重複繰返し荷重下での炭素鋼のねじり塑性疲労 : S45Cの場合

概要

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The authors have carried out the low-cycle torsional fatigue tests under multiple repeated loads by using annealed carbon steel S45C, and investigated experimentally the applicability of the fatigue fracture criterion 1/(C_0)∫^N_0γ_p^adn=1 based on varying plastic strains, which was introduced instead of the linear damage criterion Σ(n/N)=1 based on stresses. Furthermore, the applicability of the above fracture criterion has been also discussed on the basis of the experimentally determined correlation between the equivalent stress amplitude and the equivalent plastic strain amplitude. The main conclusions obtained are summarized as follows: (1) The present test results were similar to the ones that the authors carried out previously under the periodical 2-step or 3-step multiple repeated loads by using 0.84%C piano wires. The values of fatigue life obtained from the fatigue fracture criterion based on varying plastic strains were slightly closer to unity than those calculated from the linear damage criterion. Therefore, when used for predicting the fatigue life under the stress control test, the fatigue fracture criterion based on varying plastic strains is better than the linear damage criterion. (2) From the test results, a log-log straight line relationship was found to hold between the equivalent stress amplitude and the equivalent plastic strain amplitude.
1976-08-15