Deep rock mass possesses some unusual properties due to high earth stress,which further result in new problems that have not been well understood and explained up to date.In order to investigate the deformation mechan...Deep rock mass possesses some unusual properties due to high earth stress,which further result in new problems that have not been well understood and explained up to date.In order to investigate the deformation mechanism,the complete deformation process of deep rock mass,with a great emphasis on local shear deformation stage,was analyzed in detail.The quasi continuous shear deformation of the deep rock mass is described by a combination of smooth functions:the averaged distribution of the original deformation field,and the local discontinuities along the slip lines.Hence,an elasto-plastic model is established for the shear deformation process,in which the rotational displacement is taken into account as well as the translational component.Numerical analysis method was developed for case study.Deformation process of a tunnel under high earth stress was investigated for verification.展开更多
The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties...The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties and constant rate creep properties, almost have no accelerated creep properties. The exponential type empirical formula is selected to fit creep grading curves by polynomial regression analysis method, and the square sums of the fitting results residual are in the order of 10^(-7). Then grade creep curves at every shear loads are set up. Combining creep rate-time curve, the creep properties of limestone are analyzed. As the physical meaning of component model is clearer, the Poytin–Thomson model is set up. Through the least square method, the optimal parameters of Poytin–Thomson model are obtained,and the sums of squared residuals belong to 10^(-3)order of magnitude, which can meet the accuracy requirements of engineering calculation. So the Poytin–Thomson model can reflect the shear creep characteristics of limestone very well.展开更多
An efficient and accurate analytical model for piezoelectric bimorph based on the improved first-order shear deformation theory （FSDT） is developed in this work. The model combines the equivalent single-layer approa...An efficient and accurate analytical model for piezoelectric bimorph based on the improved first-order shear deformation theory （FSDT） is developed in this work. The model combines the equivalent single-layer approach for mechanical displacements and a layerwise-type modelling of the electric potential. Particular attention is devoted to the boundary conditions on the outside faces and to the interface continuity conditions of the bimorphs for the electromechanical variables. Shear correction factor （k） is introduced to modilfy both the shear stress and the electric displacement of each layer. And the detailed mathematical derivations are presented. Free vibration problem of simply supported piezoelectric bimorphs with series or parallel arrangement is investigated for the closed circuit condition, and the results for different length-to-thickness ratios are compared with those obtained from the exact 2D solution. Excellent agreements between the present model prediction with k=-8/9 and the exact solutions are observed for the resonant frequencies.展开更多
The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to...The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to describe the stress deformation characteristics of plastic structural plane and brittle structural plane.The relation of stress and strain to the failure mode of structural plane considering the effect of its shape was investigated,and a model which could reflect the relation between undulate angle and shear strength was built.The result indicates that structural plane presents nonlinear characteristics,specifically,the value of undulate angle,as well as corresponding shear strength,becomes larger as the normal stress decreases.展开更多
Constitutive models aimed at predicting the mechanical response of lead-core bearing devices for passive seismic isolation are discussed in this paper. The study is focused on single-degree-of-freedom models which pro...Constitutive models aimed at predicting the mechanical response of lead-core bearing devices for passive seismic isolation are discussed in this paper. The study is focused on single-degree-of-freedom models which provide a relation between the shear displacement （shear strain） and the shear force （shear stress） in elastomeric and lad-core rubber bearings. Classical Bouc-Wen model along with a numerical procedure for identification of the model constants is described. Alternatively, a constitutive relation introducing a damage variable aimed at assessing the material degradation is also considered.展开更多
