Damage tolerance analysis and fatigue life prediction of hydraulic shell

Under prolonged operational conditions, the servo motor housing is prone to developing numerous fatigue cracks, which compromise its structural integrity and service lifespan. To address this issue, we apply a fatigue life prediction method rooted in small crack theory to the servo motor housing, while also exploring innovative approaches for damage tolerance design and life prediction. This study conducts extensive tests on the propagation of both long and small cracks in the L-T and T-L directions at room temperature, utilizing 7050 aluminum alloy single-sided notch tensile specimens. Based on the propagation data of small and long cracks, the da/dN-ΔK data of crack propagation are obtained by fitting. Scanning electron microscopy（SEM） is used to conduct microscopic analysis of the specimen’s fracture surface and to quantitatively assess the material’s initial defects. Based on the initial crack size and crack propagation data, the three-dimensional crack propagation theory analysis method based on fracture mechanics and the finite element simulation method of ABAQUS-Franc3D software are used to predict the fatigue life of the servo housing. The predicted results are evaluated using the actual fatigue life, and the predicted and experimental results are in good agreement.