以核电安全端异种金属焊接接头(DMWJ)为研究对象,选用含中心裂纹三点弯曲(SENB)试样,分别在试样左右两面、上下两面、前后两面、左右上下前后六面施加不同载荷以在裂尖产生不同的应力,通过restart方法,将该应力作为残余应力引入SENB试样,系统研究考虑残余应力时不同拘束下DMWJ的断裂行为及残余应力与拘束效应的交互作用。结果表明：残余应力的变化对不同拘束下DMWJ的断裂行为有很大的影响。与低拘束试样相比,高拘束试样的J-R曲线对残余应力的变化更加敏感,这主要与裂尖的Mises应力和三向应力有关。残余应力对不同拘束下DMWJ J-R曲线的影响也与残余应力的方向相关。

In nuclear power pressure vessels, dissimilar metal welded joints (DMWJs) are the weak link owing to their highly heterogeneous microstructure, mechanical, thermal, and fracture properties; and some defects that occur at different positions within the DMWJs. To ensure the safety of nuclear power pressure vessels, it is important to examine the fracture behavior of DMWJ in detail. In addition to residual stress, constraint is an important factor affecting the fracture behavior of DMWJ. To understand this behavior, both constraint and residual stress must be considered. In this work, taking nuclear safety and DMWJ as the research objects, three-point bending (SENB) specimens with a central crack were selected. Different loads were applied to different sides of the specimen to produce different stresses at the crack tip, such as left and right, up and down, front and back, and both six sides, and the stresses were introduced into the SENB specimen as the residual stress by restart method. The fracture behavior of DMWJ was then systematically studied under various constraints considering residual stresses and the interaction between residual stress and constraint. The results showed that the change in residual stress significantly influenced the fracture behavior of DMWJ under different constraints. In contrast to the DMWJ with low constraint, the J-R curve of the DMWJ with high constraint was more sensitive to the change in residual stress. The main cause was the Mises stress at the crack tip and the triaxial stress. The direction of residual stress also influenced the J-R curve.