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In the present study, thermoelastic behavior of a semi-infinite rod, which is subjected to a time exponentially decaying laser pulse, is formulated. The rod is free at the left end and the laser pulse moves along the axial direction from the left end. The non-Fourier effect of the heat conduction equation is considered and the Laplace transformation method is employed in solving the governing equations. The temperature, displacement, strain, and stress in the rod are derived and the distributions of the parameters at different positions are analyzed. Also the influence of the laser speed is investigated. Key words: movable heat source, laser pulse, thermoelastic response, semi-infinite rod, non-Fourier effect. Nous presentons ici une formulation pour etudier le comportement thermo-elastique d'une tige semi-infinie soumise a une impulsion laser a decroissance exponentielle dans le temps. L'extremite gauche de la tige est fixee et l'impulsion se deplace axialement de la gauche vers la droite. Nous considerons l'equation de conduction non Fourier de la chaleur et nous utilisons la transformation de Laplace pour resoudre les equations directrices. Nous obtenons la temperature, le deplacement, l'effort et la deformation dans la tige et nous analysons la distribution des parametres a differentes positions. Nous regardons aussi l'influence de la vitesse du laser. [Traduit par la Redaction] Mots-cles : source de chaleur deplacable, impulsion laser, reponse thermoplastique, tige semi-infinie, effet non Fourier., 1. Introduction Boeing Company has developed a kind of high-energy laser weapon, which have successfully destroyed more than 150 target drones in three series of tests. This technology can be [...]

The resilient modulus of unbound materials is an important parameter in the mechanistic design of pavements. Although unbound layers are frequently in a partially saturated state, a total stress approach is conventionally used in modeling the material behaviour, and therefore pore pressure effects are not considered. In fine-grained unbound materials, the saturation state can affect their mechanical behaviour due to pore pressure effects. In this study a modified test procedure and a predictive resilient modulus model that takes into account the subgrade soil matric suction as a stress state variable is presented. Two different silty sand subgrade materials were tested in unsaturated conditions using a series of repeated load triaxial tests under controlled pore suction conditions to study its influence on the resilient modulus. The test data were further used to obtain the resilient modulus model regression parameters that account for moisture content variations through the matric suction parameter. Generally, the prediction model could effectively capture the resilient modulus behaviour of the subgrades with respect to changes in the normal stress state and the matric suction. Given the completeness of this method, this prediction model is recommended as an improved approach in capturing the moisture content effects on the material stiffness properties. Key words: subgrade, resilient modulus, unsaturated soil, matric suction, environmental effects, moisture content. Le module de resilience de materiaux non relies est un parametre important dans la conception mecanistique des chaussees. Meme si les couches non reliees sont frequemment dans un etat partiellement sature, une approche de contrainte totale est generalement utilisee pour la modelisation du comportement des materiaux, donc les effets des pressions interstitielles ne sont pas consideres. Pour des materiaux non relies a granulometrie fine, l'etat de saturation peut affecter leur comportement mecanique en raison des effets des pressions interstitielles. Dans cette etude, une procedure d'essai modifiee et un modele predictif du module de resilience qui considere la succion du sol sous la chaussee comme une variable de l'etat de contrainte sont presentes. Deux sables silteux utilises comme sol sous la chaussee ont ete testes dans des conditions non saturees a l'aide d'une serie d'essais triaxiaux repetes realises en conditions de succion dans les pores controlee afin d'etudier son influence sur le module de resilience. Des donnees d'essais ont ete aussi utilisees pour obtenir les parametres de regression du modele du module de resilience qui considere les variations de teneur en eau a travers le parametre de succion. De facon generale, le modele de prediction pouvait representer efficacement le comportement du module de resilience des sols sous la chaussee relativement aux changements dans l'etat de contrainte normale et de succion. Ce modele de prediction est recommande en tant qu'approche amelioree pour representer les effets de la teneur en eau sur les proprietes de rigidite des materiaux, puisque cette methode est complete. [Traduit par la Redaction] Mots-cles: sol sous la chaussee, module de resilience, sol non sature, succion, effets environnementaux, teneur en eau., Introduction A large part of the operating road network around the world consists of flexible pavement structures with a relatively thin bituminous surface layer (≤100 mm). In thin flexible pavement [...]

First-principles calculations have been performed to investigate the structural stability, elastic, lattice dynamic, and thermodynamic properties of [Na.sub.2]Se under high pressure. Our results demonstrate that [Na.sub.2]Se in the antifluorite structure phase keeps dynamically stable until 30 GPa. The elastic constants and thermodynamic quantities under high pressure are also calculated and discussed. PACS Nos.: 62.20.D-, 67.80.de, 05.70.-a. Nous presentons des calculs ab initio pour analyser la stabilite structurale, la dynamique de reseau et les proprietes thermodynamiques du compose [Na.sub.2]Se sous haute pression. Nos resultats montrent que le [Na.sub.2]Se, dans la structure de phase anti-fluorine, demeure dynamiquement stable jusqu'a 30 GPa. Nous calculons et analysons les constantes elastiques et thermodynamiques sous haute pression. [Traduit par la Redaction], 1. Introduction Sodium chalcogenide compounds [Na.sub.2]S, [Na.sub.2]Se, and [Na.sub.2]Te, also crystallize in the cubic antifluorite structure (anti-CaF2 type; No 225) at ambient conditions. They have attracted increasing research interest as [...]

A two-dimensional problem in a transversely isotropic thermoelastic medium without energy dissipation and with two temperatures due to a thermal source is investigated. As an application of the problem, a particular type of continuous thermal source has been taken to illustrate the utility of the approach. The problem is solved numerically by using a finite element method. The displacement components, conductive temperature, and stress components have been obtained numerically and illustrated graphically for our particular model. Some special cases of interest are also discussed. The implementation of finite element method codes used C++. Numerical work is also performed for a suitable material with the aim of illustrating the results. PACS Nos.: 47.11.Fg, 46.25.Hf. Nous considerons un probleme bidimensionnel dans un milieu thermo-elastique transversalement isotrope, sans dissipation d'energie et avec deux temperatures a cause de la source thermique. Comme application, nous prenons un type particulier de source thermique continue, afin d'illustrer l'utilite de notre methode. Pour ce modele particulier, nous evaluons numeriquement et illustrons graphiquement les composantes du deplacement, la temperature de conduction et les composantes d'effort. Nous poussons l'etude de quelques cas d'interet. La methode numerique par elements finis est en C++. Les calculs sont faits pour un materiau en particulier, afin d'illustrer notre approche. [Traduit par la Redaction], 1. Introduction The classical theory of thermoelasticity as exposed, for example, in Carlson's article [1] has found generalizations and modifications into various thermoelastic models that run under the label hyperbolic [...]

The present investigation is aimed at studying the effect of rotation on the thermomicrostretch elastic solid. The formulation is applied in the context of the generalized thermoelasticity Lord-Shulman theory with one relaxation time and Green-Lindsay's theory with two relaxation times, as well as the classical dynamical coupled theory. The problem has been solved numerically using a finite element method. Numerical results for the temperature distribution, the displacement components, the force stresses, the couple stresses, and the microstress distribution are represented graphically. The results indicate that the effects of rotation are very pronounced. Comparisons are made with the results in the presence and absence of rotation and in the presence and absence of microstretch constants between the two theories. PACS Nos.: 46.25.Hf, 62.20.D-, 81.40.Jj. La presente vise l'etude des effets de la rotation sur le micro-etirement thermique de solides elastiques. Nous travaillons dans le contexte de la theorie de la thermo-elasticite de Lord-Shulman avec un temps de relaxation et de la theorie de Green-Lindsay avec deux temps de relaxation, ainsi que de la theorie de la dynamique classique couplee. Nous solutionnons numeriquement par methode d'elements finis. Nous presentons graphiquement les resultats numeriques pour la distribution de temperature, les composants de deplacement, les forces de charge, les couples de charge et la distribution de micro- efforts. Les resultats indiquent que les effets de la rotation sont tres prononces. Nous comparons les resultats pour les deux theories, avec et sans rotation, ainsi qu'en presence et absence de constante de micro-etirement. [Traduit par la Redaction], 1. Introduction It is well known that material response to external stimuli depends heavily on the motion of its inner structures. Classical elasticity ignores this effect by ascribing only translational [...]

