Microstructure-based modelling and simulation of the mechanical behaviour of dual-phase steels
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This project is concerned with the behaviour and modelling techniques of ferrite-martensite dual-phase steels, with the intention of creating a general relation between the microstructural properties of the materials and the mechanical response. An axisymetric finite element model is constructed in Abaqus/CAE, and evaluated as a CPU-efficient modelling possibility by comparison with both experimental data and 3D finite element models. The model consists of a spherical martensite island within a cylindrical ferrite matrix, where the volume fraction of each phase is defined by the radius ratio. Mainly two material models, widely used in the literature, are tested for describing the material response of each phase, referred to as the Ramazani- and the Pierman model respectively. The first include a variety of physically based parameters and has few fitting parameters, where the latter only depends on the carbon content and has fitted parameters for steels of different martensite volume fractions. The combination of the Ramazani model and the axisymtric model provides relatively accurate estimates of the DP steel behaviour, and almost coincides with experimental results when some adjustments are included. An analytical model, initially proposed as a homogenizing model for the phases in ferrite-austenite steels is tested through an iterative process, but is found to be unsuitable for ferrite-martensite modelling.