Reduction of Springback for Hat Channel with High-Strength Steel Sheets by Stroke-Returning Deep-Drawing Process

Abstract

High-strength steel sheets are increasingly applied to automotive bodies for weight reduction in order to meet the needs for reduced environmental impact. However, dimensional defects resulting from springback are serious issues, and effective methods of predicting and reducing such defects are required. In this study, we propose and validate the advantage of the stroke-returning deep-drawing process, in which stroke is returned to the specified depth after drawing to the bottom dead point. The following results were obtained. Firstly, by the stroke-returning deep-drawing process, the twist angle became approximately zero. Secondly, the occurrence of bottom curvature made the sidewall curvature increase. Thirdly, when bottom curvature did not occur, sidewall curvature decreased in accordance with the equation of wide direction stress. Finally, the twist angle and sidewall curvature decreased concurrently upon deeply drawing and the greatly returning stroke process.

Development of Forming Technology to Reduce Dimensional Scattering of Automotive Parts with Cambers by Using Bauschinger Effect

“…Various countermeasure technologies have been proposed for wall opening in the past. 79) The proposed measures for springback in curved parts include a method of controlling stresses by changing the width of the product in the pre-process and post-process, 10) a method of cancelling the springback factor stress by using a drawing-redrawing process 11) and others, but effective countermeasures are still lacking.…”