrope, viscoélastique et inhomogène, en vue d'une meilleure maîtrise des paramètres d'une expérimentation d'ERM. Dans le solveur a été implémentée la méthode des éléments finis étendue (XFEM); cette formulation de la MEF provient de la mécanique des fractures et a été largement utilisée au cours des deux dernières décennies pour modéliser des discontinuités comme les fissures et les inclusions. A l'aide de l'outil numérique développé, nous avons étudié le comportement des ondes au voisinage d'une interface (oblique ou complexe), en particulier les phénomènes de réflexion et de conversion des ondes. Nous avons pu montrer que l'utilisation de la méthode XFEM réduit sensiblement les temps de calcul tout en assurant une précision équivalente, en termes de champs de déplacement et de rigidité reconstruite. Par ailleurs, nous avons abordé, par simulation, le critère d'établissement du régime stationnaire des ondes qui doit être atteint pour assurer l'enregistrement correct par IRM. Or aujourd'hui ce critère est empirique et peut influencer la qualité des données ERM. Nous avons ainsi proposé une métrique pour quantifier l'atteinte du régime stationnaire de propagation des ondes dans un tissu avec ou sans inclusion. Enfin, ces méthodes ont été mises en oeuvre sur un cas pratique d'ERM du sein. Avec les modèles du sein, nous avons évalué l'influence des paramètres expérimentaux (taille et position de l'inclusion, polarisation de l'excitation, conditions aux limites, etc.) sur l'atteinte du régime stationnaire.
- Published
- 2022
10. Structure optimization for improving the strength and ductility of heterogeneous carbon nanotube/Al–Cu–Mg composites
- Abstract
Heterogeneous carbon nanotube (CNT)/Al–Cu–Mg composites, consisting of ductile zones (DZs) free of CNTs and brittle zones (BZs) rich of CNTs, were fabricated in powder metallurgy route. It was shown that the grain size and width of the DZs in the heterogeneous composites could be controlled by high energy ball milling (HEBM) on additional Al–Cu–Mg alloy powders. Appropriate grain refinement in the DZs and a medium DZ width were identified to be beneficial for improving the strength-ductility. Under the optimized condition, a heterogeneous CNT/Al–Cu–Mg composite exhibited 88% increase in the elongation and 2% increase in the tensile strength compared to the uniform composite. Although the yield strength of the heterogeneous composite was lower than that of the uniform composite, the appropriate grain refinement in the DZs was good for alleviating the low yield phenomenon. Furthermore, the abundant grain boundaries could reduce the local slip bands passing through the DZs, which could significantly relax the stress concentration of the BZs. As a result, the medium width DZs could contribute more to the plastic deformation, thereby further improving the strength-ductility. Finally, a model was proposed to assist the design of the heterogeneous structure parameters. The calculated optimized DZ size was in accordance with the DZ width of the heterogeneous composite with the best strength-ductility.
- Published
- 2021
11. Variations des caractéristiques physiques et mécaniques du bois de Balanites aegyptiaca en fonction de trois provenances
- Abstract
Balanites aegyptiaca est une espèce caractéristique et emblématique des zones sèches d'Afrique et d'Asie. Elle revêt une grande importance socio-économique dans toute sa zone naturelle de répartition du fait de ses multiples usages. Toutefois, les propriétés technologiques de son bois sont mal connues, d'où des utilisations parfois inappropriées mais qui pourraient être élargies. Afin de mieux adapter ses applications à ses caractéristiques, nous avons déterminé les indicateurs de stabilité physique (masse volumique, infradensité, retrait radial total, retrait tangentiel total, retrait volumique total et point de saturation des fibres) et les indicateurs de comportement mécanique (module d'élasticité longitudinal, contrainte de rupture en flexion et compression) de ce bois. Quatre-vingt-treize éprouvettes prélevées dans 13 arbres provenant des zones sahélienne et soudanienne tchadiennes, et de la zone sahélienne sénégalaise ont été testées. Les résultats obtenus montrent que, pour les trois provenances, le bois de B. aegyptiaca est mi-lourd (797 kg/m3) avec une stabilité dimensionnelle moyenne : l'anisotropie de retrait est supérieure à 2 (2,2), le retrait radial total et le retrait tangentiel total sont moyens, respectivement égaux à 4 % et 8,5 %. Ses caractéristiques mécaniques sont moyennes (contraintes de rupture en compression et flexion statique respectivement égales à 49,4 MPa et 104,5 MPa) à faible (module d'élasticité longitudinal de 10 473 MPa). Une comparaison des résultats obtenus en fonction des zones de prélèvement a mis en évidence des tendances variables selon les caractéristiques étudiées. Ces variations entre les trois provenances restent cependant limitées. Les résultats de l'étude montrent que le bois de B. aegyptiaca pourrait être utilisé de façon appropriée sous forme de matériau pour une plus large gamme d'emplois, sous réserve de la mise en place d'une gestion adaptée permettant sa restauration par plantation.
- Published
- 2021
12. Valorisation de déchets plastiques et d'industrie du bois en composite moule à froid : effet des paramètres de fabrication sur les propriétés mécaniques
- Abstract
Ce travail concerne le domaine du recyclage de déchets en matériaux. Il rend compte d'une possibilité de valorisation de déchets plastiques et de produits connexes de l'industrie du bois dans la construction. L'étude vise à donner une valeur ajoutée à un composite bois-plastique élaboré suivant un procédé de moulage par compression à froid, par l'amélioration de ses propriétés mécaniques. A travers un essai de flexion, l'influence de deux paramètres de fabrication - pression de compactage et température de séchage postmoulage- sur les propriétés mécaniques, a été évaluée dans le cas d'un composite à base de sciures de bois tropicaux venant du Bénin et de polystyrène (CBPo) recyclés. Il en ressort que la pression de compactage et la température de séchage, sont deux facteurs essentiels à considérer lors de l'évaluation des performances mécaniques du composite. L'augmentation de la pression de compactage jusqu'à une valeur limite améliore significativement les propriétés du matériau. Les propriétés optimales du CBPo ont été obtenues à la pression de 7 MPa. Le séchage post-moulage à 100°C, a également amélioré de façon significative les performances du composite. Aussi, par ses nouvelles performances mécaniques, le CBPo se repositionne par rapport à d'autres matériaux existants permettant ainsi d'en envisager de nouvelles applications dans la construction.
- Published
- 2021
13. Etude des propriétés technologiques d'un composite bois-plastique élaboré au Bénin
- Abstract
Au Bénin, les déchets issus de la transformation du bois sont très insuffisamment valorisés dans une perspective de réutilisation par l'industrie du bois. Les technologies de transformation de ces produits connexes, économiquement accessibles aux populations des pays en développement, constituent un domaine très peu abordé dans la littérature internationale. Dans le présent travail, un matériau constitué d'un mélange de sciure de bois de teck et de pâte de polystyrène recyclés, suivant une technologie simple à mettre en oeuvre et de type low-tech, a été caractérisé. Les résultats obtenus ont montré que les propriétés du composite varient significativement avec la granulométrie de la sciure utilisée. La masse volumique apparente du matériau est comprise entre 686 à 826 kg/m3, son taux d'absorption d'eau est inférieur à 15 % et son taux de gonflement en épaisseur est inférieur à 5 % après 24 heures d'immersion. Une corrélation élevée a été observée entre ses propriétés physiques et sa porosité qui varie de 34 et 43 % suivant la granulométrie des sciures de bois utilisées. Le composite présente un module d'élasticité en traction compris entre 582 à 1 057 MPa, une résistance en traction comprise entre 2 et 3 MPa et un coefficient de Poisson variant de 0,14 à 0,24. En compression, son module d'élasticité varie entre 270 à 470 MPa et sa résistance entre 6 à 9 MPa. Une mise en oeuvre du composite ainsi élaboré peut être envisagée en substitution du bois pour des éléments faiblement chargés comme des pièces de coffrage de construction légère.
- Published
- 2021
14. Etude des propriétés technologiques d'un composite bois-plastique élaboré au Bénin
- Abstract
Au Bénin, les déchets issus de la transformation du bois sont très insuffisamment valorisés dans une perspective de réutilisation par l'industrie du bois. Les technologies de transformation de ces produits connexes, économiquement accessibles aux populations des pays en développement, constituent un domaine très peu abordé dans la littérature internationale. Dans le présent travail, un matériau constitué d'un mélange de sciure de bois de teck et de pâte de polystyrène recyclés, suivant une technologie simple à mettre en oeuvre et de type low-tech, a été caractérisé. Les résultats obtenus ont montré que les propriétés du composite varient significativement avec la granulométrie de la sciure utilisée. La masse volumique apparente du matériau est comprise entre 686 à 826 kg/m3, son taux d'absorption d'eau est inférieur à 15 % et son taux de gonflement en épaisseur est inférieur à 5 % après 24 heures d'immersion. Une corrélation élevée a été observée entre ses propriétés physiques et sa porosité qui varie de 34 et 43 % suivant la granulométrie des sciures de bois utilisées. Le composite présente un module d'élasticité en traction compris entre 582 à 1 057 MPa, une résistance en traction comprise entre 2 et 3 MPa et un coefficient de Poisson variant de 0,14 à 0,24. En compression, son module d'élasticité varie entre 270 à 470 MPa et sa résistance entre 6 à 9 MPa. Une mise en oeuvre du composite ainsi élaboré peut être envisagée en substitution du bois pour des éléments faiblement chargés comme des pièces de coffrage de construction légère.
