The Experts below are selected from a list of 3840 Experts worldwide ranked by ideXlab platform

Oana Cazacu - One of the best experts on this subject based on the ideXlab platform.

  • The effect of tension-Compression Asymmetry on the formation of dynamic necking instabilities under plane strain stretching
    International Journal of Plasticity, 2020
    Co-Authors: K.e. N’souglo, J.a. Rodríguez-martínez, Oana Cazacu
    Abstract:

    Abstract This paper brings to light the effect of tension-Compression Asymmetry in flow stresses on the formation of dynamic necking instabilities in isotropic metallic plates subjected to plane strain stretching. For that purpose, a two-pronged approach which includes finite element calculations and linear stability analysis has been used. In both approaches, for the description of the plastic behavior the isotropic form of Cazacu et al. (2006) criterion and isotropic hardening was assumed. It is shown that although this criterion involves dependence of the third-invariant of the stress deviator, it is possible to develop a linear stability analysis and obtain the value of the growth rate of the perturbation at different loading times, and track the history of the growth rate of all the growing modes during the post-critical deformation process. Furthermore, an original procedure for calibration of linear stability analysis from finite element calculations was developed. Both linear stability analysis and finite element results indicate an important effect of the tension-Compression Asymmetry on the necking behavior and the same overall trends. In particular, the results show that while the necking time, and thus the specimen elongation when necking occurs, is roughly the same irrespective of the tension-Compression Asymmetry ratio, the necking strain and the necking energy are significantly greater for a material that displays a larger flow stress in uniaxial Compression than in uniaxial tension. A key outcome of this investigation is to demonstrate that such behavior is due to the larger plastic dissipation undergone, under plane strain stretching, by such a material as compared to a von Mises material and a material with larger flow stress in uniaxial tension than in uniaxial Compression.

  • combined effects of anisotropy and tension Compression Asymmetry on the torsional response of az31 mg
    International Journal of Solids and Structures, 2015
    Co-Authors: Nitin Chandola, Oana Cazacu, Ricardo A. Lebensohn, Raja K. Mishra, Benoit Revilbaudard, Frédéric Barlat
    Abstract:

    Abstract In this paper it is demonstrated that only by accounting for the combined effects of anisotropy and tension–Compression Asymmetry at polycrystal level, it is possible to explain and accurately predict the room-temperature torsional response of a strongly textured AZ31 Mg material. This is shown by using two modeling frameworks, namely: a viscoplastic self-consistent (VPSC) polycrystal model, and a macroscopic plasticity model based on an yield criterion, developed by Cazacu et al. (2006) , that accounts for both orthotropy and tension–Compression Asymmetry in plastic flow. It is shown that unlike Hill’s (1948) criterion, the latter macroscopic criterion quantitatively predicts the experimental results, namely: that the sample with axial direction along the rolling direction contracts, while the sample with axial direction along the normal direction elongates. Moreover, it is demonstrated that these experimentally observed axial strain effects can be quantitatively predicted with the VPSC polycrystal model, only if both slip and twinning are considered operational at single crystal level. On the other hand, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the axial strains predicted by VPSC are very close with that predicted with Hill (1948) criterion, which largely underestimates the measured axial strain in the rolling direction, and predicts zero axial strain in the normal direction.

  • correlation between swift effects and tension Compression Asymmetry in various polycrystalline materials
    Journal of The Mechanics and Physics of Solids, 2014
    Co-Authors: Benoit Revilbaudard, Oana Cazacu, Nitin Chandola, Frédéric Barlat
    Abstract:

    Abstract The Swift phenomenon, which refers to the occurrence of permanent axial deformation during monotonic free-end torsion, has been known for a very long time. While plastic anisotropy is considered to be its main cause, there is no explanation as to why in certain materials irreversible elongation occurs while in others permanent shortening is observed. In this paper, a correlation between Swift effects and the stress–strain behavior in uniaxial tension and Compression is established. It is based on an elastic–plastic model that accounts for the combined influence of anisotropy and tension–Compression Asymmetry. It is shown that, if for a given orientation the uniaxial yield stress in tension is larger than that in Compression, the specimen will shorten when twisted about that direction; however, if the yield stress in uniaxial Compression is larger than that in uniaxial tension, axial elongation will occur. Furthermore, it is shown that on the basis of a few simple mechanical tests it is possible to predict the particularities of the plastic response in torsion for both isotropic and initially anisotropic materials. Unlike other previous interpretations of the Swift effects, which were mainly based on crystal plasticity and/or texture evolution, it is explained the occurrence of Swift effects at small to moderate plastic strains. In particular, the very good quantitative agreement between model and data for a strongly anisotropic AZ31–Mg alloy confirm the correlation established in this work between tension–Compression Asymmetry and Swift effects. Furthermore, it is explained why the sign of the axial plastic strains that develop depends on the twisting direction.

