• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.757-762
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• 2010

Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.331-342
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• 2009

A reliability analysis of the fatigue failure of highway steel bridges was performed by applying the Miner's fatigue damage rule for the fatigue design truck proposed for the LRFD code and for the current DB 24 truck. The limit state function for fatigue failure is expressed as a function of various random variables that affect fatigue damage. Among these variables, the statistical parameters for the equivalent moment, the impact factor, and the loadometer were obtained by analyzing recently measured domestic traffic data, and the parameters for the fatigue strength, the girder distribution factor, and the headway factor were obtained from the measured data reported in literature. Based on the reliability analysis, the fatigue truck model for the LRFD code was proposed. After applying the proposed fatigue truck to the LRFD code, 16 composite plate and box girder bridges were designed based on the LRFD method, and the LRFD design results for the fatigue limit state were compared with those by the current KHBDC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1181-1187
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• 2012

For the fatigue design of aircraft landing gear, the safe-life approach is applied. Structural defects such as cracks or detrimental deformations should not occur under the fatigue load spectrum depicting the entire lifetime usage of the aircraft. In the design phase, the fatigue life of the landing gear is estimated analytically by adopting the stress-based approach because the fatigue of aircraft landing gear is generally high-cycle fatigue. This utilizes S-N curves that are factored to produce design curves that account for the scatter and surface finish of the material. In the test and evaluation phases, a fatigue test should be conducted for full-scale landing gear to substantiate the fatigue design requirement in the end. In this study, the procedure for the fatigue test and evaluation of aircraft landing gear is presented with real application cases.

• Composites Research
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• v.16 no.6
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• pp.48-55
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• 2003

This research makes comparisons of empirical fatigue-lives between AC8A A1 alloy and the metal matrix composites(A1/A12O3, A1/A12O3/A12O3p), and also includes comparisons of fatigue-lives between empirical fatigue-lives and estimated fatigue-lives from regular-periodic load testing, AE method to predict fatigue-crack initiation before visible in sight and SEM(scanning electron microscope) photographs of each material. According to the test results of the notched specimen. the fatigue life of the hybrid metal matrix composites and the metal matrix composites, which are more brittle than the base matrix was shorter than that of the base matrix under both types of loads. In addition, the fatigue-life estimated from the damage summation method and that from experiments at random loads were fairly identical.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.211-221
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• 2007

A structural reliability analysis of fatigue truck model for fatigue failure of highway steel bridges was performed by applying the Miner's fatigue damage rule expressed as a function of various random variables affecting fatigue damage. Among the variables, the statistical parameters for equivalent moment, impact factor, and loadometer were obtained by analyzing recently measured domestic traffic data, whereas the parameters on fatigue strength, girder distribution factor, and headway factor of the measured data available in the literature were used. The effects of various fatigue truck models, fatigue life, ADTT, fatigue detail category, loadometer, and gross vehicle weight of fatigue truck on the reliability index of fatigue damage were analyzed. It is expected that the analytical results presented herein can be used as a basic background material in the calibration of both fatigue design truck and fatigue load factor of LRFD specification.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.11a
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• pp.251-254
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• 2001

조명 색온도에 따른 작업자의 피로도를 평가하기 위하여 세 종류의 조명 색온도 (2700K, 4000K, 6500K)를 실험변수로 하여 오류수정작업이 수행되었다. 작업수행 중 피로도와 집중도에 관한 주관평가를 실시한 결과, 시각 및 정신피로가 가장 적고 집중도가 높은 2700 K에서 작업수행도가 가장 좋았다. 6500 K에서는 정신피로를 가장 많이 느끼고 집중도가 제일 낮았으며, 4000 K에서 시각 및 정신피로를 가장 많이 느끼며 작업수행도는 가장 낮았다.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.813-816
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• 2010