- Published
- 2021
15. Valorisation de déchets plastiques et d'industrie du bois en composite moule à froid : effet des paramètres de fabrication sur les propriétés mécaniques
- Abstract
Ce travail concerne le domaine du recyclage de déchets en matériaux. Il rend compte d'une possibilité de valorisation de déchets plastiques et de produits connexes de l'industrie du bois dans la construction. L'étude vise à donner une valeur ajoutée à un composite bois-plastique élaboré suivant un procédé de moulage par compression à froid, par l'amélioration de ses propriétés mécaniques. A travers un essai de flexion, l'influence de deux paramètres de fabrication - pression de compactage et température de séchage postmoulage- sur les propriétés mécaniques, a été évaluée dans le cas d'un composite à base de sciures de bois tropicaux venant du Bénin et de polystyrène (CBPo) recyclés. Il en ressort que la pression de compactage et la température de séchage, sont deux facteurs essentiels à considérer lors de l'évaluation des performances mécaniques du composite. L'augmentation de la pression de compactage jusqu'à une valeur limite améliore significativement les propriétés du matériau. Les propriétés optimales du CBPo ont été obtenues à la pression de 7 MPa. Le séchage post-moulage à 100°C, a également amélioré de façon significative les performances du composite. Aussi, par ses nouvelles performances mécaniques, le CBPo se repositionne par rapport à d'autres matériaux existants permettant ainsi d'en envisager de nouvelles applications dans la construction.
- Published
- 2021
16. Influence of Sahelian and Sudanian provenances on the physical and mechanical properties of Faidherbia albida wood from Chad
- Abstract
Faidherbia albida is a typical emblematic species of African dryland areas. In Chad, it is used for many purposes, but very little is known about the technological properties of its wood, which sometimes leads to inappropriate uses. This work consisted to study the physical and mechanical properties of this wood, collected in the Sahelian and Sudanian chadian zone. As well as the impact study of the sampling areas of these properties. The result obtained shows that, the density, infradensity; modulus of elasticity, compression strength were significantly higher in the Sahelian zone than in the Sudanian zone, i.e. 508 and 409 kg·m−3; 5555 and 23.7 MPa, compared to 444 and 359 kg·m−3; 4150 and 19.6 MPa. The total tangential shrinkage, total volumetric shrinkage, fibre saturation point; static bending strength were significantly lower in wood from the Sahelian zone compared to the Sudanian zone, i.e. 4.6%, 7.7%, 23.7%; 42.5 MPa, compared to 6.6%, 9.5%, 28.9%; 52.6 MPa. The total radial shrinkage values obtained were not significantly different between the two provenances (mean: 3.1%).
- Published
- 2021
17. Variations des caractéristiques physiques et mécaniques du bois de Balanites aegyptiaca en fonction de trois provenances
- Abstract
Balanites aegyptiaca est une espèce caractéristique et emblématique des zones sèches d'Afrique et d'Asie. Elle revêt une grande importance socio-économique dans toute sa zone naturelle de répartition du fait de ses multiples usages. Toutefois, les propriétés technologiques de son bois sont mal connues, d'où des utilisations parfois inappropriées mais qui pourraient être élargies. Afin de mieux adapter ses applications à ses caractéristiques, nous avons déterminé les indicateurs de stabilité physique (masse volumique, infradensité, retrait radial total, retrait tangentiel total, retrait volumique total et point de saturation des fibres) et les indicateurs de comportement mécanique (module d'élasticité longitudinal, contrainte de rupture en flexion et compression) de ce bois. Quatre-vingt-treize éprouvettes prélevées dans 13 arbres provenant des zones sahélienne et soudanienne tchadiennes, et de la zone sahélienne sénégalaise ont été testées. Les résultats obtenus montrent que, pour les trois provenances, le bois de B. aegyptiaca est mi-lourd (797 kg/m3) avec une stabilité dimensionnelle moyenne : l'anisotropie de retrait est supérieure à 2 (2,2), le retrait radial total et le retrait tangentiel total sont moyens, respectivement égaux à 4 % et 8,5 %. Ses caractéristiques mécaniques sont moyennes (contraintes de rupture en compression et flexion statique respectivement égales à 49,4 MPa et 104,5 MPa) à faible (module d'élasticité longitudinal de 10 473 MPa). Une comparaison des résultats obtenus en fonction des zones de prélèvement a mis en évidence des tendances variables selon les caractéristiques étudiées. Ces variations entre les trois provenances restent cependant limitées. Les résultats de l'étude montrent que le bois de B. aegyptiaca pourrait être utilisé de façon appropriée sous forme de matériau pour une plus large gamme d'emplois, sous réserve de la mise en place d'une gestion adaptée permettant sa restauration par plantation.
- Published
- 2021
18. Physicochemical and mechanical properties of biomass coal briquettes produced by artisanal method
- Author
-
Lat Grand Ndiaye, Philippe Bernard Himbane, Alfredo Napoli, and Diouma Kobor
- Subjects
K50 - Technologie des produits forestiers ,Briquette ,Materials science ,P06 - Sources d'énergie renouvelable ,020209 energy ,Combustion ,Biomass ,02 engineering and technology ,Raw material ,Déchet agricole ,0202 electrical engineering, electronic engineering, information engineering ,Coal ,Coque ,Propriété physicochimique ,Carbonization ,business.industry ,Metallurgy ,Q70 - Traitement des déchets agricoles ,General Medicine ,Gomme arabique ,Compressive strength ,Produit forestier non ligneux ,Propriété mécanique ,Bioénergie ,Heat of combustion ,business - Abstract
In this study, carbonized peanut shells, cashew shells and millet stalks were used as raw materials to produce coal briquettes. Clay and arabic gum were applied as binders during briquetting by use of manual press. Physicochemical and mechanical tests of the obtained briquettes were conducted. The results show that the lower heating values of coal briquettes remain higher to that of wood; however, their ash contents are very high compared to wood. Combustion of coal briquettes samples show also that coal briquettes of peanut shells, cashew shells, and millet stalks ignite respectively at 312, 202.5 and 150.5°C. Bulk densities of these briquettes are respectively 543, 765 and 579 kg/m3. Briquette made with arabic gum presents mechanical compressive strength above 1 MPa. Key words: Coal briquettes, binders, heating value, bulk density, compressive strength.
- Published
- 2018
19. Antioxidant properties of flax fibers in polyethylene matrix composites
- Author
-
Peter Davies, Marielle Gueguen Minerbe, Laetitia Van Schoors, Sandrine Moscardelli, Hajer Rabii, Comportement Physico-chimique et Durabilité des Matériaux (IFSTTAR/MAST/CPDM), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Communauté Université Paris-Est, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
- Subjects
Antioxidant ,FIBRE ,medicine.medical_treatment ,MATERIAU COMPOSITE ,02 engineering and technology ,010402 general chemistry ,PROPRIETE MECANIQUE ,01 natural sciences ,[SPI.MAT]Engineering Sciences [physics]/Materials ,chemistry.chemical_compound ,ANTIOXIDANT ,medicine ,Lignin ,THERMOOXIDATIVE AGEING ,Phenols ,Composite material ,Thermal analysis ,POLYETHYLENE ,TRAITEMENT CHIMIQUE ,Chemistry ,Polyethylene matrix ,Induction time ,Polyethylene ,LIN ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,FLAX ,POLYMERE ,Degradation (geology) ,VEGETATION ,MATERIAU BIOSOURCE ,0210 nano-technology ,Agronomy and Crop Science ,LIGNIN - Abstract
Flax fibers are commonly used to reinforce mechanical properties of polymer-matrix composites, but can also enhance antioxidative properties of polyethylene matrix: lignin, which is one of the components of plant fibers has the advantage of containing phenols, molecules well known for their antioxidant properties. In this study, its oxidative stabilization effect on unstabilized polyethylene matrix has been demonstrated. It has then been shown by thermal analysis, that the Oxidation Induction Time of the polyethylene matrix increases from 0 to 25 min when the flax fiber content is raised from 0 to 54%, and that the flax fibers cause a slight increase in the degradation temperature of the polyethylene matrix. During thermooxidative ageing, this study has highlighted that the flax fibers also improve the oxidative stability of the polyethylene by inhibiting the oxidation mechanisms of the polyethylene matrix.