The present paper attempts to investigate the propagation of plane waves in an isotropic elastic medium under the effect of initial stress and temperature-dependent properties. The modulus of elasticity is taken as a linear function of reference temperature. The formulation is applied under the thermoelasticity theory with three-phase-lag, proposed by Choudhuri (J. Thermal Stresses, 30, 231 (2007)). Normal mode analysis is used to obtain the expressions for the displacement components, the temperature, the stress, and the strain components. Numerical results for the field quantities are given in the physical domain and illustrated graphically. Comparisons are made with the results predicted by different theories (Lord-Shulman theory, the theory of thermoelasticity type III, and the three-phase-lag model) in the absence and presence of the initial stress as well as the case where the modulus of elasticity is independent of temperature. PACS Nos.: 46.25.Hf, 62.20.D-, 81.40.Jj. Nous etudions ici la propagation d'ondes planes dans un milieu elastique isotrope et leur dependance sur la charge initiale et les proprietes qui varient avec la temperature. Nous prenons pour acquis que le module d'elasticite est une fonction lineaire de la temperature de reference. Nous appliquons la theorie de la thermo-elasticite avec trois retards de phase, proposee par Choudhuri (J. Thermal Stresses, 30, 231 (2007)). L'analyse en modes normaux nous permet d'obtenir les expressions pour les composantes du deplacement, la temperature, la charge et les deformations. Nous presentons les resultats numeriques pour les champs dans le domaine physique et les illustrons graphiquement. Nous comparons ces resultats avec ceux d'autres theories (la theorie de Lord-Shulman, la theorie de la thermo-elasticite de type III et le modele a trois retards de phase), en presence et en absence de charge initiale, et lorsque le module d'elasticite est independant de la temperature., 1. Introduction Generalized theories of thermoelasticity have been developed to overcome the infinite propagation speed of thermal signals predicted by the classical coupled dynamical theory of thermoelasticity [1]. The subject [...]

In the present paper, we introduce the dual-phase lag theory to study the effect of the rotation on a two-dimensional problem of micropolar thermoelastic isotropic medium with two temperatures. A normal mode method is proposed to analyze the problem and obtain numerical solutions for the displacement, the conductive temperature, the thermodynamic temperature, the microrotation, and the stresses. The results of the physical quantities have been obtained numerically and illustrated graphically. The results show the effect of phase lag of the heat flux [τ.sub.q], a phase lag of temperature gradient [τ.sub.θ] and two-temperature parameter on all the physical quantities. PACS Nos.: 46.25.Hf, 62.20.D-, 81.40.Jj. Nous introduisons ici la theorie du retard de phase dual pour etudier l'effet de la rotation sur un probleme a deux dimensions d'un milieu thermoelastique micropolaire avec deux temperatures. Nous proposons une methode de modes normaux afin d'analyser le probleme et obtenir des solutions numeriques pour le deplacement, la temperature conductrice, la temperature thermodynamique, la micro-rotation et les contraintes. Les resultats des calculs numeriques pour les quantites physiques sont presentes graphiquement. Ces resultats montrent l'effet d'un retard de phase du flux de chaleur [τ.sub.q], d'un retard de phase du gradient de temperature [τ.sub.θ] et des deux temperatures sur toutes les quantites physiques. [Traduit par la Redaction], 1. Introduction The linear theory of elasticity is of paramount importance in the stress analysis of steel, which is the commonest engineering structural material. To a lesser extent, linear elasticity [...]

: Mixed models combining random coefficient effect and covariance patterns were used to investigate mechanical property variations in jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) trees. Modulus of elasticity (MOE) and modulus of rupture (MOR) were measured by conducting three-point bending tests on small defect-free samples selected from different radial positions and at a height of 2.5 m above ground within the stems. The objective of the paper was to build statistical predictive models describing the radial variations in stems for wood mechanical properties using easily measurable explanatory variables that are typically available in the wood manufacturing industry: distance from pith, tree height and diameter, and spacing. The explanatory variables integrated into the models explained MOE adequately, whereas MOR appeared harder to predict with only these variables and at this resolution. For white spruce, the best mixed-effects models explained 80% and 61% of the variation in MOE and MOR, respectively. For jack pine, it was 51% and 33% for the same response variables. These results are a step toward models that could be used in sawing simulation software designed to estimate the internal properties of sawlogs and, as a result, better predict lumber and pulp chip quality. Key words: jack pine, white spruce, MOE, MOR, modeling. Resume: Des modeles mixtes combinant l'effet aleatoire des coefficients et des patrons de covariance ont ete utilises pour etudier les variations des proprietes mecaniques dans les tiges de pin gris (Pinus banksiana Lamb.) et d'epinette blanche (Picea glauca (Moench) Voss). Le module d'elasticite (MOE) et le module de rupture (MOR) ont ete mesures en effectuant des tests de flexion trois points sur de petits echantillons exempts de defauts, selectionnes dans differentes positions radiales dans le tronc a une hauteur de 2,5 m au-dessus du niveau du sol. L'objectif de cette etude etait d'elaborer des modeles statistiques de prevision des variations radiales des proprietes mecaniques du bois dans la tige a l'aide de variables descriptives facilement mesurables et generalement disponibles dans l'industrie de transformation du bois: distance de la moelle, hauteur et diametre de l'arbre et espacement. Les variables descriptives integrees dans les modeles expliquaient adequatement le MOE tandis que le MOR semblait plus difficile a predire avec seulement ces variables et a cette resolution. Dans le cas de l'epinette blanche, les meilleurs modeles a effets mixtes expliquaient respectivement 80 et 61 % de la variation du MOE et du MOR. Dans le cas du pin gris, c'etait 51 et 33 % pour les memes variables-reponses. Ces resultats constituent un pas vers des modeles qui pourraient etre utilises dans un logiciel de simulation du sciage concu pour estimer les proprietes internes des billes de sciage et, par consequent, mieux predire la qualite du bois d'ceuvre et des copeaux a pate. [Traduit par la Redaction] Mots-cles: pin gris, epinette blanche, MOE, MOR, modelisation., Introduction Optimization of log primary breakdown is an active research topic that can be addressed in different ways. For example, we could quote integrating models, volume yield, and log property [...]

The influence of high strain-rate loading on the flexural response of typical light-frame wood construction has been investigated. A total of 30 stud grade 38 mm x 140 mm x 2440 mm (2' x6' x8') spruce-pine-fir (S-P-F) lumber specimens were tested within a range of low and high strain-rates between 6 x [10.sup.-6] [s.sup.-1] and 0.4 [s.sup.-1]. A single- degree-of-freedom iterative solution procedure was used to compute the high strain-rate modulus of rupture (MOR) and modulus of elasticity (MOE). The MOR was statistically enhanced by high strain-rates, while the MOE and strain at rupture were not. Since equilibrium of the dynamic stress-strain relationship requires that one or both of the MOE and strain at rupture must be sensitive to strain-rate effects, the lack of observed rate enhancement on these material properties was attributed to large scatter within a small sample set. Based on the results, material dynamic increase factors and a stress-strain relationship suitable for blast resistant design of timber structures were also proposed. Key words: blast, high strain-rate, dynamic increase factor, modulus of rupture, modulus of elasticity, S-P-F, timber, wood, lumber, shock tube. L'influence d'un chargement tres rapide sur la reponse en flexion d'une construction typique a ossature de bois a ete etudiee. Un total de 30 echantillons de categorie colombage de 38 mm x 140 mm x 2440 mm (2' x 6' x 8') en epinette - pin - sapin (E-P-S) a ete mis a l'epreuve sous diverses vitesses, basses et elevees, situees entre 6 x [10.sup.-6] [s.sup.-1] a 0,4 [s.sup.-1]. Le MOR (moment de resistance) et le MOE (module d'elasticite) sous une vitesse de chargement elevee ont ete calcules selon une procedure iterative a un seul degre de liberte. Le MOR a ete statistiquement accru par les vitesses de chargement elevees alors que le MOE et la contrainte a la rupture ne l'ont pas ete. Puisque l'equilibre de la relation tension-contrainte dynamique exige que le MOE et-ou la contrainte a la rupture soient sensibles aux effets de la vitesse de chargement, le manque d'observation d'un accroissement de la vitesse sur ces proprietes de materiaux a ete attribue a une grande dispersion dans un petit ensemble d'echantillons. En se basant sur les resultats, des facteurs d'augmentation du rapport resistance dynamique/resistance statique et une relation tension-deformation adequate pour la conception resistante aux vitesses de chargement rapides pour les structures a ossature de bois sont proposes. [Traduit par la Redaction] Mots-cles: explosion, vitesse de deformation elevee, facteur d'augmentation du rapport resistance dynamique/resistance statique, module de rupture, module d'elasticite, E-P-S, bois d'ceuvre, bois, montant, tube a chocs., Introduction Blast-resistant structures are designed to have sufficient strength to resist blast loads and are detailed to ensure ductility and continuity during response. Furthermore, these hardened facilities have higher structural [...]

