SCM 440材의 疲勞龜裂進展擧動 評價에 關한 實驗的 硏究 = An Experimental Study on the Evaluation of Fatigue Crack Propagation of SCM 440

다국어 초록 (Multilingual Abstract)

Using the CT specimen of SCM 440, we estimated the fatigue crack propagation behavior in stable crack propagation range. Furthermore the fatigue crack propagation rate, Acoustic Emission(AE) count rate, and fractography charactristics were also compared among others. The following results were confirmed by experimental obser- vation. Near-threshold stress intensity factor range(△K_th) is influenced by stress ratio, but not at the upper limit of stable crack propagation range. As stress intensity factor range (△K) and(or) stress amplitude increase(s), both crack propagation rate(da / dN) and AE count rate(dn/ dN ) increase. Effective stress intensity factor range(△Keff) determined from the crack closure point measurement by AE method is useful for the evaluation of fatigue crack propagation rate. Fractography in stable crack propagation range showed striation, and agreed with the crack propagation rate obtained either by experiment or by the results of microscopic measurements.
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