  • Combined effects of anisotropy and tension-Compression Asymmetry on the torsional response of AZ31 Mg
    arXiv: Materials Science, 2014
    Co-Authors: Nitin Chandola, Oana Cazacu, Ricardo A. Lebensohn, Benoit Revil-baudard, Raja K. Mishra, Frédéric Barlat
    Abstract:

    In this paper it is demonstrated that only by accounting for the combined effects of anisotropy and tension-Compression Asymmetry both at single crystal and polycrystal levels, it is possible to explain and accurately predict the peculiarities of the room-temperature torsional response of a strongly textured AZ31 Mg material. This is shown by using two modeling frameworks, namely: the viscoplastic self-consistent (VPSC) polycrystal model that accounts for tension-Compression Asymmetry of the mechanical response of a polycrystalline aggregate due to the occurrence of twinning at single crystal level, and an anisotropic plasticity model based on an orthotropic yield criterion that accounts for tension-Compression Asymmetry in plastic flow at macroscopic level, developed by Cazacu et al. (2006). It is shown that unlike Hill's (1948), the latter macroscopic criterion quantitatively predicts the experimental results, namely: that the sample with axial direction along the rolling direction contracts, while the sample with axial direction along the normal direction elongates. Moreover, it is demonstrated that these experimentally observed axial effects in torsion can be also quantitatively predicted with the VPSC polycrystal model only if both slip and twinning are considered active at single crystal level. On the other hand, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the predicted axial strains are very close with that obtained with Hill (1948) criterion, which largely underestimate the measured axial strains.

  • Correlation between swift effects and tension–Compression Asymmetry in various polycrystalline materials
    Journal of the Mechanics and Physics of Solids, 2014
    Co-Authors: Benoit Revil-baudard, Oana Cazacu, Nitin Chandola, Frédéric Barlat
    Abstract:

    Abstract The Swift phenomenon, which refers to the occurrence of permanent axial deformation during monotonic free-end torsion, has been known for a very long time. While plastic anisotropy is considered to be its main cause, there is no explanation as to why in certain materials irreversible elongation occurs while in others permanent shortening is observed. In this paper, a correlation between Swift effects and the stress–strain behavior in uniaxial tension and Compression is established. It is based on an elastic–plastic model that accounts for the combined influence of anisotropy and tension–Compression Asymmetry. It is shown that, if for a given orientation the uniaxial yield stress in tension is larger than that in Compression, the specimen will shorten when twisted about that direction; however, if the yield stress in uniaxial Compression is larger than that in uniaxial tension, axial elongation will occur. Furthermore, it is shown that on the basis of a few simple mechanical tests it is possible to predict the particularities of the plastic response in torsion for both isotropic and initially anisotropic materials. Unlike other previous interpretations of the Swift effects, which were mainly based on crystal plasticity and/or texture evolution, it is explained the occurrence of Swift effects at small to moderate plastic strains. In particular, the very good quantitative agreement between model and data for a strongly anisotropic AZ31–Mg alloy confirm the correlation established in this work between tension–Compression Asymmetry and Swift effects. Furthermore, it is explained why the sign of the axial plastic strains that develop depends on the twisting direction.

W.w. Milligan - One of the best experts on this subject based on the ideXlab platform.

