Stress analysis of a functionally graded hollow cylinder with fixed and free ends

A homogenous machine element under both mechanical and thermal loads may not be safe for all loading conditions during its operation. Material properties such as toughness, thermal expansion, thermal conductivity, and rigidness may not be suitable simultaneously for any kind of mechanical and thermal boundry conditions. A material with high thermal resistance may have low toughness or a material with high tougness may have low thermal resistance and as a result material rigidity may weaken. Since functionally graded materials (FGM) with improved thermomechanical properties maintain properties and functions that can not be achieved by homogenous materials and conventional homogenous composites, they are widely used as heat-shielding material for the frame of space plane and have wide application fields in nuclear, electrical, chemical, optical and biomedical treatments due the combined properties of high material toughness and thermal resistance at the same time. Due to this fact, production of FGM composed of a metal on one side, a ceramic on the other and an intermediate layer between the two becomes more important.IV In this study stresses and radial displacement developed in a functionally graded hollow cylinder with fixed and free ends are calculated. FGM cylinder has uniform internal heat production and mechanically loaded at the inner surface (inner pressure). Elasticity modulus, thermal expansion and thermal conductivity coefficients of hollow cylinder are defined as power functions of radial coordinate. The stresses developed in the functionally graded cylinder are compared with stresses in a homogenous cylinder which is obtained by setting the material parameters of the power function as zero. It is seen that the stresses in FGM cylinder are lower. Then Tresca Yield Criteria is applied for the stress state of FGM cylinder of which material property parameters are defined in a certain range. As a result optimum material property parameters which minimize the stresses are obtained approximately in specified range of parameters. Key Words : Thermal stress, functionally graded cylinder, stress analysis