The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xiao Ping Zhou - One of the best experts on this subject based on the ideXlab platform.
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micromechanical modelling of the Complete Stress strain relationship for crack weakened rock subjected to compressive loading
Rock Mechanics and Rock Engineering, 2008Co-Authors: Xiao Ping Zhou, Yunhuai Zhang, Keshan ZhuAbstract:A micromechanics-based model, able to quantify the effect of various parameters on the Complete Stress–strain relationship, is described. The closed-form explicit expression for the Complete Stress–strain relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The Complete Stress–strain relationship including the stages of linear elasticity, non-linear hardening and strain softening is established. The results show that the Complete Stress–strain relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the Complete Stress–strain relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the Complete Stress–strain relationship seem to be in good agreement with the measured values.
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localization of deformation and Stress strain relation for mesoscopic heterogeneous brittle rock materials under unloading
Theoretical and Applied Fracture Mechanics, 2005Co-Authors: Xiao Ping ZhouAbstract:Abstract Stress redistribution induced by excavation of underground engineering and slope engineering results in the unloading zone in parts of surrounding rock masses. The mechanical behaviors of crack-weakened rock masses under unloading are different from those of crack-weakened rock masses under loading. A micromechanics-based model has been proposed for brittle rock material undergoing irreversible changes of their microscopic structures due to microcrack growth when axial Stress is held constant while lateral confinement is reduced. The basic idea of the present model is to classify the constitution relation of rock material into four stages including some of the stages of linear elasticity, pre-peak nonlinear hardening, rapid Stress drop, and strain softening, and to investigate their corresponding micromechanical damage mechanisms individually. Special attention is paid to the transition from structure rearrangements on microscale to the macroscopic inelastic strain, to the transition from distribution damage to localization of damage and the transition from homogeneous deformation to localization of deformation. The closed-form explicit expression for the Complete Stress–strain relation of rock materials containing cracks under unloading is obtained. The results show that the Complete Stress–strain relation and the strength of rock materials under unloading depend on the crack spacing, the fracture toughness of rock materials, orientation of the cracks, the crack half-length and the crack density parameter.
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analysis of the localization of deformation and the Complete Stress strain relation for mesoscopic heterogeneous brittle rock under dynamic uniaxial tensile loading
International Journal of Solids and Structures, 2004Co-Authors: Xiao Ping ZhouAbstract:Abstract Stress redistribution induced by excavation results in the tensile zone in parts of the surrounding rock mass. It is significant to analyze the localization of deformation and damage, and to study the Complete Stress–strain relation for mesoscopic heterogeneous rock under dynamic uniaxial tensile loading. On the basis of micromechanics, the Complete Stress–strain relation including linear elasticity, nonlinear hardening, rapid Stress drop and strain softening is obtained. The behaviors of rapid Stress drop and strain softening are due to localization of deformation and damage. The constitutive model, which analyze localization of deformation and damage, is distinct from the conventional model. Theoretical predictions have shown to consistent with the experimental results.
Christopher Roberts - One of the best experts on this subject based on the ideXlab platform.
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Complete Stress induced depolarization of relaxor ferroelectric crystals without transition through a non polar phase
Applied Physics Letters, 2018Co-Authors: Sergey I Shkuratov, Shujun Zhang, Jason Baird, Vladimir G Antipov, Wesley S Hackenberger, Jun Luo, Christopher S Lynch, Jay B Chase, Christopher RobertsAbstract:The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for Complete Stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultra...
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Complete Stress induced depolarization of relaxor ferroelectric crystals without transition through a non polar phase
Applied Physics Letters, 2018Co-Authors: Sergey I Shkuratov, Shujun Zhang, Jason Baird, Vladimir G Antipov, Wesley S Hackenberger, Jun Luo, Christopher S Lynch, Jay B Chase, Christopher RobertsAbstract:The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for Complete Stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.
P J Withers - One of the best experts on this subject based on the ideXlab platform.
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eigenstrain modelling of residual Stress generated by arrays of laser shock peening shots and determination of the Complete Stress field using limited strain measurements
Surface & Coatings Technology, 2013Co-Authors: Mithila Achintha, David Nowell, K Shapiro, P J WithersAbstract:Abstract This paper presents a hybrid explicit finite element (FE)/eigenstrain model for predicting the residual Stress generated by arrays of adjacent/overlapping laser shock peening (LSP) shots where the use of a Completely explicit FE analysis may be impractical. It shows that for a given material, the underlying eigenstrain distribution (in contrast to the resulting Stress field) representing a laser shock peen is primarily dependent on the parameters of the laser pulse and the number of overlays rather than the precise component geometry. Consequently the residual Stress introduced by complex laser peening treatments can be built up by using static FE models and superposition of individual eigenstrain distributions without recourse to further computationally demanding explicit FE analyses. It is found that beneath a small LSP array the magnitude of the compressive residual Stress is higher than for a wider array of LSP shots and that with increasing numbers of layers the compressive Stress increases as does the depth of the compressive zone. The model predictions for the eigenstrain distributions are compared well with experimental measurements of plastic strain (full-width-at-half-maximum) obtained by neutron diffraction. The eigenstrain method is also extended to construct the full residual Stress field using measured residual elastic strains at a finite number of measurement locations in a component.
