Study On The Fatigue Characteristic Of Containing Intermittent Cracked Rock-like Samples

Based on a large numbers of model/simulation test of the intermittent cracked Rock-like Samples, fatigue strength, fatigue deformation and crack appear in preexisting cracks tips, the growth of crack, the pattern of crack coalescence are studied/analysed systemically by means of cyclic load and static load, in the course of the model test, the difference between cyclic load and static load of crack appear in preexisting cracks tips, the growth of crack and the pattern of crack coalescence are observed and analysed. The mechanism of fatigue crack appear, the growth of crack and the pattern of crack coalescence are discussed. The influence of loading frequency and loading level on fatigue strength and fatigue deformation are studied. The test results show that fatigue strength of intermittent cracked Rock-like Samples is 70% -75% of static load strain rate is 10-5/s) maximal strength, under cyclic number exceed 3000 and loading frequency ranged from 0.02Hz to 2Hz (relevant strain rate ranged from 10-4/s to 10-2/s) cyclic load. The concerned research results show that fatigue strength of no-cracked sandstone samples is 83% of static maximal strength.Based on test result of Load-deformation hysteresis curve under cyclic load, fatigue damage variable is defined from energy angle, the change rule of fatigue damage is pointed out. Lastly, the rule of fatigue crack appear in preexisting cracks tips is established according to the principle of maximal tensile stress using the theory fracture and damage.