- Published
- 2018
20. Elaboration of Metallic Materials by SPS: Processing, Microstructures, Properties, and Shaping
- Author
-
Monchoux, Jean-Philippe, Couret, Alain, Durand, Lise, Voisin, Thomas, Trzaska, Zofia, Thomas, Marc, Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Lawrence Livermore National Laboratory (LLNL), Institut de Chimie et des Matériaux Paris-Est (ICMPE), Institut de Chimie du CNRS (INC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Sorbonne Paris Nord, DMAS, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), and Université Fédérale Toulouse Midi-Pyrénées
- Subjects
[PHYS]Physics [physics] ,Mise en forme des métaux ,Frittage flash ,Mechanical properties ,Spark plasma sintering SPS ,Shaping ,TiAl ,[SPI]Engineering Sciences [physics] ,Métaux ,Metals ,Propriété mécanique ,[CHIM]Chemical Sciences ,Microstructure ,Aluminiure de titane - Abstract
International audience; After a few decades of increasing interest, spark plasma sintering (SPS) has now become a mature powder metallurgy technique, which allows assessing its performances toward fabricating enhanced materials. Here, the case of metals and alloys will be presented. The main advantage of SPS lies in its rapid heating capability enabled by the application of high intensity electric currents to a metallic powder. This presents numerous advantages balanced by some limitations that will be addressed in this review. The first section will be devoted to sintering issues, with an emphasis on the effect of the electric current on the densification mechanisms. Then, typical as-SPS microstructures and properties will be presented. In some cases, they will be compared with that of materials processed by conventional techniques. As such, examples of nanostructured materials, intermetallics, metallic glasses, and high entropy alloys, will be presented. Finally, the implementation of SPS as a technique to manufacture complex, near-net shape industrial parts will be discussed.; Après quelques dizaines d‘années d'intérêt croissant, le frittage-flash ou spark plasma sintering (SPS) a atteint un stade de maturité en tant que technique de métallurgie des poudres, qui permet d'évaluer ses performances au travers de la fabrication de matériaux avancés. Nous présenterons ici le cas des métaux et alliages. Le principal avantage du SPS réside dans sa capacité de chauffage rapide qui est rendue possible par l'application de courants électriques de haute intensité à une poudre métallique. Cela présente de nombreux avantages contrebalancés par certaines limitations qui seront abordées dans cette revue. La première partie sera consacrée à la problématique du frittage, avec un accent particulier sur l'effet du courant électrique sur les mécanismes de densification. Ensuite, nous présenterons un certain nombre de microstructures et propriétés types à l’état brut de SPS. Dans certains cas, une comparaison sera faite avec les matériaux élaborés par des techniques conventionnelles. A ce titre, des exemples de matériaux nanostructurés, d‘intermétalliques, de verres métalliques et d‘alliages à haute entropie seront présentés. Enfin, nous discuterons de la mise en œuvre du SPS en tant que technique de fabrication de pièces industrielles complexes et proches des cotes.
- Published
- 2021
21. Elaboration de Matériaux Métalliques par SPS: Procédé, Microstructures, Propriétés, et Mise en Forme
- Author
-
Alain Couret, Thomas Voisin, Jean-Philippe Monchoux, Zofia Trzaska, Marc Thomas, Lise Durand, Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées (INSA)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Lawrence Livermore National Laboratory (LLNL), Institut de Chimie et des Matériaux Paris-Est (ICMPE), Institut de Chimie du CNRS (INC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Sorbonne Paris Nord, DMAS, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)
- Subjects
lcsh:TN1-997 ,Materials science ,microstructure ,Intermetallic ,Spark plasma sintering ,Sintering ,metals ,SPS ,02 engineering and technology ,mechanical properties ,01 natural sciences ,TiAl ,[SPI]Engineering Sciences [physics] ,Métaux ,Powder metallurgy ,0103 physical sciences ,[CHIM]Chemical Sciences ,General Materials Science ,lcsh:Mining engineering. Metallurgy ,010302 applied physics ,[PHYS]Physics [physics] ,Amorphous metal ,High entropy alloys ,Mise en forme des métaux ,Metals and Alloys ,Frittage flash ,021001 nanoscience & nanotechnology ,Microstructure ,Spark plasma sintering SPS ,Engineering physics ,Propriété mécanique ,shaping ,Electric current ,0210 nano-technology ,Aluminiure de titane - Abstract
International audience; After a few decades of increasing interest, spark plasma sintering (SPS) has now become a mature powder metallurgy technique, which allows assessing its performances toward fabricating enhanced materials. Here, the case of metals and alloys will be presented. The main advantage of SPS lies in its rapid heating capability enabled by the application of high intensity electric currents to a metallic powder. This presents numerous advantages balanced by some limitations that will be addressed in this review. The first section will be devoted to sintering issues, with an emphasis on the effect of the electric current on the densification mechanisms. Then, typical as-SPS microstructures and properties will be presented. In some cases, they will be compared with that of materials processed by conventional techniques. As such, examples of nanostructured materials, intermetallics, metallic glasses, and high entropy alloys, will be presented. Finally, the implementation of SPS as a technique to manufacture complex, near-net shape industrial parts will be discussed.; Après quelques dizaines d‘années d'intérêt croissant, le frittage-flash ou spark plasma sintering (SPS) a atteint un stade de maturité en tant que technique de métallurgie des poudres, qui permet d'évaluer ses performances au travers de la fabrication de matériaux avancés. Nous présenterons ici le cas des métaux et alliages. Le principal avantage du SPS réside dans sa capacité de chauffage rapide qui est rendue possible par l'application de courants électriques de haute intensité à une poudre métallique. Cela présente de nombreux avantages contrebalancés par certaines limitations qui seront abordées dans cette revue. La première partie sera consacrée à la problématique du frittage, avec un accent particulier sur l'effet du courant électrique sur les mécanismes de densification. Ensuite, nous présenterons un certain nombre de microstructures et propriétés types à l’état brut de SPS. Dans certains cas, une comparaison sera faite avec les matériaux élaborés par des techniques conventionnelles. A ce titre, des exemples de matériaux nanostructurés, d‘intermétalliques, de verres métalliques et d‘alliages à haute entropie seront présentés. Enfin, nous discuterons de la mise en œuvre du SPS en tant que technique de fabrication de pièces industrielles complexes et proches des cotes.
- Published
- 2021
22. Etude des propriétés technologiques d'un composite bois-plastique élaboré au Bénin
- Author
-
Edmond Codjo Adjovi, Jean Gérard, Togbé Armel Amadji, Vincent Huon, and Jonathan Barés
- Subjects
K50 - Technologie des produits forestiers ,Polystyrène ,Ecology ,Forestry ,Q70 - Traitement des déchets agricoles ,Déchet de bois ,matériaux composites ,produits de bois composite ,Propriété mécanique ,Tectona grandis ,Ecology, Evolution, Behavior and Systematics ,Technologie du bois ,Propriété physicochimique ,Propriété du bois - Abstract
Au Bénin, les déchets issus de la transformation du bois sont très insuffisamment valorisés dans une perspective de réutilisation par l’industrie du bois. Les technologies de transformation de ces produits connexes, économiquement accessibles aux populations des pays en développement, constituent un domaine très peu abordé dans la littérature internationale. Dans le présent travail, un matériau constitué d’un mélange de sciure de bois de teck et de pâte de polystyrène recyclés, suivant une technologie simple à mettre en œuvre et de type low-tech, a été caractérisé. Les résultats obtenus ont montré que les propriétés du composite varient significativement avec la granulométrie de la sciure utilisée. La masse volumique apparente du matériau est comprise entre 686 à 826 kg/m3, son taux d’absorption d’eau est inférieur à 15 % et son taux de gonflement en épaisseur est inférieur à 5 % après 24 heures d’immersion. Une corrélation élevée a été observée entre ses propriétés physiques et sa porosité qui varie de 34 et 43 % suivant la granulométrie des sciures de bois utilisées. Le composite présente un module d’élasticité en traction compris entre 582 à 1 057 MPa, une résistance en traction comprise entre 2 et 3 MPa et un coefficient de Poisson variant de 0,14 à 0,24. En compression, son module d’élasticité varie entre 270 à 470 MPa et sa résistance entre 6 à 9 MPa. Une mise en œuvre du composite ainsi élaboré peut être envisagée en substitution du bois pour des éléments faiblement chargés comme des pièces de coffrage de construction légère.
