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Two silane-based hybrid coatings were developed to modify the surface energy of phenolic resin impregnated paper. The coated paper samples were further pressed onto surfaces of plywood. The surface properties and water repellence of coated paper were investigated by AFM, XPS and water contact angle measurements. The water absorption of plywood with pressed paper was studied by water uptake tests. It was found that the sol-gel coatings had slightly improved the water repellence of the impregnated paper. The water absorption of plywood was also slightly decreased.

The sintering behaviour of several ceramics prepared using a previously selected mixture of incinerated paper mill sludge and glass cullet which was blended with 10, 20, 30 and 40 wt% of some natural clayey materials has been studied. Three natural commercial product were used: a red clay, a yellow clay and a kaolin. Mixtures were blended by wet attrition milling, dried, sieved, pressed into specimens and then fired for 1 h at temperatures ranging from 1040 to 1140 °C. The resulting materials were characterized by water absorption, shrinkage and crystallographic composition. It was observed that materials containing kaolin display the best overall behaviour independently of the quantity of kaolin introduced. Conversely the optimal sintering temperature, and consequently the best properties of materials prepared using red or yellow clay was found above 1080 °C and depends of their specific composition being affected by the amount of clay added.

21st Symposium on Composites, Bremen, Germany, 5 Jul 2017 - 7 Jul 2017 ; Key engineering materials : KEM 742, 62-69 (2017). doi:10.4028/www.scientific.net/KEM.742.62 special issue: "21st Symposium on Composites : selected, peer reviewed papers from the 21st Symposium on Composites, July 5-7, Bremen, Germany / edited by Axel F. Herrmann" (978-3-0357-1198-1), Published by Trans Tech Publications, Uetikon a.S.

21st Symposium on Composites, Bremen, Germany, 5 Jul 2017 - 7 Jul 2017 ; Key engineering materials 742, 473-481 (2017). doi:10.4028/www.scientific.net/KEM.742.473 special issue: "21st Symposium on Composites : selected, peer reviewed papers from the 21st Symposium on Composites, July 5-7, Bremen, Germany / edited by Axel F. Herrmann" (978-3-0357-1198-1), Published by Trans Tech Publications, Uetikon a.S.

Heat treatable aluminium alloys show their best properties when properly heat treated. Most of the high-strength alloys are usually serviced in the so-called T6 temper consisting of ageing at moderate temperature after a solution treatment and a subsequent quenching. A large extrusion was investigated in this paper. The part was solution annealed at 505°C, water quenched and aged at 160°C for 16 hours. Each stage of the heat treatment is analyzed in this paper in the light of the properties achieved, by experimental investigations and several kinds of numerical simulations. In particular, a thermodynamic calculation (Pandat® software) provides solidification temperatures and equilibrium phases, in order to check whether the solution temperature is adequate. A finite element analysis (performed with COMSOL Multiphysics® software) supplies a simulation of the temperature field during water quenching. The cooling curves obtained are drawn on CCT (Continuous Cooling Transformation) curves, calculated by means of JMatPro® software, to verify if any undesired high temperature precipitation could occur during quenching. Finally, calculated TTT (Time Temperature Transformation) curves can be related to the ageing treatment.Thermal analyses, microstructural investigations and microhardness profile measurements on extrusion sections are also performed to validate calculated results.

In this paper, an innovative approach is presented for joining two sheets with an extruded profile all made by AA6082-T6 aluminum alloy. The tested configuration is the T-joint and the innovation presented in this paper is the use of a specially design appendix of the extruded profile as filler material during the friction welding. In particular three configurations were analyzed: without appendix, with I appendix and with T appendix. In the experiments, several process parameters and PIN shapes were investigated in order to determine optimal processing conditions able to produce an effective sound weld. Specimens were extracted from the joint and tensile tests were performed along the sheet direction thus allowing a comparison of the welded sections respect to the base material. It was found that the appendixes of the extrude profile are able to effectively fill the distance between the sheets and, in particular with the T shape, a gap up to 1,7 mm on the retreating side was successfully welded.

