J_n-积分和裂纹扩展的控制参数

J_n-INTERGRAL AND THE CONTROLLING PARAMETER FOR CRACK GROWTH

Hutchinson和Paris将J-积分作为控制参数应用于裂纹扩展。某些文献还推荐基于J-积分的工程方法。然而,J-积分是否真是基本的控制参数尚需研究。本文的结果表明,J-积分不是,而本文定义的J_n-积分是裂纹扩展的基本控制参数。

The J-integral as a controlling parameter was applied to the crack growing process by Hutchinson and Paris. An engineering approach based on J-integral was proposed by some Ref. However, it is necessary to study whether the J-integral is really a basic controlling parameter. It has been shown from the results given in this paper that J-integral is not basic while the Jn-intergral defined in this paper is a basic controlling parameter for crack growth in elastic -plastic state.In this paper, a method combining experimental observation with elastic-plastic finite element numerical calculation is used to study the feature of J and Jn. It is shown form Equ.(20) that the essential feature of local stress/strain field can be characterized by Jn, but it can be seen from Equ(8) that J-integral includes the energy dissipated in geometry-dependent plastic deformation remote from the advancing crack-tip.Thus , Jn should be the basic parameter controlling crack growth, but J is not basic. Jn-integral may be the most promissing parameter for elastic-plastic fracture.