A Semi-Analytical numerical non-stationary creep analysis of a rotating disk made of Polyamid66 under mechanical and thermal loads

A semi-analytical numerical non-stationary creep analysis of constant and variable thickness rotating disks made of polyamide 66 under mechanical and thermal loads is presented using Mendelson's method of successive approximation. The material properties are time, temperature, and stress-dependent, which vary along the disk's radius due to effective stress variation and temperature distribution and are represented by Burger's model. A non-homogeneous differential equation in terms of radial displacement with variable and time-dependent coefficients was established using equilibrium, strain-displacement, and stress-strain relations. First, the initial thermo-elastic stresses at zero time were calculated using the Galerkin method and Hermitian elements. The history of stresses and strains was then calculated using Burger's viscoelastic model and Prandtl-Reuss relations. To validate the results, an analysis of a disk with constant thickness made of PVDF material was also carried out using the same method employed in this study. Very good agreement of the results was observed in both elastic and creep conditions. Creep analysis was performed for PA66 disks of constant and variable thickness conditions, and the results were compared together. It has been found that the radial displacements and effective stresses are increasing with time for both disks. However, effective stresses and radial displacements of variable-thickness disks are much lower than constant-thickness disks.