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최성대,三澤啓志 금오공과대학교 산업기술개발연구원 2001 産業技術開發硏究 Vol.17 No.-
Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are 200㎛ and 1000㎛. For this material, △Kth is about 8MPa√m which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especially in the low △K regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the △Keff was represented by narrow band regardless of the stress ratio.
해양구조물 TMCP강의 피로균열진전거동에 미치는 용접이방성 및 과대하중의 영향
최성대,이종형,三澤啓志 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.6
The effect of the welding for the offshore structure in the TMCP steel on the fatigue crack propagation rate and crack opening-and-closure behavior was examined. The welding anisotropy of the TMCP steel and crack propagation character-istics of the excessive loading were reviewed (1) It seemed that a heat which was generated by the welding made a compressive residual stress over the base metal, so fatigue crack propagation rate was placed lower than in case of the base metal. (2) In the base metal, an effect of the anisotropy which has an effect on fatigue crack propagation rate of the excessive load and the constant amplitude load was not found but in the welding material case, fatigue crack propagation rate of the excessive load in the specimen of the width direction was located in the retard side as compared with a specimen rolling direction. (3) A crack opening ratio of the used TMCP steel in this study was not changed after excessive loading but a retard phe-nomenon of crack propagation was observed. Consequently, it was thought that all of the retard phenomenon of crack propagation did not only a cause of the crack opening-arid-closure phenomenon.
최성대,鈴木 裕土,秋田 貢一,三澤 啓志 金烏工科大學校 2000 論文集 Vol.21 No.-
X-ray stress measurements of a single crystal silicon were carried out using characteristic X-rays. The χy-oscillation method was used as the oscillation method of a specimen for obtaining a perfect diffraction profile. Applied stress measurements of a single crystal silicon were carried out using characteristic X-rays. The stresses in three steps were applied on a specimen using a four-point bending device. The diffraction angles of three different diffraction planes were measured in each step using a φ800 ㎛ collimator, and the stresses were calculated from the peak shift. The measured stresses agreed well with the applied stresses evaluated using a strain gage. Therefore, the possibility of X-ray stress measurements of a single crystal was confirmed.