Study on elastic modulus of skarn under uniaxial cyclic loading and unloading

In order to explore the influence of different stress paths and different loading and unloading rates on the elastic modulus of skarn under cyclic loading, the conventional uniaxial compression test and two different schemes of five-stage cyclic loading and unloading test of skarn are carried out by using YAW-2000 microcomputer controlled electro-hydraulic servo rigid testing machine. The load control is selected for the cyclic loading and unloading test scheme. The loading and unloading rates are set to 1 kN/s, 2 kN/s and 3 kN/s. The upper limit ratios of cyclic stress are 60%, 70%, 80%, 90% and 100%. The single-stage stress amplitude is 6 vibration cycles. The results show that the hysteresis loops in the stress-strain curve of skarn show strip shape and needle tip shape under different cyclic paths, and the change trend is from dense to sparse, that is, the residual deformation increases gradually during the cyclic process. The peak strength increases with the increase of loading and unloading rate. The evolution law of elastic modulus in the whole process of cyclic loading and unloading increases first and then decreases, while the unloading elastic modulus increases steadily. It is concluded that the change of elastic modulus of skarn is greatly affected by the stress path, the curve is typical wavy, and the influence of loading and unloading rate is not significant. The loading and unloading response ratio fluctuates around 1, which can accurately reflect the damage development degree of the sample during the cycle.