Three-dimensional modelling of rail steel microstructure and crack growth

A three-dimensional model of microstructure based on convex polyhedra, generated using the Voronoi method, is used to model the early stages of crack growth. The statistical properties of the polyhedraʹs volumes, and the corresponding polygon areas in a cross-section, are studied and some simple relationships are revealed which are useful for extrapolating 3D microstructure properties from analysis of a 2D micrograph. This representation of microstructure can be used to map grain boundaries, to determine potential routes for, and obstacles to, crack propagation. The model is used to investigate the effect of severe deformation on crack growth, and data from examination of test samples is used to support this.