Through FRANC3D software, the life curves of samples containing surface crack and through crack are analyzed respectively under the same stress ratio, whose life results are calculated when reaching each critical condition. The test results show that the sample containing surface crack whose life N3D is 65870, and the sample containing through crack whose life N2D is 6434, N3D is about 10.4 times of N2D. In addition, the life test results of samples with different initial surface crack sizes

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... er the stress ratio R=0.1, 0.2, 0.3, 0.4, 0.5 cyclic load are also studied. Results show that the life N3D and the stress ratio R are obvious nonlinear relationship. Similarly, the life N3D and the initial crack half length c also show obvious nonlinear relationship.