モードIIIねじり荷重下における下限界近傍の疲労き裂伝ぱ挙動

概要

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Near-threshold fatigue crack propagation tests were performed on circumferentially precracked round bars of medium carbon steel under mode III torsional loading. The crack propagation rate was decreased with crack extension because of the shear contact of the crack faces. The crack propagation rate without the influence of crack surface contact was determined by extrapolating the relationship between the crack propagation rate and the crack extension to the zero crack extension. The applied stress intensity factor range was divided into two parts : one was the effective value which was responsible for crack growth and the other was the shielding value. The resistance curve method was used to predict the fatigue limits for crack initiation and fracture. The R curve was constructed using the experimentally determined threshold value of the stress intensity range which was the sum of the threshold effective stress intensity range and the threshold shielding stress intensity range. The threshold effective stress intensity range was constant. The R curve was independent of the crack length and specimen dimensions. The predicted values agreed well with the experimental results.
一般社団法人日本機械学会の論文
1997-08-25