Improvement of fatigue performance by applying tandem GMAW in lap joints with gaps

Abstract

Chassis parts that support the entire load of an automobile, such as the frame, cross-member, and lower arm, require fatigue performance. Chassis parts require different fatigue performances, depending on the shape and role of the components. For chassis components manufactured through gas metal arc welding (GMAW), joint gaps cannot be eliminated or constantly managed owing to spring-back and dimensional errors. When a joint gap occurs, the fatigue performance of a joint welded through GMAW decreases. Therefore, in this study, tandem GMAW (T-GMAW) was applied to weld joints with improved fatigue performance, compared to those welded through single-wire GMAW. The effectiveness of the proposed method was verified by comparing the fatigue performance of the joints with that of those welded through single-wire GMAW. The welding torch of the T-GMAW system was designed in a compact form suitable for automotive sites. In this study, joint gaps of 0 and 10 mm were selected, and the welding conditions were selected with the same deposit amount per unit area. The melt-pool behavior of T-GMAW and single-wire GMAW was confirmed using a high-speed camera. Results revealed that the fatigue strength of the weld of the T-GMA was approximately twice that of a single-wire GMA weld, regardless of the joint spacing.