Failure analysis of air interceptor missile rocket motors

This research conducted an analysis on three failed rocket motors, which are of different types and were used at different times, in order to identify the root cause of cracks occurring in the wing attachment of the Aim-9 (Air Interceptor Missile) rocket motors. Through visual inspection, it was found that the corrosion severity was in proportion to the failure rate in each crack surface. Chemical analysis, microscopic examination, and residual stress determination on the crack surfaces have been carried out to find out the cause of crack initiation and the mechanism of crack growth. The crack origin was covered with mud cracks produced by an interaction of corrosion and stress, and the cracks were propagated along the grain boundary in the longitudinal direction. Also, corrosion-promoting components were found on the crack surface, and the tensile residual stress acted on the channel area of the rocket motor. As a result of the analysis, it is concluded that stress corrosion cracking occurred due to the interaction of corrosive environment and tensile residual stress, which are latent in the rocket motor body.