高温における線材の定ひずみ塑性ねじり疲労

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In this paper is presented a report of tests of constant strain low cycle torsional fatigue that were carried out on 0.81%C piano wires at room temperature and at elevated temperatures 270℃, 300℃ and 400℃ respectively, with a view to the investigation of the plastic fatigue phenomena. Three kinds of torsions were worked for the tests, completely reversed, fluctuating and pulsating, under the test speed of 1rpm. The main results obtained are as follows. (1)There is larger effect of temperature on the fatigue life than that of the mean strain. Let the strain amplitude stand as it is, there is longer fatigue life at 270℃ and shorter fatigue life at 400℃ than room temperature, the former case being considered to be annealing effect. (2)The time-strength diagram show linear decrease in strain amplitude γ_a against increase in the mean strain γ_m which the latter represents the number of cycles from the initiation of macrocrack N'=50 to its fracture N=200 or N=1 000. (3)The test result shows that there exists linear relationship between the total plastic strain γ_<p. total> and N' when they are plotted on a log-log scale. It is found also that the same relationship holds for the total hysteresis energy W, the not-total hysteresis w' and the strain amplitude γ_a. In the completely reversed tests, γ_<p.total> and W are defined as γ_<p.total>=4Σ^^N__<n=1>γ_p+γ_<mf> and W=w・N, in which γ_p and γ_<mf> are the plastic strain amplitude and the mean strain just before fracture, respectively.
社団法人日本材料学会の論文
1972-09-15

高温における線材の定ひずみ塑性ねじり疲労

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