Polyolefins are especially difficult to bond due to their non-polar, non-porous and chemically inert surfaces. Acrylic adhesives used in industry are particularly suited to bond these materials, including many grades of polypropylene (PP) and polyethylene (PE), without special surface preparation. In this work, the tensile strength of single-lap PE and mixed joints bonded with an acrylic adhesive was investigated. The mixed joints included PE with aluminium (AL) or carbon fibre reinforced plastic (CFRP) substrates. The PE substrates were only cleaned with isopropanol, which assured cohesive failures. For the PE CFRP joints, three different surfaces preparations were employed for the CFRP substrates: cleaning with acetone, abrasion with 100 grit sand paper and peel-ply finishing. In the PE AL joints, the AL bonding surfaces were prepared by the following methods: cleaning with acetone, abrasion with 180 and 320 grit sand papers, grit blasting and chemical etching with chromic acid. After abrasion of the CFRP and AL substrates, the surfaces were always cleaned with acetone. The tensile strengths were compared with numerical results from ABAQUS® and a mixed mode (I+II) cohesive damage model. A good agreement was found between the experimental and numerical results, except for the PE AL joints, since the AL surface treatments were not found to be effective.

Dielectric elastomer (DE) actuators are able to typically show significant electromechanical performances, which make this electroactive polymer technology particularly attractive for so-called ‘artificial muscle’ devices. This paper deals with two types of DE actuators recently developed in our lab. The first type is represented by the so-called ‘folded actuators’, based on a simple configuration suitable to easily implement linear contractile devices. The structure consists of a monolithic electroded sheet of elastomer, which is folded up and compacted; the resulting contractile actuator is functionally equivalent to a multilayer stack with interdigitated electrodes, but can be manufactured more easily. The second type of devices is represented by the so-called ‘buckling actuators’. They operate with out-of-plane unidirectional displacements of an elastomer membrane. This paper describes the structure and the properties of both these actuators, along with different examples of applications currently being developed in our lab for the biomedical, the robotic and the space fields.

EIS measurements in reinforced concrete have been carried out from the first studies of J. Dawson et al at the beginning of the eighties. Since their first papers already proposing an electrical equivalent circuit having in series two individual Randles ones, not very much advances have been achieved in the interpretation of the results. In the present paper a contribution to the understanding of the physical meaning of the EIS results obtained is presented. Three main frequency regions with processes having very different capacitive behaviour and therefore, time constant responses, are identified. Finally, it is pointed out the need to use specimens with well defined geometry in order to enable the correct frequency analysis and dielectric constant calculation to be made.

Ti-6Al-4V titanium alloy is a high strength-to-mass ratio material common in a lot of engineering fields. Its surface oxide can guarantee the protection of the substrate from various corrosive media. Unluckily, this film can be scratched in presence of mechanical and chemical loads and for this reason the corrosion resistance can decrease. The Structural Mechanics Laboratory (SM-Lab) is carrying out a characterization of the alloy in different environments under quasi-static loading. In this paper, a summary of the outcomes of the investigation and the description of the fracture surface of a specimen with EDM notches quasi-statically tested in methanol is provided

Acknowledgements: This work is supported by the Fundação para a Ciência e a Tecnologia (FCT) and Centro2020 through the Project references: UID/Multi/04044/2013; PAMI – ROTEIRO/0328/2013 (Nº 022158) and MATIS (CENTRO-01-0145-FEDER-000014 – 3362). Rosins are the non-volatile exudates of pine resins with hydrophobic characteristics that are widely used as a precursor for many industrial applications. In this paper we discuss the nature, process and its applications as a matrix for a composite material for additive manufacturing. The composite material has been tailored to chemical and mechanical properties with respect to their applications. info:eu-repo/semantics/publishedVersion

This work was supported by the Portuguese Foundation for Science and Technology (FCT) through the following project: UID/Multi/04044/2013 and PAMI ROTEIRO/0328/2013 (Nº 022158). In addition, the authors acknowledge the funding from the project Coolgrafeno, copromoção n. 17883 from the Portuguese National Innovation Agency. For many years traditional injection moulding has been the norm for obtaining polymer based products, and yet this cycle still shows potential for improvement. This paper will encompass the potential in the thermal part of the cycle, by introducing a novel approach to conventional tubular cooling designs, empowered by additive technologies this reiterates what’s being known as conformal cooling. Different geometries and techniques are compared to determine the optimal cross section layout of the fluid channels and inner surface of the moulding parts. If the cooling achieved is sufficiently fast the crystallographic growth of the material can be manipulated to obtain specific properties observable in the mesoscale. This however can be transversely applied in other heat exchanging structures in future studies. info:eu-repo/semantics/publishedVersion

International audience; In this paper, the laser welding of thin titanium sheet in a butt joint configuration are investigated using a continuous Yb: YAG disk source, with high beam quality and a particular fiber configuration, enable to provide a broad range of beam diameters with different intensity distribution. The thermal efficiency of the laser process is discussed as a function of the fiber type. The weldability results for the CP Ti grade 2 and the Ti-6Al-4V titanium alloy are expressed in terms of full penetration, and correct bead geometry (NF L06-395-2000). Full penetration welds are easily achieved with the core fiber, but the outer fiber produces welds with limited geometric defects. Butt joints microstructure consists of an acicular α phase in the fusion zone for CP Ti, and a martensitic α’ phase for the Ti-6Al-4V alloy. Tensile test results confirm a similar or slightly higher joint strength for the full penetration welds, compared with the parent metal.

