• Journal of the KSME
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• v.35 no.6
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• pp.504-516
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• 1995

작년에 발생한 성수대교의 파손사고는 인적손실은 물론 경제적 그리고 사회적으로 심각한 영향을 미쳤다. 현재 수많은 공장에서 가동되고 있는 크레인 관련 시설들은 변동응력의 작용과 용접구 조물이라는 점에서 성수대교와 유사한 조건을 가지고 있다. 또한 그중에서 많은 부분은 설계시 에는 고려치 못했던 부하조건의 가혹화와 노후화 때문에 손상 가능성이 항상 존재하고 있다. 이러한 점을 고려하여 필자들은 설비의 예방정비 차원에서 크레인 거더 및 런웨이 거더의 안정성 평가에 주목하게 되었고 나름대로 얻은 경험을 지면에 정리하여 보았다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.222-223
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• 2005

The Any failure of piston of marine diesel engine must be regarded as serious, and any steps which can be taken to prevent such failure are desirable. The purposes of this study is to investigate and to analyse the failure causes of piston of marine diesel engine. If this paper has accomplished that end it can be counted as being of some slight value to the marine industry.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.167-174
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• 2011

This research was conducted to propose the design methodologies of post-tensioned concrete pavements (PTCPs) for specialized section pavements. The specialized sections considered in this study included bus stop sections in urban bus-only lanes and culvert existing highway sections that often showed severe failures. The PTCP designs of those specialized sections were performed based on both the stresses and the fatigue failures, and more conservative design results were selected. In the stress based design, the maximum tensile stress under extreme load conditions was obtained using finite element analyses first. Then, the number of tendons and the tendon spacing were determined so that the tensile stress was less than the allowable flexural strength. The AASHTO fatigue failure equations were used in the fatigue failure based design. From this study, the design methodologies of PTCP for bus stop sections in bus-only lanes and culvert existing highway sections were successfully suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.911-917
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• 2010

In this study, we performed structural and fatigue analyses of the engine exhaust manifold that was subjected to thermo-mechanical cyclic loading. The methodologies used in this study are based on an approach in which the techniques for modeling the exhaust system, the temperature-dependent properties of the material, and thermal cyclic loading are taken into consideration and a reliable strategy is adopted for failure prediction. An application example shows that at an elevated temperature, considerable compressive plastic deformation is observed and that at a low temperature, tensile stresses remain in those parts of the test exhaust manifold where failure is observed. In order to predict fatigue life, mechanical damage is determined on the basis of the stress.strain hysteresis loops by using the classical Coffin.Manson equation and by adopting a method in which the dissipated plastic energy is taken into consideration.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.95-105
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• 2009

This study was conducted to investigate the effects of concrete flexural strength and surface smoothness, which were pay factors of concrete pavements, on pavement performance, and to develop the methodologies to determine the proper allowable ranges according to the magnitudes of those pay factors. The concrete flexural strength was analyzed using the AASHTO, power, and linear fatigue failure models, and the surface smoothness was analyzed for the roughness indices of PSI, IRI, and PrI using the AASHTO model. The analysis results showed that the allowable range of the flexural strength should be determined using the rate between the deficiency and strength, and the penalty should be linearly proportional to the strength deficiency rate because the linear relationship between the strength deficiency rate and the reduction in pavement life was observed. As the initial surface smoothness became better, the smoothness deficiency rate should be larger. The penalty due to the surface smoothness deficiency should also be linearly proportional to the smoothness deficiency rate.

• Composites Research
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• v.14 no.2
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• pp.50-59
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• 2001

The predictions of residual strength evolution and fatigue life of full scale composite rotor blade for multipurpose helicopter were studied using a strength degradation model. Flight-by-flight load spectrum was developed on the basis of FELIX standard spectrum data. The laminated structural analysis was also performed to obtain corresponding local stress and/or strain spectra for each ply of laminate skin and glass roving spar structures around the blade root where fatigue damage was severely anticipated.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.7-17
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• 2020

Heat recovery steam generator(HRSG) generate steam using the high-temperature exhaust energy of gas turbines. Structures of HRSG are damaged by flow induced vibration of flue gas in some cases. In order to evaluate fatigue life to predict damage to a structure, a vibration analysis caused from flue gas should be used to derive the Power Spectral Density(PSD). However, it is very difficult to experimentally derive the vibrations generated by the exhaust gas form of gas turbines, which is very fast and complex. It was able to establish a way to identify vibration characteristics depending on the location of the structure by using high computing resources, large eddy simulation (LES). Random vibration analysis through these vibration characteristics(PSD) can evaluate the fatigue life of a structure.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.85-93
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• 2012

In this study, the geometry of the weld is used to develop the process of fatigue life prediction. For the development of fatigue life prediction process, bending fatigue test of muffler is conducted to obtain M(Moment)-N(Fatigue life) diagram. Modeling the geometry of the weld which is failed is performed to conduct static load analysis and analysis results are used to calculate the stress concentration factor. The stress concentration factor is used to get the fatigue notch factor and this was based on the fatigue life prediction. As a result of the comparison of test values and predicted values, predicted values are verified.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.5
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• pp.34-45
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• 1989

성장하는 균열에 의한 변형 에너지해방에 기반을 둔 간단한 파괴역학적인 접근법이 고무의 여러가지 특성을 규명하는데 성공적으로 응용되는 예들을 논의하였다. 이 방법은 전통적인 강도, 즉 찢김, 균열성장, 피로, 인장파손 등 뿐만 아니라 오존내습(ozone attack), 예리한 공구들에 의한 마쇄, 절단현상을 규명하는데도 응용가능함을 밝혔다. 특히 에너지해방율은 여러가지의 다른 시험편에 대한 실험값들이 서로 연관성을 갖도록 허용하기 때문에 매우 유용한 특성이라 할 수 있다.

• Journal of the KSME
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• v.49 no.12
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• pp.54-59
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• 2009

자동차 부품 등 내구재의 파손은 긴 시간 동안 누적된 비교적 크기가 작고 빈도가 많은 입력하중에 기인하거나 상대적으로 적은 수의 큰 입력하중에 의해 유발된다. 미션 프로파일화(Mission Profiling)와 미션 합성(Mission Synthesis)은 어느 시험실에서나 공통된 장비를 이용하여 실제 환경에서 제품이 받는 동일한 수준의 피로 손상도를 보장하면서 훨씬 단축된 시험을 구현할 수 있는 시험 규격을 만들어 내는 과정이다. 이 글에서는 최신의 기술을 이용하여 이와 같은 가속화 진동내구 시험의 목적을 이루는 것에 관해서 소개한다.