Formability characterization of AI6014 and DP600 alloys considering the effects of non linear strain paths, temperature and bending

Sheet metal forming operations are widely used in automotive industries for manufacturing the automotive panels. The industrial stamping processes are mainly limited by the appearance of localized necking. This necessitates the development of a forming limit curve (FLC). FLC is a graphical tool which is used in finite element based process simulations of sheet metal forming operations. FLC represents as to what combination of major and minor strains can be imposed upon the sheet metal during forming. The conventional FLC has some limitations such as; it fails to predict the formability in case of nonlinear strain paths and bending operations. The present work focuses on design of new punch geometry for improved formability testing considering the effects of non-linear strain paths. Al6014 and DP600 alloys were used in experimentation as they are widely used in automotive outer and inner body panels respectively. To quantify the effect of temperature on the FLC of Al6014 and DP600, forming experiments were carried out at 200 and 250 deg C. Since bending operation is not governed by FLC, therefore, bending limit curves (BLC) were also determined for Al6014 and DP600. In order to minimize the experimental efforts, theoretical models are also used to investigate the formability. In this work, FLCs of Al6014 and DP600 were evaluated using modified maximum force criterion (MMFC) and M-K model. The FLCs were plotted using different yield functions. Effect of inhomogeneity factor on FLC level was also investigated.