Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） rods were abraded to different surface roughnesses using different types of waterproof abrasive papers and sometimes polishing pastes, and the compressive deformat...Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） rods were abraded to different surface roughnesses using different types of waterproof abrasive papers and sometimes polishing pastes, and the compressive deformation behavior was examined. The results show that the yield strength of the BMG is hardly affected while the compressive plasticity increases from 2.3% to 4.5% with decreasing the surface roughness. Observation of the fractured samples under a scanning electron microscope indicates that the rise in plasticity is accompanied with an increase in shear band density. The results suggest that it is necessary to reduce the surface roughness of BMGs for achieving a large plasticity.展开更多
Some micromechanics-based constitutive models are presented in this study for porous geomaterials.These micro-macro mechanical models focus on the effect of porosity and the inclusions on the macroscopic elastoplastic...Some micromechanics-based constitutive models are presented in this study for porous geomaterials.These micro-macro mechanical models focus on the effect of porosity and the inclusions on the macroscopic elastoplastic behaviors of porous materials. In order to consider the effect of pores and the compressibility of the matrix, some macroscopic criteria are presented firstly for ductile porous medium having one population of pores with different types of matrix(von Mises, Green type, Misese Schleicher and Druckere Prager). Based on different homogenization techniques, these models are extended to the double porous materials with two populations of pores at different scales and a Druckere Prager solid phase at the microscale. Based on these macroscopic criteria, complete constitutive models are formulated and implemented to describe the overall responses of typical porous geomaterials(sandstone,porous chalk and argillite). Comparisons between the numerical predictions and experimental data with different confining pressures or different mineralogical composites show the capabilities of these micromechanics-based models, which take into account the effects of microstructure on the macroscopic behavior and significantly improve the phenomenological ones.展开更多
Inspired by research into the association between icosahedral local orders and the plasticity of metallic glasses(MGs),beryllium(Be) is added to the icosahedral quasi-crystal forming alloy Zr40Ti40Ni20. In this way, b...Inspired by research into the association between icosahedral local orders and the plasticity of metallic glasses(MGs),beryllium(Be) is added to the icosahedral quasi-crystal forming alloy Zr40Ti40Ni20. In this way, bulk metallic glasses(BMGs) with favorable compressive plasticity are fabricated. Therein, the icosahedral quasi-crystalline phase is the main competing phase of amorphous phases and icosahedral local orders are the main local atomic motifs in amorphous phases.The alloys of(Zr40Ti40Ni20)76Be24and (Zr40Ti40Ni20)72Be28with their greater plastic strain capacity show similar characteristics to highly plastic amorphous systems: The serrated flow of compression curves always follows a near-exponential distribution. The primary and secondary shear bands intersect each other, bifurcate, and bend. Typical vein patterns are densely distributed on the fracture surfaces. The relaxation enthalpy of four MGs is linearly correlated with the plastic strain, that is, the greater the relaxation enthalpy, the larger the plastic strain.展开更多
The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive ...The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.展开更多
A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a...A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.展开更多
In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with differ...In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with different cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64 K·s^(-1) for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and highresolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.展开更多
基金Projects (50771064,50831003) supported by the National Natural Science Foundation of ChinaProject (10PJ1405900) supported by Shanghai Pujiang Program,China
文摘Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） rods were abraded to different surface roughnesses using different types of waterproof abrasive papers and sometimes polishing pastes, and the compressive deformation behavior was examined. The results show that the yield strength of the BMG is hardly affected while the compressive plasticity increases from 2.3% to 4.5% with decreasing the surface roughness. Observation of the fractured samples under a scanning electron microscope indicates that the rise in plasticity is accompanied with an increase in shear band density. The results suggest that it is necessary to reduce the surface roughness of BMGs for achieving a large plasticity.
文摘Some micromechanics-based constitutive models are presented in this study for porous geomaterials.These micro-macro mechanical models focus on the effect of porosity and the inclusions on the macroscopic elastoplastic behaviors of porous materials. In order to consider the effect of pores and the compressibility of the matrix, some macroscopic criteria are presented firstly for ductile porous medium having one population of pores with different types of matrix(von Mises, Green type, Misese Schleicher and Druckere Prager). Based on different homogenization techniques, these models are extended to the double porous materials with two populations of pores at different scales and a Druckere Prager solid phase at the microscale. Based on these macroscopic criteria, complete constitutive models are formulated and implemented to describe the overall responses of typical porous geomaterials(sandstone,porous chalk and argillite). Comparisons between the numerical predictions and experimental data with different confining pressures or different mineralogical composites show the capabilities of these micromechanics-based models, which take into account the effects of microstructure on the macroscopic behavior and significantly improve the phenomenological ones.
基金supported by the National Key R&D Program of China (Grant No. 2018YFA0703602)the National Natural Science Foundation of China (Grant Nos. 51871193, 52271155 and 52271154)+2 种基金the Natural Science Foundation for Excellent Young Scholars of Hebei Province (Grant No. E2021203050)the Hundred Talent Program of Hebei Province (Grant No. E2020050018)the Hebei Province Innovation Ability Promotion Project (Grant No. 22567609H)。
文摘Inspired by research into the association between icosahedral local orders and the plasticity of metallic glasses(MGs),beryllium(Be) is added to the icosahedral quasi-crystal forming alloy Zr40Ti40Ni20. In this way, bulk metallic glasses(BMGs) with favorable compressive plasticity are fabricated. Therein, the icosahedral quasi-crystalline phase is the main competing phase of amorphous phases and icosahedral local orders are the main local atomic motifs in amorphous phases.The alloys of(Zr40Ti40Ni20)76Be24and (Zr40Ti40Ni20)72Be28with their greater plastic strain capacity show similar characteristics to highly plastic amorphous systems: The serrated flow of compression curves always follows a near-exponential distribution. The primary and secondary shear bands intersect each other, bifurcate, and bend. Typical vein patterns are densely distributed on the fracture surfaces. The relaxation enthalpy of four MGs is linearly correlated with the plastic strain, that is, the greater the relaxation enthalpy, the larger the plastic strain.
文摘The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.
基金Project(SWJT11ZT04)supported by the Central College Foundation of ChinaProject(2008g032-A)supported by the Major Projects S&T Foundation of China’s Ministry of Railways,China
文摘A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.
基金supported by the National Natural Science Foundation of China(Grant no.52071278/51827801)the National Key Research and Development Program of China(Grant no.2018YFA0703603)。
文摘In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with different cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64 K·s^(-1) for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and highresolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.
