Finite element prediction of failure modes of ductile materials

A multiscale finite element simulation model has been recently developed to simulate the failure process (crack initiation and development) of ductile metals subjected to a variety of loading conditions involved with and without tool contact. Although the original model was specifically developed for sheet metals, it has also been applied to tube materials subjected to high internal pressure, which is a typical primary loading of steam generator tubes. The major contributions of this model include: (1) it captures the physical sound sequence of deformation: namely uniform deformation, diffuse necking, localized necking, and crack initiation and development; (2) localization is not trigger by the damage model. Rather it is localization that promotes the damage; (3) it can be easily transferred to any commercial finite element packages. The model has been validated by several carefully controlled tests using state of the art equipment and techniques, e.g. automatic strain mapping system, high-resolution in-situ SEM etc. The model has also proven to work very well over a large span of scales from a few micrometers up to several hundred millimeters. The outlook of applying the model to analyze structural integrity of feeder and steam generator tubes in CANDU reactor is also demonstrated. (author)