The use of Shape Memory Alloys in dampers devices able to reduce the wind, rain or traffic induced oscillations in stayed cables is well represented in the literature. An analysis realized on standard cables at existing facilities shows the reliable efficiency of the SMA wire in damping oscillations. Such studies also provide tools to build the SMA dampers and to account for the effects of the external temperature in the SMA. The particular study reported in this paper focuses on a critical discussion on the relation between the wire diameter and macroscopic behavior and external temperature effects. The damping requires the absorption of the mechanical energy and its conversion to heat via the action of hysteresis cycles. The study was realized on wires of different diameters. In particular, the study centers on wires of diameter 0.2, 0.5 and 2.46 mm. The flat cycles showed by the thin wires (i.e., diameter 0.2 and 0.5 mm) and the non-classical S-shaped cycles of wires of diameter 2.46 mm establish clear differences of the response under external summer-winter temperature actions. Depending of the room temperature and SMA composition, a complete flat transformation in thin wires requires stresses, in general, near 300-400 MPa. A complete transformation for an S-shaped cycle need stresses as higher as 600 MPa. The analysis of the behavior of these wires under the action of warm temperatures in summer and cold temperatures in winter, suggests that thin wires lose their pseudo-elastic state in winter. The S-shaped permits positive working in extended temperature domain and a supplementary investigation establishes that S-shaped can be increased by strain aging. The hysteretic behavior in S-shaped permits practical working under external temperatures as applications in bridges require. From a fundamental point of view, the flat cycles are coherent with the classical treatment of the SMA as a first order phase transition but the S-shaped can be considered associated to an anomaly in heat capacity.

This paper describes the thermo-elasto-plastic analysis of bath and spray quenched AISI 316L cylinders. A suitably detailed continuum deformation analysis approach presented here is implemented within the framework of commercial Finite Element (FE) package ABAQUS. The results of the numerical analysis are compared with the residual elastic strains measured experimentally using neutron diffraction. The good agreement between measured and modelled residual elastic strains provides a basis for careful analysis of the residual elastic strain development resulting from two different quench methods. The conclusions drawn from the analysis provides a better understanding of quench processsing, so that the effects of different heat removal efficiencies of such processing technique can be taken advantage of to generate favourable residual elastic stress and deformation and microstructural distributions with quench processed components.

An advanced forming process involving hot forming and cold-die quenching, also known as HFQ®, has been employed to form AA6082 tailor welded blanks (TWBs). The HFQ® process combines both forming and heat treatment in a single operation, whereby upon heating the TWB, it is stamped and held between cold tools to quench the component to room temperature. The material therefore undergoes temperature, strain rate or strain path changes during the operation. In this paper, a finite element model (FEM) was developed to investigate the formability and deformation characteristics of the TWBs under HFQ® conditions. Experimental results, i.e. strain distribution, were used to compare and validate the simulation results. A good agreement between the experiment and simulation has been achieved. The developed temperature, strain rate and strain path dependent forming limit prediction model has been implemented into FE simulation to capture the complicated failure features of the HFQ® formed TWBs. It is found from both experiment and simulation that the forming speed has important effects on the occurrence of failure position, where the failure mode for the 1.5-2 mm TWBs may change from localised circumferential necking to parallel weld necking.HFQ® is a registered trademark of Impression Technologies Ltd.

The present work analyses the behaviour of different binder matrices in order to implement the addition of paper pulp as reinforcement for cementitious composites and assesses the composites flexural properties with time. To prevent microfibers degradation in high-alkaline environments, lower alkaline matrices may be developed. In the present study ternary binder matrices containing ordinary Portland cement (OPC), gypsum (G) and fluid catalytic cracking catalyst residue (FC3R) are presented for that purpose. To assess the performance of the alternatives matrices, pH and conductivity evolution with time were monitored. Also flexural tests were carried out with the intention of evaluate the efficiency of the matrix to preserve fibres within the composite. According to pH and conductivity results is proved that this ternary system offers lower values at early stages (at 3 days) when compared to OPC systems. This inferior alkalinity might be associated to the better mechanical performance with time of the composites when the ternary matrix is used. After 10 months ageing, all the mechanical properties were higher when compared to composites using OPC. Particularly remarkable is the preservation after ageing of the specific energy and deflection at the modulus of rupture when the low-alkalinity matrices were employed, on the contrary what occurred with samples containing OPC where specific energy and deflection were nearly disappeared.

