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In recent years, the use of new advanced materials plays an ever-more significant role in modern structures and machine components. In comparison with conventional metallurgy procedures, sintering, also known as powder metallurgy, presents significant advantages. However, the porosity of the sintered materials causes stress concentration, strain localization and damage accumulation in a material microstructure, which can lead to the material failure. Therefore, fracture modelling on the material microscale level is necessary for the reliable behaviour assessment and life-time determination of sintered materials on the macroscale. During recent years, the phase-field (P-F) method has gained huge popularity within the computational fracture mechanics field. It is a diffusive method that regularizes the sharp crack discontinuity within a volume, which is often controlled by some length-scale parameter. In the present paper, a 2D P-F formulation is used for modelling microcrack propagation in heterogeneous and homogeneous materials. Different porous models are extracted from metallographic images. The heterogeneous materials consist of two constituents: ferrite and bainite. Elasto-plastic material properties of ferrite and bainite are obtained by the sharp instrumented indentation. The numerical results are compared with metallographic images after uniaxial test to observe intra-or transgranular crack formation. [ABSTRACT FROM AUTHOR]

The paper presents a separated staggered phase field methodology for modelling of brittle fracture. The basic relations of the phase field formulation are derived, along with decomposition of the strain energy. In separated scheme, displacement model is computed separately from the phase field model in concurrent fashion. The transfer of variables among models, loading imposition and incrementation are governed by the head routine. A convergence criterion has been suggested, which is based on the norm-2 of the phase field variable. The framework has been implemented into FE software Abaqus and Fortran via user subroutines. The proposed framework has been verified on the standard benchmark problems. The solutions obtained have been compared to the other staggered schemes found in the literature. It has been presented that separated scheme provides correct solutions and requires shorter computational time. [ABSTRACT FROM AUTHOR]