Analysis of Drawbead Behaviour for Sandwich Sheets in Sheet Forming Simulation

Lightweight sandwich sheets represent an alternative in the framework of body lightweight construction. They are made of metal face sheets which form a shear-resistant bond with the thermoplastic core layer. The present work describes the drawbead behavior of sandwich sheets and how it can be modelled in a numerical simulation. Drawbeads are used to control the rate of material flow into the die cavity and are located in the binder area. In the numerical simulation they are either modelled as physical drawbeads or replaced by an equivalent drawbead in which a certain drawbead restraining force (DBRF) is specified as a boundary condition. The values of DBRF can be obtained in a strip test, via numerical simulation or predicted with the aid of a drawbead model. In the current study, strip tensile tests through different physical drawbeads are conducted for sandwich materials. With the obtained variables, restraining forces and thinning values, the results from numerical simulations can be evaluated. Once an optimal simulation approach is found, a parameter study can be conducted to analyze the main influencing factors on drawbead behavior. The results from this study can be leveraged to create a semi-empirical drawbead model.