- Published
- 2021
23. Valorisation de déchets plastiques et d'industrie du bois en composite moule à froid : effet des paramètres de fabrication sur les propriétés mécaniques
- Author
-
Guibal Daniel, Doko Kouandété Valéry, Gerard Jean, Togbé Armel Amadji, Adjovi Codjo, Laboratoire d’Énergétique et de Mécanique Appliquée (LEMA), and Université d’Abomey-Calavi (UAC)
- Subjects
K50 - Technologie des produits forestiers ,Recyclage des déchets ,drying temperature ,pression de compactage ,température de séchage ,matériaux composites ,waste recycling ,compaction pressure ,effet des paramètres de fabrication ,technologie des matériaux ,Déchet ,[SDE.IE]Environmental Sciences/Environmental Engineering ,composite boispolystyrène ,Q70 - Traitement des déchets agricoles ,propriétés mécaniques ,Déchet de bois ,Utilisation des déchets ,wood-polystyrene composite ,mechanical properties ,Propriété mécanique ,Technologie du bois ,effect of manufacturing parameters - Abstract
This work concerns the field of recycling of waste intobuilding materials. It reports on the possibility ofrecovering plastic waste and related products fromthe wood industry, in construction. The objective ofthe study is to give added value to wood-plasticcomposites produced using the cold compressionmolding process, by improving their mechanicalproperties. Through the bending test, the influence oftwo manufacturing parameters - compactionpressure and drying temperature after molding - onthe mechanical properties, was evaluated for the caseof a composite based on tropical wood sawdustcoming from Benin and recycled polystyrene (CBPo).It appears that the compaction pressure and thedrying temperature are essential factors to considerwhen evaluating the mechanical performance of thecomposite. Increasing the compaction pressure to alimit value significantly improves the properties of thematerial. The optimal properties of CBPo wereobtained at a pressure of 7 MPa. Post-forming dryingat 100 ° C also significantly improved the performanceof the composite. In addition, thanks to its enhancednew mechanical properties, the CBPo is repositionedrelatively to other existing materials, thus making itpossible to think about new applications inconstruction., Ce travail concerne le domaine du recyclage dedéchets en matériaux. Il rend compte d’unepossibilité de valorisation de déchets plastiques et deproduits connexes de l’industrie du bois dans laconstruction. L’étude vise à donner une valeurajoutée à un composite bois-plastique élaborésuivant un procédé de moulage par compression àfroid, par l’amélioration de ses propriétésmécaniques. A travers un essai de flexion, l’influencede deux paramètres de fabrication - pression decompactage et température de séchage postmoulage- sur les propriétés mécaniques, a étéévaluée dans le cas d’un composite à base de sciuresde bois tropicaux venant du Bénin et de polystyrène(CBPo) recyclés. Il en ressort que la pression decompactage et la température de séchage, sont deuxfacteurs essentiels à considérer lors de l’évaluationdes performances mécaniques du composite.L’augmentation de la pression de compactage jusqu’àune valeur limite améliore significativement lespropriétés du matériau. Les propriétés optimales duCBPo ont été obtenues à la pression de 7 MPa. Leséchage post-moulage à 100°C, a également amélioréde façon significative les performances du composite.Aussi, par ses nouvelles performances mécaniques, leCBPo se repositionne par rapport à d’autresmatériaux existants permettant ainsi d’en envisagerde nouvelles applications dans la construction.
- Published
- 2021
24. Towards a better understanding of the mechanical behavior of a fixed bed of eucalyptus charcoal in a blast furnace using a specific compression test
- Abstract
The properties of wood charcoal layers have an effect on the performance of small-scale blast furnaces. In order to characterize the mechanical behavior of a fixed bed of eucalyptus charcoal, a specific uniaxial compression test was designed and used with charcoal layers of different characteristics. This layer test has the potential to be standardized,and it made it possible to consider the bulk properties of randomly layout charcoal pieces, which was better adapted than single specimen tests in the fiber direction. A total of eight charcoal layers were prepared with two carbonization temperatures (500°C and 900 °C), two granularities (10 mm and 20 mm), and two different testing temperatures (20 °C and 300 °C). Characteristic parameters of the compression tests were then determined as the particle size distribution, the mechanical energy, and the mean power. The charcoal produced at 900°C and with a granularity of 20 mm was more resistant to breakage than the others were, and a high quantity of large particles remained after the tests. Significant correlations existed between the carbonization temperature, granularity, and mechanical power of the compression test. The mechanical power was the main parameter that determined the resistance to break age of a charcoal bed in compression.
- Published
- 2020
25. Towards a better understanding of the mechanical behavior of a fixed bed of eucalyptus charcoal in a blast furnace using a specific compression test
- Abstract
The properties of wood charcoal layers have an effect on the performance of small-scale blast furnaces. In order to characterize the mechanical behavior of a fixed bed of eucalyptus charcoal, a specific uniaxial compression test was designed and used with charcoal layers of different characteristics. This layer test has the potential to be standardized,and it made it possible to consider the bulk properties of randomly layout charcoal pieces, which was better adapted than single specimen tests in the fiber direction. A total of eight charcoal layers were prepared with two carbonization temperatures (500°C and 900 °C), two granularities (10 mm and 20 mm), and two different testing temperatures (20 °C and 300 °C). Characteristic parameters of the compression tests were then determined as the particle size distribution, the mechanical energy, and the mean power. The charcoal produced at 900°C and with a granularity of 20 mm was more resistant to breakage than the others were, and a high quantity of large particles remained after the tests. Significant correlations existed between the carbonization temperature, granularity, and mechanical power of the compression test. The mechanical power was the main parameter that determined the resistance to break age of a charcoal bed in compression.
- Published
- 2020
26. Experimental and Numerical Strategy for the Determination of Mechanical Properties Related to Human Cortical Bone Fracture
- Author
-
Yves Godio-Raboutet, Jean-Louis Tailhan, C. Boulay, Expérimentation et modélisation pour le génie civil et urbain (MAST-EMGCU), Université Gustave Eiffel, Laboratoire de Biomécanique Appliquée (LBA UMR T24), and Aix Marseille Université (AMU)-Université Gustave Eiffel
- Subjects
Computer science ,Three point flexural test ,Long bone ,0211 other engineering and technologies ,Human bone ,Context (language use) ,EXPERIMENT ,02 engineering and technology ,01 natural sciences ,PROPRIETE MECANIQUE ,Displacement (vector) ,Fe simulation ,NUMERICAL MODEL ,021105 building & construction ,0103 physical sciences ,medicine ,BONE CRACKING ,EXPERIMENTATION ,010306 general physics ,business.industry ,MODELE NUMERIQUE ,OS ,Structural engineering ,[SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph] ,COMPLIANCE METHOD ,FRACTURE OSSEUSE ,medicine.anatomical_structure ,Fracture (geology) ,Cortical bone ,business - Abstract
ICTAEM 2020, Proceedings of the Third International Conference on Theoretical, Applied and Experimental Mechanics , Athenes, GRECE, 14-/06/2020 - 17/06/2020; The paper presents an experimental test of macrocrack propagation in bones associated with a numerical strategy to determine from this test some mechanical properties by inverse identification. A 3 point bending test is performed on a notched segment of long human bone, and the load vs notch opening displacement is measured. The compliance method is applied in the context of a realistic FE simulation of the test. A first application of this methodology is described and shows its feasibility and capabilities. The ultimate objective of this research project is to develop a probabilistic modelling of the macrocracking processes in human long bone tissues based on an experimental database of mechanical parameters fed up by this methodology.
- Published
- 2020
27. Fabrication, microstructure, and properties of fired clay bricks using construction and demolition waste sludge as the main additive
- Author
-
Philippe Poullain, Glaydson Simões dos Reis, Alexis Cothenet, Jean-Michel Torrenti, Bogdan Cazacliu, Weslei Monteiro Ambrós, Michaela Wilhelm, Carlos Hoffmann Sampaio, Eder C. Lima, Universitat Politècnica de Catalunya. Departament d'Enginyeria Minera, Industrial i TIC, Universitat Politècnica de Catalunya. GREMS - Grup de Recerca en Mineria Sostenible, Granulats et Procédés d'Elaboration des Matériaux (MAST-GPEM ), Université Gustave Eiffel, Institut de Recherche en Génie Civil et Mécanique (GeM), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS), University of Bremen, Universitat Politècnica de Catalunya [Barcelona] (UPC), Universidade Federal do Rio Grande do Sul [Porto Alegre] (UFRGS), and Département Matériaux et Structures (MAST)
- Subjects
Reciclatge (Residus, etc.) ,Strategy and Management ,RECYCLING AND VALORIZATION ,Mechanical properties ,02 engineering and technology ,Maó refractari ,BRIQUE ,Industrial and Manufacturing Engineering ,Edificació::Impacte ambiental [Àrees temàtiques de la UPC] ,[SPI.MAT]Engineering Sciences [physics]/Materials ,11. Sustainability ,BOUE ,0202 electrical engineering, electronic engineering, information engineering ,Enginyeria dels materials::Assaig de materials [Àrees temàtiques de la UPC] ,Construction and demolition waste sludge ,Brickwork ,General Environmental Science ,Inert ,Enderrocament -- Residus ,TRAITEMENT DES DECHETS ,Concrete -- Recycling ,Waste management ,PROPRIETE THERMIQUE ,05 social sciences ,Microstructure ,Compressive strength ,Recycling and valorization ,ISOLATION ,Formigó -- Reciclatge ,Firebrick ,MECHANICAL PROPERTIES ,Fabrication ,CONSTRUCTION AND DEMOLITION WASTE SLUDGE ,020209 energy ,INSULATION PROPERTIES ,Raw material ,PROPRIETE MECANIQUE ,12. Responsible consumption ,RECYCLAGE DES MATERIAUX ,BRICKS PRODUCTION ,Construction and demolition debris ,0505 law ,PRODUCTION ,Brick ,Renewable Energy, Sustainability and the Environment ,Insulation properties ,Bricks production ,[SPI.GCIV]Engineering Sciences [physics]/Civil Engineering ,Demolition waste ,Recycling (Waste, etc.) ,050501 criminology ,Environmental science - Abstract
Green routes to prepare or manufacture sustainable building materials have been attracting much attention over the years targeting sustainability issues. In this investigation, for the first time, sludge from the inert mineral part of the construction and demolition waste (RA-S) is used as a primary raw material in the fabrication of fired bricks for building purposes. Fired bricks fabricated with different dosages of RA-S and earth material (i.e., 0%, 30%, 50%, 70%, and 100% by weight) were prepared and evaluated in terms of their physical-chemical properties. The RA-S was characterized, and the results showed that it could be classified as a clayey material and richly graded silty sand according to the French Standards. XRD analysis revealed that the addition of the RA sludge into raw earth material provoked changes slightly in the fired bricks. The compressive strength (CS) results indicated that the CS of the fired bricks increased with the addition of the RA-S from 30% to 70%. The highest CS was attained at the firing temperature of 800 °C. The density of the fired brick slightly reduced with the RA-S addition. The thermal conductivity results suggest that RA-S has better insulation properties compared to earth material. The RA-S sludge can be used in combination with earth material to fabricate fired bricks, which can meet the requirements of many Standards all over the World. In the light of these results, it is possible to say that the RA-S generated from recycling inert mineral part of construction and demolition waste plant is an excellent raw material to prepare efficient fired bricks that can be successfully employed in the real construction sector. Also, the highlighted results suggest that brickwork factories have the opportunity to improve production quality while significantly reducing manufacturing time, energy consumption, resource depletion, and environmental impact. The authors are also grateful to the Council for the Development of Higher Education at Graduate Level, Brazil (CAPES) for the postdoctoral scholarship granted through the National Postdoctoral Program (PNPD). The authors also thank Mr. Ferro, president of Esterel Terassement, for financial support and for providing the RA-S samples. Dr. Simoes dos Reis gives a special thanks to the cooperation opportunity between UFRGS and IFSTTAR through his Post-doctoral studies provided by PNPD. E.C. Lima thanks to Foundation for Research Support of the State of Rio Grande do Sul (FAPERGS), and National Council for Scientific and Technological Development (CNPq, Brazil) for financial support and sponsorship.
