Effect of Hygrothermal Environmental Conditions on the Time-dependent Creep Response of Functionally Graded Magneto-electro-elastic Hollow Sphere

In this paper, hygro-thermo-magneto-electro-elastic creep stress redistribution of a functionally graded magneto-electro-elastic (FGMEE) hollow sphere is examined. It is supposed that all material properties are a power-law function of radius. Temperature and moisture concentration functions are obtained analytically and then, a differential equation with creep strains is obtained using equations of electrostatic, magnetostatic and equilibrium, At first, ignoring the creep strains, a solution for the initial hygro-thermo-magneto-electroelastic stresses at zero time is achieved. Subsequently, creep strains are considered and creep stress rates are obtained. The Prandtl-Reuss equations and Norton’s law are taken for the creep analysis. Finally, time-dependent creep stresses as well as magnetic and potential field redistributions at any time are obtained using an iterative method. Results show that the radial stress, radial displacement, electric potential and magnetic potentials increase as time goes by at a decreasing rate. Also, the grading index and hygrothermal condition have more considerable effect on the radial stress after creep evolution rather than initial case. Thus, their effects must be considered in creep evolution analysis.