Experimental and Numerical Approaches of Springback of High Performances Steels Drawn with U-Shaped Tools and an Industrial Side Member Tool 2002-01-2099

In order to reduce the gas emission without reducing passive safety, high performances materials are more and more used in automotive industries. The main advantage of introducing these steels is to lighten the body of the car, whereas one of the main difficulties is to control the springback after deep drawing of the parts.

In order to control the springback of some typical deep-drawn parts, PSA PEUGEOT CITROEN and LEDEPP ARCELOR have initiated a collaboration based on an omega-shape tool with different geometries. Several materials chosen in different metallurgical families (HSLA, DP600, TRIP800) have been drawn with single effect presses. Two geometries have been proposed:

• a small tool, provided by the LEDEPP (USINOR, Florange, France), with a range of die radii from 2 to 12 mm,
• a larger tool, provided by PSA PEUGEOT CITROEN (Poissy, France), with die radii equal to 4 and 10mm.

In order to determine the springback angles and the curvature radii of the side wall of the omega parts, several sections for each drawn parts have been either scanned and analysed with AutoCAD^® or mechanically measured with a three-dimensional measurements machine TRI-D-AXE^®. The influence of sheet thickness, mechanical properties as well as metallurgical family, and some geometrical parameters (die radii, drawing depth, …) on the springback angle and the curvature radius of the side wall has been examined. The influence of the clearance and the blank holder pressure have also been tested. Furthermore, springback calculations, based on the experimental geometries, have been performed with OPTRIS^® V6.1, in accordance with the standard mathematical material definitions.

The results show the interaction between parameters such as die radius and sheet thickness or clearance and blank holder forces.

The numerical try-out seems to confirm in some cases the trends brought by the experimental results.

This present paper analyses and discusses the experimental and numerical results.