The high-cycle accumulation (HCA) model proposed by the authors can be used to predict permanent deformations or stress relaxation due to a large number (e.g., several millions) of load cycles with relative small strain amplitudes ( Key words: high-cycle accumulation model, elastic stiffness, bulk modulus, Poisson's ratio, cyclic tests, fine sand. Le modele d'accumulation elevee de cycles (AEC) propose par les auteurs peut etre utilise pour predire les deformations permanentes ou la relaxation des contraintes causees par le grand nombre (ex. plusieurs millions) de cycles de chargement avec des amplitudes relatives de faibles deformations (> E isotrope utilisee dans le modele AEC. Afin de calibrer le module de compressibilite K, le taux d'accumulation des pressions interstitielles obtenu par un essai cyclique non draine et le taux d'accumulation des deformations volumetriques mesure dans un essai cyclique draine ont ete compares. Le coefficient de Poisson v peut etre determine a partir de la forme du chemin de relaxation des contraintes mesure lors d'un essai non draine incluant des cycles de contraintes et deformations anisotropes en consolidation. Malheureusement, le calibrage de K presente dans l'article precedent par Wichtman et al. en 2010 etait affecte par les effets de penetration de la membrane. Ainsi, les etudes subsequentes ont ete realisees sur un sable fin pour lequel les effets de penetration de la membrane sont negligeables. Le present article rapporte ces nouveaux resultats. La forte dependance de K sur la pression et son independance sur l'amplitude observees lors de l'etude precedente ont pu etre confirmees par les nouveaux essais. De plus, les nouveaux resultats experimentaux ont revele une dependance de K sur la densite, tandis que le module de compressibilite est plutot independant du coefficient de contrainte. En addition, le coefficient de Poisson v utilise dans le modele AEC a, pour la premiere fois, ete calibre a partir d'essais realises a differentes amplitudes, densites et contraintes initiales. [Traduit par la Redaction] Mots-cles: modele d'accumulation elevee de cycles, rigidite elastique, module de compressibilite, coefficient de Poisson, essais cycliques, sable fin., Introduction High-cycle accumulation (HCA) models can be used for the prediction of permanent deformations or stress relaxation in soils caused by a large number (N > [10.sup.3]) of cycles with [...]

A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer-nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle-matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/[A1.sub.2][0.sub.3] (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/Si[0.sub.2] with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus [C.sub.11] obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymer-nanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix. POLYM. ENG. SCI., 53: 1502-1511, 2013. [C] 2012 Society of Plastics Engineers, INTRODUCTION The power of nanotechnology is rooted in its potential to transform and revolutionize multiple technology and industry sectors, including aerospace, agriculture, biotechnology, energy, environmental improvement, information technology, medicine, and [...]

Contact resonance force microscopy has been used to evaluate the effect of maleated polypropylene (MAPP) concentration on interphase thickness as well as the spatial distribution of mechanical properties within the interphase of cellulose fiber-reinforced polypropylene composites. The average interphase thickness values ranged from 25 nm to 104 nm for different concentrations of MAPP. The interphase region showed a gradient in the elastic modulus, with a gradual decrease in modulus from fiber to matrix. The interphase region in the specimen containing 0% MAPP showed a narrow interphase with steep gradient in modulus from fiber to matrix, whereas the use of MAPP significantly increased the interphase thickness which resulted in a more gradual change in modulus from fiber to matrix. POLYM. ENG. SCI., 53:888-896, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION The structural integrity of a composite mainly depends on the quality of stress transfer across the interphase. Extending over lengths from nanometeis to micrometers, a well-engineered interphase is essential [...]

Different micromechanical models which account for the presence of dispersed and agglomerated nanofillers, specifically carbon nanotubes (CNTs) and cellulose nanowhiskers (CWs), in a polymeric matrix and consider the effect of a percolation threshold on the elastic modulus of the composite are derived and compared. We demonstrate that the critical filler volume fraction where a percolating network is forming marks a 'turning point' in the reinforcement efficiency. The suitability of these models is verified by comparing simulated values with experimental data from literature. The results show that the models are able to predict mechanical properties over a wide range of testing conditions. POLYM. ENG. Sd., 53:882-887, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Nanocomposites are a class of composites in which one of the dimensions of the reinforcement phase is in the range of 1-100 nm. Because of the filler nanometer size [...]

Although a large number of tunnels and deep excavations have been constructed in Shanghai, small-strain stiffness properties of natural Shanghai clay have rarely been reported in the literature. In this study, the degree of inherent stiffness anisotropy of natural Shanghai clay was investigated in a triaxial apparatus equipped with local strain transducers and a shear-wave velocity measurement system. Three sets of side-mounted bender elements, consisting of one transmitter and two receivers each, were installed on a prismatic specimen. Two series of triaxial tests on prismatic specimens of intact Shanghai clay were carried out under an isotropic stress state. Shear-wave velocities and hence elastic shear moduli in different planes were determined from bender element measurements. The cross-correlation method using two received signals gives rise to the most objective and repeatable results on shear-wave velocities in comparison with other commonly used methods. Intact Shanghai clay clearly exhibits inherent stiffness anisotropy in terms of its elastic shear modulus ratio ([G.sub.0(hh)]/[G.sub.0(hv)]) of about 1.2 for a mean effective stress varying from 50 to 400 kPa. The measured higher stiffness in the horizontal plane may be attributed to the stronger layering structure in the horizontal bedding plane. A unique relationship is found that relates the normalized shear moduli to the stress state in each plane by incorporating a void ratio function in the form of F(e) = [e.sup.- 2.6]. Key words: intact Shanghai clay, prismatic, side-mounted bender element, small-strain stiffness anisotropy. Les proprietes en rigidite a faible deformation de l'argile naturelle de Shanghai ont rarement ete rapportees dans la litterature, et ce, malgre le nombre important de tunnels et d'excavations profondes realisees a Shanghai. Dans cette etude, le degre d'anisotropie inherente en rigidite de l'argile naturelle de Shanghai est evalue a l'aide d'un appareil triaxial equipe de capteurs de deformation locale et d'un systeme de mesure de la vitesse des ondes de cisaillement. Trois series d'elements flechisseurs places sur les cotes, chacune avec un capteur et deux recepteurs, ont ete installes sur un echantillon prismatique. Deux series d'essais triaxiaux ont ete realisees sur des echantillons prismatiques intacts d'argile de Shanghai dans un etat de contrainte isotrope. Les vitesses des ondes de cisaillement, et ainsi les modules de cisaillement elastiques dans differents plans, ont ete determines a partir des mesures provenant des elements flechisseurs. La methode de correlation croisee avec deux signaux recus a fourni des resultats les plus objectifs et repetables de vitesses des ondes de cisaillement, comparativement aux autres methodes communement utilisees. L'argile de Shanghai intacte presente de l'anisotropie inherente en rigidite sous forme d'un ratio du module de cisaillement elastique ([G.sub.0(hh)]/[G.sub.0(hv)]) d'environ 1,2 pour une contrainte effective moyenne variant entre 50 et 400 kPa. La rigidite plus elevee mesuree dans le plan horizontal peut etre attribuee a la structure en couche plus resistante dans le plan de stratification horizontal. Une relation unique est determinee afin de relier les modules de cisaillement normalises a l'etat des contraintes dans chaque plan, en integrant une fonction de l' indice des vides definie comme F(e) = [e.sup.-2,6]. Mots-cles : argile de Shanghai intact, prismatique, elements flechisseurs places sur les cotes, anisotropie en rigidite a faible deformation. [Traduit par la Redaction], Introduction Natural sedimentary clays are generally anisotropic owing to their depositional environments and subsequent one-dimensional deformation. Small-strain stiffness anisotropy is widely considered to be a fundamental property for predicting ground [...]

