The Experts below are selected from a list of 11550 Experts worldwide ranked by ideXlab platform
Viggo Tvergaard - One of the best experts on this subject based on the ideXlab platform.
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predictions of mixed mode interface crack growth using a cohesive zone model for ductile fracture
Journal of The Mechanics and Physics of Solids, 2004Co-Authors: Viggo TvergaardAbstract:Abstract Special interface elements that account for ductile failure by the nucleation and growth of voids to coalescence are used to analyse crack growth. In these elements the stress component Tangential to the interface is accounted for, as determined by the requirement of compatibility with the surrounding material in the Tangential Direction. Thus, the present interface description incorporates the important effect of stress triaxiality on damage evolution, which is not part of the usual cohesive zone models. The interface elements have been used previously for mode I loading conditions, but are here extended to cover non-symmetric mixed mode loading conditions for crack growth along an interface between dissimilar elastic–plastic solids. Crack growth resistance curves are calculated, and the dependence of the interface fracture toughness on the degree of mode mixity is studied.
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crack growth predictions by cohesive zone model for ductile fracture
Journal of The Mechanics and Physics of Solids, 2001Co-Authors: Viggo TvergaardAbstract:For crack growth by a ductile failure mechanism, the fracture process zone is represented in terms of special interface elements in the crack plane ahead of the crack. A porous ductile material model is used in the interface elements to represent the growth of voids to coalescence. In relation to the finite element mesh, the initial width of the interface is taken to be zero, but the traction separation relations represented by the interface are based on assuming an interface width of the order of the void spacing. The Tangential stresses inside the interface are determined by the requirement of compatibility with the surrounding material in the Tangential Direction. Some comparison with predictions based on related crack growth models is used to discuss the performance of the special cohesive zone model presented here.
Hideo Koguchi - One of the best experts on this subject based on the ideXlab platform.
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adhesive contact analysis for anisotropic materials considering surface stress and surface elasticity
International Journal of Solids and Structures, 2015Co-Authors: Takao Hayashi, Hideo KoguchiAbstract:Abstract In this study, an adhesive contact problem for anisotropic materials is analyzed by considering surface stress and surface elasticity. The displacement field on the surface is obtained from the surface Green’s function considering the surface stress and surface elasticity. The displacement due to the adhesive force, i.e., the van der Waals force, calculated from the Lennard–Jones potential is used in the analysis. The adhesive force is calculated from the distance between two surfaces. First, an adhesive contact problem of a rigid spherical indenter and an isotropic substrate with various material properties is analyzed under a condition in which no surface mechanical property is considered, and the results are compared with the Johnson–Kendall–Roberts theory in order to validate the calculation algorithm of the analysis. Next, a substrate with orthotropic properties is subjected to adhesive contact analysis. When the elastic modulus in the normal Direction to the substrate surface increases, the maximum adhesion force increases, similar to the case of the isotropic substrate. However, when the elastic modulus in the Tangential Direction of the substrate surface is varied, the maximum adhesion force does not vary much. Finally, an anisotropic half-substrate is subjected to adhesive contact analysis considering the surface mechanical property. This analysis reveals that when the values of the surface mechanical property are varied, the maximum adhesion force changes, similar to the case of varying the elastic modulus in the Tangential Direction of the surface.
En-hua Yang - One of the best experts on this subject based on the ideXlab platform.
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quantitative characterization of anisotropic properties of the interfacial transition zone itz between microfiber and cement paste
Cement and Concrete Research, 2019Co-Authors: En-hua YangAbstract:Abstract A new approach to characterize ITZ between microfiber and cement matrix is reported. Results show that microstructure of hydrated cement paste is highly modified in the vicinity of microfibers, with higher porosity and less anhydrous cement. ITZ can extend up to 100 μm from the interface into the matrix. The larger extent of ITZ suggests that perturbation due to inclusion of microfibers to packing of cement grains is severer than that due to inclusion of aggregates. Furthermore, ITZ between microfiber and cement matrix is highly heterogeneous along its axial Direction. Existing ITZ analysis methods performed on 2-D cross-sectional plane intersecting with fiber axis thus can lead to errors and uncertainties. Mechanical properties of ITZ between microfiber and cement matrix are anisotropic. Stiffness and ductility of ITZ in the radial Direction are 31% and 28% higher than that in the Tangential Direction, respectively.
Murat Kilic - One of the best experts on this subject based on the ideXlab platform.
