Minimization of Weld Line Movement and Improvement of Accuracy in Heat Assisted Forming of Tailor Welded Blanks

Reducing the weight of Body-in-White (BIW) components in the vehicle leads to improvement in fuel efficiency, thus to reduction in harmful emissions into the atmosphere. Most of the Tailor welded blank (TWBs) components are either stamped or deep drawn. In the stamping of TWBs, the current challenges being faced are related to the heterogeneous nature of the TWB, where the two parent sheet metals may undergo unequal plastic deformation resulting in the movement of weld line. When the weld line movement (WLM) exceeds the allowable range, it may lead to forming problems such as wrinkles, fractures, and springback, which affects the accuracy of the stamped components.

In order to reduce the flow stress in the stronger material, a new heat assisted forming of tailor welded blank (HAFTWB) process has been suggested in this work. In HAFTWB, the stronger material is selectively heated so that its flow stress is decreased, thereby allowing more material to flow into the die cavity. In order to understand the WLM properly, a parametric study has been conducted on the individual and combined effects of thickness ratio (TR) and weld line location (WLL) on the WLM at different temperatures. This research work also emphasized on the geometric and dimensional accuracy of the TWB cups manufactured using HAFTWB process. The results show a significant improvement in the geometric accuracy, particularly in perpendicularity and cylindricity measurements.

By adopting the HAFTWB method of heating, the undesirable WLM has been reduced considerably without detrimental to the geometric accuracy of the components. Thus, it is found that there is a significant improvement in the formability and accuracy of the TWB cup formed by HAFTWB process.