Numerical computation of thermal fatigue crack growth of cast iron

Thermal fatigue experiments have been carried out on a single-edge wedge specimen of the SiMo cast iron to reproduce the conditions experienced by exhaust manifolds during operation. The leading edge temperature was cycled between 20 and 750 degrees C and the temperature distribution on the specimen surface was measured by thermocouples throughout the thermal cycle. Due to the complexity of the loading and interaction effects between cracks, numerical simulation of crack propagation and shielding effects in multicracked structures appear a useful way to analyze this problem. Therefore, 3D thermo-mechanical computation was performed with the finite element code ABAQUS of both un-cracked and multicracked specimen. This computation allowed us to assess the temperature, stresses and strains distribution over a thermal fatigue specimen and the estimation of the crack growth rate using the energy criteria based on the calculation of the J-integral crack tip.