Stress Analysis Of FGM Pressure Vessel Under Internal Pressure And Temperature Loads

Functionally graded material (FGM) is one of the most promising novel materials in21st century, which holds many excellent properties such as good heat resistant, strong corrosion resistant and good designability. FGM pressure vessel can be designed to be an axisymmetric composite shell with gradient material distribution according to the requirement of practical situation. The internal layer or outer layer is used to prevent corrosion or heat conduction. FGM pressure vessel can be manufactured using two or several kinds of materials according to given graded factors. So far, the mechanical behavior analysis of FGM structures subjected to internal pressure and temperature loads have became the difficult and hot issues of research in the domestic and foreign. In order to track these research focuses, this article mainly carried out the following several aspects of the research work on the basis of previous research.(1) Only taking the internal pressure load into consideration, the analytic solution of the three-dimensional stresses for an FGM pressure vessel, consisting of a hollow cylinder and two hemispherical head, was derived based on the small strain linear elastic theory and differential equations Euler method. The finite element numerical model of the FGM pressure vessel was also created to verify the accuracy of the theoretical solution. According to a specific case, the stress curves of the theoretical and numerical solutions along the radial wall thickness were plotted, respectively. Moreover, the comparative study of the stress distribution for the different elastic modulus gradient factor was further discussed.(2) As FGMs have good performance of alleviating the thermal stress, this paper also investigated the stress distribution of the FGM pressure vessel subjected to the temperature load. Firstly, the temperature distribution function of FGM was created. And then, the analytical solution of the thermal stress for the FGM pressure vessel was derived.Lastly, the analytical solution was verified based on the finite element method. Moreover, the calculation formula of the three-dimensional stress of FGM pressure vessel both subjected to internal pressure and temperature loads were constructed based on the linear superposition principle. And the comparative study on the stress distribution was carried out under different gradient factors of the elastic modulus, thermal expansion coefficient and thermal conductivity.(3) Taking the material and manufacture costs as well as the rapid development coating technology into account, this thesis also investigated the three-dimensional stress properties of the FGM "sandwich" pressure vessel, which is consist of two layer homogeneous sheets and a FGM core layer. The analytical solution was verified by the numerical solution using finite element method, and detailed discussions of the stress distribution were carried out for the "sandwich" structure pressure vessel subjected to internal pressure and temperature loads, which the results also can be applied other structures, such as single metal pressure vessel with a layer FGM coating.