  • strength and tension Compression Asymmetry in nanostructured and ultrafine grain metals
    Acta Materialia, 2003
    Co-Authors: S. Cheng, J.a. Spencer, W.w. Milligan
    Abstract:

    Abstract The recent literature is reviewed with respect to the strength-limiting deformation mechanisms in nanocrystalline and ultrafine-grain metals. Based on these results, a deformation mechanism map is proposed for FCC metals with ultrafine-grain sizes. In the absence of flaw-controlled brittle fracture, it is concluded that the strength-limiting mechanism in metals with grain sizes between approximately 10 and 500–1000 nm is dislocation emission from grain boundary sources. A simple model for the strength in this regime of grain sizes is developed from classical dislocation theory, based on the bow-out of a dislocation from a grain boundary dislocation source. The model predicts not only the strength as a function of grain size, but also the observed tension/Compression Asymmetry of the yield strength. The tension/Compression Asymmetry arises from the pressure dependence of the dislocation self-energy during bow-out. The pressure dependence is a function of material and grain size, consistent with experimental observations. Finally, the model provides a physical basis for a pressure-dependent yield criterion.

  • Strength and tension/Compression Asymmetry in nanostructured and ultrafine-grain metals
    Acta Materialia, 2003
    Co-Authors: S. Cheng, J.a. Spencer, W.w. Milligan
    Abstract:

    Abstract The recent literature is reviewed with respect to the strength-limiting deformation mechanisms in nanocrystalline and ultrafine-grain metals. Based on these results, a deformation mechanism map is proposed for FCC metals with ultrafine-grain sizes. In the absence of flaw-controlled brittle fracture, it is concluded that the strength-limiting mechanism in metals with grain sizes between approximately 10 and 500–1000 nm is dislocation emission from grain boundary sources. A simple model for the strength in this regime of grain sizes is developed from classical dislocation theory, based on the bow-out of a dislocation from a grain boundary dislocation source. The model predicts not only the strength as a function of grain size, but also the observed tension/Compression Asymmetry of the yield strength. The tension/Compression Asymmetry arises from the pressure dependence of the dislocation self-energy during bow-out. The pressure dependence is a function of material and grain size, consistent with experimental observations. Finally, the model provides a physical basis for a pressure-dependent yield criterion.

Xi-qiao Feng - One of the best experts on this subject based on the ideXlab platform.

  • effects of tension Compression Asymmetry on the surface wrinkling of film substrate systems
    Journal of The Mechanics and Physics of Solids, 2016
    Co-Authors: Xiao Huang, Wei Hong, Yanping Cao, Xi-qiao Feng
    Abstract:

    Abstract Many soft materials and biological tissues are featured with the tension–Compression Asymmetry of constitutive relations. The surface wrinkling of a stiff thin film lying on a compliant substrate is investigated through theoretical analysis and numerical simulations. It is found that the tension–Compression Asymmetry of the soft substrate not only affects the critical strain of buckling but, more importantly, may also influence the wrinkling pattern that occurs in the film–substrate system under specified loading conditions. Due to this mechanism, the thin film subjected to equi-biaxial Compression may first buckle into a hexagonal array of dimples or bulges, instead of the checkerboard pattern, and consequently evolve into labyrinths with further loading. Under non-equi-biaxial Compression, the system may buckle either into a parallel bead-chain pattern or a stripe pattern, depending on the substrate nonlinearity and the loading biaxiality. Phase diagrams are established for the wrinkling patterns in a wide range of geometric and mechanical parameters, which facilitate the design of surface patterns with desired properties and functions.

  • Effects of tension–Compression Asymmetry on the surface wrinkling of film–substrate systems
    Journal of the Mechanics and Physics of Solids, 2016
    Co-Authors: Xiao Huang, Wei Hong, Yanping Cao, Xi-qiao Feng
    Abstract:

    Abstract Many soft materials and biological tissues are featured with the tension–Compression Asymmetry of constitutive relations. The surface wrinkling of a stiff thin film lying on a compliant substrate is investigated through theoretical analysis and numerical simulations. It is found that the tension–Compression Asymmetry of the soft substrate not only affects the critical strain of buckling but, more importantly, may also influence the wrinkling pattern that occurs in the film–substrate system under specified loading conditions. Due to this mechanism, the thin film subjected to equi-biaxial Compression may first buckle into a hexagonal array of dimples or bulges, instead of the checkerboard pattern, and consequently evolve into labyrinths with further loading. Under non-equi-biaxial Compression, the system may buckle either into a parallel bead-chain pattern or a stripe pattern, depending on the substrate nonlinearity and the loading biaxiality. Phase diagrams are established for the wrinkling patterns in a wide range of geometric and mechanical parameters, which facilitate the design of surface patterns with desired properties and functions.

