3-Dimensional Numerical Simulation For Surface Cracks In FGMs Under Thermal/Mechacal Loading

Functionally graded materials(FGMs), a kind of new type nonhomogeneous materials, have significant applications in the astronautic and aeronautic fields. Due to the reasons from the design, manufacture, working environment, etc., there usually are all kinds of cracks or defects, which may cause the failure of various functionally graded structures under different loads for the design,optimization and application of FGMs.The thermomechanical fracture problems and development of FGMs are reviewed in Chapter One, including the advances of mechanical fracture and thermal fracture about FGMs.The basic conception of the FGMs frature was summarized in Chapter Two, including the expression of the stress field and the strain field near the crack tip in the FGM medium.In Chapter Three, the surface fracture was studied for a functionally graded plate with a semi-elliptical surface crack under mechanical loads, including the normalized stress-intensity factors along a crack-front under remote tension or bending loads, and studied the influence of crack sizes, aspect ratios and material property on the stress intensity factors.In Chapter Four, the surface fracture was studied for a functionally graded plate with a semi-elliptical surface crack under state thermal loading, and studied the influence of crack sizes, aspect ratios and material property on the stress intensity factors along a crack-front under two types thermal loading: calefactive state thermal loading and descent state thermal loading.