Fatigue crack propagation analyses based on plastic energy approach

Abstract

Plasticity effects at the crack tip had been recognized as “motor” of crack propagation. The growth of cracks is related to the existence of a crack tip plastic zone, whose formation and intensification is accompanied by energy dissipation. In the actual state of knowledge, fatigue crack propagation is modeled using crack closure concept. Recent studies demonstrated that closure effects and the role of plasticity-induced crack closure are more pronounced at the early stage of the crack growth at low stress ratio R. In this paper, an analysis of fatigue crack propagation based on energetic approach is proposed. A model describing the material behavior is also proposed. It is expressed by a unique linear relation between the crack growth rate and the hysteretic energy per cycle by including an energetic correction factor ζ M which takes into account the over evaluations obtained by hysteresis loops and shows the different effects of plasticity, crack closure and opening mode.