The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate bas...The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate based model is developed to de-scribe the mechanical behaviour for both unstructured and structured clays under one-dimensional loading.The advantage of the proposed model lies in the determination of model parameters in a straightforward way,which leads to an easy use of the model for practical problems.Coupled with consolidation,the model is used to simulate oedometer tests at constant rate of strain and long-term creep oedometer tests on two structured clays.All comparisons between predicted and measured results demonstrate that the proposed model can reasonably describe the effect of destructuration on the time-dependent behaviour of soft structured clay under one-dimensional condition.Although the model is proposed for one-dimensional analysis,it can be a good base for developing a more general 3D model.展开更多
Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-depend...Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-dependent behavior of concrcte subjected to earthquake loading is examined, emphasizing the properties of concrete under cyclic and biaxial loading conditions. Second, a modified four-parameter Hsieh-Ting-Chen viscoplastic consistency model is developed to simulate the rate-dependent behavior of concrete. The earthquake response of a 278m high arch dam is analyzed, and the results show that the strain-rate effects become noticeable in the inelastic range, Third, a more accurate non-smooth Newton algorithm for the solution of three-dimensional frictional contact problems is developed to study the joint opening effects of arch dams during strong earthquakes. Such effects on two nearly 300m high arch dams have been studied. It was found that the canyon shape has great influence on the magnitude and distribution of the joint opening along the dam axis. Fourth, the scaled boundary finite element method presented by Song and Wolf is employed to study the dam-reservoir-foundation interaction effects of concrete dams. Particular emphases were placed on the variation of foundation stiffness and the anisotropic behavior of the foundation material on the dynamic response of concrete dams. Finally, nonlinear modeling of concrete to study the damage evolution of concrete dams during strong earthquakes is discussed. An elastic-damage mechanics approach for damage prediction of concrete gravity dams is described as an example. These findings are helpful in understanding the dynamic behavior of concrete dams and promoting the improvement of seismic safety assessment methods.展开更多
Material embrittlement is often encountered in machining,heat treatment,hydrogen and lowtemperature conditions among which machining is strain-rate related.More strain-rate evoked embrittlement is expected in material...Material embrittlement is often encountered in machining,heat treatment,hydrogen and lowtemperature conditions among which machining is strain-rate related.More strain-rate evoked embrittlement is expected in material loading processes,such as in high-speed machining and projectile penetration.In order to understand the fundamental mechanisms of the strain-rate evoked material embrittlement,this study is concerned with the material responses to loading at high strain-rates.It then explores the strain-rate evoked material embrittlement and fragmentation during high strain-rate loading processes and evaluates various empirical and physical models from different researchers for the assessment of the material embrittlement.The study proposes strain-rate sensitivity for the characterization of material embrittlement and the concept of the pseudo embrittlement for material responses to very high strain-rates.A discussion section is arranged to explore the underlying mechanisms of the strain-rate evoked material embrittlement and fragmentation based on dislocation kinetics.展开更多
Background：Strain and strain-rate imaging （SRI） have been found clinically useful in the assessment of cardiac systolic and diastolic function as well as providing new insights in deciphering cardiac physiology and...Background：Strain and strain-rate imaging （SRI） have been found clinically useful in the assessment of cardiac systolic and diastolic function as well as providing new insights in deciphering cardiac physiology and mechanics in cardiomyopathies,and identifying early subclinical changes in various pathologies.The aim of this study was to evaluate the regional and global left ventricular （LV） myocardial function in metabolic syndrome （MS） with SRI so that we can provide more myocardial small lesions in patients with MS,which is robust and reliable basis for early detection of LV function.Methods：Thirty-nine adults with MS were enrolled in the study.There was a control group of 39 healthy adults.In addition to classic echocardiographic assessment of LV global functional changes,SRI was used to evaluate regional and global LV function.Including：Peak systolic strain （S）,peak systolic strain-rate （SR-s）,peak diastolic strain-rate （SR-e）.Results：There were no statistically significant differences between MS and controls in all traditional parameters of LV systolic function.On the other hand,significant differences were observed between MS and the control group in most of the parameters of S,SR-s,SR-e in regional LV function.Multiple stepwise regression analyses revealed that S and SR significantly were negatively correlated with blood pressure,waist circumference,fasting plasma glucose,uric acid,suggesting that risk factories were relevant to regional systolic dysfunction.Conclusion：In MS with normal LV ejection fraction,there was regional myocardial dysfunction,risk factors contributed to the impairment of systolic and diastolic function of the regional myocardium.Assessment of myocardial function using SRI could be more accurate in MS patient evaluation than conventional echocardiography alone.展开更多
文摘The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate based model is developed to de-scribe the mechanical behaviour for both unstructured and structured clays under one-dimensional loading.The advantage of the proposed model lies in the determination of model parameters in a straightforward way,which leads to an easy use of the model for practical problems.Coupled with consolidation,the model is used to simulate oedometer tests at constant rate of strain and long-term creep oedometer tests on two structured clays.All comparisons between predicted and measured results demonstrate that the proposed model can reasonably describe the effect of destructuration on the time-dependent behaviour of soft structured clay under one-dimensional condition.Although the model is proposed for one-dimensional analysis,it can be a good base for developing a more general 3D model.
