Predicting Forming Limit Diagrams with Explicit and Implicit Finite Element Codes

An internal state variable plasticity/damage model was employed in explicit and implicit finite element codes to predict forming limit diagrams. The finite element analyses showed that either the explicit or implicit methods can be used to determine sheet metal thickness effects, temperature and rate effects, and loading history effects. A novel way of introducing instability was introduced by different initial void volume fractions in neighboring materials. Shell elements can be used to shorten cpu times, given that shell bending assumptions are not violated.