Performance of stringer sheet parts under static and dynamic load

Abstract

The stringer sheet forming process chain enables the cost-effective production of components with significantly increased stiffness for mass markets such as the automotive sector. In the first process step, a stringer is added to a conventional sheet by laser welding. In the subsequent process step, the stringer sheet parts are formed by a deep drawing operation. Previous investigations of component performance focused in particular on the static stiffness of the stringer sheets. The behavior under dynamic load, such as in crash events, has not been systematically investigated to date. Static testing focused on the stringer height as the only influence on part performance. This study characterizes the crash performance of stringer sheet components by means of a drop hammer test. The energy absorption of the components is evaluated in the experiment based on the rebound height of the drop hammer, whereas the structural integrity is characterized based on the maximum dynamic as well as permanent deformation. Furthermore, a quasi-static compression test is carried out to obtain the static stiffness of the parts. In these tests, the geometric design of the stringer sheets as well as two forming process parameters are varied individually. The influence of these parameters on the static stiffness, energy absorption and structural integrity is assessed and discussed on their own and with regard to their influence on the part weight.