将材料热、动力学与中试试验相结合,针对商用淬火配分(Q&P,Quenching and Partitioning)钢的贝氏体进行优化设计。基于试验膨胀数据建立Bohemen切变模型,充分考虑淬火配分工艺下过时效等温阶段的组织演变复杂性,特别是回火阶段马氏...将材料热、动力学与中试试验相结合,针对商用淬火配分(Q&P,Quenching and Partitioning)钢的贝氏体进行优化设计。基于试验膨胀数据建立Bohemen切变模型,充分考虑淬火配分工艺下过时效等温阶段的组织演变复杂性,特别是回火阶段马氏体中碳化物析出特性以及对膨胀结果的影响,通过合理化数据对Bohemen模型进行修订,建立等温贝氏体相变动力学模型,实现贝氏体相变的精准预测。结合修订的Bohemen模型计算结果分析淬火配分钢中贝氏体/马氏体交互作用对残余奥氏体保留及稳定性的影响。结果显示,低淬火温度下马氏体板条间的残余奥氏体含量高,占据变形过程中的主导地位;反之,高淬火温度下贝氏体中的残余奥氏体含量高。由此形成基于材料计算下淬火配分钢的贝氏体优化设计。展开更多
A dynamic hysteretic constitutive model for soil dynamics, Ramberg-Osgood model, is introduced and improved in the paper. Since the model is inherently 1D and is assumed to apply to shear components only, other compon...A dynamic hysteretic constitutive model for soil dynamics, Ramberg-Osgood model, is introduced and improved in the paper. Since the model is inherently 1D and is assumed to apply to shear components only, other components of the deviatorie stress and strain and their relations in 3D case could not be fully described. Two parameters, the equivalent shear stress and the equivalent shear strain, are defined to reasonably establish relations between each of stress and strain components respectively. The constitutive equations of the initial Ramberg-Osgood model are extended to generalize the theory into multidimensional cases. Difficulties of the definition of load reversal in 3D are also addressed and solved. The improved constitutive model for soil dynamics is verified by comparisons with different soil dynamic testing data covering both sands and clays. Results show that the dynamic nonlinear hysteretie behaviors of soils can be well predicted with the improved constitutive model.展开更多
基金Project(50825403) supported by the National Science Fund for Distinguished Young ScholarsProject(2010CB732003) supported by the National Key Basic Research Program of ChinaProject(51021001) supported by the Science Fund for Creative Research Group of the National Natural Science Foundation of China
文摘Deep rock mass possesses some unusual properties due to high earth stress,which further result in new problems that have not been well understood and explained up to date.In order to investigate the deformation mechanism,the complete deformation process of deep rock mass,with a great emphasis on local shear deformation stage,was analyzed in detail.The quasi continuous shear deformation of the deep rock mass is described by a combination of smooth functions:the averaged distribution of the original deformation field,and the local discontinuities along the slip lines.Hence,an elasto-plastic model is established for the shear deformation process,in which the rotational displacement is taken into account as well as the translational component.Numerical analysis method was developed for case study.Deformation process of a tunnel under high earth stress was investigated for verification.
基金funded by the State Key Development Program for Basic Research of China(No.2013CB227900)the Joint Funds of the National Natural Science Foundation of China(NoU1261201)Prof.Mao Xianbiao for his valuable assistance in the preparation of manuscript
文摘The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties and constant rate creep properties, almost have no accelerated creep properties. The exponential type empirical formula is selected to fit creep grading curves by polynomial regression analysis method, and the square sums of the fitting results residual are in the order of 10^(-7). Then grade creep curves at every shear loads are set up. Combining creep rate-time curve, the creep properties of limestone are analyzed. As the physical meaning of component model is clearer, the Poytin–Thomson model is set up. Through the least square method, the optimal parameters of Poytin–Thomson model are obtained,and the sums of squared residuals belong to 10^(-3)order of magnitude, which can meet the accuracy requirements of engineering calculation. So the Poytin–Thomson model can reflect the shear creep characteristics of limestone very well.