This paper investigates thermal and strain behaviour in the selective laser sintering process with a mixture of SCM, Cu and Ni metal powder. In-process monitoring of strain change and temperature at the base plate is proposed in order to investigate thermal and strain behaviour induced by selective laser sintering. A strain gauge was attached to the bottom surface of the base plate while a thermocouple was inserted at a distance of 2 mm from the top surface of the base plate. Changes in the strain and the base plate temperature were observed using an oscilloscope during the laser sintering process. The results showed that the development of strain within the sintered structure was affected by the processing temperature. Besides that, after the laser sintering process was completed, the strain value increased gradually and became constant as it reached room temperature. This strain value was found to correspond with the test model's deformation. In addition, the effects of laser scanning direction and laser energy density during the process were observed. Measurement of the test model's deformation was also carried out to discover its relationships to strain change and processing temperature. The results showed that the sintered structure produced by laser scanning of a sector along the width induced less residual strain, which resulted in less deformation. In contrast, both residual strain and deformation were found to be higher when the laser scanning was carried out along the length. Furthermore, when a low laser energy density was used, less deformation of the sintered structure could also be obtained. © (2012) Trans Tech Publications.

Selective Laser Melting (SLM) is a direct fabrication of part through layer by layer powder deposition and successive laser beam irradiation based on Computer Aided Design (CAD) data. One of the important properties in SLM is thermal conductivity of metal powder. This is because the ability of metal powder to conduct heat will affect the consolidation process during SLM. In this paper, thermal conductivity of metal powders with different particle diameters and their mixture was analysed. Other than that, thermal conductivity of consolidated materials fabricated via SLM process was also studied. In order to measure the thermal conductivity of metal powder, a theoretically verified method which was previously developed by the authors was used. Determination of thermal conductivity of consolidated material was analysed using laser flash technique. It was found that the thermal conductivity of powder metal was influenced by bulk density and particle diameter of metal powder. In this study also, metal powders of different particle diameters were mixed with various volume ratios, and its effect was discussed. Thermal conductivity of the consolidated materials was also examined, and its relation to porosity was elaborated. © (2012) Trans Tech Publications, Switzerland.

This paper deals with an analysis of a crack-tip field of particulate-reinforced composites which can describe the evolution of debonding damage, matrix plasticity and particle size effect on deformation and damage. Numerical analyses were carried out on a crack-tip field in elastic-plastic matrix composites reinforced with elastic particles by using a finite element method developed based on an incremental damage theory. The particle size effect on damage is described by a critical energy criterion for particle-matrix interfacial debonding. The effect of debonding damage on a crack-tip field is discussed based on numerical results. The debonding damage initiates and progresses ahead of a crack-tip. The stress distribution shifts downward in the debonding damage area. It is concluded that a crack-tip field is strongly affected by debonding damage.

Experimental works using a drop weight impact test method have been performed on a circular sheet specimen to evaluate and to characterize the impact resistance of the sheet-type plastic components designed for automotive wheel covers. Evaluation has been conducted for a set of engineering plastics: polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and their blend (PC/ABS). The testing results showed that the PC/ABS blend specimens failed in brittle manner under higher impact speeds with very few of whitening zones. Secondary cracks captured perpendicular to fracture surface were also found in the mid-plane of the scattered PC/ABS blend specimens. Investigation is then focused on this blend and the testing results describe that impact resistance of the specimen made of this alternative material is determined by ABS not by PC. Combination of structures between PC and ABS through the thickness in the core due to their immiscibility was observed by scanning electron microscope (SEM) on the etched PC/ABS specimen. This latter result well correlates the results obtained from the testing. It therefore reveals that immiscibility between PC and ABS in the blend plays an important role in determining the impact resistance of the components. This paper also presents simulative results of the test obtained from a FEA work by introducing a 3D- layered finite element (FE) model of the PC/ABS specimen to take into account effect of a layer in the core on the behavior of the blend.

