Failure predictions in warm forming of 7075-T6 aluminum structural parts

Today's automotive industry is increasingly adopting aluminum alloys. The main benefit of aluminum is a higher ratio of strength density compared to common steel alloys. Replacing steel with aluminum can give a weight reduction without loss of frame rigidity or crash safety. However, stamping aluminum is more difficult than steel because of its limited formability and the lack of experience with aluminum alloys for design and manufacturing requirements. Warm forming aluminum can help improve formability. Finite element analysis is a useful tool for predicting stamping failures. With accurate predictions stamping countermeasures can be made before tooling is cut and production has begun. Simulation was used to predict splits in a sidebar part formed at room and elevated temperatures. Forming limit curves were developed and used to test the formability using forming limit diagrams. Both forming limit diagrams and thinning were insufficient to predict the splits seen in the parts. This led to the use of additional fracture criteria that were successful in predicting the severity and locations of the splits.