Environmentally Assisted Fracturing under Sustained Loading

Abstract

One of the risks involved in the structural integrity of military equipment is environmentally assisted fracture under sustained (or, for that matter, under cyclic) loading. This risk has increased with increasing levels of technology, as illustrated by three examples: the brass cartridge case was all too prone to “season cracking”, although its paper predecessor was immune; the aluminum airframe has had a long history of stress corrosion cracking (SCC), and indeed the titanium alloy counterpart has not been immune, whereas the fabric-covered fuselage was, of course, imaune to SCC; and the modern high strength steel rocket motor case is susceptible to SCC and hydrogen embrittlement cracking whereas cast iron and bronze canon were not. No reason is evident for expecting this pattern of increased threat of SCC to subside, and it may even spread.