본 논문에서는 자동차 배기계를 구성하고 있는 Flexible Tube의 형상에 따른 응력 해석 결과를 이용하여 피로 해석을 하였다. 아울러 Flexible Tube의 변위량이 크게 발생하는 것을 고려하여 기하학적 비선형 해석을 실시하였으며 Flexible Tube의 변형량은 끝단에서 6mm의 변위가 발생하도록 하였다. 본 연구에서 얻어진 결과는 다음과 같다. (1) Tube의 반경이 증가하면 피로한계 응력반복수는 선형적으로 감소한다. (2) 본 연구에서 사용된 tube중 주름의 반경이 1.7mm일때 피로 수명이 가장 긴 것을 알 수 있다.

• Journal of the KSME
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• v.28 no.4
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• pp.349-365
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• 1988

항공기 엔진, 발전 설비, 원자로 등과 같이 고온에서 작동하는 구조물 및 부품은 피로 파괴, 크립 파괴 또는 복합된 크립-피로(creep fatigue) 파괴에 대비하여 설계될 것이 요구된다. 관련 소 재를 살펴보면 항공기 엔진에 많이 사용되는 nickel-based superalloy로부터, land-based turbine rotor 등에 사용되는 low alloy ferritic steel 등으로 다양하다. 이외에도 austenitic stainless steel(Type 300 series)이 원자로에 많이 쓰이고 있다. 따라서 이러한 여러 가지 재료에 대한 고온 피로와 복합된 크립 파괴에 대하여 많은 연구가 진행되어 왔고, 앞으로도 보다 안전한 설 계를 위하여 계속될 전망이다.

• Journal of the KSME
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• v.31 no.4
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• pp.356-363
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• 1991

선형 탄성 유한요소 응력해석과 평균응력 효과를 고려한 저주기 피로실험으로부터 결정된 피로 특성, 그리고 국부변형률 방법을 종합하여 외경에 흠이 존재하는 자긴가공된 두꺼운 압력 용기의 피로수명이 평가되었다. 직사각형의 매우 날카로운 흠에서의 응력집중계수는 타원형 홈에서의 응력집중계수의 약 두배의 값이 얻어졌으며, 고강도 압력용기강인 ASTM A723의 저주기 피 로거동에 대한 평균응력 영향은 Morrow 및 SWT 파라메타를 이용하여 충분히 고려되었다. 균열발생이 예상되는 위험한 부분인 홈의 뿌리부분에서의 국부적인 응력, 변형률이 계산되었으며 예측된 피로수명은 실험적으로 얻어진 수명과 비교했을 때 2에서 4배의 오차를 보이면서 일치 하는 결과를 얻었다.

• Applied Biological Chemistry
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• v.36 no.3
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• pp.163-171
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• 1993

The collagens from filefish (Novoden modestus) and cod (Gadus macrocephalus Tilesius) skin were isolated and their physicochemical properties were investigated. Glutamic acid, hydroxyproline, valine and phenylalanine in the filefish skin collagen (FSC) were presented at higher levels than those of cod skin collagen (CSC), but the contents of glycine, proline and serine were contrary. The content of essential amino acids of FSC (265 residues/1000 residues) was higher than CSC (229 residues). The solubilities of both collagens were the lowest at pH 7.0, but precipitously increased at acid zone(below pH 5.0). FSC has lower viscosity than CSC. Furthermore, while the viscosities of both collagens were the lowest at pH 7.0, the viscosities of FSC and CSC were the highest at pH 4.0 and pH 2.0, respectively. The denaturation temperature of $FS(25^{\circ}C)$ was higher than $CSD\;(17^{\circ}C)$. The free hydrophobic residue contents of FSC and CSC tended to increase till $60^{\circ}C,\;and\;50^{\circ}C$ respectively, and to decrease thereafter. Hydration capacities of both collagens were the lowest at pH 7.0, and CSC had the superior hydration capacity to FSC. In addition, emulsifying and emulsifying stability of CSC was also superior to FSC.