13th International Conference on Fracture June 16–21, 2013,Beijing, China -9- considered carefully. Figure 7 displays that the fracture strain in the plate specimens decreases with the pre-strain, which seems to be corrected by the total equivalent plastic strain. This result shows the fracture strain for the SS304 is independent of loading history. Martensite transformation seems not to change the fracture strain significantly. Figure 7: Fracture strains as a function of pre-strains. Fracture strain with pre-strain denotes the total equivalent strain including the initial deformations. The other curves represent fracture strain measured in specimens. Effects of the pre-strain to fatigue life are not studied systematically. Observations of Miao et al. [14] reveal non-monotonic correlations between LCF life and initial plastic strains. By giving strain amplitudes, stress variations depend on initial treatment of the specimens significantly. In this sense, stress-controlled tests provide totally different results than the strain-controlled tests. Figure 8: Strain-fatigue life curves for both base material and pressed material from strain-controlled fatigue tests.
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