Speaker
Description
In order to save resources in component production, the use of finite element (FE) simulations is state of the art during the design of the process. Thus, expensive tool modifications can be prevented and laborious experimental tests can be reduced. For a high accuracy of a FE simulation, realistic material data is required to model the material behaviour. Unlike the flow behaviour, the characterisation and modelling of the failure behaviour has not yet been standardised. Conventionally, tensile tests with different specimen geometries are performed and monitored with an optical measurement system. The failure of the material is determined contact-free on the specimen surface. However, for many materials the initiation of material failure is assumed already to initiate of the specimen prior to a macroscopic visible fracture on the specimen surface. To take this effect into account, various tests with butterfly specimen were performed for an HCT980X steel and monitored with an optical as well as acoustical measurement system. The displacement at failure of the HCT980X was evaluated conventionally for fracture on the specimen surface based on pictures of the optical measurement system. Further, the displacement at material failure was evaluated unconventionally for fracture initiation inside the specimen by a sharp increase of the amplitude based on the signals of the acoustical measurement system. FE models of the butterfly tests were created with failure displacements of both evaluation methods as boundary conditions. Using the numerically determined stress state and plastic strain from the butterfly tests, the Modified Mohr-Coulomb (MMC) failure model was parametrised for both evaluation methods and compared. The two methods lead to a significant difference in the course and slope of the two MMC failure models. The accuracy of the two models will be evaluated based on forming simulations using both failure models.