腐食疲労き裂伝ぱに及ぼす応力波形効果

概要

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A study was made on the effects of stress increasing time or stress rise time T_1, maximum stress holding time T_2, stress decreasing time T_3 and minimum stress holding time T_4 in a wave on fatigue crack growth for a low alloy carbon steel (σ_u=91.8 kg/mm^2, σ_y=81.5 kg/mm^2) in 3% NaCl solution. Measurements of the effective stress intensity range ratio U and observation of crack tip were performed to clarify the cause of waveform effect. The results were summarized as follows. (1) T_1 had a strong accelerating effect due to corrosive dissolution of fresh surface of the crack which was formed during T_1. The crack growth rate was enhanced as T_1 increased and reached to a constant value (about 3 times than that in air) after T_1=10 sec. The crack growth rate at low ΔK, however, decreased as T_1 increased (more than T_1 = 1 sec). (2) T_2, T_3 and T_4 decreased the crack growth rate, respectively. The extent of decrease not only depended on the period of T_2 (or T_3, T_4), but also on ΔK and T_1. (3) The crack growth law which was derived by considering the effects of waveform and frequencies in the previous paper, is also valid to first approximation for the present results.
社団法人日本材料学会の論文
1978-10-15