The stochastic nature of aluminum foam structure, having a random distribution of voids, makes it difficult to model its compressive deformation behavior accurately. In this paper, a 2-dimensional simplified modeling approach is introduced to analyze the compressive deformation behavior that occurs in Alporas aluminum foam (Al foam). This has been achieved using image analysis on real undeformed aluminum foam images obtained by VHX-100 digital microscope. Finite element mesh for the cross sectional model is generated with Object Oriented Finite element (OOF) method combined with ABAQUS structural analysis. It is expected that OOF modeling enable prediction of the origin of failure in terms of localized deformation with respect to the microstructural details. Furthermore, strain concentration sites leading to the evolution of the deformation band can be visualized. Thus, this investigation addresses the local inhomogeneity in the Al foam structure. This study implies that the OOF modeling approach combined with experimental observations can provide better insight into the understanding of aluminum foam compressive deformation behavior.

In order to obtain GFRP reinforcement bars it is necessary to undertake tests regulated code which require important mechanical tools. This paper presents a method which allows for determining GFRP rebars tensile strength value from their flexural strength value which has been obtained with a simple, inexpensive and reliable test. This method results will be verified by applying it to values obtained in a series of bending tests and comparing these results with values obtained in tensile tests. Values concordance for small diameter GFRP rebars is very good.

Experimental and numerical results show that the predominant failure mode of FRP strengthened masonry structures is the interfacial debonding, which occurs prior to reaching the compressive strength of the substrate and/or the tensile strength of the FRP composite. In this paper, a three-dimensional numerical model is developed to simulate the experimental response of direct shear test applied to a FRP sheet on the masonry substrate. A damage model is adopted for both mortar and bricks characterized by different behavior in tension and compression.

This paper deals with the characterization of acoustic insulation behaviour of hybrid sandwich composite panels for application in modular house construction. These sandwich panels are a sustainable, light-weight and durable solution, since are based on natural fibers structure impregnated with a thermosetting polymer. In this way, three different types of hybrid composite panels containing polyurethane core and laminated composite skins were produced and analyzed, varying the composition of laminates. The composite laminates of the prototypes were produced using a vacuum infusion technique and were composed of glass and jute fibers, impregnated with a polyester resin. The solutions developed were compared with a standard, composed of plasterboards having different thicknesses and used for thermal and acoustic insulation. Acoustic insulation characterization was performed on specimens with 220x220 mm size in a sound proof acoustic chamber. The tested sandwich panels showed promising results; however, their overall performance was lower as compared to the performance of standard solutions used for comparison. Nevertheless, the specific acoustic insulation performance, i.e. sound reduction per unit mass of material for the developed sandwich panels was significantly higher as compared to the standard materials, indicating better suitability of this innovative solution for light-weight construction and modular housing., Quadro de Referência Estratégica Nacional (QREN), FEDER funds through the Operational Program for Competitiveness Factors - COMPETE under the project in co-promotion with reference "FCOMP-01-0202-FEDER-021581".

This paper deals with an identification methodology of the interfacial fracture parameters to predict the lifetime of a metallic brazed joint. The methodology is based on an experimental-numerical study whereby the optimal parameters are obtained. The experimental data, using the scanning electron microscope analysis, allowed approving that failure of the assembly based AuGe solder seems first to appear near the interfaces. These results were confirmed by micrographs analysis of the solder/insert and solder/substrate interfaces. Then, using shear test results and parametric identification coupled with a finite elements model (FEM) simulation, the damage constitutive law of the interfacial fracture based on a bilinear cohesive zone model are identified. The agreement between the numerical results and the experimental data shows the applicability of the cohesive zone model to fatigue crack growth analysis and life estimation of brazed joints.

This paper describes the deposition of PZT thin films on soda-lime glass substrate with ITO bottom electrode by CSD (Chemical Solution Deposition). The transmittance of the obtained PZT thin film on ITO/glass substrate was about 60 % in the visible light region. The deposited transparent PZT thin film exhibited the ferroelectricity of P_r = 36.3 μC/cm^2 and E_c = 71.3 kV/cm. In addition, the piezoelectric property of the resultant PZT thin film was relatively large and exhibited the measured effective d_33 of 120 pC/N after the polarization., application/pdf

A novel direct chill (DC) casting process, melt conditioned direct chill (MC-DC) casting process, has been developed for production of high quality aluminium alloy billets. In the MC-DC casting process, a high shear device is submerged in the sump of the DC mould to provide intensive melt shearing, which in turn, disperses potential nucleating particles, creates a macroscopic melt flow to uniformly distribute the dispersed particles, and maintains a uniform temperature and chemical composition throughout the melt in the sump. Experimental results have demonstrated that, the MC-DC casting process can produce aluminium alloy billets with significantly refined microstructure and reduced cast defects. In this paper, we give an overview of the MC-DC casting process and report on results obtained from an industrial scale trial.