- Published
- 2020
28. Effet de l'incorporation des sédiments fluviaux sur les propriétés physico-chimiques, mécaniques et de durabilité des bétons
- Author
-
BEDDAA, Hamza
- Subjects
THESE ,BETON ,COQUILLAGE ,ROCHE SEDIMENTAIRE ,MICROMECANIQUE ,PATE DE CIMENT ,SEDIMENT ,PROPRIETE MECANIQUE - Abstract
Les sédiiments de dragage, considéréees aujourd'hui comme déchets, semblent être une alternative prometteuse aux matériaux conventionnels. Les opérations de dragage, réaliséees par la Direction Territoriale du Bassin de la Seine (DTBS), génèrent un volume annuel des sédiments d'environ 150 000 m3. Dans cette thèse, nous nous intéreresserons tout d'abord au potentiel de valorisation de ces sédiments en tant qu'alternative aux granulats ou au ciment (comme addition). Pour ce faire, une étude de variabilité du gisement francilien et de son effet sur les propriétés du béton est réalisée. La compilation des propriétés du gisement montre que 30 % du volume dragué pourrait être considéré comme une source stable et propre de granulats, alors que les sédiments non inertes ne représentent que 6 %. L'étude expérimentale montre que la substitution de 30 % en volume des granulats ou la substitution de 10 % en volume de ciment respectivement par des sédiments grossiers ou par des sédiments fins affecte que légèrement la cinétique d'hydratation, la résistance à la compression et le retrait. Ensuite, nous avons approfondi l'effet de la matière organique des sédiments sur les propriétés rhéologiques, physico-chimiques (hydratation et retrait) et mécaniques d'une pâte de ciment. Les résultats obtenus montrent que les substances humiques, matières organiques présentes dans les sédiments, ont un effet analogue à celui des lignosulfonates de calcium, un plastifiant, tant sur la cinétique d'hydratation que sur la rhéologie de la pâte cimentaire. La dernière partie de la thèse traite de l'effet de l'incorporation des coquillages sur les propriétés mécaniques et de durabilité du béton. Cette partie est scindée en deux volets ; un volet expérimental et un volet numérique. Le premier a comme objectif d'évaluer l'effet de l'incorporation des coquillages, comme graviers, sur les propriétés macroscopiques des bétons (propriétés mécaniques et propriétés de durabilité). Les résultats expérimentaux montrent qu'il n'y a aucun effet de l'incorporation des coquillages sur l'affaissement, le retrait et les propriétés de durabilité (la porosité, la diffusion des ions chlore et la carbonatation) du béton pour des substitutions inférieures à 20 %. En revanche, les propriétés mécaniques diminuent avec l'augmentation du taux de substitution ; pour une substitution volumique de 20 %, la résistance à la compression et le module élastique diminuent respectivement de 20 % et 17 %. Le volet numérique a pour objectif de construire un outil numérique cohérent permettant de prédire les propriétés mécaniques et de diffusion d'un béton en fonction de sa composition et des paramètres physiques et géométriques de la microstructure. Par des observations microscopiques (MEB) et en modélisant les coquillages comme des inclusions plongées dans une matrice cimentaire, nous montrons que l'adhérence entre le coquillage et la matrice est limitée, et doit être prise en compte pour estimer les propriétés des bétons à base de coquillages. Dredged sediments, considered as waste, seem to be a promising alternative to conventional materials. Dredging operations, carried out by the Territorial Directorate of the Seine Basin (DTBS), generate an annual volume of sediments of about 150,000 m3. In this thesis, we are first interested in the potential of valorization of these sediments as an alternative to aggregates or cement (as an addition). To this end, a study of the variability of the Ile-de-France deposit and its effect on the properties of concrete is carried out. The compilation of the deposit properties shows that 30 % of the dredged volume could be considered as a stable and clean source of aggregates, while non-inert sediments represent only 6 %. The experimental study shows that the substitution of 30 % by volume of aggregates or the substitution of 10 % by volume of cement respectively by coarse or fine sediments affects only slightly the hydration kinetics, the compressive strength and the shrinkage. Next, we investigated the eect of the organic matter of sediments on the rheological, physico-chemical (hydration and shrinkage) and mechanical properties of a cement paste. The results obtained show that humic substances, organic matter present in the sediments, have an effect similar to that of calcium lignosulfonates, a plasticizer, both on the hydration kinetics and on the rheology of the cement paste. The last part of the thesis deals with the effect of the incorporation of shells on the mechanical and durability properties of concrete. This part is divided into two parts ; an experimental part and a numerical part. The first one aims at evaluating the effect of the incorporation of shells, as gravels, on the macroscopic properties of concretes (mechanical properties and durability properties). The experimental results show that there is no eect of the incorporation of shells on the slump, shrinkage and durability properties (porosity, diffusion of chloride and carbonation) of concrete for substitutions lower than 20 %. On the other hand, the mechanical properties decrease with the increase in the substitution rate ; for a volume substitution of 20 %, the compressive strength and elastic modulus decrease respectively by 20 % and 17 %. The numerical part aims at building a coherent numerical tool to predict the mechanical and diusion properties of a concrete according to its composition and the physical and geometrical parameters of the microstructure. By microscopic observations (SEM) and by modeling shells as inclusions embedded in a cementitious matrix, we show that the adhesion between the shell and the matrix is weak and must be taken into account to estimate the properties of shell-based concretes.
- Published
- 2020
29. Towards a better understanding of the mechanical behavior of a fixed bed of eucalyptus charcoal in a blast furnace using a specific compression test
- Author
-
Paulo Fernando Trugilho, Alfredo Napoli, Daniel Guibal, Loïc Brancheriau, and Maíra Reis de Assis
- Subjects
K50 - Technologie des produits forestiers ,Blast furnace ,Environmental Engineering ,Materials science ,Bioengineering ,Four à carboniser ,Breakage ,Fiber ,Composite material ,Charbon de bois ,Charcoal ,Waste Management and Disposal ,Q60 - Traitement des produits agricoles non alimentaires ,Eucalyptus ,Carbonization ,Compression (physics) ,Carbonisation du bois ,visual_art ,Propriété mécanique ,Particle-size distribution ,visual_art.visual_art_medium ,Granularity ,Propriété du bois - Abstract
The properties of wood charcoal layers have an effect on the performance of small-scale blast furnaces. In order to characterize the mechanical behavior of a fixed bed of eucalyptus charcoal, a specific uniaxial compression test was designed and used with charcoal layers of different characteristics. This layer test has the potential to be standardized, and it made it possible to consider the bulk properties of randomly layout charcoal pieces, which was better adapted than single specimen tests in the fiber direction. A total of eight charcoal layers were prepared with two carbonization temperatures (500 °C and 900 °C), two granularities (10 mm and 20 mm), and two different testing temperatures (20 °C and 300 °C). Characteristic parameters of the compression tests were then determined as the particle size distribution, the mechanical energy, and the mean power. The charcoal produced at 900 °C and with a granularity of 20 mm was more resistant to breakage than the others were, and a high quantity of large particles remained after the tests. Significant correlations existed between the carbonization temperature, granularity, and mechanical power of the compression test. The mechanical power was the main parameter that determined the resistance to breakage of a charcoal bed in compression.