Lam and Jefferis (2011) have produced a timely, well written, and worthy paper. I would like to add a few comments to the authors' presentation of the strain measurements. Moreover, [...]

We have investigated the elastic and thermodynamic properties of transition metal carbides (TiC, ZrC, HfC, VC, NbC, and TaC) using the three body force potential model and density functional theory based ab initio approach. The computed second-order elastic constants ([C.sub.11], [C.sub.12], [C.sub.44]) are in close agreement with the available experimental as well as theoretical results. The other related elastic parameters ([B.sub.0], [B.sub.0]', [C.sub.S], [C.sub.L], G, v, E, A, [beta], [xi], [lambda], Cauchy pressure ([C.sub.12] - [C.sub.44]), [B.sub.0]/G, and E/[rho] ratio) have also been computed successfully. The calculated Debye temperatures are in reasonably good agreement with the available data. PACS Nos: 60:00B, 79:00, 62.20.de, 62.20.dq Utilisant l'approche ab initio de fonctionnelle de densite et un potentiel modelisant la force a trois corps, nous etudions les proprietes elastiques et thermodynamiques de carbures de metaux de transition, TiC, ZrC, HfC, VC, NbC et TaC. Les valeurs calculees des constantes elastiques du second ordre, [C.sub.11], [C.sub.12] et [C.sub.44], sont en bon accord avec les valeurs experimentales disponibles et avec d'autres resultats theoriques. Nous avons egalement calcule avec succes les autres parametres elastiques relies, [B.sub.0], [B.sub.0]', [C.sub.S], [C.sub.L], G, v, E, A, [beta], [xi], [lambda], la pression de Cauchy ([C.sub.12] - [C.sub.44]), [B.sub.0]/G et le rapport E/[rho]. Les temperatures de Debye calculees sont en bon accord avec les donnees disponibles. [Traduit par la Redaction], 1. Introduction Refractory compounds, particularly nitrides and carbides of transition metals, have attracted a great deal of attention from the scientific community because of their unique physical and chemical properties, [...]

The extensional rheological properties of three grades of polyethylene melts, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE) were measured using a melt spinning technique under the test conditions with temperature ranging from 150 to 210°C and extrusion rate varying from 11.25 to 22.50 mm [s.sup.-1]. The results showed that the melt strength decreased with a rise of temperature while increased with an increase of extensional rate. With the rise of extensional strain rate and temperature, the melt extensional viscosity decreased. The extensional stress and viscosity reduced with increasing extrusion velocity when the temperature and extensional rate were constant. Moreover, the melt strength and extensional viscosity of the LDPE resin was the highest and the LLDPE was the lowest under the same experimental conditions. POLYM. ENG. SCI., 51:2490-2494, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION In polymer processing, melt extensional flow is a common flow pattern, such as entrance converging flow in die extrusion or runner injection of polymer melts from an extruder barrel [...]

Expressions for the temperature dependence of elastic constants have been formulated by taking into account volume dependence of the Anderson-Gruneisen parameters. These expressions have been applied to ionic materials such as NaCl, KCl, MgO, and CaO to determine elastic constants at different temperatures. It is found that the linear relationship between isothermal bulk modulus and thermal energy ([E.sub.th]) is also applicable to other elastic constants. This linear relationship is valid, starting from room temperature. PACS Nos: 62.20, 65.70, 65.40.-b Nous avons obtenu des expressions pour la dependance en temperature des constantes elastiques, en tenant compte de la dependance en volume des parametres de Anderson-Gruneisen. Nous avons applique ces expressions aux materiaux ioniques NaCl, KCl, MgO et CaO, afin de determiner leurs constantes elastiques a differentes temperatures. Nous trouvons que la relation lineaire entre le module d'elasticite isostatique isotherme et l'energie thermique ([E.sub.th]) peut aussi s'appliquer a d'autres constantes elastiques. Cette relation lineaire est valide a partir de la temperature ambiante. [Traduit par la Redaction], 1. Introduction Knowledge of elastic constants is necessary for an understanding of various fundamental properties such as interatomic potentials, specific heat, thermal expansion, Debye temperature, melting point, and the Gruneisen [...]

The elastic behaviour of lanthanum mono-chalcogenides is investigated at elevated temperatures. This study includes second- and third-order elastic constants of compound semiconductors LaS, LaSe, and LaTe, starting from primary physical parameters, that is, nearest neighbour distance and hardness parameters, assuming long- and short-range potentials. The variations of elastic constants with temperature follow a systematic trend identical to that observed in other chalcogenides in the NaCl-type structure family. The present approach can also succeed in predicting the pressure derivatives of the elastic constants. The obtained results are compared with available theoretical data and are found to be in satisfactory agreement with present values. PACS Nos: 62.20.dc, 81.40.Jj, 63.20.kg Nous etudions ici le comportement elastique de chalcogenures simples de lanthane a haute temperature. Nous incluons les constantes elastiques de second et troisieme ordre des semi-conducteurs LaS, LaSe et LaTe, commencant avec les parametres physiques primaires, comme la distance entre plus proches voisins et le parametre de durete, supposant des potentiels de courte et de longue portee. La variation en temperature des constantes elastiques suit une tendance systematique identique a celle observee dans d'autres chalcogenures de la famille NaCl. Notre approche peut egalement predire les derivees des constantes par rapport a la pression. Les resultats obtenus sont compares aux resultats theoriques existants avec lesquels ils sont en bon accord. [Traduit par la Redaction], 1. Introduction The lanthanum mono-chalcogenides belong to the wide class of binary rare-earth mono-chalcogenides with the NaCl-type structure (space group Fm3m, Z =1, also called the B1 structure), which has [...]

The study of the nuclear structure for the elements [sup.12]C, [sup.40]Ca, and [sup.6]Li has been performed in the momentum range from 0 to 0.8 GeV/c by using [K.sup.+]N phase shifts. An optical potential is used to calculate the elastic differential cross section and total cross section for [K.sup.+] scattering from [sup.12]C, [sup.40]Ca, and [sup.6]Li. Comparison with previous experiments shows better results for the elements [sup.6]Li and [sup.40]Ca and fair agreement for the element [sup.12]C. PACS Nos: 21.10.Ft, 25.80.Dj, 25.80.Nv Nous avons complete une etude de la structure nucleaire des elements [sup.12]C, [sup.40]Ca et [sup.6]Li dans le domaine allant de 0 a 0,8 GeV/c en utilisant le dephasage [K.sup.+]N. Nous utilisons un potentiel optique pour calculer la section efficace differentielle elastique et la section efficace totale dans la diffusion du [K.sup.+] sur les noyaux [sup.12]C, [sup.40]Ca et [sup.6]Li. La comparaison avec des experiences precedentes indique de meilleurs resultats pour [sup.6]Li et [sup.40]Ca et un accord raisonnable pour le [sup.12]C. [Traduit par la Redaction], 1. Introduction Study of the physics of nuclear structures requires mastery of suitable techniques to effectively obtain quantitative results of scattering between nuclei and lighter particles (mesons). The study of [...]

