The Propagation of the Fatigue Crack Crossing the Inrerrace of Metal Composites Under the Effect of Residual Thermal Stress

Abstract

Push-pull fatigue tests were conducted on the butt-bonded composite plates composed of iron and copper, to study the effects of the residual thermal stress and the difference of the elastic moduli on the propagation behavior of a crack across the interface. The composite plate specimens used in this investigation were fabricated by means of a diffusion bonding method. The experimental results indicated as a general trend that, when a fatigue crack propagated from a material of lower elastic modulus to one of higher modulus, the propagation was decelerated when the crack approached the interface, but after crossing the interface it was accelerated as the crack tip moved away from the interface, and the reverse was true for a crack propagating from a material of higher elastic modulus to one of lower modulus. The effect of the residual stress is clearly observed particularly in the former case where the crack propagation was markedly accelerated in the vicinity of the interface due to the tensile residual stress.