The Fracture Of Penny Shaped Crack Under Thermal Shock Based On Non-classical Heat Conduction

With the development of science and technology, the modern equipments and therecomponents are being miniaturization and integration. The piezoelectric ceramic filmfrom advanced materials and ceramic coating used in thermal protection are thin layersubjected to thermal shock when they are working. The fracture studies to theseparticular devices are essential for their design and safe in usage. And it is testified thatthe impact of heat load to the material's fracture is significant and even primary.Classical Fourier heat conduction law has been successfully applied to thedetermination of thermal flux and temperature fields in solid materials. However,non-Fourier effect should be taken into account in the situations like great temperaturegradient, super low temperature and micro/nano space and so on. Thus, in thisdissertation, the thin layer with internal penny shaped crack under sudden temperaturechange and thermal flux change is respectively studied based on linear thermoelastictheory with non-Fourier heat conduction. In the method of integral transformation, thethermal shock problems are described by several Fredholm integral equations. Applyingan appropriate collocation deduced from Gauss-Chebyshev formula, the numericalsolutions of Fredholm integral equations are gained, which result the thermal field andassociate elastic field and thermal stress intensity near the front of crack. The results arecompared to the ones deduced from Fourier law. The thermal shock resistant of the layerdepended on the size of layer and the thermal relaxation time of material is discussed.It is found that Fourier law always overestimates the resistant of the layer tothermal shock. When the layer with insulated crack subjects to a sudden temperaturechange on surface, the resistant of the layer increase as the ratio of thickness to cracklength decrease, and increase as the thermal relaxation time decrease. When the layerwith heated crack subjects to a sudden temperature change on crack surface and the fluxon layer surface is fixed, the resistant of the layer increase as the ratio of thickness tocrack length decrease, and increase as the thermal relaxation time decrease. Theconclusion of this dissertation will be of great importance in the design and predictionon residual intensity of equipments work in heat environment.