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Micromechanical Modeling of Fatigue Crack Initiation in Polycrystals

By Alexander Hartmaier (ICAMS / Ruhr-Universit├Ąt Bochum)
Co-authors: Martin Boeff (ICAMS)
Hamad ul Hassan (ICAMS)

Fatigue is an important mechanism for the failure of components in many engineering applications. In particular under high-cycle fatigue conditions, a significant proportion of the fatigue life is spent in the crack initiation phase. Although a large number of research work addresses fatigue life and fatigue crack growth, the problem of modeling crack initiation remains a major challenge in the scientific and engineering community. In the present work, a micromechanical model with a discrete representation of a polycrystalline microstructure is implemented and subjected to cyclic mechanical loads. We monitor the accumulated plastic slip in every element within the microstructure and use it as fatigue indicator parameter that indicates whether a microcrack evolves in this element. By virtue of a damage model, nucleated cracks can also propagate through the microstructure. This allows us to quantify the crack initiation life time and to study the early phases of crack growth in model microstructures. This model is applied to investigate the effect of different hardening mechanisms on fatigue crack initiation. With this work, it is demonstrated how the micromechanical modeling can support the understanding of damage and failure mechanisms occurring during fatigue.

Ⓒ Photos:Toerisme Leuven