Green’s function for the T-stress near a crack tip is addressed with an analytic function method for a semi-infinite crack lying in an elastical, isotropic, and infinite plate. The cracked plate is loaded by a single...Green’s function for the T-stress near a crack tip is addressed with an analytic function method for a semi-infinite crack lying in an elastical, isotropic, and infinite plate. The cracked plate is loaded by a single inclined concentrated force at an interior point. The complex potentials are obtained based on a superposition principle, which provide the solutions to the plane problems of elasticity. The regular parts of the potentials are extracted in an asymptotic analysis. Based on the regular parts, Green’s function for the T-stress is obtained in a straightforward manner. Furthermore, Green’s functions are derived for a pair of symmetrically and anti-symmetrically concentrated forces by the superimposing method. Then, Green’s function is used to predict the domain-switch-induced T-stress in a ferroelectric double cantilever beam （DCB） test. The T-stress induced by the electromechanical loading is used to judge the stable and unstable crack growth behaviors observed in the test. The prediction results generally agree with the experimental data.展开更多
A method that uses finite element analysis to determine the non-singular stress(T-stress) at a crack tip is proposed in this study.T-stress includes two components:the T_x-stress parallel to the tangent of the crack a...A method that uses finite element analysis to determine the non-singular stress(T-stress) at a crack tip is proposed in this study.T-stress includes two components:the T_x-stress parallel to the tangent of the crack at its tip and the 7Vstress perpendicular to this tangent.The effects of contact and friction on both the T_x-and T_y-stresses on the crack flanks are considered in the method.Because the method uses a single standard elastic finite element analysis derived directly from the equation of the stress fields around the crack tip and does not require any assumptions or simplification,it can be used to determine the T-stress for any given geometry and loading condition.Theoretical results are used to calibrate the results,which exhibited good agreement and to discuss the T-stress computational methodology.Furthermore,the T_x-and T_y-stresses in center-cracked Brazilian disc(CCBD) specimens subjected to diametrical or partially distributed compression were numerically computed,and the effects of contact and friction on the T_x-and T_y-stresses are discussed.展开更多
Several cardiac outcomes have been reported with West Nile-encephalitis;however, the underlying pathophysiology remains complex. We present a 42-year-old female, with multiple sclerosis, whose neurological symptoms an...Several cardiac outcomes have been reported with West Nile-encephalitis;however, the underlying pathophysiology remains complex. We present a 42-year-old female, with multiple sclerosis, whose neurological symptoms and respiratory decline were finally explained by the diagnosis of West Nile-encephalitis. During her admission, the isolated peaked T-waves indicated the underlying stress-induced cardiomyopathy. The absence of all other causes of hyperacute T-waves, their subsequent resolution with the resolution of infection and improvement in wall motion abnormalities, further supported the association. This case highlights the importance of considering hyperacute T-waves in an approach towards the diagnosis of WNV-encephalitis related atypical variant of stress-induced cardiomyopathy.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.10702071 and 11090334)the China Postdoctoral Science Foundation(No.201003281)+2 种基金the Shanghai Postdoctoral Scientific Program(No.10R21415800)the Shanghai Leading Academic Discipline Project(No.B302)sponsored by the"Sino-German Center for Research Promotion"under a project of"Crack Growth in Ferroelectrics Driven by Cyclic Electric Loading"
文摘Green’s function for the T-stress near a crack tip is addressed with an analytic function method for a semi-infinite crack lying in an elastical, isotropic, and infinite plate. The cracked plate is loaded by a single inclined concentrated force at an interior point. The complex potentials are obtained based on a superposition principle, which provide the solutions to the plane problems of elasticity. The regular parts of the potentials are extracted in an asymptotic analysis. Based on the regular parts, Green’s function for the T-stress is obtained in a straightforward manner. Furthermore, Green’s functions are derived for a pair of symmetrically and anti-symmetrically concentrated forces by the superimposing method. Then, Green’s function is used to predict the domain-switch-induced T-stress in a ferroelectric double cantilever beam （DCB） test. The T-stress induced by the electromechanical loading is used to judge the stable and unstable crack growth behaviors observed in the test. The prediction results generally agree with the experimental data.
文摘工程结构在制造工艺过程中或使用期间会产生裂纹,对结构断裂路径的预测和研究是防治工程安全问题发生的重要手段。在考虑裂纹尖端应力场常数项T应力的基础上对传统的最大周向应力准则(Maximum tangential stress criterion,MTS)和最小应变能密度因子准则(Minimum strain energy density criterion,SED)进行修正,采用Python语言对ABAQUS的前、后处理和有限元计算模块进行二次开发,通过计算最优解的粒子群算法(Particle swarm optimization,PSO)将修正后的准则编入裂纹自动扩展程序脚本中。利用上述二次开发程序对初始纯Ⅰ型裂纹的扩展路径进行模拟,结果表明:采用ABAQUS脚本程序模拟结果与相关文献实验结果吻合,表明了程序的有效性,进而实现考虑T应力的多种断裂准则对裂纹扩展路径的预测;当T应力值处于一定范围内时,修正的MTS准则无法预测裂纹发生的偏转现象,扩展路径呈直线,此时可采用修正的SED准则进行预测。
基金supported by the National Basic Research Program of China(Grant No.2014CB047100)the National Natural Science Foundation of China(Grant Nos.51474046,U1562103)the Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology)(Grant No.SKLGP2014K017)
文摘A method that uses finite element analysis to determine the non-singular stress(T-stress) at a crack tip is proposed in this study.T-stress includes two components:the T_x-stress parallel to the tangent of the crack at its tip and the 7Vstress perpendicular to this tangent.The effects of contact and friction on both the T_x-and T_y-stresses on the crack flanks are considered in the method.Because the method uses a single standard elastic finite element analysis derived directly from the equation of the stress fields around the crack tip and does not require any assumptions or simplification,it can be used to determine the T-stress for any given geometry and loading condition.Theoretical results are used to calibrate the results,which exhibited good agreement and to discuss the T-stress computational methodology.Furthermore,the T_x-and T_y-stresses in center-cracked Brazilian disc(CCBD) specimens subjected to diametrical or partially distributed compression were numerically computed,and the effects of contact and friction on the T_x-and T_y-stresses are discussed.
文摘Several cardiac outcomes have been reported with West Nile-encephalitis;however, the underlying pathophysiology remains complex. We present a 42-year-old female, with multiple sclerosis, whose neurological symptoms and respiratory decline were finally explained by the diagnosis of West Nile-encephalitis. During her admission, the isolated peaked T-waves indicated the underlying stress-induced cardiomyopathy. The absence of all other causes of hyperacute T-waves, their subsequent resolution with the resolution of infection and improvement in wall motion abnormalities, further supported the association. This case highlights the importance of considering hyperacute T-waves in an approach towards the diagnosis of WNV-encephalitis related atypical variant of stress-induced cardiomyopathy.
