The stability of a circumferential crack in a pipe

The paper examines the case where a pipe of length L is built-in at one end and the other end is subject to an imposed displacement or rotation. The criterion for instability of growth of a circumferential through-wall crack is shown to depend on the pipe-end boundary conditions as well as the pipe geometry, crack size and crack location. The worst possible case is that where there is only a force, but no moment, at the pipe-end. However, this is probably an artificial situation which is unlikely to arise in practice. A pipe is more likely to be built-in at both ends, and for this situation, it is concluded that the instability criterion is the same irrespective of whether a displacement or rotation is imposed at a built-in end. (author)