Creep torsion of non circular bars

This report is a theoretical and experimental investigation of the creep-torsion of non-circular prismatic bars. The theory is developed using an energy approach and assumes the material is homogeneous, isotropic and incompressible, the deformations are small and the total strain theory is valid. An isochronous stress-strain diagram, which is approximated by an arc hyperbolic sine function, is used to represent the stress-strain-time relation for the material. As a closed solution could not be obtained, the Rayleigh-Ritz procedure was used. Experimental data was obtained by applying pure torque to specimens of high density polyethylene. Four cross-sectional shapes were tested, a square, a rectangle, a triangle and an I-section. The theory and experiment in most cases were in good agreement