Study On Two Kinds Of Crack Boundary Value Problems Of Orthotropic Thermoelastic Strip

Fracture mechanic mainly studies the propagation law of crack under various loads,which can provide theoretical support for reliability analysis and life estimation of materials and structures.In this thesis,the temperature field and elastic field distribution of the crack tip under uniform heat flux and mechanical load are studied.Many results are offered as follows:First,the central-located crack problem in orthotropic strip is studied under the combination of thermal load and mechanical load.The thermal medium crack model is used to adress the effect of thermal conductivity of crack on crack propagation.By is transformed Fourier transform technique,the boundary value problem is transformed to solve the singular integral equation with Cauchy kernel,and the closed form solution of the temperature field is determined.In solving the elastic field,the singular integral equation is discretized by Lobatto-Chebyshev integral formula,and the linear algebraic equations are obtained.Numerical results are reported to illustrate the effects of the thermal conductivity inside crack and the thickness of orthotropic strip on the temperature change across crack,the partial insulation coefficient and the thermal stress intensity factor.The observations reveal that the crack growth in an orthotropic strip is dependent on the combined effects of the thermoelastic loadings,the physical and geometrical properties of material.Second,the eccentric crack problem in orthotropic strip under thermoelasti-c loadings is studied.The Fourier transform is used to transform the boundary value problem into a singular integral equation.The Lobatto-Chebyshev formula is used to obtain the nonlinear algebraic equations,and the numerical solutions of the temperature field and elastic field induced by crack are given.The variation of temperature difference on crack surface is analyzed by numerical calculation.The influence of mechanical load,crack position and crack size on the thermoelastic field is showed by the numerical results.In the above study,using the new thermal-medium crack model,the objective actual situation can be simulated more accurately,and the influence of various factors on the crack surface temperature change and thermal stress intensity factor are considered more comprehensively and carefully.The study in this paper has certain practical significance.