INFLUENCE OF THE FORMING PROCESS ON CRASH AND FATIGUE PERFORMANCE OF HIGH STRENGTH STEELS FOR AUTOMOTIVE COMPONENTS

Weight reduction, economy in the use of material and energy resources are among the most important goals of steel users. Usinor proposes a wide range of very high strength steels (HSLA, DP, TRIP, etc.) for weight reduction, fatigue considerations and impact resistance. This text deals with the mechanical testing and different design solutions associated with these steel grades. Tensile and mechanical properties are presented in order to classify the different steels. In addition to this, the crash resistance is investigated by using a dynamic axial compression test on structural components with closed cross sections. For each steel grade, the estimated weight saving potential is compared with respect to parts manufactured in deep drawing quality. The use of high strength steel like Dual Phase steel or TRIP steel improves crash and fatigue performance due to their great work hardening during the forming compared to HSLA or Complex Phase steel. To benefit of this lightweight potential, numerical simulation of the behavior in crash or in fatigue has to take into account the mechanical properties of these steels after forming.