Destruction of a protective pipe coating under cyclic loading by internal pressure

An analytical method has been developed for determining the moment of destruction of thin pipe coatings whose material retains elasticity during cyclic changes in internal pressure. The coating material has the property of strain softening, that is, destruction with increasing deformation occurs as stresses drop. The properties of the coating material are described by a convex-concave potential. Due to damage accumulation resulting from fatigue loading, the properties of the coating material change. Hence, the complete deformation curve degenerates. To determine the moment of destruction, the methods of the mathematical theory of catastrophes are used, which make it possible to find all the equilibrium positions of the system and the point of instability of the deformation process. Due to the degeneration of the properties of the coating material, the catastrophe (loss of stability) approaches the parameters of fatigue loading.