【作者】 杨大鹏；

【导师】 赵耀；

【作者基本信息】 华中科技大学 ， 船舶与海洋结构物设计制造， 2007， 博士

【摘要】 本文从理论上比较精确地研究了弯曲延伸裂纹尖端塑性区域边界上正应力和剪应力的分布状况。综合考虑了静态作用应力,塑性区域边界上的正应力和剪应力,利用二阶摄动方法,研究分析了弯曲延伸裂纹尖端塑性区域的范围。利用二阶摄动方法与卡氏定理比较精确地计算了弹塑性弯曲延伸裂纹尖端的张开位移。以弯曲延伸裂纹尖端塑性区域的边界曲线为积分回路,求解了弹塑性弯曲延伸裂纹尖端的J积分。本文利用二阶摄动方法分析研究了疲劳载荷作用下弯曲延伸裂纹尖端应力强度因子的变化幅度,进一步得到了疲劳载荷作用下弯曲延伸裂纹尖端应力强度因子变化幅值的近似表达式。以匹配渐进扩张的形式考虑了远场区域边界条件的效果,研究了弯曲延伸裂纹尖端附近的渐进应力场。利用Irwin公式计算出由于裂纹发展而引起的应变能释放率变化幅值。研究了在具有非均匀断裂韧度的物质中裂纹的弯曲延伸。考虑了疲劳载荷、残余应力、以及由于焊接而引起的物质衰变等因素,利用了二阶摄动方法预测了沿着焊接点传播的线弹性裂纹路径。本文从理论上比较精确地研究了疲劳载荷作用下弯曲延伸裂纹尖端塑性区域边界上的交变正应力和交变剪应力的分布状况。综合考虑了疲劳作用应力,塑性区域交变正应力和交变剪应力,利用二阶摄动方法,研究分析了疲劳载荷作用下弯曲延伸裂纹尖端塑性区域的范围。利用二阶摄动方法与卡氏定理计算了疲劳载荷作用下弯曲延伸裂纹尖端张开位移的最大值及变化幅值。以弯曲延伸裂纹尖端塑性区域的边界曲线为积分回路,求解了疲劳载荷作用下弹塑性弯曲延伸裂纹尖端J积分的最大值与变化幅值。本文利用二阶摄动方法研究计算了轻微弯曲延伸裂纹尖端动态应力强度因子,进一步得到了在动态载荷作用下弯曲延伸裂纹尖端动态应力强度因子的近似表达式。以匹配渐进扩张的形式考虑了远区域动态边界条件的效果,研究了弯曲延伸裂纹尖端附近的动态渐进应力场。利用Irwin公式计算出由于弯曲延伸裂纹扩展而产生的动态应变能释放率。预测了动态载荷作用下,在具有非均匀断裂韧度的物质中裂纹的弯曲延伸扩展。全面考虑了远场动态载荷、残余应力、以及由于焊接而引起的物质衰变等因素,利用二阶摄动方法预测了动载荷作用下沿着焊接点传播的线弹性裂纹路径。利用二阶摄动方法研究了动态载荷作用下的工程结构中线弹性裂纹弯曲延伸问题。本文理论上比较精确地研究了动载荷作用下弯曲延伸裂纹尖端塑性区域的范围和塑性区域边界上的动态正应力和动态剪应力的分布状况。综合考虑了动态作用应力,塑性区域边界上的动态正应力和动态剪应力,利用二阶摄动方法与卡氏定理精确地推导出动载荷作用下弹塑性弯曲延伸裂纹尖端张开位移关于时间变化的函数表达式;以弯曲延伸裂纹尖端塑性区域的边界曲线为积分回路,研究了动载荷作用下弹塑性弯曲延伸裂纹尖端动态J积分。更多还原

【Abstract】 In this article, the distributing state of normal and shear stresses on the boundaries of plasticity area of curved extension crack tip has been worked over theoretically and accurately. Plasticity area at the tip of the curved extension crack has been studied and analyzed. Elasticity-plasticity curved extension crack tip opening displacement are calculated as a practical application of the second order perturbation method、theorem of surname KA. Elasticity-plasticity curved extension crack tip J integral are calculated making use of the boundary curve of splinter strip plasticity area of original curved extension crack tip as an integral loop,where the effects of static applied stresses,normal and shear stresses on the boundaries of plasticity area of curved extension crack tip are taken into considerations.Amplitude of stress intensity factors is analyzed for a slightly curved crack by using a second order perturbation method. This method is extended to obtain an approximate representation of the amplitude of stress intensity factors at the tip of slightly curved extension crack under cyclic loading. Having examined the near tip asymptotic stress field,effects of the remote boundary conditions are taken into account in the sense of a matched asymptotic expansion. Amplitude of an energy release rate due to the crack growth can be calculated by using Irwin’s formula. Prediction of crack extension in materials with inhomogeneous fracture toughness is considered. Paths of brittle crack propagation along a welded joint are predicted as an application of the method, where the effects of cyclic loading, residual stresses, and material deterioration due to welding are considered.In this article, the distributing state of cyclic normal stresses and cyclic shear stresses on the boundaries of plasticity area at fatigue curved extension crack tip has been worked over theoretically and accurately. Plasticity area at the tip of fatigue curved extension crack has been studied and analyzed. Maximum and amplitude of fatigue curved extension crack tip opening displacement are calculated as a practical application of the second order perturbation method、theorem of surname KA. Maximum and amplitude of fatigue curved extension crack tip J integral are calculated using the boundary curve of plasticity area of original curved extension crack tip as an integral loop,where the effects of cyclic applied stresses, cyclic normal stresses and cyclic shear stresses on the boundaries of plasticity area at fatigue curved extension crack tip are taken into considerations.Dynamic stress intensity factors are analyzed for slightly curved extension crack by means of a second order perturbation method. The method is extended to obtain an approximate representation of dynamic stress intensity factors at the tip of slightly curved extension crack. Having examined the near tip asymptotic stress field,the effects of far field boundary conditions are taken into account in the sense of a matched asymptotic expansion. An dynamic energy release rate due to curved extension crack growth can be calculated by using Irwin’s formula. Considerations are made for growth of curved extension crack in materials with inhomogeneous fracture toughness. Paths of brittle cracks propagating along a welded joint are predicted as a practical application of the present method, where the effects of dynamic applied stresses, residual stresses, and material deterioration due to welding are taken into considerations.In this article, plasticity area at the tip of curved extension crack tip and the distributing state of dynamic normal stresses and dynamic shear stresses on the boundaries of it has been worked over theoretically and accurately. Function expression concerning time of elasticity-plasticity curved extension crack tip opening displacement under dynamic loads are deduced as a practical application of the second order perturbation method、theorem of surname KA;Dynamic J integral of elasticity-plasticity curved extension crack tip under dynamic loads are studied using the boundary curve of plasticity area of original curved extension crack tip as an integral loop,where the effects of dynamic applied stresses,dynamic normal stresses and dynamic shear stresses on the boundaries of plasticity area of curved extension crack tip are taken into considerations.更多还原