Time-dependent thermo-creep analysis of rotating FGM thick-walled cylindrical pressure vessels under heat flux

Abstract

In the present study, time-dependent thermoelastic creep response for isotropic rotating thick-walled cylindrical pressure vessels made of functionally graded material (FGM) has been investigated, taking into account the creep behavior of the FGM pressure vessels, as described in Norton’s model. For the purpose of stress analysis in an FGM pressure vessel, material creep behavior and the solutions of the stresses at a time equal to zero (i.e. the initial stress state) are needed. This corresponds to the solution of materials with linear elastic behavior. Therefore, using equations of equilibrium, stress–strain and strain–displacement, a differential equation for displacement is obtained and subsequently the stresses at a time equal to zero are calculated. Using Norton’s law in the multi-axial form in conjunction with the above-mentioned equations in the rate form, the radial displacement rate is obtained and then the radial, circumferential and axial creep stress rates are calculated for the conditions of plane strain and plane stress. When the stress rates are known, the stresses at any time are calculated iteratively. Assuming that the inner surface is exposed to a uniform flux, and that the outer surface is exposed to an airstream, the heat conduction equation for the one-dimensional problem in polar coordinates is used to obtain temperature distribution in the cylinder. Assuming that material properties are a function of the radius of the cylinder and that the Poisson’s ratio is constant, creep stresses, creep strains and radial displacement are plotted against dimensionless radius and time for different values of the powers of the material properties. It has been found that in-homogeneity constants have significant influence on the distributions of the creep stresses and radial displacement.