Optimised parametrisation of the MMC fracture model using AE and FE analysis

Abstract

To save resources in component production, finite element (FE) simulations are state of the art during process design to prevent expensive tool modifications. For a high accuracy of a FE simulation, realistic material data is required. Unlike for flow behaviour, the determination of the fracture behaviour is not standardised. Conventionally, tensile tests with different geometries are performed, monitored with digital image correlation (DIC) and fracture is determined on the surface. However, for many specimens the initiation of fracture is assumed to occur inside the material prior to a macroscopic fracture on the surface. Therefore, various tensile tests with butterfly specimens were performed for a HCT980X steel and monitored with a DIC as well as an acoustic emission analysis (AEA) system. The displacement at fracture was evaluated conventionally for fracture on the specimen’s surface based on the DIC and unconventionally for fracture inside the specimen by AEA. FE models of the butterfly tests were created with fracture displacements of both evaluation methods as boundary conditions. Using the numerically determined stress state and fracture strain from the butterfly models, the MMC fracture model was parametrised for both evaluation methods and compared by applying both models to a FE simulation of a forming process.