Numerical Simulation of Residual Stresses in Multipass Gas Metal Arc-Welded Joints of Thick Aluminum Alloy Plates

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Numerical Simulation of Residual Stresses in Multipass Gas Metal Arc-Welded Joints of Thick Aluminum Alloy Plates Fengyuan Shu, Lei Wu, Yuxin Liu, Yaohui Lv, Ting Wang, Gang Chen, Fujia Xu, and Binshi Xu (Submitted August 24, 2018; in revised form February 15, 2019; published online June 18, 2019) Numerical simulation was utilized to investigate the residual stresses in the multipass gas metal arc-welded joints of high-strength Al-Zn-Mg alloy plates. In order to elevate the reliability of numerical simulation, the heat source model, parameters characterizing the thermal and mechanical properties, boundary conditions, material constitutive model and finite element meshing were discussed in detail. As a novelty of this paper, the modified Arrhenius constitutive equation of the base material and the filled material was obtained according to the results of high-temperature tensile tests. Distributions of stress on the upper and bottom surface of the joint were obtained based on numerical simulation. Special attention was paid to the evolutions of local residual stress on the bottom surface of the joint, and itÕs found that residual stresses on the bottom surface of the joint were almost unchanged after the weld seam approached a certain thickness. Blind-hole method and x-ray method were adopted to detect the residual stresses on the surfaces to verify the accuracy of the results obtained by numerical simulation. Keywords

modified Arrhenius constitutive equation, multipass GMA welding, residual stress

1. Introduction Al-Zn-Mg aluminum alloys exhibited high specific strength and excellent overall performances after rolling, solution and aging heat treatment (Ref 1, 2). 7A52 aluminum alloy (AA7A52) as this series of aluminum alloy also possessed special and attractive properties including wide quenching temperature range, excellent casting, semi-solid-state and solidstate formability. Therefore, AA7A52 had been widely used in bridges, high-rise buildings, civil engineering structures, military facilities and light amphibious equipment. Welding was used extensively in these industries. However, it was difficult to weld the thick plates of such high-strength aluminum alloy, and the most serious problem was the high residual stresses in the welded joints. The mechanical properties and service lives of high-strength aluminum alloy-welded structures were greatly affected by residual stress, especially for the structures made by multilayer and multipass welding processes. It was found that shot peening mechanical treatment imparted high induced compressive residual stresses on the surface of the welded joints obtained by shielded metal arc welding (SMAW) and flux cored

Fengyuan Shu, Lei Wu, Ting Wang, and Gang Chen, Shandong Provincial Key Laboratory of Special Welding Technology, State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Weihai 264209, China; Yuxin Liu, Yaohui Lv, and Binshi Xu, National Key Laboratory of Remanufacturing, Beijing 100072, China; and Fuji