Thermal Fatigue Behaviour of Cast Iron Induced by Pulse Laser Heating: Numerical Simulation and Experimental Studies
H. Liu, P-J. Chen, J-B. Hao, H-F. Yang, X-L. He and G. Yu
Thermal fatigue is one of the key damage mechanisms in components suffering high temperature cycles. To shorten the duration of a thermal fatigue test and improve its reliability, apparatus was designed using a laser as the heat source, considering the good controllability and high energy density of a laser in both time and space. The temperature and stress fields induced by a laser under high temperature cycling were investigated by a coupled thermo-mechanical finite element method (FEM) model. Results show that, under the cyclic action of the laser, pulse compressive stresses were produced and were non-uniformly distributed on the cast iron surface, providing essential conditions for cracking. After 1000 thermal cycles, network cracks occurred on the surface area irradiated by the laser. It is believed that the cracks initiated from holes formed by the spalling of graphite, and propagated to connect with each other under the effects of the pulsed compressive stresses.
Keywords: Nd:YAG laser, cast iron, cracking, thermal fatigue, temperature field, numerical model, finite element method (FEM)