This paper presents experimental results of compressive behavior of aluminium alloy metal foams with controlled pore morphology. Different types of metal foams were analyzed, having uniform cell structure with different pore size and gradient variation of cellular structure along length. The test samples were manufactured by lost-wax casting using 3D printed components for internal structure definition. Results for stiffness and energy absorption were obtained and compared on weight efficiency basis. The results are analyzed regarding the efficiency of the different cell structures and its suitability for energy absorbing application in components subjected to impact or compression loading., (undefined)

Alkali activated binders require the addition of a mineral-rich amorphous silica and alumina. This paper proposes the use of a mineral residue from the burning of sugar cane bagasse. The alkali activated mixtures were prepared containing binary mixtures of sugar cane bagasse ash (SCBA) and other mineral admixtures: fly ash (FA) or blast furnace slag (BFS). As alkaline activators, mixtures of alkali (Na+ or K+) hydroxide and alkali (Na+ or K+) silicate were used. Alkali-activated pastes and mortars containing binary systems SCBA/FA or SCBA/BFS were prepared and cured at 65 oC. Microstructural properties of these alternative binders were assessed by means of TGA, SEM, XRD and pH measurements. Mechanical strength of mortars was performed after 3 and 7 days at 65 oC. Compressive mechanical strengths of these mortars were in the range 30-55 MPa, showing the good mechanical performance achieved by the alkali activation. Microstructural studies suggested the development of stable matrices and the formation of typical gel.

This paper presents the laboratory work performed with the purpose of understanding the mechanical performance of 340x20x20 mm maritime pine wood samples degraded by rot fungi when treated with a biocide product followed by consolidation through impregnation with a polymeric product.Four commercially available products were used: a water-based biocide, BC, a solvent-based biocide, X, an acrylic consolidant, PB (PB 72), and an epoxy-based consolidant, E.Seven sets of specimens each one having a varied range of fungal degradation were prepared. Then the product combinations were applied by brush to six sets of specimens (E, X-E, BC-E, PB, X-PB, BC-PB) of which one was left untreated for control, 0-0. Finally all sets were subjected to static bending strength test until rupture.Results showed that the acrylic and epoxy-based products lead to increased mechanical capacity of the consolidated wood up to 100% in some cases in specimens with 70% of MOE loss. The results presented the same order of magnitude for both wood consolidants. The previous application of biocide did not have a significant impact in the behavioral pattern of the consolidant: a marked improvement of the bending strength of the degraded specimens after treatment and consolidation. These results demonstrated the feasibility of combining biocide/consolidation products, and provide indications of interest to the application of this technique to extend the lifespan of wood elements moderately degraded by fungi in old buildings.

Sintered lamellar soft magnetic composite (SL-SMC) is a promising material for power frequency applications and for all types of electric motors, including induction motors. Alumina coated Fe-3%Si particles cut from steel sheets offer both the advantages of standard laminated steel products, and of soft magnetic composites (SMC). As SMC’s, this material can be shaped using standard near-net shape powder metallurgy (P/M) techniques, which represents a big advantage over coated laminated steel assemblies. Indeed, the P/M process, as compared to laminated steel assemblies, gives access to better design and improved motor assembling techniques, at lower production costs, by limiting machining and stamping. The unique structure of the SL-SMC offers better DC magnetic properties than standard SMC’s, allowing them to cover a larger range of applications. However, there still remains work to be done in developing this new technology to its full potential, using low cost industrial techniques. This paper is divided into two main parts. The first is dedicated towards assessing the possibility of producing SL-SMC parts using an automatic industrial compaction press. The impact of two different lubrication systems, admixed solid lubricants and die wall lubrication, on the density and green strength of the motor parts, will be determined. Also, the process capability will be evaluated on the basis of “part to part” stability. The second section of this study will determine the impact of different processing parameters on the mechanical and magnetic properties of the Fe-3%Si alloy. Results show that by carefully controlling heat treatment, very high maximum induction, low magnetic loss and good mechanical property, can all be reached in fabricated parts., THERMEC'2011, 7th International Conference on Processing & Manufacturing of Advanced Materials, 1-5 August 2011, Québec City, Canada, Québec City, Canada

