13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- а) b) Figure 2. Surface images of failured specimens at static tensile tests: а) specimen without treatment; b) after nanostructuring surface; а), b) optical images, axis of loading is oriented horizontally 2.4. Cycling tension tests 2.4.1. Low-cycle fatigue (LCF) 12Cr1MoV Results of cyclic tension tests have shown that under LCF the number of cycles prior to the fracture of the specimens with nanostructured surface layer is increased by 3 times. In doing so, the time before main crack initiation is increased approximately by3 times. The graphs of dependence of the main crack length versusthe number of cycles were plotted. It is clear that for the treated specimen later origination and more slow development of the main crack in the specimen is characteristic feature as compared with oneswithout the treatment. For the latter the rate of crack growth makes 0.085 μm/cycle while for one with nanostructured surface layer it makes 0.023 μm/cycle which is lower by more than 3.5 times. Thus, a modified surface layer effectively hinders the fatigue crack origination. In doing so the number of cycles before the main crack appearance is enlarged by 3 times and reduces the rate of its growth. 2.4.2. High-cycle fatigue (HCF) 12Cr1MoV The results of tensile tests under HCF showed that the number of cycles prior to the fracture of specimens with nanostructured surface layer is increased by 2 times.The number of cycles before the crack nucleation is increased approximately by 2 times. Based on analysis of optical images the
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