Modulus of elasticity (MOE), modulus of rupture (MOR), and specific gravity (SG) are important properties for determining the end-use and value of a piece of lumber. This study addressed the variation in MOE, MOR, and SG with physiographic region, tree height, and wood type. Properties were measured from two static bending samples (dimensions 25.4 mm x 25.4 mm x 406.4 mm) representing each wood type (corewood and outerwood) at heights 2.4, 7.3, and 12.2 m from three trees sampled from 135 loblolly pine (Pinus taeda L.) stands distributed across the natural range of the species. An analysis of variance was conducted to detect the effect of physiographpic region, height, and wood type on each property. Significant regional variation was observed for MOE, MOR, and SG for both wood types with high values in the Gulf and South Atlantic Coastal Plains compared with other regions. A significant height-related trend in MOE, MOR, and SG within a tree was identified; MOE and MOR increased in corewood and decreased in outerwood with height. Maps showing regional variation in MOE and MOR at different heights by wood type were produced and showed significant variation for both properties. Resume: Le module d'elasticite (MOE), le module de rupture (MOR) et le poids specifique (PS) sont des proprietes importantes pour determiner l'usage final et la valeur d'une piece de bois. Cette etude a porte sur la variation de ces proprietes en fonction de la region physiographique, de la hauteur de l'arbre et du type de bois. Les proprietes ont ete mesurees en flexion statique sur deux eprouvettes (dimensions de 25,4 mm x 25,4 mm x 406,4 mm) representant chaque type de bois (bois juvenile et bois mature) a des hauteurs de 2,4, 7,3 et 12,2 m dans trois arbres preleves au sein de 135 peuplements de pin a encens (Pinus taeda L.) distribues dans l'ensemble de l'aire de repartition naturelle de l'espece. Une analyse de variance a ete realisee afin de detecter les effets de la region physiographique, de la hauteur et du type de bois sur chaque pro-priete. Une variation regionale significative du MOE, du MOR et du PS a ete observee dans les deux types de bois, avec des valeurs elevees dans le Golfe et dans les plaines cotieres de l'Atlantique Sud comparativement aux autres regions. A l'interieur de l'arbre, une tendance significative reliee a la hauteur a ete identifiee pour le MOE, le MOR et le PS; le MOE et le MOR augmentaient dans le bois juvenile et diminuaient dans le bois mature en fonction de la hauteur. La cartographie des variations regionales du MOE et du MOR a differentes hauteurs et par type de bois montrent que ces deux proprietes varient grandement. [Traduit par la Redaction], Introduction The southeastern United States is a critically important region of the world in terms of lumber manufacture, with production greater than any other single nation in the world. It [...]

For the past few decades, the stiffness of asphalt material has been commonly characterized by means of resilient modulus. However, the resilient modulus is not a fundamental material property, and hence, the concept of resilient modulus has been subsequently diminished in the latest Mechanistic-Empirical Pavement Design Guide (MEPDG). Although the MEPDG could not endorse the resilient modulus as the primary means for asphalt concrete characterization, it has been a primary mixture test, and a considerable amount of laboratory testing has been conducted to date. In this paper, an analysis methodology for backcalculating the dynamic modulus from the resilient modulus test data is introduced. The strong advantage of such a methodology is that the existing resilient modulus data can be reused for estimating the dynamic modulus. The approach would significantly save time and effort in reevaluating the dynamic modulus of asphalt mixture for which the resilient modulus test data are available. Key words: asphalts, mixtures, viscoelasticity, resilient modulus, creep, cyclic tests Au cours des quelques dernieres decennies, la rigidite des materiaux bitumineux a ete caracterisee au moyen du module de resilience. Toutefois, le module de resilience n'est pas une propriete fondamentale des materiaux et, ainsi, l'importance accordee au module de resilience a ete subsequemment amoindrie dans le plus recent Mechanistic-Empirical Pavement Design Guide (MEPDG) americain. Bien que le MEPDG ne puisse endosser le module de resilience comme principal moyen de caracterisation du beton bitumineux, il a servi a elaborer des essais de melange et de nombreux essais en laboratoire ont ete realises a ce jour. Dans le present article, une methode analytique d' extrapolation du module dynamique a partir des donnees d'essai du module de resilience est presentee. Le grand avantage d'une telle methode est que les donnees existantes du module de resilience peuvent etre reutilisees pour estimer le module dynamique. L'approche pourrait sauver considerablement de temps et d'effort a reevaluer le module dynamique du melange bitumineux pour lequel des donnees d'essai du module de resilience sont disponibles. Mots-cles : asphaltes, melanges, viscoelasticite, module de resilience, fluage, essais cycliques. [Traduit par la Redaction], Introduction Unlike an elastic material, the fundamental properties that govern the stress-strain relationship of a viscoelastic material are functions of either time or frequency. In the time domain, these properties [...]

Phenolic and amine epoxy systems are widely used as hardeners in underfill materials for. flip chip packaging. A comparison was made between these two systems in order to evaluate the reliability performance of a flip chip plastic ball grid array (FC-PBGA). The coefficient of thermal expansion, glass transition temperature ([T.sub.g]), Young's modulus (E), and fracture toughness were revealed by using a thermal mechanical analyzer, a dynamic mechanical analyzer, and a single-edge notch three-point bending test, while moisture absorption study was performed using an 85[degrees]C/85% relative humidity chamber. The adhesion strength with different conditions of temperature and humidity was performed using a die shear test. The series of standard reliability tests such as accelerated temperature cycle test, pressure cooker test, thermal humidity storage test, and high temperature storage test were executed upon the FC-PBGA, which was filled by phenolic and amine epoxy systems of underfill materials. It was found that the adhesion strength of phenolic-based underfills is better than that of amine-based underfills in almost all test conditions. Phenolic-based underfills also demonstrated better reliability compared with amine-based underfills. [DOI: 10.1115/1.4002741] Keywords: amine-based, phenolic-based, reliability, underfill

We previously proposed an elastic-plastic-creep model to estimate the fatigue strength of lead-free solder joints subjected to cyclic thermal loading. The proposed model requires detailed experimental data regarding the time-independent plastic strain and the time-dependent creep strain during cyclic thermal loading. This paper proposes an experimental method for determining the characteristics of both the plastic and creep strains generated during cyclic loading that employs stepped ramp waves. This method is applied to cyclic tension-compression loadings using a Sn-3.0Ag-9.5Cu lead-free solder for several loading conditions. The method can separate between the time-independent plastic strain and the time-dependent creep strain in cyclic inelastic deformation of solder alloys. [DOI: 10.1115/1.4002897] Keywords: lead-free solder alloy, elastic-plastic-creep constitutive model, time-independent strain, time-dependent strain, cyclic plasticity, stress relaxation

Computationally expensive finite element (FE) methods are generally used for indirect evaluation of tissue mechanical properties of trabecular specimens, which is vital for fracture risk prediction in the elderly. This work presents the application of reduced-basis (RB) methods for rapid evaluation of simulation results. Three cylindrical transiliac crest specimens (diameter: 7.5 min, length: 10-12 mm) were obtained from healthy subjects (20 year-old, 22 year-old, and 24 year-old females) and scanned using microcomputed tomography imaging. Cubic samples of dimensions 5 X5 X5 mm3 were extracted from the core of the cylindrical specimens for FE analysis. Subsequently, a FE solution library (test space) was constructed for each of the specimens by varying the material property parameters: tissue elastic modulus and Poisson's ratio, to develop RB algorithms. The computational speed gain obtained by the RB methods and their accuracy relative to the FE analysis were evaluated. Speed gains greater than 4000 times, were obtained for all three specimens for a loss in accuracy of less than 1% in the maxima of von-Mises stress with respect to the FE-based value. The computational time decreased from more than 6 h to less than 18 s. RB algorithms can be successfully utilized for real-time reliable evaluation of trabecular bone elastic properties. [DOI: 10.1115/1.4001254] Keywords: iliae crest trabeculae, reduced-basis method, elastic property, computational speed gain, finite element methods

