Simulation of Fatigue Crack Growth in a Detonation Tube

Abstract

Internal gaseous detonation in cylindrical tubes can cause pressure loadings that move at high speeds. The resulting flexural waves in the tube wall can lead to high strains, which may exceed the equivalent static strains by up to a factor of 4. This paper starts with a brief review of an analytical model for the transient dynamic response of cylindrical tubes with finite length to internal detonation loading. The formulation of this analytical model considers the effects of transverse shear and rotary inertia and also accounts for the effects of reflected waves. The strain history obtained from this model is used to predict the cyclic growth of a hypothetical preexisting crack in a detonation tube using the AFGROW software. The second part of the paper describes the numerical investigation of the whole process. A simulated detonation loading is applied and the resulting fatigue crack growth is modeled using the FRANC3D software and its boundary element solver. The results indicate that realistic fatigue life predictions for tubes subjected to internal detonation require the consideration of the entire spectrum of strain and stress fluctuations, including the reflected flexural waves.