FATIGUE LIFE PREDICTION BASED ON FINITE-ELEMENT MODELING DAMAGE ACCUMULATION INCLUDING MATERIAL INHOMOGENEITY

The article presents the results of modeling two-dimensional fatigue cracks evolving and growing in steel smooth specimens through finite-element modeling using the procedure of discrete assessment of damage accumulation in the structural elements of the material. Fatigue life is estimated by the linear damage accumulation rule and the strain life criterion with regard to the elastic-plastic material response. The initial material inhomogeneity is simulated by varying the cyclic hardening of the experimentally observed material fractions, ferrite and perlite. The results obtained on crack front evolution indicate that its predominantly occurs in the subsurface layers in the material element clusters with the smallest cyclic hardening. The simulated life scatter for several FE-mesh densities satisfactorily fits the experimentally obtained data at different values of stress amplitude and is more pronounced in the high-cycle regimes. It is shown that crack growth stage can reach 25% of the total fatigue life for smooth specimens. A reasonable selection of the variable fatigue resistance parameters would be needed for further experimental material investigation at different structural levels.