Frédéric Barlat - One of the best experts on this subject based on the ideXlab platform.

  • combined effects of anisotropy and tension Compression Asymmetry on the torsional response of az31 mg
    International Journal of Solids and Structures, 2015
    Co-Authors: Nitin Chandola, Oana Cazacu, Ricardo A. Lebensohn, Raja K. Mishra, Benoit Revilbaudard, Frédéric Barlat
    Abstract:

    Abstract In this paper it is demonstrated that only by accounting for the combined effects of anisotropy and tension–Compression Asymmetry at polycrystal level, it is possible to explain and accurately predict the room-temperature torsional response of a strongly textured AZ31 Mg material. This is shown by using two modeling frameworks, namely: a viscoplastic self-consistent (VPSC) polycrystal model, and a macroscopic plasticity model based on an yield criterion, developed by Cazacu et al. (2006) , that accounts for both orthotropy and tension–Compression Asymmetry in plastic flow. It is shown that unlike Hill’s (1948) criterion, the latter macroscopic criterion quantitatively predicts the experimental results, namely: that the sample with axial direction along the rolling direction contracts, while the sample with axial direction along the normal direction elongates. Moreover, it is demonstrated that these experimentally observed axial strain effects can be quantitatively predicted with the VPSC polycrystal model, only if both slip and twinning are considered operational at single crystal level. On the other hand, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the axial strains predicted by VPSC are very close with that predicted with Hill (1948) criterion, which largely underestimates the measured axial strain in the rolling direction, and predicts zero axial strain in the normal direction.

  • correlation between swift effects and tension Compression Asymmetry in various polycrystalline materials
    Journal of The Mechanics and Physics of Solids, 2014
    Co-Authors: Benoit Revilbaudard, Oana Cazacu, Nitin Chandola, Frédéric Barlat
    Abstract:

    Abstract The Swift phenomenon, which refers to the occurrence of permanent axial deformation during monotonic free-end torsion, has been known for a very long time. While plastic anisotropy is considered to be its main cause, there is no explanation as to why in certain materials irreversible elongation occurs while in others permanent shortening is observed. In this paper, a correlation between Swift effects and the stress–strain behavior in uniaxial tension and Compression is established. It is based on an elastic–plastic model that accounts for the combined influence of anisotropy and tension–Compression Asymmetry. It is shown that, if for a given orientation the uniaxial yield stress in tension is larger than that in Compression, the specimen will shorten when twisted about that direction; however, if the yield stress in uniaxial Compression is larger than that in uniaxial tension, axial elongation will occur. Furthermore, it is shown that on the basis of a few simple mechanical tests it is possible to predict the particularities of the plastic response in torsion for both isotropic and initially anisotropic materials. Unlike other previous interpretations of the Swift effects, which were mainly based on crystal plasticity and/or texture evolution, it is explained the occurrence of Swift effects at small to moderate plastic strains. In particular, the very good quantitative agreement between model and data for a strongly anisotropic AZ31–Mg alloy confirm the correlation established in this work between tension–Compression Asymmetry and Swift effects. Furthermore, it is explained why the sign of the axial plastic strains that develop depends on the twisting direction.

  • Combined effects of anisotropy and tension-Compression Asymmetry on the torsional response of AZ31 Mg
    arXiv: Materials Science, 2014
    Co-Authors: Nitin Chandola, Oana Cazacu, Ricardo A. Lebensohn, Benoit Revil-baudard, Raja K. Mishra, Frédéric Barlat
    Abstract:

    In this paper it is demonstrated that only by accounting for the combined effects of anisotropy and tension-Compression Asymmetry both at single crystal and polycrystal levels, it is possible to explain and accurately predict the peculiarities of the room-temperature torsional response of a strongly textured AZ31 Mg material. This is shown by using two modeling frameworks, namely: the viscoplastic self-consistent (VPSC) polycrystal model that accounts for tension-Compression Asymmetry of the mechanical response of a polycrystalline aggregate due to the occurrence of twinning at single crystal level, and an anisotropic plasticity model based on an orthotropic yield criterion that accounts for tension-Compression Asymmetry in plastic flow at macroscopic level, developed by Cazacu et al. (2006). It is shown that unlike Hill's (1948), the latter macroscopic criterion quantitatively predicts the experimental results, namely: that the sample with axial direction along the rolling direction contracts, while the sample with axial direction along the normal direction elongates. Moreover, it is demonstrated that these experimentally observed axial effects in torsion can be also quantitatively predicted with the VPSC polycrystal model only if both slip and twinning are considered active at single crystal level. On the other hand, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the predicted axial strains are very close with that obtained with Hill (1948) criterion, which largely underestimate the measured axial strains.