基金Project (Nos. 10472102 and 10372089) supported by the NationalNatural Science Foundation of China
文摘An efficient and accurate analytical model for piezoelectric bimorph based on the improved first-order shear deformation theory （FSDT） is developed in this work. The model combines the equivalent single-layer approach for mechanical displacements and a layerwise-type modelling of the electric potential. Particular attention is devoted to the boundary conditions on the outside faces and to the interface continuity conditions of the bimorphs for the electromechanical variables. Shear correction factor （k） is introduced to modilfy both the shear stress and the electric displacement of each layer. And the detailed mathematical derivations are presented. Free vibration problem of simply supported piezoelectric bimorphs with series or parallel arrangement is investigated for the closed circuit condition, and the results for different length-to-thickness ratios are compared with those obtained from the exact 2D solution. Excellent agreements between the present model prediction with k=-8/9 and the exact solutions are observed for the resonant frequencies.
基金Project(50878212) supported by National Natural Science Foundation of ChinaProject(1298011-2) supported by the Funding of Scientific Research and Technology Development Projects of Guangxi Province,China+2 种基金Project(12JJ6052) supported by Natural Science Foundation of Hunan Province,ChinaProject(kfj120402) supported Open Fund of Key Laboratory of Special Environment Road Engineering of Hunan Province(Changsha University of Science&Technology),ChinaProject(13C1010) supported by the Research Foundation of Education Bureau of Hunan Province,China
文摘The original descriptive model of shear stress and shear displacement only reflects the stress deformation characteristics of plastic structural plane.The index model was revised and piecewise index model was built to describe the stress deformation characteristics of plastic structural plane and brittle structural plane.The relation of stress and strain to the failure mode of structural plane considering the effect of its shape was investigated,and a model which could reflect the relation between undulate angle and shear strength was built.The result indicates that structural plane presents nonlinear characteristics,specifically,the value of undulate angle,as well as corresponding shear strength,becomes larger as the normal stress decreases.
文摘Constitutive models aimed at predicting the mechanical response of lead-core bearing devices for passive seismic isolation are discussed in this paper. The study is focused on single-degree-of-freedom models which provide a relation between the shear displacement （shear strain） and the shear force （shear stress） in elastomeric and lad-core rubber bearings. Classical Bouc-Wen model along with a numerical procedure for identification of the model constants is described. Alternatively, a constitutive relation introducing a damage variable aimed at assessing the material degradation is also considered.
文摘将材料热、动力学与中试试验相结合,针对商用淬火配分(Q&P,Quenching and Partitioning)钢的贝氏体进行优化设计。基于试验膨胀数据建立Bohemen切变模型,充分考虑淬火配分工艺下过时效等温阶段的组织演变复杂性,特别是回火阶段马氏体中碳化物析出特性以及对膨胀结果的影响,通过合理化数据对Bohemen模型进行修订,建立等温贝氏体相变动力学模型,实现贝氏体相变的精准预测。结合修订的Bohemen模型计算结果分析淬火配分钢中贝氏体/马氏体交互作用对残余奥氏体保留及稳定性的影响。结果显示,低淬火温度下马氏体板条间的残余奥氏体含量高,占据变形过程中的主导地位;反之,高淬火温度下贝氏体中的残余奥氏体含量高。由此形成基于材料计算下淬火配分钢的贝氏体优化设计。
基金the National Natural Science Foundation of China(No.51208296)the National Key Technology R&D Program(Nos.2011BAG07B01 and 2012BAK24B00)the National Basic Research Program(973)of China(No.2011CB013600)
文摘A dynamic hysteretic constitutive model for soil dynamics, Ramberg-Osgood model, is introduced and improved in the paper. Since the model is inherently 1D and is assumed to apply to shear components only, other components of the deviatorie stress and strain and their relations in 3D case could not be fully described. Two parameters, the equivalent shear stress and the equivalent shear strain, are defined to reasonably establish relations between each of stress and strain components respectively. The constitutive equations of the initial Ramberg-Osgood model are extended to generalize the theory into multidimensional cases. Difficulties of the definition of load reversal in 3D are also addressed and solved. The improved constitutive model for soil dynamics is verified by comparisons with different soil dynamic testing data covering both sands and clays. Results show that the dynamic nonlinear hysteretie behaviors of soils can be well predicted with the improved constitutive model.
