Failure Analysis of Bearing Cups of Braking Unit

Several bearing cups mounted on a braking shell of an aircraft braking unit cracked during service. Through macro and micro appearance observation, EDS analysis, metallurgical structure inspection, hardness and hydrogen content testing, FEA simulation and simulation test, the failure cause was analyzed. The results show that the cracking of the bearing cups was cadmium brittleness cracking. The failure took place under the co-effect of higher temperature service environment, bigger tensile stress near the round angle, and improper cadmium -plating process. The fundamental cause for this failure was inadequate consideration on the structure and stress of the bearing cups.