Abstract: According to the forming theory of hemisphere bulge of tailor-weld blanks (TWBs) and the classic mechanics theory, based on the hemisphere bulge test of liner-weld-line TWBs with different thickness ratios for mild steel, the relationship between the thickness ratio of liner-weld-line TWBs and the formability is analyzed. Meanwhile, the mechanics model for the correlation between the thickness ratio and formability is proposed. Combining the physical experiment and finite element simulation model, the relationship between the weld-line movement and thickness ratio, as well as the relationship between the bulge height and the thickness ratio, are studied. The formability results of TWBs with different thickness ratios are observed. The mechanism the weld-line movement and the decrease of formability is analyzed. The rules among the thickness ratio, weld-line movement and forming height are summarized, which can provide theoretical guidance for the production in practice.

Key words: Dome test, Finite element method, Forming limit, Mechanics model, Movement of weld line, Tailor-welded blanks, Thickness ratio