Twisting bar stiffness attenuation analysis based on damage theory

To predict the residual torque of a twisted bar after reserving for certain years, the damage theory is adopted to analyze the long period effect. The twisting test is carried out at a fixed twisting angle equal to twisting one in reserved state, and the experimental curve between torque and time is obtained. Then the material constants in the damage evolution equation are determined with the experimental data, and the function between torque and time is expressed with the twisting angle and material constants, the corresponding curve is plotted to predict the residual torque within a required period.