• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.116.2-116.2
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• 2005

• 대한기계학회논문집A
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• 제28권6호
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• pp.791-798
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• 2004

Fatigue crack initiation lives of round cylindrical notch specimen were investigated. Firstly, local strain approximation methods, such as the modified incremental Neuber's rule and the modified incremental Glinka's equivalent strain energy density(ESED) rule, were used to get multiaxial stress and strain state components at the notch tip. Based on the history of local stress and strain, multiaxial fatigue models were used to obtain fatigue crack initiation lives. Because the solution of Neuber's rule and Glinka's ESED rule make the upper and lower bound of local strain approximations, fatigue crack initiation lives are expected to place between life predictions by two local strain approximations. Experimental data were compared with the fatigue crack initiation life prediction results.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.80-89
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• 1996

Fatigue life of a notched shaft was evaluated in order to estimate the durability and integrity of the notched shaft in design stage. Cumulative fatigue dama- ge analysis was performed using local strain approach based on the assumption that the fatigue life of a notched component is approximately same as that of a smooth specimen is subjected to the same strain at the notched component. In this paper, shafts with different notch root radius of 1, 2㎜ resulting in different values of stress concentration factors were tested under||rotating bending fatigue loading condition. Theoretical stress concentration factor for each notch type was calculated using finite element method. Fatigue life prediction program, FALIPS, written in C language was developed using the strain-life curve, and the local strain approach integrating Neuber's rule, cyclic stress-strain, and hysteresis loop equations. The fatigue life evaluated using the fatigue notch factor obtained from the experimentally determined fatigue strength showed very large scattering with nonconservatism, but the fatigue notch factors derived from the stress concentration factors and Peterson's equation reduced the considerablely accurate fatigue life evaluation within a factor of three.

• 대한기계학회논문집A
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• 제21권2호
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• pp.199-208
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• 1997

A local strain approach was applied to an external single and double grooved C-shaped specimen in order to evaluate and predict the fatigue crack initiation life by using low cycle fatigue properties. The low cycle fatigue properties were determined from the strain-controlled fatigue tests using smooth cylindrical axial specimens. Fatigue crack initiation life was evaluated by a life prediction software, FALIPS, based on the local strain approach. The fatigue life was significantly influenced by the mean stress, and SWT parameter represented the fatigue life effectively. The predicted fatigue crack initiation life was then compared to the experimental fatigue life evaluated from the C-shaped fatigue test specimens. A good correlation was found between the experimental and predicted fatigue lives within factors of 2 and 4 for the single and double grooved C-shaped specimens respectively. Also, experimental fatigue life of the double grooved specimen was 10-12 times longer than that of the single grooved specimen.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.131-139
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• 1993

Low cycle fatigue characteristics of cast aluminum alloy A356 with a yield strength and ultimate strength of 229 and 283 MPa respectively was evaluated using smooth axial specimen under strain controlled condition. Reversals to failure ranged from 16 to 107. The cast aluminum alloy exhibited cyclically strain-gardening behavior. The results of low cycle fatigue tests indicated that the conventional low cycle fatigue tests indicated that the conventional low cycle fatigue life model was not a satisfactory representation of the data. This occurred because the elastic strain-life curve was not-log-log linear and this phenomena caused a nonconservative and unsafe fatigue life prediction at both extremes of long and short lives. A linear log-log total strain-life model and a bilinear log-log elastic strain-life model were proposed in order to improve the representation of data compared to the conventional low cycle fatigue life model. Both proposed fatigue life models were statistically analyzed using F tests and successfully satisfied. However, the low cycle fatigue life model generated by the bilinear log-log elastic strain-life equation yielded a discontinuous curve with nonconservatism in the region of discontinuity. Among the models examined, the linear log-log total strain-life model provided the best representation of the low cycle fatigue data. Low cycle fatigue life prediction method based on the local strain approach could conveniently incorporated both proposed fatigue life models.