基金National Natural Science Foundation of China Under Grant No.50139010
文摘Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-dependent behavior of concrcte subjected to earthquake loading is examined, emphasizing the properties of concrete under cyclic and biaxial loading conditions. Second, a modified four-parameter Hsieh-Ting-Chen viscoplastic consistency model is developed to simulate the rate-dependent behavior of concrete. The earthquake response of a 278m high arch dam is analyzed, and the results show that the strain-rate effects become noticeable in the inelastic range, Third, a more accurate non-smooth Newton algorithm for the solution of three-dimensional frictional contact problems is developed to study the joint opening effects of arch dams during strong earthquakes. Such effects on two nearly 300m high arch dams have been studied. It was found that the canyon shape has great influence on the magnitude and distribution of the joint opening along the dam axis. Fourth, the scaled boundary finite element method presented by Song and Wolf is employed to study the dam-reservoir-foundation interaction effects of concrete dams. Particular emphases were placed on the variation of foundation stiffness and the anisotropic behavior of the foundation material on the dynamic response of concrete dams. Finally, nonlinear modeling of concrete to study the damage evolution of concrete dams during strong earthquakes is discussed. An elastic-damage mechanics approach for damage prediction of concrete gravity dams is described as an example. These findings are helpful in understanding the dynamic behavior of concrete dams and promoting the improvement of seismic safety assessment methods.
基金The authors would like to acknowledge the supports by the National Natural Science Foundation of China(Grant No.51575084)the Peacock Program of Shenzhen(Grant No.KQJSCX20180322152221965).
文摘Material embrittlement is often encountered in machining,heat treatment,hydrogen and lowtemperature conditions among which machining is strain-rate related.More strain-rate evoked embrittlement is expected in material loading processes,such as in high-speed machining and projectile penetration.In order to understand the fundamental mechanisms of the strain-rate evoked material embrittlement,this study is concerned with the material responses to loading at high strain-rates.It then explores the strain-rate evoked material embrittlement and fragmentation during high strain-rate loading processes and evaluates various empirical and physical models from different researchers for the assessment of the material embrittlement.The study proposes strain-rate sensitivity for the characterization of material embrittlement and the concept of the pseudo embrittlement for material responses to very high strain-rates.A discussion section is arranged to explore the underlying mechanisms of the strain-rate evoked material embrittlement and fragmentation based on dislocation kinetics.
文摘Background：Strain and strain-rate imaging （SRI） have been found clinically useful in the assessment of cardiac systolic and diastolic function as well as providing new insights in deciphering cardiac physiology and mechanics in cardiomyopathies,and identifying early subclinical changes in various pathologies.The aim of this study was to evaluate the regional and global left ventricular （LV） myocardial function in metabolic syndrome （MS） with SRI so that we can provide more myocardial small lesions in patients with MS,which is robust and reliable basis for early detection of LV function.Methods：Thirty-nine adults with MS were enrolled in the study.There was a control group of 39 healthy adults.In addition to classic echocardiographic assessment of LV global functional changes,SRI was used to evaluate regional and global LV function.Including：Peak systolic strain （S）,peak systolic strain-rate （SR-s）,peak diastolic strain-rate （SR-e）.Results：There were no statistically significant differences between MS and controls in all traditional parameters of LV systolic function.On the other hand,significant differences were observed between MS and the control group in most of the parameters of S,SR-s,SR-e in regional LV function.Multiple stepwise regression analyses revealed that S and SR significantly were negatively correlated with blood pressure,waist circumference,fasting plasma glucose,uric acid,suggesting that risk factories were relevant to regional systolic dysfunction.Conclusion：In MS with normal LV ejection fraction,there was regional myocardial dysfunction,risk factors contributed to the impairment of systolic and diastolic function of the regional myocardium.Assessment of myocardial function using SRI could be more accurate in MS patient evaluation than conventional echocardiography alone.
