Structural analysis of an automotive forming tool for large presses using LS-DYNA

To improve efficiency in automotive press shops, press systems with increasingly high stroke rates are being implemented, raising thereby the structural dynamic load on the press and especially on the forming tool. A detailed knowledge of the vibrations and resulting critical loads is thus essential for accurate and reliable designs of forming tools. In this paper, dynamic finite element method (FEM) simulation of a selected automotive tool is presented enabling the identification of the vibration of its components. Furthermore regions of critical stress of those structures can be determined. The FEM model is developed within the LS-DYNA environment. Starting from a simplified pure rigid modelling approach, which uses rigid body constraints, the model is extended by enabling more and more components to be elastic to allow extra flexibility in the system. As an example, a detailed dynamic analysis in LS-DYNA is performed on a blankholder assembly to model the blankholder’s lift-off event. Each dynamic analysis is preceded by a static analysis to apply gravity loading and to pretense the bolts. A special emphasis is put on modelling the elastomer dampers, which absorb shocks at high dynamic loads. Those dampers are represented using a hyperelastic material with a hysteresis. Also an experimental validation of a blankholder vibration under operating loading is carried out, with test signal data gained by piezoelectric transducers. The results show good agreement with reality.