裂尖大变形条件下的约束研究

The Study of the Constraint Effect under Large Scale Yield at Crack Tip

通过对面内应力比T_x和离面约束T_x在塑性区分布规律的深入分析,发现约束在塑性区不同区域的影响是不同的,在裂尖的钝化区,面内应力比T_x起重要作用,而在钝化区外的塑性区内,离面约束T_x起主要作用;在J-Q理论的基础上引入离面约束T_z可以很好地描述钝化区以外的应力应变分布,在钝化区内引入面内应力比T_x可以对裂尖前方的应力应变进行大变形分析和描述。研究表明综合两个约束的共同作用,可以很好地描述大变形条件下裂尖前方的应力分布。

The effects of two parameters, the in-plane stress ratio Tx and the out-of-plane constraint T, were carefully studied by means of the finite element method. In the blunt zone, the influence of in-plane stress ratio is stronger than that of the out-of-plane constraint; while out of the blunt zone, the out-of-plane constraint is more important. Based on the J-Q theory and the influence of out-of-plane constraint, the stress and strain fields in the out of blunt zone can be predicted very well. However the blunt effect must be prescribed using the in-plane stress ratio. In a word, the stress and strain distributions at whole plastic zone are strongly affected by these two parameters under large scale yield condition.