The Dynamic Responses Of The Homogeneous Cylindrical Shell And The Functionally Graded Materials Cylindrical Shell Subjected To Thermal Shock

The cylindrical shell is one of the fundamental structures in engineering application, which is often subjected to thermal shock, such as aerodynamic heating and laser heating. In the process of thermal shock, the rapid temperature change results in the transient thermal stresses and the fast deformation of the structure, the quantitative analysis for which has great values both on theory and practice. This thesis focuses on the problems of dynamic responses of the homogeneous and the functionally graded composite materials cylindrical shells that are subjected to thermal shock, the main contents are as follows:1. Based on the classical shell theory, the model of the problem of the homogeneous thin cylindrical shell with the simply supported edges under thermal shock is derived from Hamilton theory. Firstly, the temperature field, the thermal axial force and the thermal bending moment are obtained by using the combination of Laplace transform and series expansion, for the case that the internal surface is subjected to uniform thermal shock. And then in consideration of the axisymmetric stresses and deformation, a numerical method which is named differential quadrature method (DQM) is performed to solve the dynamical governing equations so as to obtain the numerical solutions of the dynamic responses of the displacements and stresses of the shell. The effects of the thermal shock load and the geometrical conditions of the cylindrical shell on the central deflection of the shell, the axial displacement, the bending configurations and the dynamic thermal stresses are analyzed in detail.2. Based on the classical shell theory, the model of the problem of the functionally graded materials (FGM) thin cylindrical shell with the edges simply supported under thermal shock is derived from Hamilton theory. It is assumed that the physical property parameters of the FGM vary continuously in function of power along the thickness direction and the internal surface of the shell is subjected to uniform thermal shock. The method performed to solve the dynamic responses of the functionally graded materials cylindrical shell is the same as the one that is used to solve the dynamic responses of the homogeneous cylindrical shell. Above all, the combination of Laplace transform and series expansion is used to solve the one-dimensional thermal conduction equation so that the dynamic responses of the temperature, the thermal axial force and the thermal bending moment could be obtained. The effect of the parameters of material gradients on the dynamic responses of the temperature is examined afterwards. Then differential quadrature method (DQM) is developed to solve the dynamical governing equations in the form of partial differential equations with variable coefficients in order to attain the numerical solutions of the dynamic responses of the shell. The deflection of a homogeneous cylindrical shell that degradates from FGM cylindrical shell is investigated in comparison with the pre-existing numerical solutions of the central deflection of the homogeneous cylindrical shell to testify the correctness of the theoretical derivation and numerical solution of this paper. At last, the effects of the parameters of material gradients on the central deflection of the shell, the bending configurations and the dynamic thermal stresses in different positions are analyzed and discussed in detail both in the cases of ceramic surface and metallic surface subjected to thermal load, which proves the alleviation of the continuous change of the material properties on the dynamic stresses as a result of thermal shock.The results show that the thermal shock load, the parameters of material gradients and the geometrical conditions of the shell have a major effect on the dynamic responses of the displacements and the stresses of the cylindrical shell. The results also present that FGM structure has more advantages than the one of homogeneous material. The thermal stresses of the structure could be decreased while the parameters of material gradients are adapted artificially during the production of FGM.The achievements of this paper have a positive influence on the research of the mechanical property of a structure subjected to thermal shock and provide certain theory instruction value to the practical project application and the optimal design of the FGM structures.