Abstract
The accumulated plastic strain energy density at a dangerous point is studied to estimate the low cycle fatigue life that is composed of fatigue initiation life and fatigue crack propagation life. The modified Ramberg–Osgood constitutive relation is applied to characterize the stress–strain relationship of the strain-hardening material. The plastic strain energy density under uni-axial tension and cyclic load are derived, which are used as threshold and reference values, respectively. Then, a framework to assess the lives of fatigue initiation and fatigue crack propagation by accumulated plastic strain energy density is proposed. Finally, this method is applied to two types of aluminum alloy, LC9 and LY12 for low-cycle fatigue, and agreed well with the experiments.
Highlights
The failure of machinery under cyclic loading is a major engineering concern in practice, and the fatigue properties of metal has long been a focus [1,2]
It was pointed out that the coefficients of the fatigue life prediction formulae were dependent on the material properties
In this paper, a model to assess the low cycle fatigue life based on the accumulated plastic strain energy density is proposed
Summary
The failure of machinery under cyclic loading is a major engineering concern in practice, and the fatigue properties of metal has long been a focus [1,2]. The plastic strain energy density was derived both analytically and experimentally for different materials From these works, the fatigue damage in low cycle fatigue is mainly caused by the accumulation of cyclic plastic strain energy. Huffman [28] proposed a strain energy-based fatigue damage model and applied the strain energy from both the external loading and the dislocations to calculate stress-life, strain-life, and fatigue crack growth rates. It is difficult to give a simple model to predict low cycle fatigue life Those models are far from perfect especially in using the plastic strain energy density to establish relation between uni-axial tensile fracture and fatigue fracture. The accumulated plastic strain energy density is applied to analyze the fatigue life for low cycle fatigue from the point of view of energy dissipation. The fatigue life estimation formula is obtained and is used to predict the fatigue life
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