Evolution Law of Parameters in Surface Crack Propagation Rate Test under Cantilever Bend Loading

Under cantilever bend loading,a test method of six-grade nominal strain from low to high gradually as controlling mode was adopted and low cycle fatigue surface crack propagation rate test of 10CrNiMo steel were performed in three pieces of specimens. The test data manifested that under the control of every grade nominal strain,the peak and valley values of displacement and force were invariable basically,and with increase of the nominal strain grade,the average values of displacement and force had a tendency of increase to negative direction,while under the control of low nominal strain,evolution law of the three values of strain were similar as those of displacement and force,but with increase of nominal strain grade,the peak and valley values of strain trended to enlarge to the positive direction. An analysis was carried out and the results showed the reason of above phenomena was relative to residual strain.