Formability Prediction of Automotive Parts Using Forming Limit Diagrams

Abstract

The aim of this research is to study the effect of steel sheets produced by different manufacturers upon the forming limit. This work used forming limit diagram (FLD) to determine the formability of different trademarks steel sheets SPCC and SPCE, which have the same thickness of 0.8 mm. These two steel sheets are commonly used to produce automotive parts in Thai automotive industry. In order to produce FLD, the circular grid pattern was marked onto the surface of the blank sheet using electrochemical-etching technique. Subsequently, the blank sheet was continuously formed into a semi-dome shape by hydraulic press machine with a 100-mm punch. The pressing process was stopped when local necking and cracks were observed on the surface. The deformations of circular grids were accurately measured to obtain the major and minor strains. Afterward, this process was repeated again for different semi-dome's radii in order to produce FLD. The results were found that FLDs of SPCC and SPCE are slightly different. It has been also found that SPCE has the values of major and minor strains higher than SPCC. In other words, it indicates that SPCE has better formability than SPCC. The FLDs of both steel sheets have predicted failure in forming process consistent with the real experiment and finite element result.