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
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
Deformation of two-dimensional red blood cell in linear shear flow is simulated using the immersed boundary method,in which the cell is modeled as a force source instead of a real body.The effect of three constitutive...Deformation of two-dimensional red blood cell in linear shear flow is simulated using the immersed boundary method,in which the cell is modeled as a force source instead of a real body.The effect of three constitutive laws,i.e.Hookean,Neo-Hookean and Skalak elasticity,on the deformation is studied by simulating the cell movement in two linear shear flows.The results show that the effect of the constitutive laws gets more obvious as the shear rate increases.Both the aspect ratio and the inclination of the steady shapes get bigger, and the differences between the periods of the cell tank-treading motion become larger.For the same shear flow, the period with Hookean elasticity is less than the period with Neo-Hookean elasticity and bigger than the period with Skalak elasticity.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.
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.
基金the National Natural Science Foundation of China(No.10472070)the Shanghai Leading Academic Discipline Project(No.B206)
文摘Deformation of two-dimensional red blood cell in linear shear flow is simulated using the immersed boundary method,in which the cell is modeled as a force source instead of a real body.The effect of three constitutive laws,i.e.Hookean,Neo-Hookean and Skalak elasticity,on the deformation is studied by simulating the cell movement in two linear shear flows.The results show that the effect of the constitutive laws gets more obvious as the shear rate increases.Both the aspect ratio and the inclination of the steady shapes get bigger, and the differences between the periods of the cell tank-treading motion become larger.For the same shear flow, the period with Hookean elasticity is less than the period with Neo-Hookean elasticity and bigger than the period with Skalak elasticity.
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.
