It is a challenge to suggest a constitutive model for describing the stress-strain behavior of sand-fines mixtures due to that these granular mixtures exhibited very complex behaviors at different densities, pressure...It is a challenge to suggest a constitutive model for describing the stress-strain behavior of sand-fines mixtures due to that these granular mixtures exhibited very complex behaviors at different densities, pressures and fines contents. In this study, an elastoplastic constitutive model within the framework of the bounding surface plasticity and critical state theories was proposed for sand-nonplastic-fines mixtures by using the concept of the equivalent-skeleton void ratio and equivalent-skeleton void-ratio state index. The proposed model with a set of material constants calibrated from a few tests could be used to model the fines-dependent and state-dependent behaviors of the sand-nonplastic-fines mixture including the strain- softening and volumetric-expansion behaviors in the drained triaxial compression tests, and also the effects of fines content on the critical state lines in both the deviatoric stress versus mean effective stress and the void ratio versus mean effective stress planes.展开更多
The particle breakage during specimen shearing has a significant influence on the critical-state line (CSL) of the rockfill material. A series of large-scale triaxial compression tests on the rockfill material from He...The particle breakage during specimen shearing has a significant influence on the critical-state line (CSL) of the rockfill material. A series of large-scale triaxial compression tests on the rockfill material from Henan Province (HPR) were conducted in a wide range of initial void ratios and confining pressures. The influences of the particle breakage on the critical-state stress ratio Mc, the peak stress ratio Mp and dilatancy stress ratio Md were investigated. The deviatoric stress and particle breakage of the HPR at the critical state increase with the increase in confining pressure, while the influences of the initial void ratio on these behaviors are too little to be considered. The gradient of the CSL in the q-p space of the rockfilL Mc, was found to be passively correlated with the particle breakage index rather than being a constant. Additionally, the observed values of Mc at low confining pressures (low particle breakage occur) will be substantially undervalued if Mc is estimated as a constant. In the critical-state-theorybased constitutive models, Mp and Md are estimated as the combinations of Mc and state parameter 0. It is believed that the simulations of Mp and Md when Mc is correlated with Br are obviously more favorable than those when Mc is constant.展开更多
The magnetization of Gd diffused YBa2Cu3O7-x is measured by a vibrating sample magnetometer （VSM） at selected temperatures （5, 25, 50, 77 K）. The experimental results for the magnetization are analyzed in the crit...The magnetization of Gd diffused YBa2Cu3O7-x is measured by a vibrating sample magnetometer （VSM） at selected temperatures （5, 25, 50, 77 K）. The experimental results for the magnetization are analyzed in the critical state framework involving Kim-Anderson field dependence Jc（H）=Jc0/（1＋｜H｜/H0）n of critical current density and equilibrium magnetization M eq . It is found that the inclusion of the equilibrium magnetization becomes more important at higher temperatures. At 77 K, the shape of the isothermal M-H hysteresis curve is governed by the equilibrium magnetization. Some superconducting parameters are determined by fitting the calculated curves to the experimental data.展开更多
In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reprod...In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.展开更多
In this paper we study a nonlinear Maxwell＇s system in a highly conductive medium in which the displacement current is neglected. The magnetic field H satisfies a quasilinear evolution system： Ht＋△↓×[r（x,t,...In this paper we study a nonlinear Maxwell＇s system in a highly conductive medium in which the displacement current is neglected. The magnetic field H satisfies a quasilinear evolution system： Ht＋△↓×[r（x,t,｜H｜,｜△↓×H｜）△↓×H]=F（x,t,H）,where the resistivity r is assumed to depend upon the strengths of electric and magnetic fields while the internal magnetic current F depends upon the magnetic field. It is shown that under appropriate structure conditions for r and F the above nonlinear system subject to appropriate initial-boundary conditions has a unique global solution.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 51509024 and 51678094)the Fundamental Research Funds for the Central Universities (Grant No. 106112015CDJXY200008)the Project funded by China Postdoctoral Science Foundation (Grant No. 2016M590864)
文摘It is a challenge to suggest a constitutive model for describing the stress-strain behavior of sand-fines mixtures due to that these granular mixtures exhibited very complex behaviors at different densities, pressures and fines contents. In this study, an elastoplastic constitutive model within the framework of the bounding surface plasticity and critical state theories was proposed for sand-nonplastic-fines mixtures by using the concept of the equivalent-skeleton void ratio and equivalent-skeleton void-ratio state index. The proposed model with a set of material constants calibrated from a few tests could be used to model the fines-dependent and state-dependent behaviors of the sand-nonplastic-fines mixture including the strain- softening and volumetric-expansion behaviors in the drained triaxial compression tests, and also the effects of fines content on the critical state lines in both the deviatoric stress versus mean effective stress and the void ratio versus mean effective stress planes.
文摘The particle breakage during specimen shearing has a significant influence on the critical-state line (CSL) of the rockfill material. A series of large-scale triaxial compression tests on the rockfill material from Henan Province (HPR) were conducted in a wide range of initial void ratios and confining pressures. The influences of the particle breakage on the critical-state stress ratio Mc, the peak stress ratio Mp and dilatancy stress ratio Md were investigated. The deviatoric stress and particle breakage of the HPR at the critical state increase with the increase in confining pressure, while the influences of the initial void ratio on these behaviors are too little to be considered. The gradient of the CSL in the q-p space of the rockfilL Mc, was found to be passively correlated with the particle breakage index rather than being a constant. Additionally, the observed values of Mc at low confining pressures (low particle breakage occur) will be substantially undervalued if Mc is estimated as a constant. In the critical-state-theorybased constitutive models, Mp and Md are estimated as the combinations of Mc and state parameter 0. It is believed that the simulations of Mp and Md when Mc is correlated with Br are obviously more favorable than those when Mc is constant.
文摘The magnetization of Gd diffused YBa2Cu3O7-x is measured by a vibrating sample magnetometer （VSM） at selected temperatures （5, 25, 50, 77 K）. The experimental results for the magnetization are analyzed in the critical state framework involving Kim-Anderson field dependence Jc（H）=Jc0/（1＋｜H｜/H0）n of critical current density and equilibrium magnetization M eq . It is found that the inclusion of the equilibrium magnetization becomes more important at higher temperatures. At 77 K, the shape of the isothermal M-H hysteresis curve is governed by the equilibrium magnetization. Some superconducting parameters are determined by fitting the calculated curves to the experimental data.
文摘In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.
文摘In this paper we study a nonlinear Maxwell＇s system in a highly conductive medium in which the displacement current is neglected. The magnetic field H satisfies a quasilinear evolution system： Ht＋△↓×[r（x,t,｜H｜,｜△↓×H｜）△↓×H]=F（x,t,H）,where the resistivity r is assumed to depend upon the strengths of electric and magnetic fields while the internal magnetic current F depends upon the magnetic field. It is shown that under appropriate structure conditions for r and F the above nonlinear system subject to appropriate initial-boundary conditions has a unique global solution.
