Accurate evaluation of fatigue life and study of initial crack effects in diesel engine cylinder blocks based on an accurate crack propagation model

Accurate assessment of the fatigue life (N_f) of diesel engine cylinder block partitions and the influence of initial cracks is essential for engine safety. However, the large size and complex geometry of these partitions complicate the development of a reliable crack growth rate (da/dN) model. To address this, a scaling study was conducted to ensure consistent da/dN behavior before and after scaling. Fatigue crack propagation (FCP) tests and simulations, accounting for crack closure effects, were performed on scaled components to obtain da/dN and stress intensity factor (ΔK) data, which were then integrated to establish an indirect da/dN model for the partitions. N_f simulation evaluation of the partition was conducted based on this model. Additionally, microscopic analysis and finite element modeling were used to assess initial crack conditions’ effects on FCP behavior and N_f. The results show that the proposed model reduces N_f prediction error by 10.2% compared to traditional methods, with Type I as the primary FCP mode. The bolt root center, a 30° crack angle, and a 1.4 aspect ratio were identified as critical factors in fracture.