Material behaviour description frequently used in commercial codes may not be adequate to simulate real forming processes. One of the reasons is the fact that they rarely include the modeling of internal damage of material. This is a decisive feature in order to be able to predict defective parts in processes like forging or to describe processes in which fracture is a part of the process itself as in sheet blanking or metal cutting. In large deformation of metals, when plastic deformation reaches a threshold level, which may depend on the loading, the fatigue limit and the ultimate stress, a ductile damage process may occur concomitantly with the plastic deformation due to the nucleation, growth and coalescence of micro-voids. Although damage and plastic deformation are two distinct dissipative processes, they influence each other. In this paper a numerical benchmark of the uniaxial tensile tests, for aluminium alloy, has been performed using Ls-Dyna and Deform 2D without damage. Then, a numerical uniaxial tensile tests has been studied using a coupled model of elasto-plasticity and ductile damage implemented in LS-DYNA. Experimental material property present in literature has been used.

Shot peening is a mechanical treatment usually performed on metals for improving the mechanical properties of the surface layers. The application of such treatment to sintered steels causes a local surface densification and the birth of residual compression stresses. In this paper, the effect of different shot peening cycles, selected after a preliminary optimization, has been investigated focusing especially on the fatigue resistance measured by bending tests and on the surface residual stresses measured by XRD technique. Two high performances PM steels were considered: the former was sintered starting from a diffusion bonded powder, whereas the latter is based on a pre-alloyed powder. Two different nominal densities were considered, 6.9g/cm3 and 7.1g/cm3.

This paper focuses on the static mechanical behavior of Ti-6Al-4V titanium alloy when exposed to several aggressive environments. Flat samples, with very light notches (i.e.Kt= 1.16), were tested under static loads, in inert environment and aggressive solutions: the samples gage sections were exposed to air and immerged in a NaCl solution (3.5%) and in a methanol solution (95%). The results of this experimental tests were analyzed and then compared with previous data coming from fatigue tests, carried out in paraffin oil, air, 3.5 wt.% NaCl, and in a methanol solution (95%), with the intent to decouple the effect of the alternating load and of the aggressive environment.

This paper applied the Taguchi approach to investigate the effects of polishing parameters to obtain the optimal processing conditions for CoCr alloy polishing using a multiaxis CNC controlled corrective polishing machine. The polishing medium used was 1m diamond paste with a Microcloth(polishing cloth). Surface finish parameter Sa was chosen as the criterion for process optimization. The experimental results indicate that the optimal polishing conditions for CoCr alloy polishing is 50 precess angle, 800 rpm head speed, 0.2mm tool offset and 1.5 bar tool pressure. With this optimal condition, a confirmatory experiment was conducted. The surface roughness Sa reduced from an initial 24nm to 7nm and reduction ratio was 70.8% which was very close to the estimated ratio of 64%.

Cement pastes reinforced with Multi-Walled carbon NanoTubes (MWNTs) are smart materials with piezoresistivity properties. Adding carbon nanotubes to the cement matrix, in fact, the electrical resistivity of cementitious composites changes with the stress conditions under static and dynamic loads. This particular behaviour can be used to evaluate the stress level in reinforced concrete structures, to monitor the traffic flow, to weigh vehicles. In this paper data on pressure-sensitive behaviour under compressive stress of cement pastes and mortars containing different percentages (from 0.0% to 1.0% vs. cement mass) of MWNTs are presented.In order to form a conductive network and enhancethe piezoresistive properties of cementitious mixtures, Carbon NanoTubes (CNTs) need to be efficiently dispersed in the cement matrix. Two different methods to disperse CNTsin the cement matrix were used. The first one uses a surfactant (Sodium Linear Alkyl Benzene Sulphonate - LAS): MWNTs were dispersed in a LAS aqueous solution,and thenmixed with cement and a defoamer (tributyl phosphate) to decrease the air bubble in MWNT filled cement-based composites. The second method consists in mixing CNTs with about 50% of the mixing water in a becker by means of a glass wand. Then, the solution is sonicated by an ultrasonic generator for 10 minutes. Finally, the sonicatedCNT-aqueous solution ismixed with cement (and sand for the mortars). The piezoresistivity properties of the cementitious mixtures manufactured with the two above mentioned CNTs dispersing methods will be compared.Experimental results show that the electrical resistance changes synchronously with the compressive stress levelsfor the specimens manufactured with both methods. Therefore, CNTs improve the pressure-sensitivity of cementitious composites. Moreover, the piezoresistive response is better for cementitious composites manufactured by using the surfactant agent to disperse CNTs. Data indicate that – thanks to the better dispersion of nanotubes promoted by the surfactant - the pressure-sensitivity properties of cement pastes can be achieved even by using a very low percentage of CNTS (0.1% vs. cement mass). These findings seem to indicate that self-sensing CNTs/cement composite can be produced. These smart materials have great potential and they could be used in the next future in concrete field for practical applications to monitor the stress level of reinforced concrete elements subjected to static, dynamic and impact loads. In particular, informations on actual stress existing under dynamic and impact loads could be improve design procedures in protective structures.

