Research on corrosion fatigue fracture mechanism and failure analysis of aircraft main wheel hub bolts

This study systematically investigated the fracture failure mechanism of aircraft main wheel hub bolts during service using a multi-scale analysis method to address the issue of fracture failure. Macroscopic observation shows that the fracture surface has typical fatigue striation characteristics, and the crack originates from the root of the 5th thread. Microscopic analysis shows that the cadmium plating layer on the root of the thread wears off due to long-term service, and the exposed area of the matrix forms corrosion fatigue cracks under alternating stress. Energy spectrum analysis confirms the presence of coating failure and Fe element enrichment in the crack source region. Metallographic examination shows that the bolt matrix has a fine tempered martensitic structure with uniform hardness (43.77 ± 0.66 HRC), and the material properties meet the requirements. The research results indicate that the failure of coating protection and the synergistic effect of alternating stress are the main causes of bolt corrosion fatigue fracture. The research results provide a scientific basis for the reliability assessment and maintenance of wheel hub bolts.