Analysis of Strain-Path Dependent Damage and Microstructure Development for the Numerical Design of Sheet Bulk Metal Forming Processes

Funding: German Research Foundation (DFG)
Project: SFB/TR 73 • Subproject C4
Contact: Florian Gutknecht M. Sc.

For sheet-bulk metal forming processes the sheet thickness is adapted to the loading. In this context, thickening is a typical subprocess at the sheet edge (see figure a).

This process is accompanied by high plastic strains and strong non-linear strain-paths. For the reversal of the load (Indicator = -1) at high strains the in-plane torsion test is available. The torsion test for curved sheets has been developed for strain-path changes in orthogonal direction
(Indicator = 0) (see figure b). This test allows characterizing effects of orthogonal strain-path changes at high pre-strains (see figure c). The microstructure of the specimen is investigated for void evolution together with the Institute
of Materials Science at Leibniz University Hannover. Due to the combined approach the influence of strain-path on strength- and damage evolution can be directly determined.

a) Strain-path change at thickened edge, b) Principle of curved torsion test, c) Experimentally
determined cross-hardening