Studies of Artificial Cracks at Rocket Motor Liners by the Frozen Stress Method

摘要

A preliminary investigation limited to stress freezing materials was undertakenin order to develop a test method for estimating the stress intensity factor (SIF) distribution along the border of cracks in the bond line of a bi-material specimen. It was desired to measure the influence of residual stress and mixed mode effects for such specimens. A single edge notched specimen was selected, and a test procedure was devised for isolating the residual stress effect at the bond line for Mode I. Subsequently, mixed mode tests were conducted in the absence of externally induced residual stress and the SIF distribution for K1 and K2 were obtained. It was found that the level of the SIF values were increased by the bond line in cracked homogeneous bondline specimens for bondlines nearly normal to the applied load but that this effect was not increased in bonded bimaterial specimens. For larger angles of inclination to a normal to the applied load, no increase in the SIF above the homogeneous result was found.