The effect of creep constitutive and damage relationships upon the rupture time of a solid circular torsion bar

Lower bounds on the rupture times of steadily loaded solid circular torsion bars are shown to agree well with values of the rupture times computed using an iterative procedure for different constitutive and damage laws. Corresponding to the lower bound rupture time a single reference stress can be defined for the structure. Multi-axial rupture effects are included in determining a lower bound rupture time and simple statements are made regarding structural performance and different types of material behaviour. The mode of expression of the Kachanov damage parameter in the calculation method is shown to be unimportant. Good agreement is shown between the prediction method and the results of experiments conducted on bars prepared from different materials.