- Published
- 2020
30. Caractérisation mécanique et modèles de comportement de fibres cellulosiques
- Author
-
Mahjoub, Wafa
- Subjects
Modélisation ,Textile ,Propriété mécanique ,fibre ,Fibre végétale ,Coton ,Q60 - Traitement des produits agricoles non alimentaires - Abstract
La structure de la fibre de coton est une des clés pour expliquer le comportement mécanique des fibres lors de leurs transformations en textiles linéaires et en surface textiles. L'objectif de cette thèse est de modéliser les comportements mécaniques des fibres individuelles, des faisceaux de fibres et des fils de coton par une approche de type analogique. Ceci en connaissant leurs caractéristiques physiques et mécaniques. Quatre variétés de coton ont été étudiées. Une classification par longueurs des fibres a été effectuée. Les résultats de la modélisation analogique ont révélé que le comportement suite aux essais de fluage des fibres individuelles et des faisceaux de fibres suit le modèle de Zener. Tandis que celui des fils suit le modèle de Burgers. Sur les trois échelles, les résultats ont montré un effet de la longueur des fibres sur les propriétés mécaniques et les modèles analogiques. L'effet variété de coton a été observé sur certains paramètres des modèles analogiques. L'importance de la prise en compte du frottement inter-fibre et de la torsion dans les fils est aussi relevée.
- Published
- 2020
31. Anatomical and physico-mechanical properties of Acacia auriculiformis wood in relation to age and soil in Benin, West Africa
- Author
-
Basile Kounouhewa, Patrick Langbour, Samadori Sorotori Honoré Biaou, Clément Kouchade, Eméline Sêssi Pélagie Assédé, Daniel Guibal, and Jesugnon Fifamè Murielle Féty Tonouéwa
- Subjects
Vertisol ,F50 - Anatomie et morphologie des plantes ,General Materials Science ,Water content ,Shrinkage ,Acacia auriculiformis ,biology ,Forestry ,Soil classification ,biology.organism_classification ,Soil type ,Plantation forestière ,Facteur édaphique ,K10 - Production forestière ,Agronomy ,Anatomie végétale ,visual_art ,Propriété mécanique ,visual_art.visual_art_medium ,Environmental science ,Bark ,Pith ,Propriété du bois - Abstract
Acacia auriculiformis is increasingly used as timber in Benin, while little is known about its wood characteristics and the factors affecting such characteristics in the country. The determination of these characteristics is necessary for understanding the functioning of this species and its uses. The aim of this study was to evaluate anatomical and physico-mechanical properties of Acacia auriculiformis in relation to age and soil type in Benin, West Africa. Nine different age plantations (young 6–7 years old, middle-aged 9–11 years old, aged 15–29 years old) were sampled on three soil types (ferruginous, sandy and vertisol). In total, 30 trees were felled for determination of vessel diameter and vessel frequency from pith to bark, basic density, density at 12% moisture content, tangential and radial shrinkages, fiber saturation point, anisotropy of shrinkage, modulus of elasticity, compression strength, and bending strength. Age is the main factor influencing the physico-mechanical characteristics of the species and Acacia auriculiformis could be exploited at 15 years old for use as timber. Still, a high deformation ratio is noted on ferruginous soil. Besides, wood density is negatively correlated with anisotropy of shrinkage, which is an asset for the use of high density wood for structures. In contrast, the parameters of the vessels are weakly correlated with wood density. Further studies are necessary to understand the densification process of Acacia auriculiformis wood in order to optimize the production of high-density wood of the species, which is important for the use of wood as timber.
- Published
- 2020
32. Effect of heat treatment on the properties of sugarcane bagasse medium density particleboard (MDP) panels
- Author
-
Alan Pereira Vilela, Rafael Farinassi Mendes, Danillo Wisky Silva, Débora Pereira Ribeiro, and Alfredo Napoli
- Subjects
0106 biological sciences ,K50 - Technologie des produits forestiers ,Environmental Engineering ,Absorption of water ,Materials science ,Panneau composite ,020209 energy ,Young's modulus ,02 engineering and technology ,Raw material ,01 natural sciences ,Déchet agricole ,Bagasse ,symbols.namesake ,Flexural strength ,010608 biotechnology ,0202 electrical engineering, electronic engineering, information engineering ,medicine ,Composite material ,Waste Management and Disposal ,Traitement thermique ,Moisture ,Renewable Energy, Sustainability and the Environment ,Élasticité ,Q70 - Traitement des déchets agricoles ,Utilisation des déchets ,Propriété mécanique ,symbols ,Canne à sucre ,Adhesive ,Swelling ,medicine.symptom ,Panneau de particules - Abstract
Sugarcane bagasse can be used in the manufacture of panels for the furniture industry, but has a high water absorption compared to wood panels. Thus, this raw material needs heat treatment to reduce the hygroscopicity of the panels. The aim of this study was to evaluate the effect of different levels of heat treatment temperature on the particleboard properties made from sugarcane bagasse. The experiment consisted of four treatments, being evaluated three temperatures heat treatment of sugarcane bagasse (170, 200 and 230 °C) and without thermal modification treatment (Control). The particles were evaluated for their anatomical, chemical and physical characteristics. The panels were produced with nominal density of 0.70 g/cm3, relation face/core of 40:60, 11% urea–formaldehyde adhesive to the faces and 7% of adhesive to the core, pressing cycle of 160 °C temperature, pressure 3.94 MPa and for a period of 8 min. The panels were evaluated for its physical properties density, compression ratio, moisture, water absorption and thickness swelling after 2 and 24 h of immersion; their mechanical properties internal bond and modulus of rupture and modulus of elasticity at bending. The heat treatment of the bagasse particles at 230 °C promoted significant improvements in the quality of particleboard, resulting in decreased of the water absorption and thickness swelling values of the panels and increase in modulus of elasticity values, and allowing meet marketing standards regarding the thickness swelling after 24 h of immersion in water. Which demonstrates the great potential of using the heat treatment temperature of 230 °C for the production of particleboard with sugarcane bagasse.
- Published
- 2020
33. Chemical composition of processed bamboo for structural applications
- Author
-
Oren A. Scherman, Emma Rose Janeček, Bhavna Sharma, Johnny Beaugrand, Darshil U. Shah, Michael H. Ramage, University of Bath [Bath], University of Cambridge, Unité de recherche sur les Biopolymères, Interactions Assemblages (BIA), Institut National de la Recherche Agronomique (INRA), Fractionnement des AgroRessources et Environnement - UMR-A 614 (FARE), Université de Reims Champagne-Ardenne (URCA)-Institut National de la Recherche Agronomique (INRA)-SFR Condorcet, Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS), Fractionnement des AgroRessources et Environnement (FARE), Université de Reims Champagne-Ardenne (URCA)-Institut National de la Recherche Agronomique (INRA), Sharma, Bhavna [0000-0003-0516-6125], Apollo - University of Cambridge Repository, Université de Reims Champagne-Ardenne (URCA)-SFR Condorcet, Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), University of Bath, Unité de recherche sur les Biopolymères, Interactions Assemblages ( BIA ), Institut National de la Recherche Agronomique ( INRA ), Fractionnement des AgroRessources et Environnement - UMR-A 614 ( FARE ), Université de Reims Champagne-Ardenne ( URCA ) -Institut National de la Recherche Agronomique ( INRA ) -SFR Condorcet, and Université de Reims Champagne-Ardenne ( URCA ) -Université de Picardie Jules Verne ( UPJV ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Reims Champagne-Ardenne ( URCA ) -Université de Picardie Jules Verne ( UPJV ) -Centre National de la Recherche Scientifique ( CNRS )
- Subjects
0106 biological sciences ,Bamboo ,Materials science ,Polymers and Plastics ,composition chimique ,chemical treatment ,[ SPI.MAT ] Engineering Sciences [physics]/Materials ,Chemical composition ,lignin ,02 engineering and technology ,traitement hygrothermique ,01 natural sciences ,[SPI.MAT]Engineering Sciences [physics]/Materials ,010608 biotechnology ,propriété mécanique ,hygrothermal treatment ,Process engineering ,Original Paper ,Treatment methods ,Natural materials ,mechanical characteristic ,Chemical treatment ,business.industry ,Treatment method ,blanchiment ,lignine ,021001 nanoscience & nanotechnology ,Caramelisation ,bambusa ,Processing methods ,chemical analysis ,Laminated bamboo ,Bleaching ,Degradation (geology) ,0210 nano-technology ,business ,traitement chimique - Abstract
Natural materials are a focus for development of low carbon products for a variety of applications. To utilise these materials, processing is required to meet acceptable industry standards. Laminated bamboo is a commercial product that is currently being explored for structural applications, however there is a gap in knowledge about the effects of commercial processing on the chemical composition. The present study utilised interdisciplinary methods of analysis to investigate the effects of processing on the composition of bamboo. Two common commercial processing methods were investigated: bleaching (chemical treatment) and caramelisation (hygrothermal treatment). The study indicated that the bleaching process results in a more pronounced degradation of the lignin in comparison to the caramelised bamboo. This augments previous research, which has shown that the processing method (strip size) and treatment may affect the mechanical properties of the material in the form of overall strength, failure modes and crack propagation. The study provides additional understanding of the effects of processing on the properties of bamboo.
