DC05同材同厚拼焊板焊缝组织与力学性能

Microstructure and mechanical properties of DC05 joints obtained by laser welding

关键词:  激光拼焊板  激光焊缝  力学性能  混合法  数字影像相关

Key words:  tailor welded blanks  laser welds  mechanical properties  rule of mixture  digital image correlation

摘要:

焊缝对同材同厚拼焊板成形的影响远大于母材强度或厚度差异的拼焊板.焊缝的力学性能是评价同材同厚拼焊板成形性及有限元仿真的关键.文中在"混合法"的基础上,通过微观组织观测与微硬度测试,结合数字影像相关技术,获得了拼焊板单向拉伸实时的全场应变场,解析计算出了焊缝的真实应力-应变关系曲线.将此曲线与小尺寸试件单向拉伸试验曲线对比分析后发现,曲线在前期稳定变形阶段是吻合的,在屈服阶段和颈缩阶段的差异是由于标准试件中母材对焊缝变形的限制作用,阻止焊缝过早颈缩.结果表明,焊缝的应变路径(应变比为-0.63)已经偏离单向拉伸状态(应变比为-0.50),纯焊缝试件则无此限制作用.计算所得曲线才是包含母材焊缝的真实应力应变曲线.

Abstract:

The laser welding joint has marked influence on the formability of similar tailor welded blanks. Mechanical properties of these joint are the key parameters to evaluate the formability of similar tailor welded blanks and establish the finite element models. To determine the mechanical properties of laser welds,true stress-strain curve of laser weld was analyzed base on rule of mixture in addition to the utilization of microstructure approach and Digital Image Correlation (DIC). DIC was utilized to determine full-field strain during uniaxial tensile tests and local strains were derived from the strain field and were used to calculate the stress-strain curve. It is shown that the analysis curve is agreed well with the experimental curve of small specimen within the stable deformation stage. However,there are very great differences in the necking behavior,which is probably due to the constraint effect of base material adjacent to the joint. As a result, necking behavior of laser weld is hindered. The strain ratio of laser weld was approximately -0.63,which was deviate from the status of uniaxial tension in which the strain ratio is -0.5. Analytic curve is the true stress-strain curve of laser welds.