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A data driven computational microstructure analysis on the influence of martensite banding on damage in DP-steels
Material design and optimisation for specific applications are key factors to reduce material usage. Thus, they are an important component towards more sustainable materials and process engineering. Additionally to optimising the chemical composition and the processing chain, the microstructure is another important factor. Especially for the damage properties, which are especially influential for forming processes. To achieve the best possible component performance it is important to understand the influences of the material and its microstructure on the performance. While damage evolution during forming is not equivalent to failure, understanding the characteristics and implications is extremely important for optimal service behaviour. However, a comprehensive way to quantify the influence of the microstructure on the damage properties is still not fully available. Thus, it is unclear how individual parameters of the microstructure influence the damage properties and, in extension, the mechanical properties. For dual phase (DP) steels the martensite phase plays an important role for strength, ductility, formability and damage resistance. While the influence of martensite phase fraction and morphology was often investigated experimentally, it is not possible to draw comprehensive, quantitative conclusions from such tests, as there are many factors at play in the microstructure, that cannot be changed individually. This study applies a simulative approach utilising statistically representative volume elements (sRVE) to quantify the influence of martensite banding on damage properties. Bending tests are taken as a forming process application, and investigations on the testing material show that the martensite bands play a major role during the cracking of the sample. In front of the crack tip, damage forms inside the banded structures leading to the crack running along or through the bands when enough voids have formed. To quantify the influence the bands have on the damage initiation, two microstructure states are compared: banded and without bands. For both states 29 sRVE are simulated to ensure a statistical analysis of the influence. The simulative comparison shows that the banded structures lead to an earlier damage initiation by margins of 2 to 20% of PEEQ. The methods applied in this study enable the investigation of individual influences of microstructure parameters on different mechanical or damage properties.