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소형 펀치 크리프 실험변수 변환에 의한 크리프 특성 평가
김범준(Bumjoon Kim),배시연(Siyeon Bae),심언태(Untae Shim),임병수(Byeongsoo Lim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Generally, the conventional creep specimen is tested under uniaxial stress whereas the small punch creep specimen is under multiaxial stress. The focus of this work is to investigate the relationship between the small punch creep test data and conventional creep test data by the analysis similar to the Monkman-Grant relationship using the experimentally acquired test data. Creep behavior of 9Cr-2W ferritic steel was studied at elevated temperature. Creep tests were performed using a small punch creep tester at constant loads and a conventional creep tester at constant stress. Time to fracture and the minimum displacement rate measured during the small punch tests are related in a similar manner to the corresponding conventional creep tests. From the relation derived similar to the Monkman-Grant relation, a correlation between the displacement rate in small punch creep test and the strain rate in conventional creep test is established and creep lives were evaluated by it.
김범준(Bumjoon Kim),임병수(Byeongsoo Lim),류승진(Seungjin Ryu),김대욱(D. Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3
The use of aluminum alloys is an attractive possible option in order to reduce the weight of automobile body structures and to achieve the subsequent improvement of fuel economy and driving performance. In this study, the post-weld cold working process was used to improve the fatigue strength of aluminum resistant spot welds (Al RSW). The post-weld cold working process includes the special shaped indenters that are pressed or driven into the weld nugget area in order to induce the compressive residual stresses. Comparisons of the fatigue life and the failure modes between the as-welded specimens and the post-weld cold worked Al RSW specimens are discussed. Also, in order to analyze the failure behavior, finite elements method (FEM) was employed to compare the results with the experimental results.
P92강 용접부의 피로균열 성장거동에 미치는 미세조직의 영향
김범준(Bumjoon Kim),임병수(Byeongsoo Lim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8
Fatigue strength and life of weldment at high temperature is very important for high temperature materials used in power plants. In this study, fatigue crack growth tests were performed to examine the effect of microstructure on the crack growth resistance in P92 steel weldment. Microhardness of the weldment was also investigated for better analysis. Residual stresses were removed by heat treatment to focus the study on the microstructural effect. CT specimens were made from the welded plate with notch at different distances from the fusion line. The fatigue crack growth rate was found highest along the fusion line and fusion line+2㎜ line into the heat affected zone.