A general first-order formulation of the continuous sensitivity equations is introduced that improves the accuracy of the sensitivity boundary conditions. In the continuous sensitivity method, design or shape parameter gradients are computed from a continuous system of partial differential equations instead of the discretized system, which avoids the problematic mesh sensitivity calculations of discrete methods for shape variation problems. The first-order formulation for both the underlying elasticity and sensitivity equations is amenable to solution by a high-order polynomial least-squares finite element model. The continuous sensitivity boundary-value problem, which can be posed in local or total derivative form, is generally simpler in local sensitivity form for shape variation problems. Although the local form is not unique and total material sensitivities are generally desired for structural elasticity problems, the local sensitivity solution is easily transformed to a material derivative. The first-order formulation and the transformation to material derivatives are demonstrated for two elasticity example problems. The least-squares continuous sensitivity solutions are presented and compared with analytic sensitivities and finite difference results and should prove convenient validation benchmarks for other continuous sensitivity applications. DOI: 10.2514/1.44349

This paper compares linear-elastic and nonlinear pile group analysis methods through settlement analyses of hypothetical scenarios and real case studies, and elaborates on the implications for interpretation of pile load test data. Comparisons between linear-elastic and nonlinear methods justify the proposition that pile-to-pile interaction is dominated by linear elasticity, characterized by the small-strain soil stiffness. As the size of a pile group increases, nonlinearity in individual pile behavior becomes overwhelmed by the interaction effects. In such cases, similar estimates will be achieved by both linear and nonlinear methods if the soil modulus is derived from the initial tangent, rather than some secant stiffness, assessed from the load test data. The study clarifies the capabilities and limitations of linear elasticity in pile group analysis and provides guidance on pile test interpretation for analysis of pile group response. DOI: 10.1061/(ASCE)GT.1943-5606.0000392 CE Database subject headings: Pile groups: Pile foundations: Soil-pile interactions. Author keywords: Pile groups: Pile foundations; Soil-pile interactions.

This study explores the response of spiral-reinforced lightweight concrete to short-term compression by conducting an experimental program. The response includes deformation capacity, compressive strength, concrete strain at compressive strength, modulus of elasticity, and failure mode. The response is explored by varying the pitch of spiral reinforcement, diameter of spiral wire, compressive strength of plain concrete, and specimen size. Test results show that deformation capacity of spiral- reinforced lightweight concrete decreases with an increase in compressive strength of plain lightweight concrete. Nevertheless, deformation capacity can be increased by reducing the pitch of spiral reinforcement and by increasing the diameter of spiral wire. This study also suggests the mathematical expressions to estimate the compressive strength of spiral-reinforced lightweight concrete, concrete strain at compressive strength, and modulus of elasticity of plain lightweight concrete. Understanding of the concrete response gained from the present study would be beneficial in analysis and design of lightweight concrete structural members. DOI: 10.1061/(ASCE)MT.1943-5533.0000139 CE Database subject headings: Compressive strength; Strain; Deformation; Lightweight concrete. Author keywords: Compressive strength; Concrete strain at compressive strength; Deformation capacity; Lightweight concrete; Modulus of elasticity; Spiral reinforcement.

With low modulus of elasticity, high strength, excellent ductility, excellent durability, and low price, polypropylene fiber is often used in cement-based materials to improve the toughness and anticracking performance of the matrix composite. The aim of this study was to investigate the flexural properties of cement-stabilized macadam reinforced with polypropylene fiber. Four different fiber volume fractions (0.04, 0.06, 0.08, and 0.1%) and four different cement contents (4, 5, 6, and 7%) were used. Besides, a series of tests without mixing fibers was also carried out. By means of four-point loading method, the flexural strength and flexural modulus of elasticity of cement-stabilized macadam were measured. The results indicate that polypropylene fiber can increase the flexural strength and decrease the flexural modulus of elasticity of cement-stabilized macadam. The flexural strength and flexural elastic modulus are increasing with the increase in specimen curing period. When the fiber volume fraction is not beyond 0.1%, the flexural strength is gradually increasing and the flexural modulus of elasticity is gradually decreasing with the increase in fiber volume fraction. Besides, with the increase in cement content, there is a tendency to increase both in the flexural strength and flexural elastic modulus. Furthermore, polypropylene fiber appears to be highly effective in improving the nondeformability of cement-stabilized macadam. DOI: 10.1061/(ASCE)MT.1943-5533.0000137 CE Database subject headings: Portland cement; Construction materials; Fiber reinforced materials; Base course; Mechanical properties. Author keywords: Portland cement; Construction materials; Fiber-reinforced materials; Base course; Mechanical properties.

Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined. DOI: 10.1061/(ASCE)EM.1943-7889.0000185 CE Database subject headings: Dynamic loads; Bridges, suspension; Continuum mechanics; Vibration. Author keywords: Dynamic loads; Suspension bridges; Continuum models; Linear response; Vibrations.

Hydroelasticity theory, considering the second-order fluid forces induced by the coupling of first-order wave potentials, is introduced briefly in this paper. Based on the numerical results of second-order principal coordinates induced by the difference-frequency and sum-frequency fluid forces in multidirectional irregular waves, the bending moments, as well as the vertical displacements of a floating plate used as a numerical example are obtained in an efficient manner. As the phase angle components of the multidirectional waves are random variables, the principal coordinates, the vertical displacements, and the bending moments are all random variables. Extreme values of bending moments are predicted on the basis of the theory of stationary stochastic processes. The predicted linear and nonlinear results of bending moments show that the influences of nonlinear fluid forces are different not only for the different wave phase angles, but also for the different incident wave angles. In the example very large floating structure (VLFS) considered in this paper, the influence of nonlinear fluid force on the predicted extreme bending moment may be as large as 22% of the linear wave exciting forces. For an elastic body with large rigidity, the influence of nonlinear fluid force on the responses may be larger than the first-order exciting forces and should be considered in the hydroelastic analysis. [DOI: 10.1115/1.4001415] Keywords: extreme value, nonlinear hydroelasticity, frequency domain, multidirectional waves

The mechanical properties of tissue engineering scaffolds play a critical role in the success of repairing damaged tissues/organs. Determining the mechanical properties has proven to be a challenging task as these properties are not constant but depend upon time as the scaffold degrades. In this study, the modeling of the time-dependent mechanical properties of a scaffold is performed based on the concept of finite element model updating. This modeling approach contains three steps: (1) development of a finite element model for the effective mechanical properties of the scaffold, (2) parametrizing the finite element model by selecting parameters associated with the scaffold microstructure and/or material properties, which vary with scaffold degradation, and (3) identifying selected parameters as functions of time based on measurements from the tests on the scaffold mechanical properties as they degrade. To validate the developed model, scaffolds were made from the biocompatible polymer polycaprolactone (PCL) mixed with hydroxylapatite (HA) nanoparticles and their mechanical properties were examined in terms of the Young modulus. Based on the bulk degradation exhibited by the PCL/HA scaffold, the molecular weight was selected for model updating. With the identified molecular weight, the finite element model developed was effective for predicting the time-dependent mechanical properties of PCL/HA scaffolds during degradation. [DOI: 10.1115/1.4002551] Keywords: tissue engineering, time dependency, scaffolds mechanical properties, degradation

Rubber materials have mostly been modeled by utilizing hyperelasticity, which have led to greater understanding and acceptable predictability of their stress-strain response. However, inherent inelastic behavior excluded by approximation has never been characterized by time-dependent parameters such as time, strain-rate, and strain history. We hypothesized that time, stretch rate, and stretch history were prominent factors that induce the inelasticity, and we characterized the inelasticity in terms of those factors using a randomized stretch-controlled testing protocol. We applied the custom randomized testing protocol with the fundamental statistical theory to characterize inelastic behavior imbedded in the high strain material. We hypothesized that time spent testing (T), raterelated stretch history ([H.sub.t2]), and long-term stretch history ([H.sub.t1]) give rise to the inelastic deviation from hyperelasticity. We examined the significance, effectiveness, and differences of T, [H.sub.t2], and [H.sub.t1] by looking at the derived multivariable linear regression models. Distribution of prediction deviation was also examined to see if we missed any other significant variable. Predictability of the multivariable linear regression models was validated by utilizing the unused data from the randomized testing protocol and data from the conventional cyclic testing protocol. We found that the inelasticity of the rubber-like material is highly related to T, [H.sub.t2], and [H.sub.t1], but not equally influential to all stretches. At smaller deformations, greater inelastic deviation occurs. Inelasticity exponentially decreased over stretch and was nonlinearly related to time. This study successfully determined the elastic/inelastic responses and factors that induce the inelastic response of the rubber-like material. This investigation suggests a way to better describe the elastic/ inelastic properties and phenomenological models of rubber-like materials. [DOI: 10.1115/1.4001250] Keywords: hyperelasticity, rubber, strain energy, stretch rate, stretch history

