Research Article Cracking Driving Force at the Tip of SCC under Heterogeneous Material Mechanics Model of Safe-End Dissimilar Metal-Welded Joints in PWR Yuman Sun , 1 HeXue , 1 Kuan Zhao , 1 Yubiao Zhang, 1 Youjun Zhao, 1 Weiming Yan, 1 and Rehmat Bashir 1,2 1 School of Mechanical Engineering, Xi’an University of Science & Technology, Xi’an 710054, China 2 Department of Mechanical Engineering, University of Engineering and Technology, Lahore 54890, Pakistan Correspondence should be addressed to Yuman Sun; 19205201061@stu.xust.edu.cn and He Xue; xuehe@xust.edu.cn Received 21 September 2021; Accepted 29 December 2021; Published 13 January 2022 Academic Editor: Klaudio Bari Copyright © 2022 Yuman Sun et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e complicated driving force at the stress corrosion cracking (SCC) tip of the safe-end dissimilar metal-welded joints (DMWJs) in the pressurized water reactor (PWR) is mainly caused by the heterogeneous material mechanical properties. In this research, to accurately evaluate the crack driving force at the SCC in DMWJs, the stress-strain condition, stress triaxiality, and J-integral of the crack tip at different positions are analyzed based on the heterogeneous material properties model. e results indicate that the larger driving force will be provided for the I-type crack when the crack is in the SA508 zone and the interface between the 316L region and base metal. In addition, the heterogeneous material properties inhibit the J-integral of the crack in the 316L region, which has a promoting effect when the crack is in the SA508 zone and weld metal. It provides a new idea for analyzing driving force at the crack tip and safety evaluation of DMWJs in PWRs. 1.Introduction e welded structure of the primary circuit of the pres- surized water reactors (PWR) works under irradiations, high temperature, high pressure, and corrosion environments. e austenitic stainless steel and nickel-based alloy with excellent high-temperature mechanical properties and corrosion resistance have been widely used for structural welding materials in nuclear power plant’s (NPP) primary circuits [1–4]. Previous research and practices have shown that corrosion resistance is mainly due to the formation of chromium-rich oxide film on the metal surface. However, the environment-assisted cracking (EAC) is represented by stress corrosion cracking (SCC) in high-temperature and high-pressure water environments produced by the local oxide film rupture with mechanical and material synergy [5–8]. e schematic diagram of the SCC in the welded joint at the safe-end of the primary circuit of the PWR is displayed in Figure 1. Accurate measurement of the mechanical properties of the welded joint in the safe-end of the in-service nuclear power equipment is an effective means to ensure its safe operation. Several studies have demonstrated that the mi- crostructure and mechanical properties in the heat-affected zone (HAZ) and fusion zone (FZ) of the DMWJ are com- plicatedly distributed [9–13]. On this basis, the heteroge- neous mechanical properties of the DMWJs in PWRs will cause the complexity of the driving force at the crack tip. Several studies have attempted to evaluate the local material mechanical proprieties of the safe-end DMWJ. Some scholars [14, 15] have obtained the mechanical proprieties of the Alloy52M DMWJ in the PWR by the microhardness test or minisized tensile test. e experiment illustrates the acute change in the strength (yield strength and tensile strength) at the interface between the materials. At the same time, some researchers have proposed that the driving force at the crack tip of welded structures can be analyzed by the stress tri- axiality and plastic strain condition around the crack tip Hindawi Science and Technology of Nuclear Installations Volume 2022, Article ID 6605101, 10 pages https://doi.org/10.1155/2022/6605101