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eigenstrain modelling of residual Stress generated by arrays of laser shock peening shots and determination of the Complete Stress field using limited strain measurements
Surface & Coatings Technology, 2013Co-Authors: Mithila Achintha, David Nowell, K Shapiro, P J WithersAbstract:Abstract This paper presents a hybrid explicit finite element (FE)/eigenstrain model for predicting the residual Stress generated by arrays of adjacent/overlapping laser shock peening (LSP) shots where the use of a Completely explicit FE analysis may be impractical. It shows that for a given material, the underlying eigenstrain distribution (in contrast to the resulting Stress field) representing a laser shock peen is primarily dependent on the parameters of the laser pulse and the number of overlays rather than the precise component geometry. Consequently the residual Stress introduced by complex laser peening treatments can be built up by using static FE models and superposition of individual eigenstrain distributions without recourse to further computationally demanding explicit FE analyses. It is found that beneath a small LSP array the magnitude of the compressive residual Stress is higher than for a wider array of LSP shots and that with increasing numbers of layers the compressive Stress increases as does the depth of the compressive zone. The model predictions for the eigenstrain distributions are compared well with experimental measurements of plastic strain (full-width-at-half-maximum) obtained by neutron diffraction. The eigenstrain method is also extended to construct the full residual Stress field using measured residual elastic strains at a finite number of measurement locations in a component.
Sergey I Shkuratov - One of the best experts on this subject based on the ideXlab platform.
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Complete Stress induced depolarization of relaxor ferroelectric crystals without transition through a non polar phase
Applied Physics Letters, 2018Co-Authors: Sergey I Shkuratov, Shujun Zhang, Jason Baird, Vladimir G Antipov, Wesley S Hackenberger, Jun Luo, Christopher S Lynch, Jay B Chase, Christopher RobertsAbstract:The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for Complete Stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultra...
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Complete Stress induced depolarization of relaxor ferroelectric crystals without transition through a non polar phase
Applied Physics Letters, 2018Co-Authors: Sergey I Shkuratov, Shujun Zhang, Jason Baird, Vladimir G Antipov, Wesley S Hackenberger, Jun Luo, Christopher S Lynch, Jay B Chase, Christopher RobertsAbstract:The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the Stress-induced depolarization and the associated charge released. A Complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The Complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a Stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for Complete Stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.
Mithila Achintha - One of the best experts on this subject based on the ideXlab platform.
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eigenstrain modelling of residual Stress generated by arrays of laser shock peening shots and determination of the Complete Stress field using limited strain measurements
Surface & Coatings Technology, 2013Co-Authors: Mithila Achintha, David Nowell, K Shapiro, P J WithersAbstract:Abstract This paper presents a hybrid explicit finite element (FE)/eigenstrain model for predicting the residual Stress generated by arrays of adjacent/overlapping laser shock peening (LSP) shots where the use of a Completely explicit FE analysis may be impractical. It shows that for a given material, the underlying eigenstrain distribution (in contrast to the resulting Stress field) representing a laser shock peen is primarily dependent on the parameters of the laser pulse and the number of overlays rather than the precise component geometry. Consequently the residual Stress introduced by complex laser peening treatments can be built up by using static FE models and superposition of individual eigenstrain distributions without recourse to further computationally demanding explicit FE analyses. It is found that beneath a small LSP array the magnitude of the compressive residual Stress is higher than for a wider array of LSP shots and that with increasing numbers of layers the compressive Stress increases as does the depth of the compressive zone. The model predictions for the eigenstrain distributions are compared well with experimental measurements of plastic strain (full-width-at-half-maximum) obtained by neutron diffraction. The eigenstrain method is also extended to construct the full residual Stress field using measured residual elastic strains at a finite number of measurement locations in a component.
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eigenstrain modelling of residual Stress generated by arrays of laser shock peening shots and determination of the Complete Stress field using limited strain measurements
Surface & Coatings Technology, 2013Co-Authors: Mithila Achintha, David Nowell, K Shapiro, P J WithersAbstract:Abstract This paper presents a hybrid explicit finite element (FE)/eigenstrain model for predicting the residual Stress generated by arrays of adjacent/overlapping laser shock peening (LSP) shots where the use of a Completely explicit FE analysis may be impractical. It shows that for a given material, the underlying eigenstrain distribution (in contrast to the resulting Stress field) representing a laser shock peen is primarily dependent on the parameters of the laser pulse and the number of overlays rather than the precise component geometry. Consequently the residual Stress introduced by complex laser peening treatments can be built up by using static FE models and superposition of individual eigenstrain distributions without recourse to further computationally demanding explicit FE analyses. It is found that beneath a small LSP array the magnitude of the compressive residual Stress is higher than for a wider array of LSP shots and that with increasing numbers of layers the compressive Stress increases as does the depth of the compressive zone. The model predictions for the eigenstrain distributions are compared well with experimental measurements of plastic strain (full-width-at-half-maximum) obtained by neutron diffraction. The eigenstrain method is also extended to construct the full residual Stress field using measured residual elastic strains at a finite number of measurement locations in a component.