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Studies on Path Independent Integrals in Nonlinear Dynamic Fracture Mechanics

非线性动态断裂力学中路径无关积分的研究

基本信息

批准号：
60550072
负责人：
NISHIOKA Toshihisa
金额：
$ 1.15万
依托单位：
Kobe University of Mercantile Marine
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550072/
关键词：
Dynamic fracture Mechanics Path Independent Integral <T^*> Integral J'Integral Nonlinear Fracture Mechanics Process Zone Finite Element Simulation Brittle Fracture 脆性破壊延性不安定破壊

项目摘要

Recently we have derived a path independent integral <T^*> which may give a unified theoretical background for linear (elastic) and nonlinear (elastoplastic) dynamic fracture mechanics. In this respect it is very important to find the relations between <T^*> integral and fracture process zone which exists in the vicinity of the crack-tip. In this research project, the invariance of <T^*> integral with respect to the shape of process zone was analytically and numerically verified.First, for an elastodynamically propagating crack, only the <T^*> integral (or equivalently J' integral which has the physical meaning of energy release rate) gives an invariant integral calue regardless of the shape of infinitesimal process zone. Other types of path independent integrals which are not equivalent to the energy release rate, depend on the shape of process zone. Furthermore, in the results of finite element simulation, it was found that the <T^*> integral closely relates with the energy flow into … More the process zone.For the finite element simulation of dynamic crack propagation, a comparison was made on stationary mesh procedure with various nodal release mechanisms and a simple moving mesh procedure. For elastic problems the stress intensity fractures were evaluated by the path independent J'integral. For simple moving mesh procedure is better suited for the simulation of elastodynamic crack propagation although difficulties were observed in the application of moving mesh procedure to elastoplastic dynamic crack propagation. Among the model release schemes, the linear relaxation scheme gives best results for elastodynamic as well as elastoplastic dynamic crack propagation.For cracks subject to various impact stress waves, the behavior of <T^*> integral was also investigated. In the case of a step-type stress wave loading, <T^*> integral varies linearly with time variation for any constitutive models including linear-elastic, elastic -viscoplastic and rate-independent elastoplastic cases. As the fluidity parameter of material increases, the time-slope of <T^*> integral becomes smaller and approaches to the rate-independent plastic behaviorIt was also found that the experimental measurement of <T^*> integral can be done by measuring the area under the load versus crack-opening displacement curve in an compact tension specimen. Less

最近我们导出了一个与路径无关的积分<T^*>，它可以为线性（弹性）和非线性（弹塑性）动态断裂力学提供一个统一的理论背景。在这方面，找到<T^*>积分与裂纹尖端附近断裂过程区的关系是非常重要的。本研究从解析和数值两方面验证了<T^*>积分对过程区形状的不变性：首先，对于弹性动力学扩展裂纹，只有<T^*>积分（或等价的J'积分，它具有能量释放率的物理意义）给出一个与无穷小过程区形状无关的不变积分值;其他类型的路径无关积分不等价于能量释放率，取决于过程区的形状。此外，在有限元模拟的结果中，发现<T^*>积分与能量流入密切相关， ...更多信息在裂纹动态扩展的有限元模拟中，对采用不同节点释放机制的静态网格方法和简单的动网格方法进行了比较。对于弹性问题，应力强度断裂由路径无关的J '积分评估。对于简单的移动网格程序是更适合于模拟弹塑性动态裂纹扩展，虽然观察到的困难，在弹塑性动态裂纹扩展的移动网格程序的应用。在模型释放方案中，线性松弛方案对弹塑性动态裂纹扩展的模拟效果最好，同时对不同冲击应力波作用下裂纹的<T^*>积分特性进行了研究.在阶跃应力波作用下，对于任何本构模型，包括线弹性、弹粘塑性和率无关弹塑性，<T^*>积分都随时间线性变化。随着材料流动性参数的增大，<T^*>积分的时间斜率变小，接近于与率无关的塑性行为。同时发现，<T^*>积分的实验测量可以通过测量紧凑拉伸试样的载荷-裂纹张开位移曲线下的面积来实现。少