فهرست مطالب m .ghannad

In this paper, governing nonlinear equation of pressurized axisymmetric spheres made of isotropic materials with large deformations is derived using the Nonlinear Plane Elasticity Theory (NPET). Because of large deformations along the radial direction and hence existence of nonlinear terms in kinematic equations, the governing equation is a nonlinear second-order equation with variable coefficients, which is solved using perturbation technique. According to the equilibrium equation, loading conditions of the sphere; radial and circumferential normal stresses and radial displacement in spherical shells are calculated analytically. The effect of thickness, material and loading on stresses and displacement in spherical shell is studied by the results obtained from analytical solution. For investigating the accuracy of the results obtained from the analytical solution, the numerical finite element modeling of mentioned sphere is done with ANSYS software and the results of the two methods are compared. This research reveals that the obtained results by the mentioned analytical solution procedure have good accuracy for spherical shells under pressure loading.

In this paper, the creep analysis in a thick-walled cylinder subjected to internal pressure and heat flux at the inner and outer surfaces has been investigated. The displacement field is obtained based on the first-order shear deformation theory and the thermal field is assumed two-dimensional through the thickness and along cylinder whose in radial direction the thermal field is considered linear. The equilibrium equations of the mechanical and thermal fields were derived using the energy method and the principle of virtual work for mechanical loading and heat flux. The creep behavior is described by Bailey-Norton’s time-dependent creep law. Analytical solutions with iteration methods have been used to obtain the stresses, strains, and displacement. The relationship between the temperature and the creep deformation was investigated by examining changes in the radial displacement by increasing the temperature by two to three times at a specific point. The effects of parameters such as pressure, heat flux and radial displacement at different temperatures on stress distribution were discussed. It was shown the circumferential stress accounts for the most changes caused by creep behavior. The presented method provides a semi-analytical solution to investigate the creep behavior of the thick-walled cylinders, which can be used for purposes such as designing and their optimization and parametric study under real temperature loading conditions.

In this paper, governing equation of pressurized axisymmetric cylinders made of homogeneous and isotropic materials with large deformations is derived using the Nonlinear Plane Elasticity Theory (NPET). Because of large deformations along the radial direction and hence existence of nonlinear terms in kinematic equations, the governing equation is a nonlinear second-order equation with variable coefficients, which is solved in plane stress and plane stress states using perturbation theory. According to the equilibrium equation, boundary conditions and different end conditions of the cylinder; radial and circumferential normal stresses and radial displacement in cylindrical shells are calculated analytically. The effect of thickness, material and boundary conditions on stresses and displacement in cylindrical shell is studied by the results obtained from analytical solution. For investigating the accuracy of the results obtained from the analytical solution, the numerical finite element modeling of mentioned cylinder is done with ABAQUS software and the results of the two methods are compared. This research reveals that the obtained results by the mentioned analytical solution procedure have good accuracy for cylindrical shells under pressure loading.