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the effect of the cutting Direction number of blades and grain size of the abrasives on surface roughness of taurus cedar cedrus libani a rich woods
Building and Environment, 2008Co-Authors: Salih Aslan, Hakan Coskun, Murat KilicAbstract:Abstract In this study, the surface roughness values of planed and sanded Taurus (Lebanon) cedar (Cedrus Libani A. Rich.) specimens were examined. The test specimens were cut in Tangential and radial Directions. One blade and three blades were used for planing and 60 grit and 100 grit abrasives were used for sanding. With this objective, a total of 80 specimens (2 cutting Directions × 2 different numbers of blades ×2 types of abrasive × 10 replications) were prepared. The roughnesses of the specimens were measured according to ISO 4287. The values obtained were statistically analyzed and the results were interpreted. According to the test results, it was determined statistically that the cutting Direction and the finishing techniques affected the surface roughness. It was determined that cutting in the radial Direction in Taurus cedar wood also produced smoother surfaces compared to cutting in the Tangential Direction. Smoother surfaces are obtained as the grit number of the abrasive increases.
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nail and screw withdrawal strength of laminated veneer lumber made up hardwood and softwood layers
Construction and Building Materials, 2007Co-Authors: Gulser Celebi, Murat KilicAbstract:Abstract The objective of this research was to evaluate screw and nail withdrawal strength properties of veneer laminated lumber manufactured from poplar (Populus nigra) and beech (Fagus orientalis L.) in transverse, radial, and Tangential Directions. Ten and 13 layer laminated samples were produced in different thickness veneers of both species using two types of resins, namely polyvinylacetate (PVAc) and polyurethane (PU). Based on the results of this study it was found that layer thickness did not influence the withdrawal strength in transverse Direction but strength values increased with increasing specific gravity of the samples in this Direction. Overall strength properties in radial Direction were found to be higher than that of Tangential Direction. Based on the statistical analyses resin type did not significantly effect withdrawal strength of both species.
Patrick Perre - One of the best experts on this subject based on the ideXlab platform.
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viscoelastic properties of green wood across the grain measured by harmonic tests in the range of 0 degree c to 95 degree c hardwood vs softwood and normal wood vs reaction wood
arXiv: Classical Physics, 2009Co-Authors: Vincent Placet, Joelle Passard, Patrick PerreAbstract:The viscoelastic properties of wood have been investigated with a dynamic mechanical analyser (DMA) specifically conceived for wooden materials, the WAVET device (environmental vibration analyser for wood). Measurements were carried out on four wood species in the temperature range of 0\degree C to 100\degree C at frequencies varying between 5 mHz and 10 Hz. Wood samples were tested in water-saturated conditions, in radial and Tangential Directions. As expected, the radial Direction always revealed a higher storage modulus than the Tangential Direction. Great differences were also observed in the loss factor. The tan\delta peak and the internal friction are higher in Tangential Direction than in radial Direction. This behaviour is attributed to the fact that anatomical elements act depending on the Direction. Viscoelastic behaviour of reaction wood differs from that of normal or opposite wood. Compression wood of spruce, which has higher lignin content, is denser and stiffer in transverse Directions than normal wood, and has lower softening temperature (Tg). In tension wood, the G-layer is weakly attached to the rest of the wall layers. This may explain why the storage modulus and the softening temperature of tension wood are lower than those for the opposite wood. In this work, we also point out that the time-temperature equivalence fits only around the transition region, i.e. between Tg and Tg + 30\degree C. Apart from these regions, the wood response combines the effect of all constitutive polymers, so that the equivalence is not valid anymore.
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viscoelastic properties of green wood across the grain measured by harmonic tests in the range 0 95 c hardwood vs softwood and normal wood vs reaction wood
Holzforschung, 2007Co-Authors: Vincent Placet, Joelle Passard, Patrick PerreAbstract:The viscoelastic properties of wood have been investigated with a dynamic mechanical analyser (DMA) specifically conceived for wooden materials, the WAVET device (environmental vibration analyser for wood). Measurements were carried out on four wood species in the temperature range of 0°C to 100°C at frequencies varying between 5 mHz and 10 Hz. Wood samples were tested in water-saturated conditions, in radial and Tangential Directions. As expected, the radial Direction always revealed a higher storage modulus than the Tangential Direction. Great differences were also observed in the loss factor. The tan peak and the internal friction are higher in Tangential Direction than in radial Direction. This behaviour is attributed to the fact that anatomical elements act depending on the Direction. Viscoelastic behaviour of reaction wood differs from that of normal or opposite wood. Compression wood of spruce, which has higher lignin content, is denser and stiffer in transverse Directions than normal wood, and has lower softening temperature (Tg). In tension wood, the G-layer is weakly attached to the rest of the wall layers. This may explain why the storage modulus and the softening temperature of tension wood are lower than those for the opposite wood. In this work, we also point out that the time-temperature equivalence fits only around the transition region, i.e. between Tg and Tg + 30°C. Apart from these regions, the wood response combines the effect of all constitutive polymers, so that the equivalence is not valid anymore.