Effects Of The Forming Process On The Crash Performance Of S-rail With Tailored Properties

According to the need for lightening of cars, more and more ultra-high strength parts of hot stamping are applied to car body, and the tailored properties parts based on the hot stamping technology are developed to improve safety of car. Automobile structural parts are manufactured by stamping or bending, so thickness variations, plastic strain and residual stress are imparted in the part of forming process, which will have an effect on the structure crash simulation result. However, these factors are not considered in traditional crash simulation. Taking these formability effects into structure simulation can significantly increase the results’accuracy, which in turn benefits the vehicle light-weight design and structural optimization.First of all, a B pillar is chosen as the research object in this paper. The collision characteristics of tailored hot stamping B pillar and fully hardened hot stamping B pillar is studied by the means of simulation. From these results, it is verified that the B pillar with tailored regions has an advantage on the energy absorption and anti-intrusion, What’s more, it can also be concluded that the manufacturing process of the tailored B pillar is simpler comparing with the tradition way of producing B pillar, as well as the weight of cars is reduced.Further, in order to produce tailored hot stamping S-rails, the approach of increasing the die temperature in local regions is researched by means of simulation. The simulation results reveal that the S-rail does not have tailored properties after forming process at100℃or300℃hot region temperature, Nevertheless, when the hot region temperature reach500, the S-rail obtained excellent tailored properties. At the hot region temperature of500℃, the microstructure of S-rail hot region is predominantly martensite, and the microstructure of S-rail cold region is mainly bainite. Meanwhile, the influences of blank holding force is studied in the forming process.Finally, the influence of forming history on crashworthiness was studied. The deformation history, including plastic strain, thickness changes and residual stresses are transferred from the forming models into the crash models. The analysis shows that the thickness changes is found to play the most important role in crashworthiness of the S-rail structure. In addition, the plastic strain impacts the results in the second place,, and the residual stresses influences the consequences to some extent as well. As you can see from the simulation results, the thickness changes reduce the strength of the S-rail structure, and the plastic strain leads to a stiffer response of the S-rail structure. Furthermore, the influence of blank holding force and rigid body velocity on crashworthiness was investigated.