Numerical simulation of fatigue crack propagation in heterogeneous geomaterials under varied loads using displacement discontinuity method

Heterogeneous brittle geomaterials are highly susceptible to cyclic loads. They contain inherent flaws and cracks that grow under fatigue loads and lead to failure. This study presents a numerical model for analyzing fatigue in these materials based on the two-dimensional (2D) boundary element method and linear elastic fracture mechanics. The process is formulated by coupling the displacement discontinuity method with the incorporation technique of dissimilar regions and the governing equations of fatigue. The heterogeneous media are assumed to consist of materials with different properties, and the interfaces are assumed to be completely bonded. In addition, the domains include multiple cracks exposed to constant and variable amplitude cyclic loads. The stress intensity factor is a crucial parameter in fatigue analysis, which is determined using the displacement field around crack tips. An incremental crack growth scheme is applied to calculating the fatigue life. The growth rate values are employed to estimate the length of crack extension when there are multiple cracks. The interaction between cracks is considered, which also includes the coalescence phenomenon. Finally, various structures under different cyclic loads are examined to evaluate the accuracy of this method. The results demonstrate the efficiency of the proposed approach in modeling fatigue crack growth and life estimation. The behavior of life curves for the heterogeneous domain was as expected. These curves illustrate the breakpoints caused by utilizing discrete incremental life equations. At these points, the trend of the curves changed with the material properties and fatigue characteristics of the new material around the crack tips.