The classical flexure problem of nonlinear incompressible elasticity is revisited assuming that the bending angle suffered by the block is specified instead of the usual applied moment. The general moment-bending angle relationship is then obtained and is shown to be dependent on only one nondimensional parameter: the product of the aspect ratio of the block and the bending angle. A Maclaurin series expansion in this parameter is then found. The first-order term is proportional to [mu], the shear modulus of linear elasticity; the second-order term is identically zero because the moment is an odd function of the angle; and the third-order term is proportional to [mu](4[beta] - 1), where [beta] is the nonlinear shear coefficient, involving third-order and fourth-order elasticity constants. It follows that bending experiments provide an alternative way of estimating this coefficient and the results of one such experiment are presented. In passing, the coefficients of Rivlin's expansion in exact nonlinear elasticity are connected to those of Landau in weakly (fourth-order) nonlinear elasticity. [DOI: 10.1115/1.4001282] Keywords: incompressible elasticity, flexure, nonlinear shear coefficient, experimental data

This paper studies the effects of shaft rub on a rotating system's vibration response with emphasis on heat generation at the contact point. A 3D heat transfer code, coupled to a 3D vibration code, was developed to predict the dynamic response of a rotor in the time domain. The shaft bow is represented by an equivalent bending moment and the contact forces by rotating external forces. The seal ring is modeled as a linear spring, which exerts a normal force to the rotor. The tangential force is then calculated as the product of the normal force with the friction coefficient. Stable or unstable spiraling and oscillating modes were seen to occur in well defined shaft speed zones. In the main, for the configurations studied, the shaft vibration was found to be unstable for speeds below the first critical speed and stable for speeds above the first critical speed. Limit cycle behavior was observed when the phase angle between the unbalance force and the response was around 90 deg. The vibration behavior with rub during startup and shutdown was studied by considering the effects of acceleration/deceleration rate, friction coefficient, and mass unbalance. It was found that friction coefficient and increasing mass unbalance amplified the rub effects while acceleration/deceleration rate reduced it. [DOI: 10.1115/1.4000904] Keywords: Shaft/seal rub, coupled analysis for heat transfer and vibration, thermal bending moment, rub at startup and shutdown

Extensions of the Castigliano theorems are developed in the context of modeling the behavior of both discrete coupled linear systems and various coupled beams. It is shown that the minimization of the displacement of a parallel system determined from Castigliano's second theorem can be used to formally define the apportionment of loads among the system elements, while the minimization of the load in a series system determined from Castigliano's first theorem can be used to formally define the apportionment of the displacement among the system elements. These extensions provide a means for apportioning loads in coupled continuous systems, as will be shown for the cases of coupled cantilever Timoshenko beams supporting discrete and continuous loads. [DOI: 10.1115/1.4001716]

For resonant column tests conducted in the flexure mode of excitation, a new methodology has been proposed to find the elastic modulus and associated axial strain of a cylindrical sample. The proposed method is an improvement over the existing one, and it does not require the assumption of either the mode shape or zero bending moment condition at the top of the sample. A stepwise procedure is given to perform the necessary calculations. From a number of resonant column experiments on aluminum bars and dry sand samples, it has been observed that the present method as compared with the one available in literature provides approximately (i) 5.9%-7.3% higher values of the elastic modulus and (ii) 6.5%-7.3% higher values of the associated axial strains. Key words: dynamic properties, elastic modulus, elastic strain, resonant column test, sands. Une nouvelle methodologie est proposee pour determiner le module elastique et les deformations axiales associees pour un echantillon cylindrique, a l'aide d'essais en colonne de resonance effectuees dans le mode d'excitation en flexion. La methode proposee ameeliore la methode existante puisqu'elle ne necessite pas la supposition de la forme du mode ni de la condition zeero du moment de torsion dans le haut de l'echantillon. Une procedure etape-par-etape est presentee afin d'effectuer les calculs neecessaires. Dans le cas de plusieurs essais en colonne de resonance sur des barres d'aluminium et des echantillons de sable sec, la methode proposee comparativement a la methode de la litterature offre approximativement (i) des valeurs du module elastique superieures de 5,9% a 7,3%, et (ii) des valeurs des deformations axiales associees superieures de 6,5% a 7,3%. Mots-cles: proprietes dynamiques, module elastique, deformation elastique, essai en colonne de resonance, sables. [Traduit par la Redaction], Introduction The resonant column test is often used to determine the dynamic properties of various soil samples (Richart et al. 1970; Hardin and Drnevich 1972; Drnevich et al. 1978; ASTM [...]

Abdominal aortic aneurysm (AAA) is the gradual weakening and dilation of the infrarenal aorta. This disease is progressive, asymptomatic, and can eventually lead to rupture--a catastrophic event leading to massive internal bleeding and possibly death. The mechanical environment present in AAA is currently thought to be important in disease initiation, progression, and diagnosis. In this study, we utilize porohyperelastic (PHE) finite element models (FEMs) to investigate how such modeling can be used to better understand the local biomechanical environment in AAA. A 3D hypothetical AAA was constructed with a preferential anterior bulge assuming both the intraluminal thrombus (ILT) and the AAA wall act as porous materials. A parametric study was performed to investigate how physiologically meaningful variations in AAA wall and ILT hydraulic permeabilities affect luminal interstitial fluid velocities and wall stresses within an AAA. A corresponding hyperelastic (HE) simulation was also run in order to be able to compare stress values between PHE and HE simulations. The effect of AAA size on local interstitial fluid velocity was also investigated by simulating maximum diameters (5.5 cm, 4.5 cm, and 3.5 cm) at the baseline values of ILT and AAA wall permeability. Finally, a cyclic PHE simulation was utilized to study the variation in local fluid velocities as a result of a physiologic pulsatile blood pressure. While the ILT hydraulic permeability was found to have minimal affect on interstitial velocities, our simulations demonstrated a 28% increase and a 20% decrease in luminal interstitial fluid velocity as a result of a 1 standard deviation increase and decrease in AAA wall hydraulic permeability, respectively. Peak interstitial velocities in all simulations occurred on the luminal surface adjacent to the region of maximum diameter. These values increased with increasing AAA size. PHE simulations resulted in 19.4%, 40.1%, and 81.0% increases in peak maximum principal wall stresses in comparison to HE simulations for maximum diameters of 35 mm, 45 mm, and 55 mm, respectively. The pulsatile AAA PHE FEM demonstrated a complex interstitial fluid velocity field the direction of which alternated in to and out of the luminal layer of the ILT. The biomechanical environment within both the aneurysmal wall and the ILT is involved in AAA pathogenesis and rupture. Assuming these tissues to be porohyperelastic materials may provide additional insight into the complex solid and fluid forces acting on the cells responsible for aneurysmal remodeling and weakening. [DOI: 10.1115/1.4002370] Keywords: aneurysm, porohyperelastic, permeability, finite element model

The transmission error of gears is an important factor for power transmissions, particularly automotive. Consequently, a lot of research has been conducted on the gear transmission. However, in contrast, there remains relatively little research clarifying the characteristics of gear transmission error and its relationship to the tooth flank form. The authors have proposed a general model for tooth meshing between gears. This expresses the transmission error theoretically from a quasi-infinite elastic model, which is composed of springs with stiffness specific to the gears. In this report, the influence of tooth flank form deviation on transmission error is further investigated by using this model. It is shown that the .form of the ridge curve of the tooth flank form deviation greatly influences the actual contact ratio at the minimum point of peak-to-peak value of transmission error. The peak-to-peak value of transmission error is affected by the amplitude and the form of the ridge curve. [DO]: 10.1115/1.4002458] Keywords: gear, transmission error, tooth flank form