- Published
- 2018
34. Influence of human cancer cell lines on mechanical properties of mice tibia
- Author
-
Lamia Bouazza, Marie Brevet, Jean-Baptiste Pialat, David Mitton, Hélène Follet, Marc Gardegaront, Benjamin Delpuech, Cyrille B. Confavreux, Philippe Clézardin, G. Plet, Physiopathologie, diagnostic et traitements des maladies osseuses / Pathophysiology, Diagnosis & Treatments of Bone Diseases (LYOS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Service d'Anatomo-Pathologie [Hôpital de la Croix-Rousse - HCL], Hôpital de la Croix-Rousse [CHU - HCL], Hospices Civils de Lyon (HCL)-Hospices Civils de Lyon (HCL), Service de Radiologie [Hôpital de la Croix-Rousse - HCL], Laboratoire de Biomécanique et Mécanique des Chocs (LBMC UMR T9406 ), Université de Lyon-Université de Lyon-Université Gustave Eiffel, LabEx PRIMES, Physique, Radiobiologie, Imagerie Médicale et Simulation, MSDAVENIR Research Grant, and Cadic, Ifsttar
- Subjects
0206 medical engineering ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,MOUSE ,PROPRIETE MECANIQUE ,Metastasis ,03 medical and health sciences ,0302 clinical medicine ,Medicine ,Tibia ,[PHYS.MECA.BIOM]Physics [physics]/Mechanics [physics]/Biomechanics [physics.med-ph] ,business.industry ,[PHYS.MECA.BIOM] Physics [physics]/Mechanics [physics]/Biomechanics [physics.med-ph] ,OS ,Cancer ,CANCER CELL LINE ,030229 sport sciences ,General Medicine ,medicine.disease ,020601 biomedical engineering ,3. Good health ,Computer Science Applications ,Human-Computer Interaction ,Cell culture ,METASTASIS ,Cancer research ,Cancer cell lines ,business ,Human cancer - Abstract
45e Congrès de la Société de Biomécanique, Metz, France, 26-/10/2020 - 28/10/2020; Bones are the third most affected organs by metastasis (Du et al. 2010). The qualitative effect of cancer types on metastatic bone has been largely described. Bone metastases weaken bones (Coleman 1997) by creating lytic, blastic or mixt (i.e. lytic and blastic) lesions. The prediction of fracture risk is clinically assessed by evaluating several parameters such as the size and location of the lesion or the Mirels' score. However, it seems these predictions overestimate the risk of fracture and are not specific enough to produce a reliable prediction (Van Der Linden et al. 2004). A quantification of the effect of the different cancer types on mechanical properties of the bone should improve clinical evaluation of the fracture risk. As a first step, the goal of our study was to develop a better assessment of the bone fracture risk by evaluating the mechanical properties of mice tibia affected by three different human cancer cell lines.
- Published
- 2020
35. Evaluation of Furfural/Urea complexes to improve physico-mechanical properties of birch wood
- Abstract
Background and objectives: Impregnation of wood with different monomers and their conversion to the un-leachable reacted polymers inside the wood causes a new product which is called wood polymer. The furan compounds such as Furfuryl alcohol (FA) is commercially used for wood modification, producing then wood polymer. Wood is impregnated with FA, convert to the polyFA by heating. Furfural which is in fact the primary raw material in the manufacture of FA is extensively manufactured in Iran from residues of sugar cane. Furfural could not be easily polymerized alone like FA; but it is an aldehyde which can react with urea to make polymer network. In this study, the possibility of furfural/urea polymer along with acidic catalyzer (maleic anhydride) was evaluated for the improvement of physico-mechanical properties of birch wood. Materials and methods: Birch wood (Betula sp.) imported from Russia was used for experiments. With a double treatment procedure Furfural+Urea/Maleic anhydride was impregnated into the wood according to a 2 steps vacuum/pressure technology: (1) diluted furfural in water and methanol, followed by (2) Urea/Maleic anhydride aqueous solution. For making comparison between the results, a commercial formulation based on the FA was also used as a reference. The mixes impregnated into the wood were polymerized by heating. Then, different physico-mechanical properties of wood samples were measured according to the standard guidelines of ISO 13061 series. Results: The proportion of Furfural+Urea/Maleic anhydride was appropriately selected, and approximately 60 to 80% were converted to the polymer. The leaching rate of the products once polymerized within the treated wood was around 4% which is comparable to the results of commercial formulation based on FA. The weight percentage gain (WPG) of the wood samples varied between 27 to 57% depending on the furfural concentration in the treatment solutions. Despite the bulking effect, the density of samples afte
- Published
- 2019
36. Interactions between the mechanical and hydraulic properties of eucalyptus trees under different environmental conditions of fertilization and water availability
- Abstract
Water and potassium are limiting factors for tree growth. Their influence on morphology and anatomy are well known, but their combined effects on tree growth remain to be clarified. A single clone of Eucalyptus grandis was analyzed under different treatments of rainfall exclusion and fertilization. Eight trees per treatment were sampled to investigate the influence of these treatments on the morphological, mechanical, and anatomical traits. The results showed that the fertilization mainly influenced the morphological and anatomical characteristics. Considering the difference between the fertilized and non-fertilized trees, the function of mechanical support was provided through increasing the diameter and the stiffness. Considering the fertilized trees, two different mechanisms occurred inducing a high stiffness: the wood density was higher for trees with rainfall exclusion; the specific modulus was higher for trees with a normal water supply.
- Published
- 2019
37. An architectural understanding of natural sway frequencies in trees
- Abstract
The relationship between form and function in trees is the subject of a longstanding debate in forest ecology and provides the basis for theories concerning forest ecosystem structure and metabolism. Trees interact with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to tree architecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in trees by compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed tree dynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 trees using a finite-element approach based on accurate three-dimensional model trees derived from terrestrial laser scanning data. We show that (1) residual variation, the variation not explained by the cantilever beam approximation, in fundamental frequencies of broadleaf trees is driven by their architecture; (2) slender trees behave like a simple pendulum, with a single natural frequency dominating their motion, which makes them vulnerable to wind damage and (3) the presence of leaves decreases both the fundamental frequency and the damping ratio. These findings demonstrate the value of new three-dimensional measurements for understanding wind impacts on trees and suggest new directions for improving our understanding of tree dynamics from conifer plantations to natural forests.
- Published
- 2019
38. Collapse and physical properties of native and pre-steamed Eucalyptus Camaldulensis Eucalyptus Saligna wood from Tunisa
- Abstract
Eucalyptus is the second major wood species used for Tunisian reforestation since 1957, and they are found around the country in several arboretums. Eucalyptus may be an interesting raw material to the Tunisian wood industry. The main obstacle to its industrial exploitation is its natural propensity to incur internal checking, collapse and a high transverse shrinkage during industrial drying process. This study focused on the physical and mechanical properties of reforested Eucalytus saligna and Eucalyptus camaldulensis from the north west of Tunisia. Moisture content, densities, shrinkages and mechanical properties were determined. Then, the impact of pre-steaming on the physical properties of modified wood was investigated. The results showed that both Eucalyptus possess low dimensional stability and mechanical properties compared to other Eucalyptusspecies from Tunisia, Morocco, Australia and Brazil. These wood characteristics were mainly due to their low density and sensitivity to collapse reactions, occurred during drying. Pre-steaming process reduced Eucalyptswood moisture content, changing the wood permeability and resulting in a residual collapse recovery and a decrease in wood shrinkage. Pre-steaming treated E. camaldulensis and E. saligna wood could be valuable as furniture and/or structural material without being submitted to moisture content variation.
- Published
- 2019
39. Finite element analysis of trees in the wind based on terrestrial laser scanning data
- Abstract
Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees. For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.
- Published
- 2019
40. Influence of pyrolysis conditions and the nature of the wood on the quality of charcoal as a reducing agent
- Abstract
The production of charcoal for metallurgical applications requires careful selection of the wood and control of the pyrolysis conditions to ensure acceptable charcoal quality. The main properties of charcoal to be considered are density, mechanical strength, and reactivity. In this study, charcoal was produced from two types of wood commonly used in the industry, Eucalyptus globulus (eucalyptus) and Picea abies (spruce), in a pilot scale pyrolysis fixed bed reactor at three temperatures (500, 650 and 800 °C) and two solid residence times (0 and 90 min). The yields, composition, apparent density, true density, porosity, carbon structural ordering, friability, compressive strength and CO2 reactivity of the resulting charcoals were analyzed. A new method to test compressive strength was applied to a charcoal bed. Our results show that the nature of the wood has a much greater impact on these values than the pyrolysis operating conditions. Wood apparent density is not a good indicator of the mechanical behavior of charcoal. Despite its higher density, eucalyptus charcoal showed lower mechanical stability than spruce charcoal independently of the pyrolysis conditions. When the final pyrolysis temperature was increased, the mechanical strength, porosity of the charcoal increased and CO2 reactivity decreased. The impact of solid residence time during pyrolysis on the charcoal properties was negligible except for CO2 reactivity, which decreased with an increase in residence time.
