Abstract
Fatigue considerations often distinguish between fatigue crack nucleation and fatigue crack propagation. The current work presents a modeling approach utilizing one Fatigue Damage Indicator to treat both in a unified way. The approach is implemented within the framework of the Finite Element Method. Multiaxial critical plane models with an extended damage accumulation are employed as Fatigue Indicators. Locations of fatigue crack emergence are predicted by these indicators and material degradation is utilized to model local material failure. The cyclic loading is continued on the now degraded structure and the next location prone to material failure is identified and degradation modeled. This way, fatigue crack propagation is represented by an evolving spatial zone of material failure. This propagating damage zone leads to a changing structural response of the pristine structure. By recourse to the Fatigue Damage Indicator a correlation between the number of applied load cycles and the changing structural behavior is established. Finally, the proposed approach is exemplified by cyclic bending experiments in the Low Cycle Fatigue regime.
Highlights
Fatigue failure and the mechanism leading to fatigue crack nucleation and propagation are of great concern in today’s design of engineering components
Locations of fatigue crack emergence are predicted by these indicators and material degradation is utilized to model local material failure
Crack propagation is obtained by repetitive application of the approach which results in an evolving spatial zone of material failure
Summary
Fatigue failure and the mechanism leading to fatigue crack nucleation and propagation are of great concern in today’s design of engineering components. Different fatigue laws [7,8,9,10,11,12] have been proposed to find a relation between the Paris law and the fatigue laws of Basqin and Coffin-Manson Another approach is the combination of fatigue considerations with continuum damage mechanics [13,14] or crack propagation modeling [15]. Such attempts are often suited in the field of numerical simulations especially in the framework of the Finite Element Method (FEM). A changing structural behavior is modeled by this propagating damage zone
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