A perturbation analysis of rapid crack propagation in pressurised pipe

A steady state analysis is given which models rapid crack propagation in a pressurised pipe as a beam. The interaction of the gas escaping through the crack flares the pipe giving a greatly enhanced energy release rate G. The solution shows a clear maximum in G which is confirmed with numerical results. Experimental decompression times are also predicted by the model. Perturbations in the crack speed can be deduced from the steady state solution and these are shown to be harmonic and in good agreement with observations. It is also suggested that these speed oscillations could give rise to crack snaking.