| Nonlinear thermal stress problems must be considered in many engineering designs. Finite Element and Finite Difference techniques have been commonly used in the past to analyze such problems. In the case of thermal stresses in a composite heavy-duty brake drum, these techniques involve complexities due to presence of nonlinear terms in the governing energy balance equations and in the stress-strain functions. Hence, a simplified technique is desirable for overcoming these difficulties.;The purpose of this dissertation is to develop a simplified method for nonlinear analysis of the thermal stresses that allows optimization of the thermal fatigue life of a composite cylinder. This method determines the appropriate stresses and displacements for multilayered cylindrical shells when subjected to steady state thermal loads on the inside surface.;To compute elastic-plastic thermal stresses in a multi-layered cylindrical shell, a numerical method using Mendelson and Manson's techniques of iteration and incorporating principles of equilibrium, compatibility, and theory of thin-walled pressure vessels is developed. The radial displacement function in the cylinder is approximated by a simple polynomial. The results, which are computed at seven radial stations, include temperatures; displacements; and the radial, axial, tangential, and effective stresses. These computations are based on cylinder geometry, layer thicknesses, heat input, and thermomechanical and thermophysical properties of selected materials or alloys.;Optimization is achieved by varying layer thicknesses and comparing the effective stresses for each test design. Details for the optimization and results of a cast iron-copper-steel composite cylinder for one set of thermal and physical constraints is presented and compared with the results of a pure cast-iron model with the same thickness.;It appears that this method yields satisfactory results and can be used in the design of circular cylindrical components with axially symmetric thermal loads. It also appears that the thermal fatigue phenomenon in heavy-duty brake drums can be greatly reduced if not eliminated by appropriate design. |
