Issue 53

Y. Lu et alii, Frattura ed Integrità Strutturale, 53 (2020) 325-336; DOI: 10.3221/IGF-ESIS.53.25 325 A new approach of CMT seam welding deformation forecasting based on GA-BPNN Yao Lu, Yanfeng Xing*, Xuexing Li, Sha Xu School of Mechanical and Automotive Engineering, Shanghai University of Engineering Science, China edison.lu@foxmail.com, smsmsues@163.com, megres.li@foxmail.com, xytongxing376@sina.com A BSTRACT . Welding deformation affects the quality of the welded parts. In this paper, by introducing improved back propagation neural network (BPNN), a cold metal transfer (CMT) welding deformation prediction model for aluminum-steel hybrid sheets is established. Before applying BPNN, important parameters affecting welding deformation were obtained by orthogonal test and gray relational grade theory. The accuracy of welding deformation prediction of BPNN is improved by genetic algorithm. The results show that compared with the prediction method based on traditional theory, the deformation prediction model based on GA-BPNN has higher accuracy. Predicted results were applied to the aluminum-steel CMT seam welding in the form of inverse deformation, and the deformation of the welded plate was significantly improved. K EYWORDS . Cold metal transfer welding; Orthogonal test; Gray relational grade theory; BP neural network; Genetic algorithm. Citation: Yao, Lu., Yanfeng, Xing., Xuexing, Li., Sha, Xu., A new approach of CMT seam welding deformation forecasting based on GA-BPNN, Frattura ed Integrità Strutturale, 53 (2020) 325-336. Received: 11.01.2020 Accepted: 18.05.2020 Published: 01.07.2020 Copyright: © 2020 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION luminum alloy has the advantages of light weight, strong corrosion resistance and good durability. Therefore, the replacement of the traditional steel structure by the aluminum-steel hybrid structure is an effective means to realize the lightweight of the automobile. Aluminum-steel hybrid sheet with traditional joining method has poor mechanical properties, so in recent years, new metal sheet joining technologies such as cold metal transfer welding [1], self-piercing riveting [2], and friction stir welding [3] have received increasing attention and application. CMT technology has the advantages of low heat input and no spatter transition. The basic principle of the CMT process is a short circuit transition. Each time the short circuit occurs, the welding wire is mechanically retracted, which assists the droplet to detach at relatively low welding currents, and thus the welding heat input can be significantly reduced. Therefore, the CMT process is suitable for the welding of thin gage aluminum alloys with corresponding low distortion and high quality. There is no splash in the welding process, and the weld seam is beautifully formed [4]. Due to the large difference in material properties such as linear expansion coefficient and thermal conductivity of aluminum and steel, welding deformation occurs in the aluminum alloy CMT welding process, which affects the A