Experimental Procedures and Results for Benchmark 3: Stage 2 Forming Process

The Numisheet 2005 Benchmark no. 3 consists of a two stage forming process performed on four materials (three steels and one aluminum). Stage 1 consists of forming channel sections in a channel draw die with variable penetration draw beads, and is described in detail in another report. In Stage 2, described here, the samples from Stage 1 are trimmed and subjected to near plane strain Marciniak style cup test. The plane straining is performed in 0 deg. and 90 deg. orientations. After failure limits for the cup depths are determined, trimmed samples from Stage 1 are strained to specific cup depths (less than the depth of failure) and stresses are measured in situ using a unique X-ray diffraction technique. The results are repeatable and consistent with expectations. The goal of this benchmark is to check not only the strain achieved during a two stage forming process, but also to develop data that include the stresses achieved. These results may then be used to further test the ability of numerical models to predict not only strains but stresses during a forming process