The application of the essential work of fracture (EWF) methodology for the fracture behavior characterization of closed-cell low density polyethylene flexible foams is discussed in the present paper. The thickness of the foamed sheet and the relative orientation of the initial crack were the main parameters studied. The interpretation of the results is carried out on the basis of the material microstructure and the applicability of the testing method.

This paper examines the erosion and cyclic oxidation performance of novel thermal barrier coatings produced via the sol-gel route. The ceramic top coat, with a thickness of 5-80 m, was deposited via a sol-gel route onto standard MCrAlY and PtAl bond coats. In both the erosion and the cyclic oxidation tests it was found that the bond coat had a profound affect on the results. The erosion of the sol-gel coatings were compared to standard EB PVD and PS TBCs and were found to be significantly higher. The effect of aging (100 h at 1100°C) on the erosion rates was also evaluated and was found to increase the erosion rates. The information obtained from the erosion and cyclic oxidation tests have highlighted the need to develop and optimise the parameters for producing thicker coatings

In this paper, we report the preparation of polyethylene composites with organically modified montmorillonite. Three different Na+-montmorillonites were modified in order to obtain organoclays and two grades of high-density polyethylene were used as composite matrices. All composites were prepared by melt blending, and their physical and mechanical properties were thoroughly characterized. The extent of clay platelet exfoliation in the composites was confirmed by X-ray diffraction (XRD). Mechanical properties under static and impact conditions were evaluated to assess the influence of the reinforcement on the properties of polyethylene. Fil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Pita, Victor. Universidade Federal do Rio de Janeiro; Brasil Fil: Valenzuela Diaz, Francisco. Universidade de Sao Paulo; Brasil Fil: Moschiar, Stella Maris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Seltzer, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Lopes Dias, Marcos. Universidade Federal do Rio de Janeiro; Brasil Fil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina

This paper conducted Electro-Contact Discharge (ECD) dressing experiment for #600 diamond grinding wheel to understand how fine diamond grits protrude from metal-bonded wheel surface. The SEM observation, EDS analysis, image processing and 3D grit modeling on wheel surface were carried out to investigate grit protrusion characteristics. Then ECD dressing and mechanical dressing experiments were carried out to identify the effect of grit protrusion feature on grinding performance. It is confirmed that the dressed wheel surface topography is sensitive to open circuit voltage Ei, discharge polarity and electrode composition. Meanwhile, ECD dressing with Ei=15V and straight polarity can produce superior protrusion topography without the damage of diamond crystal faces and the bond tail behind protrusive grit. It can obtain better ground surface of hard-brittle material than mechanical dressing with the bond tail.

When testing the resistance to oxidation of high temperature materials, the cyclic oxidation test is used as a reference because it integrates isothermal oxidation kinetics, oxide scale adherence, mechanical stresses, metallic alloy and oxide mechanical behavior and their evolution with time, in conditions close to the actual conditions of use. To fill the gap between the measurements of physical data (oxidation kinetics, interfacial energy, oxide toughness, growth stresses, coefficients of thermal expansion, mechanical properties of the alloy under the oxide scale,...) and the cyclic oxidation test, comprehensive scientific work is necessary, but also technological development and understanding of the practice of the cyclic oxidation test. This paper presents a new experimental tool, which allows the simultaneous measurement of the mass of several samples placed in the same controlled atmosphere during fast thermal cycles. This multi-sample thermobalance is described, in association with the description of the measurement methodology (i.e. “cyclic thermogravimetry”). First tests of performance of the apparatus are given, including heating and cooling rates and continuous Samass measurements for a P91 alloy.

The present paper deals with the corrosion behaviour of locally active steel rebars after six years of atmospheric exposure. At this testing period the initially active areas reach a kind of passivation state which allows them to act as cathodes in the galvanic macrocells of the studied systems. Even if the galvanic currents are reduced to the nA range, some macrocell activity remains in the structure and the current flow, i.e., the anode-to-cathode behaviour depends very much on the degree of humidity in concrete. These changes are interpreted in function of the electrical properties of the passivating layers and oxygen availability.