Failure mechanism models for cyclic fatigue

This work illustrates design situations where mechanical fatigue under cyclic loading, of one or more components, can compromise system performance. In this failure mechanism, damage accumulates with each load cycle, thereby causing a physical wearout failure mechanism. Phenomenological continuum length-scale models, based on micromechanical considerations, are presented to predict the onset (or initiation) of fatigue cracking in ductile materials. Fatigue crack propagation is modeled with continuum fracture mechanics principles. The number of load cycles required to cause failure is predicted based on these models. Approaches for modeling creep fatigue interactions are briefly discussed. Analytic physics-of-failure method and examples are presented for designing against wearout failure due to cyclic fatigue. These models can be implemented in an engineering design environment. The associated stress analysis requires numerical finite element techniques in many cases. The associated material property characterization techniques have matured since the 1950s and are specified in engineering handbooks