Part-Through Crack Test—Relation to Solid-Propellant Rocket Cases

Abstract

Propagation of a crack from a flaw that escaped nondestructive inspection is shown to be an important mode of failure of rocket motor cases. The notch strengths of part-through crack tensile specimens containing a range of flaw sizes provide a good empirical measure of the material property that governs this mode. Flaw sizes in the specimens simulate those found in failure analyses of Minuteman cases. Starting from this basic simulation of service, it seems possible to correct for the remaining difference between the case and the specimen by experimental and analytical means.