The multiple normal loading-unloading process of an elastic-plastic sphere by a rigid flat is analyzed using finite element method for stick contact condition and both kinematic and isotropic hardening models. The behavior of the global contact parameters as well as the stress field within the sphere tip is presented for several loading cycles. It was found that under stick contact condition, secondary plastification occurs even after the second loading cycle and that the hardening model used has little effect on the loading-unloading process. The cyclic loading process gradually converges into elastic shakedown. [DOI: 10.1115/1.4002103] Keywords: spherical contact, elastic-plastic contact, contact condition, multiple loadings, hardening

The pure squeeze magneto-elastohydrodynamic lubrication (MEHL) motion of circular contacts with an electrically conducting fluid in the presence of a transverse magnetic field is explored under constant load condition. The differences between classical elastohydrodynamic lubrication and MEHL are discussed. The results reveal that the effect of an externally applied magnetic field is equivalent to enhancing effective lubricant viscosity. Therefore, as the Hartmann number increases, the enhancing effect becomes more obvious. Furthermore, the transient pressure profiles, film shapes, normal squeeze velocities, and effective viscosity during the pure squeeze process under various operating conditions are discussed. [DOI: 10.1115/1.4002182] Keywords: magneto-elastohydrodynamic lubrication, squeeze-film, constant load

A contact mechanics (CM) based model of a fixed-length rigid cylinder impacting a homogeneous elastic-plastic homogeneous body was developed and includes an improved method of estimating the residual depth after impact. The nonlinear elastic behavior during unloading was accounted for to develop an improved coefficient of restitution model The impact model was applied to study a practical case of a cylindrical feature on the slider of a magnetic storage hard disk drive impacting the disk to predict various critical impact contact parameters. The CM model was validated using a plane strain finite element model and it was found that a cylindrical feature with a longer length results in a substantial alleviation of impact damage. [DOI: 10.1115/1.4002331] Keywords: contact mechanics, oblique impact, elastic-plastic impact, coefficient of restitution, magnetic storage

An experimental program was conducted to examine fluidelastic instability in in-line and rotated square finned tube arrays. Three arrays of each geometry type were studied: two with serrated, helically wound finned tubes of different fin densities and the third is a bare tube, which had the same base diameter as the finned tubes. The finned tubes under consideration were commercial finned tubes of a type typically used in the fossil and process industries. The addition of fins to tubes in heat exchangers enhances heat transfer due to the increased surface area and the turbulence produced by the flow moving over the fins. The resulting flow pattern/distribution due to the fins is, therefore, more complex than in bare tube arrays. Previous research has shown that an effective diameter of a finned tube is useful in the prediction of vortex shedding. This concept is used to compare the finned tube results with the existing bare tube array guidelines for fluidelastic instability. All of the tube arrays in the present study have the same tube pitch and have been scaled to have the same mass ratio. The results for rotated square arrays suggest that the use of an effective diameter is beneficial in the scaling of fluidelastic instability and the finned tube results are found to fit within the scatter of the existing data for fluidelastic instability. For in-line square arrays, the results indicate that fins significantly increase the stability threshold. An earlier version of this paper appeared at the ASME 2007 PVP Division Conference, PVP2007-26597. [DOI: 10.1115/1.4001201]

The thermoelastic coupling vibration characteristics of the axially moving beam with frictional contact are investigated. The piecewise differential equation of motion for the axially moving beam in the thermoelastic coupling case and the continuous conditions at the contact point are established. The eigenequation is derived by the differential quadrature method, and the first order dimensionless complex frequencies of the simply supported axially moving beam under the coupled thermoelastic case are calculated. The effects of the dimensionless thermoelastic coupling factor, the dimensionless moving speed, the spring stiffness, the friction coefficient, and the normal pressure on the thermoelastic coupling vibration characteristics of the axially moving beam with frictional contact are discussed. [DOI: 10.1115/1.4001513] Keywords: thermoelastic coupling, axially moving beam, frictional contact, vibration characteristics, differential quadrature method

This paper reports the application of the space-time conservation element and solution element (CESE) method to the numerical solution of nonlinear waves in elastic solids. The governing equations consist of a pair of coupled first-order nonlinear hyperbolic partial differential equations, formulated in the Eulerian frame. We report their derivations and present conservative, nonconservative, and diagonal forms. The conservative form is solved numerically by the CESE method; the other forms are used to study the eigenstructure of the hyperbolic system (which reveals the underlying wave physics) and deduce the Riemann invariants. The proposed theoretical/numerical approach is demonstrated by directly solving two benchmark elastic wave problems: one involving linear propagating extensional waves, the other involving nonlinear resonant standing waves. For the extensional wave problem, the CESE method accurately captures the sharp propagating wavefront without excessive numerical diffusion or spurious oscillations, and predicts correct reflection characteristics at the boundaries. For the resonant vibrations problem, the CESE method captures the linear-to-nonlinear evolution of the resonant waves and the distribution of wave energy among multiple modes in the nonlinear regime. [DOI: 10.1115/1.4001499] Keywords: nonlinear elastic waves, nonlinear hyperbolic systems, conservation element and solution element method

A folding wing structure consisting of three components (a fuselage, an inboard wing, and an outboard wing) is modeled computationally using a geometrically nonlinear structural dynamics theory based upon van Karman strains and a three-dimensional vortex lattice aerodynamic model with an exact tangent flow boundary condition and planar wake assumption. The structural dynamic equations of motion are discretized in space using a discrete Ritz basis derived from finite element analysis and component synthesis. Results from the computational model are compared with those from experiments designed and tested in the Duke University wind tunnel for three folding wing configurations. Stable limit cycle oscillations at flow velocities beyond the linear flutter velocity are measured in wind-tunnel experiments and predicted using the computational model. Overall, the limit cycle oscillation magnitude and dominant response frequency results from theory show good agreement with those measured in the experiment. Qualitatively, both the experimental and theoretical limit cycle oscillation curves for the inboard wing show limited nonlinear stiffening with flow velocity for the range of velocities tested. The theoretical model also predicts that the outboard wing limit cycle oscillation tip displacements for the folding wing configuration with the largest outboard folding angle is significantly higher than the two other configurations. Unlike the inboard wing, for each configuration, the outboard wing theoretical limit cycle oscillation curves do show a trend that is reminiscent of a stiffening nonlinearity. DOI: 10.2514/1.44868

This paper deals with a pressure-displacement formulation based on the finite-element method of an elastoacoustic coupling problem. Since directly solving the resulting system is CPU intensive for large models, the solution is usually based on only a few uncoupled structural modes in vacuum and rigid cavity modes. However this classical pressure-displacement formulation leads to nonsymmetric eigenvalue problems. Furthermore, if this method is accurate for weak coupling models, significant errors occur when the truncated modes are coupled to the ones used in the analysis. The present paper suggests a method combining the pseudostatic correction of the truncated modes in modal analysis with a synunetrizatlon technique of the eigenvalue problems. It allows the calculation of the real coupled modes and frequencies, as well as the computation of an accurate elastoacoustic response, even for the strong coupling of a structure with a heavy fluid (liquid). It is less CPU expensive than the classical method, because it leads to a diagonalized system. DOI: 10.2514/1.J050056

Toroidal shells are widely used in structural engineering. The governing equations of toroidal shells are very complicated because of its variable coefficients with singularity. To find their analytical solution, traditionally, the complex form governing equations were proposed and some useful solutions were obtained. Unfortunately, no any closed-form solution has even been obtained for either general or slender toroidal shells. This paper focus on a special case of toroidal shells, i.e., slender symmetrical toroidal shells. For the first time, the closed-form solution of this kind of shell has been successfully obtained from displacement form governing equations. The closed-form solution is demonstrated for the example of thermal compensation devices. The correction of well-known Dahl formula for slender toroidal shell has been proposed based on the solution obtained in this paper. DOI: 10.1061/(ASCE)EM.1943-7889.0000175 CE Database subject headings: Shells; Axisymmetry; Bending; Deformation; Elasticity; Closed form solutions. Author keywords: Toroidal shells; Axisymmetry; Revolution shells; Slender shells; Bending; Deformation; Elastic materials.