Digital Caustic Investigation of Near Surface Cracks Under Transient Thermal Loading

In this dissertation, the digital caustics technique was used to determine the transient thermal stress intensity factors of near-surface internal cracks in a semi-infinite thin plate, when the plate edge experiences a rapid temperature change. The internal cracks of different crack lengths and different crack orientations were studied. A series of computer programs were developed on the digital caustic system to analyze the caustics patterns. Then, the variations of transient thermal stress intensity factors with time were discussed. Finally, the correlation expressions between the variations of transient thermal stress intensity factors with the time, temperature difference and geometrical parameters of cracks were obtained by the regression procedure.