Fatigue Crack Growth Simulation of R260 Rail Grade Pearlitic Steel Using the Discrete Element Method

Fatigue-induced crack initiation and propagation is a major concern in pearlitic railway rails and wheels. Rails and wheels undergo significant plastic deformation on their surface-near layers during service, leading to the initiation and propagation of cracks within the deformed region. Existing models typically use finite element models (FEM) to describe these kind of fatigue phenomena. However, they fail to establish a strong connection between the microstructure of the undeformed and the deformed materials and their corresponding fatigue properties. Therefore, we developed a model based on the soft-contact Discrete Element Method (DEM) that considers microstructural details such as prior austenite grains (PAG), pearlite blocks, pearlite colonies, and lamellar orientation of the ferrite-cementite structure of the pearlite. The Voronoi Tessellation method was used to generate a hierarchical mesh to represent these microstructural details, considering the distribution of microstructural details. The crack propagation is simulated by applying damage laws on the microstructural interface level that degrades the stiffness of the fibers connecting the mesh elements. The model's crack growth predictions are compared to experimental results from the literature to validate its accuracy for different deformation degrees.