**Jie Yang \* and Lei Wang**

School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; wl\_21th@126.com

**\*** Correspondence: yangjie@usst.edu.cn; Tel.: +86-21-5527-2320

Received: 30 November 2018; Accepted: 24 December 2018; Published: 25 December 2018

**Abstract:** Material constraints are important factor effects on the fracture behavior of welded joints. The effect range of the material constraint is an important and interesting issue which needs to be clarified, including whether the effect range of a material constraint exists or not, who will affect it, and whether the material constraint is affected by the no adjacent area or not. In this study, different basic models which reflect different single metallic welded joints, bimetallic welded joints and dissimilar metal welded joints were designed, and the fracture resistance curves and crack tip strain fields of the different models with various material constraints were calculated. Based on the results, the questions above were answered. This study has significance for developing solid mechanics, optimizing joint design, structure integrity assessment, and so on.

**Keywords:** material constraint; effect range; fracture resistance curve; strain field; center crack