  • Correlation between swift effects and tension–Compression Asymmetry in various polycrystalline materials
    Journal of the Mechanics and Physics of Solids, 2014
    Co-Authors: Benoit Revil-baudard, Oana Cazacu, Nitin Chandola, Frédéric Barlat
    Abstract:

    Abstract The Swift phenomenon, which refers to the occurrence of permanent axial deformation during monotonic free-end torsion, has been known for a very long time. While plastic anisotropy is considered to be its main cause, there is no explanation as to why in certain materials irreversible elongation occurs while in others permanent shortening is observed. In this paper, a correlation between Swift effects and the stress–strain behavior in uniaxial tension and Compression is established. It is based on an elastic–plastic model that accounts for the combined influence of anisotropy and tension–Compression Asymmetry. It is shown that, if for a given orientation the uniaxial yield stress in tension is larger than that in Compression, the specimen will shorten when twisted about that direction; however, if the yield stress in uniaxial Compression is larger than that in uniaxial tension, axial elongation will occur. Furthermore, it is shown that on the basis of a few simple mechanical tests it is possible to predict the particularities of the plastic response in torsion for both isotropic and initially anisotropic materials. Unlike other previous interpretations of the Swift effects, which were mainly based on crystal plasticity and/or texture evolution, it is explained the occurrence of Swift effects at small to moderate plastic strains. In particular, the very good quantitative agreement between model and data for a strongly anisotropic AZ31–Mg alloy confirm the correlation established in this work between tension–Compression Asymmetry and Swift effects. Furthermore, it is explained why the sign of the axial plastic strains that develop depends on the twisting direction.

S. Cheng - One of the best experts on this subject based on the ideXlab platform.

  • strength and tension Compression Asymmetry in nanostructured and ultrafine grain metals
    Acta Materialia, 2003
    Co-Authors: S. Cheng, J.a. Spencer, W.w. Milligan
    Abstract:

    Abstract The recent literature is reviewed with respect to the strength-limiting deformation mechanisms in nanocrystalline and ultrafine-grain metals. Based on these results, a deformation mechanism map is proposed for FCC metals with ultrafine-grain sizes. In the absence of flaw-controlled brittle fracture, it is concluded that the strength-limiting mechanism in metals with grain sizes between approximately 10 and 500–1000 nm is dislocation emission from grain boundary sources. A simple model for the strength in this regime of grain sizes is developed from classical dislocation theory, based on the bow-out of a dislocation from a grain boundary dislocation source. The model predicts not only the strength as a function of grain size, but also the observed tension/Compression Asymmetry of the yield strength. The tension/Compression Asymmetry arises from the pressure dependence of the dislocation self-energy during bow-out. The pressure dependence is a function of material and grain size, consistent with experimental observations. Finally, the model provides a physical basis for a pressure-dependent yield criterion.

  • Strength and tension/Compression Asymmetry in nanostructured and ultrafine-grain metals
    Acta Materialia, 2003
    Co-Authors: S. Cheng, J.a. Spencer, W.w. Milligan
    Abstract:

    Abstract The recent literature is reviewed with respect to the strength-limiting deformation mechanisms in nanocrystalline and ultrafine-grain metals. Based on these results, a deformation mechanism map is proposed for FCC metals with ultrafine-grain sizes. In the absence of flaw-controlled brittle fracture, it is concluded that the strength-limiting mechanism in metals with grain sizes between approximately 10 and 500–1000 nm is dislocation emission from grain boundary sources. A simple model for the strength in this regime of grain sizes is developed from classical dislocation theory, based on the bow-out of a dislocation from a grain boundary dislocation source. The model predicts not only the strength as a function of grain size, but also the observed tension/Compression Asymmetry of the yield strength. The tension/Compression Asymmetry arises from the pressure dependence of the dislocation self-energy during bow-out. The pressure dependence is a function of material and grain size, consistent with experimental observations. Finally, the model provides a physical basis for a pressure-dependent yield criterion.