Damage mechanics analysis of accelerating experiment on stiffness attenuation of twisting bar

Firstly, based on the theory of damage mechanics, the function of the relation between torque and time is given by twisting angle and material constants, which is also the theoretical curve between torque and time and the relation between the torque threshold and the shear stress threshold. The function shows that the torque attenuation is more rapid under larger twisting angle. Therefore, in order to shorten the experimental period, the accelerating experiment method is put forward based on the above theoretical analysis. The torque threshold is obtained by the experiment under large twisting angle, which is much larger than reserved twisting angle. Then the shear strain threshold is determined accordingly. Afterwards, the torque threshold under small twisting angle, which is also the reserved twisting angle, is deduced indirectly, and this torque threshold can be used to determine the residual torque according to given time. Besides, in order to prove the correctness of the above theory and the method in this article, the experiment under middle twisting angle, which is larger than reserved twisting angle, is carried out to obtain the shear strain threshold accordingly and the torque threshold under small twisting angle is also deduced. The two thresholds determined by the above two kinds of experiments are well accordant, which greatly proves the correctness of the above theory and the method.