中文摘要：

对0．7mm／1．0mm厚度组合的B170P1钢激光拼焊板试件进行半球凸模胀形试验，分析不同应变状态下拼焊板的变形、失稳特点及应变分布情况，研究其拉伸失稳规律。研究表明，拼焊板试件的变形失稳主要发生于薄侧母材，且随应变状态由单拉向平面等双拉的转变，应变分布趋于均匀，失稳位置向焊缝靠近；在变形过程中，靠近焊缝的薄侧母材在平行于焊缝方向的变形受到厚侧母材及焊接区的影响，其应变路径快速向平面应变漂移，达到成形极限状态，降低了拼焊板的成形性能。焊缝的存在导致差厚激光拼焊板各部分变形不均匀，在差厚激光拼焊板的实际应用中，应采取适当措施抑制薄侧母材的局部变形，增加厚侧母材塑性变形的比例，提高差厚拼焊板的冲压成形性。

英文摘要：

The hemisphere punch bulging test was applied to test the formability of B170P1 steel laser tailor-welded blank （LT- WB） with thickness of 0. 7mm and 1.0mm. The deformation characteristic, failure and strain distribution of LTWB was studied to obtain the tensile instability law. The results show that the deformation of LTWB was mainly discovered on the base metals of thinner sides. With the strain state changing from tensile to biaxial tension, strain distribution becomes uniform and the failure position approaches weld. The deforming of thinner base metal parallel and dose to weld is restricted by thicker base metal and welded zone, which leads the strain path to convert into plane strain state quickly. Then the LTWB reaches the forming limit and its formability declines. The existence of weld causes deforming concentration which leads to failure of LTWB. And appropriate measures should be taken to restrain local deformation in thin base metal, increase the proportion of deformation of thick base metal and improve the formability of LTWB.