- Published
- 2019
41. Mechanical contribution of secondary phloem to postural control in trees: The bark side of the force
- Abstract
To grow straight, plants need a motor system that controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up‐righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.
- Published
- 2019
42. Influence of pyrolysis conditions and the nature of the wood on the quality of charcoal as a reducing agent
- Abstract
The production of charcoal for metallurgical applications requires careful selection of the wood and control of the pyrolysis conditions to ensure acceptable charcoal quality. The main properties of charcoal to be considered are density, mechanical strength, and reactivity. In this study, charcoal was produced from two types of wood commonly used in the industry, Eucalyptus globulus (eucalyptus) and Picea abies (spruce), in a pilot scale pyrolysis fixed bed reactor at three temperatures (500, 650 and 800 °C) and two solid residence times (0 and 90 min). The yields, composition, apparent density, true density, porosity, carbon structural ordering, friability, compressive strength and CO2 reactivity of the resulting charcoals were analyzed. A new method to test compressive strength was applied to a charcoal bed. Our results show that the nature of the wood has a much greater impact on these values than the pyrolysis operating conditions. Wood apparent density is not a good indicator of the mechanical behavior of charcoal. Despite its higher density, eucalyptus charcoal showed lower mechanical stability than spruce charcoal independently of the pyrolysis conditions. When the final pyrolysis temperature was increased, the mechanical strength, porosity of the charcoal increased and CO2 reactivity decreased. The impact of solid residence time during pyrolysis on the charcoal properties was negligible except for CO2 reactivity, which decreased with an increase in residence time.
- Published
- 2019
43. Evaluation of Furfural/Urea complexes to improve physico-mechanical properties of birch wood
- Abstract
Background and objectives: Impregnation of wood with different monomers and their conversion to the un-leachable reacted polymers inside the wood causes a new product which is called wood polymer. The furan compounds such as Furfuryl alcohol (FA) is commercially used for wood modification, producing then wood polymer. Wood is impregnated with FA, convert to the polyFA by heating. Furfural which is in fact the primary raw material in the manufacture of FA is extensively manufactured in Iran from residues of sugar cane. Furfural could not be easily polymerized alone like FA; but it is an aldehyde which can react with urea to make polymer network. In this study, the possibility of furfural/urea polymer along with acidic catalyzer (maleic anhydride) was evaluated for the improvement of physico-mechanical properties of birch wood. Materials and methods: Birch wood (Betula sp.) imported from Russia was used for experiments. With a double treatment procedure Furfural+Urea/Maleic anhydride was impregnated into the wood according to a 2 steps vacuum/pressure technology: (1) diluted furfural in water and methanol, followed by (2) Urea/Maleic anhydride aqueous solution. For making comparison between the results, a commercial formulation based on the FA was also used as a reference. The mixes impregnated into the wood were polymerized by heating. Then, different physico-mechanical properties of wood samples were measured according to the standard guidelines of ISO 13061 series. Results: The proportion of Furfural+Urea/Maleic anhydride was appropriately selected, and approximately 60 to 80% were converted to the polymer. The leaching rate of the products once polymerized within the treated wood was around 4% which is comparable to the results of commercial formulation based on FA. The weight percentage gain (WPG) of the wood samples varied between 27 to 57% depending on the furfural concentration in the treatment solutions. Despite the bulking effect, the density of samples afte
- Published
- 2019
44. Mechanical contribution of secondary phloem to postural control in trees: The bark side of the force
- Abstract
To grow straight, plants need a motor system that controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up‐righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.
- Published
- 2019
45. Interactions between the mechanical and hydraulic properties of eucalyptus trees under different environmental conditions of fertilization and water availability
- Abstract
Water and potassium are limiting factors for tree growth. Their influence on morphology and anatomy are well known, but their combined effects on tree growth remain to be clarified. A single clone of Eucalyptus grandis was analyzed under different treatments of rainfall exclusion and fertilization. Eight trees per treatment were sampled to investigate the influence of these treatments on the morphological, mechanical, and anatomical traits. The results showed that the fertilization mainly influenced the morphological and anatomical characteristics. Considering the difference between the fertilized and non-fertilized trees, the function of mechanical support was provided through increasing the diameter and the stiffness. Considering the fertilized trees, two different mechanisms occurred inducing a high stiffness: the wood density was higher for trees with rainfall exclusion; the specific modulus was higher for trees with a normal water supply.
- Published
- 2019
46. An architectural understanding of natural sway frequencies in trees
- Abstract
The relationship between form and function in trees is the subject of a longstanding debate in forest ecology and provides the basis for theories concerning forest ecosystem structure and metabolism. Trees interact with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to tree architecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in trees by compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed tree dynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 trees using a finite-element approach based on accurate three-dimensional model trees derived from terrestrial laser scanning data. We show that (1) residual variation, the variation not explained by the cantilever beam approximation, in fundamental frequencies of broadleaf trees is driven by their architecture; (2) slender trees behave like a simple pendulum, with a single natural frequency dominating their motion, which makes them vulnerable to wind damage and (3) the presence of leaves decreases both the fundamental frequency and the damping ratio. These findings demonstrate the value of new three-dimensional measurements for understanding wind impacts on trees and suggest new directions for improving our understanding of tree dynamics from conifer plantations to natural forests.
- Published
- 2019
47. Collapse and physical properties of native and pre-steamed Eucalyptus Camaldulensis Eucalyptus Saligna wood from Tunisa
- Abstract
Eucalyptus is the second major wood species used for Tunisian reforestation since 1957, and they are found around the country in several arboretums. Eucalyptus may be an interesting raw material to the Tunisian wood industry. The main obstacle to its industrial exploitation is its natural propensity to incur internal checking, collapse and a high transverse shrinkage during industrial drying process. This study focused on the physical and mechanical properties of reforested Eucalytus saligna and Eucalyptus camaldulensis from the north west of Tunisia. Moisture content, densities, shrinkages and mechanical properties were determined. Then, the impact of pre-steaming on the physical properties of modified wood was investigated. The results showed that both Eucalyptus possess low dimensional stability and mechanical properties compared to other Eucalyptusspecies from Tunisia, Morocco, Australia and Brazil. These wood characteristics were mainly due to their low density and sensitivity to collapse reactions, occurred during drying. Pre-steaming process reduced Eucalyptswood moisture content, changing the wood permeability and resulting in a residual collapse recovery and a decrease in wood shrinkage. Pre-steaming treated E. camaldulensis and E. saligna wood could be valuable as furniture and/or structural material without being submitted to moisture content variation.
- Published
- 2019
48. Finite element analysis of trees in the wind based on terrestrial laser scanning data
- Abstract
Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees. For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.
- Published
- 2019
49. Dynamic analysis of an electrostatic compressor
- Author
-
Sathe, Abhijit A., Groll, Eckhard A., and Garimella, Suresh V.
- Subjects
- *
TRANSIENTS (Dynamics) , *ELECTROSTATICS , *COMPRESSORS , *DIAPHRAGMS (Mechanical devices) , *COOLING systems , *ELECTRONICS , *MATHEMATICAL models , *ELECTRIC potential - Abstract
Abstract: This paper presents an analytical approach for modeling the transient dynamic forces in a diaphragm compressor which operates under the action of an electrostatically actuated diaphragm. An experimentally validated, quasi-static model for a diaphragm compressor for electronics cooling was previously developed in which dynamic effects were neglected. In the new model, the dynamic forces induced due to the finite time necessary for deflection of the diaphragm are taken into consideration using the segmentation approach developed earlier. Results from the analytical model compare favorably with those from a detailed numerical simulation as well as with experimental measurements available in the literature. The analytical dynamic model is applied to two different pumping devices to illustrate the effects of the dynamic forces on the overall performance of the device. The effect of pumping frequency of the device on the operating voltage is also explored. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
50. Study of scraping force of ice growing on cooling solid surface
- Author
-
Matsumoto, Koji, Akimoto, Takahiro, and Teraoka, Yoshikazu
- Subjects
- *
HEAT storage devices , *SUPERCOOLING , *CARBON steel , *ADSORPTION (Chemistry) , *SURFACE roughness , *TEMPERATURE measurements - Abstract
Abstract: In a dynamic ice storage system, one of typical methods to form ice slurry is a “Harvest method” where ice growing on the cooling surface is scraped by a rotary knife. This method has an advantage that ice adhesion to a cooling wall, which is a serious problem in a conventional method, is not necessary to be considered. In this study, ice was formed on a carbon steel surface by cooling an ethylene-glycol solution with stirring, and ice growing on the cooling surface was scraped. At that time, scraping force was measured, varying supercooling degrees of the solution, ice formation times, concentrations of the solution and surface temperatures and surface roughness of the carbon steel. And, influences of the above parameters on scraping force were clarified, and behaviors of ice scraped from the carbon steel surface were classified. Moreover, ice growing on the surface was continuously scraped repeatedly. At that time, influence of the number of scrapings on scraping force was clarified. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
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