High cycle fatigue analysis and modelling of cast Al–Si alloys extracted from cylinder heads considering microstructure characteristics

The high cycle fatigue behaviour of the Al–Si alloy extracted from a cylinder head is investigated through experiments and finite element simulations. Due to the complexity of the structure and the differences in cooling rates and local melt flow, the microstructure characteristics of the cylinder head studied exhibit high spatial heterogeneity. The scatter of the fatigue life of the alloy is high, which is significantly affected by the microstructure, especially by crack nucleation pores. The characteristics of the nucleation pores have a great effect on the dissipated inelastic energy (W_p) around the pores, which is used as the indicator for crack nucleation. W_p has the highest sensitivity to pore shape, followed by pore location and pore size. The nonlinear empirical relationship between W_p and pore characteristics is established with high reliability and accuracy, and the crack nucleation model is modified by considering pore characteristics. Based on the multistage fatigue model and the modified crack nucleation model, the fatigue life of cast Al–Si alloy extracted from cylinder heads can be predicted accurately within a feasible scatter band.