Failure analysis of the rod-end bearing of an actuating cylinder

Abstract The failure analysis of the rod-end bearing from an actuating cylinder used to open and close the left main landing gear inboard door by hydraulic pressure of an aircraft has been studied. The rod was manufactured with a quenched and tempered AISI 4130 steel and coated with cadmium. A chemical analysis of the rod-end bearing material was performed using a XRF equipment. To characterize the steel microstructure, metallographic samples were prepared to be inspected in an optical microscope. The grain size was obtained using a software according to the standard ASTM E112. The fractographic study was carried out or accomplished using a stereo microscope and a FE-SEM equipped with a microanalysis system by EDX. The macroscopic appearance of fracture surfaces indicated that cracking had initiated by multiple origins in the lubrication passage. The microfractographic analysis showed tear and transgranular cleavage/quasi-cleavage fracture mechanisms. Scanning electron microscopy indicated that cadmium metal was present in the steel material and on the fracture surfaces near the origin area. It was concluded that the failure of the rod resulted in a solid metal-induced embrittlement (SMIE) followed by tearing and transgranular cleavage/quasi-cleavage and a final catastrophic overload.