• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1403-1409
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• 2010

For many years, high-strength nickel-base superalloys have been used to manufacture turbine blades because of their excellent performance at high temperatures. The prediction of fatigue life of superalloys is important for improving the efficiency of the turbine blades. In this study, low cycle fatigue tests are performed for different values of total strain and temperature. The relations between strain energy density and number of cycles before failure occurs are examined in order to predict the low cycle fatigue life of IN738LC super alloy. The results of low cycle fatigue lives predicted by strain energy methods are found to coincide with experimental data and with the results obtained by the Coffin-Manson method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.753-758
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• 2011

The Ni-base super-heat-resistant alloy, GTD-111, is employed in gas turbines because of its high temperature strength and oxidation resistance. It is important to predict the fatigue life of this superalloy in order to improve the efficiency of gas turbines. In this study, low-cycle fatigue tests are performed as variables of total strain range and temperature. The relationship between the strain energy density and number of cycles to failure is examined in order to predict the low-cycle fatigue life of the GTD-111 superalloy. The fatigue life predicted by using the strain-energy methods is found to coincide with that obtained from the experimental data and from the Coffin-Manson method.

• Korean Journal of Materials Research
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• v.7 no.11
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• pp.1007-1011
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• 1997

영활화혁발전소 보일러헤다 재질인 1Cr0.5Mo강의 파형에 따른 저주기 피로특성을 규명하고자 상온(298K) 및 고온(177K)의 삼각파와 사인파형 저주기 피로시험을 수행하였고 소성에너지법을 이용하여 파형에 따른 소성변형에너지와 피로수명과의 +관계를 분석하였다. 저주기 피로시 재료내부의 소성변형에너지를 히스테리시스루프의 면적으로 계산하여 구하였으며 이를통해 저주기 피로수명을 예측하였고 Coffin-Manson법 및 변형률분할법을 이용한 저주기 피로수명 결과와 서로 잘 일치하였다. 또한 상온 및 고온에서 피로반복수의 증가와 함께 재료가 반봅연화됨을 알 수 있었다.

• Elastomers and Composites
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• v.42 no.4
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• pp.209-216
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• 2007

Fatigue life prediction methodology of the rubber component made of vulcanized natural rubber under variable amplitude loadings was studied. The displacement-controlled fatigue tests were conducted at different levels and the maximum Green-Lagrange strain was selected as damage parameters. A fatigue life curve of the rubber represented by the maximum Green-Lagrange strain was determined from the nonlinear finite element analysis. The transmission load history of SAE as variable amplitude loading was used to perform the fatigue life prediction. And then a signal processing of variable loading by racetrack and simplified rainflow cycle counting methods were performed. The modified miner's rule as cumulative damage summation was used. Finally, when the gate value is 30%, the predicted fatigue life of the rubber component agreed well with the experimental fatigue lives with a factor of two.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.845-851
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• 2017

Fatigue failure of an autofrettaged pressure vessel with a groove at the outside surface occurs owing to the fatigue crack initiation and propagation at the groove root. In order to predict the fatigue life of the autofrettaged pressure vessel, residual stresses in the autofrettaged pressure vessel were evaluated using the finite element method, and the fatigue properties of the pressure vessel steel were obtained from the fatigue tests. Fatigue life of a pressure vessel obtained through summation of the crack initiation and propagation lives was calculated to be 2,598 cycles for an 80% autofrettaged pressure vessel subjected to a pulsating internal pressure of 424 MPa.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.285-290
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• 2004

Low cycle fatigue tests are performed on the Inconel 617 that be used for a hot gas casing. The relation between strain energy density and numbers of cycles to failure is examined in order to predict the low cycle fatigue life of Inconel 617. The life predicted by the strain energy method is found to coincide with experimental data and results obtained from the Coffin-Manson method. Also the cyclic behavior of Inconel 617 is characterized by cyclic hardening with increasing number of cycle at room temperature.

• Journal of the KSME
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• v.28 no.4
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• pp.377-386
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• 1988

선박, 해양구조물을 중심으로 파괴손상례, 파괴해석방법, 파괴의 방지대책에 대해 기술하였다. 실제 구조물의 파괴는 매우 복합적인 요인에 의해 발생되기 때문에 그 요인 분석이 쉽지 않으나 최근 들어 파괴역학, microfractography의 발달로 비교적 상세하게 파괴요인이 밝혀지게 되었다. 일단 파괴가 발생하면 그 사고를 case study하여 대책을 강구함으로서 같은 류의 사고 발생률을 감소시킬 수 있다. 그러나 새로운 성능을 갖춘 구조물, 특수한 환경에 사용되는 구조물 등과 같 이 이제까지 경험하지 못한 구조물의 경우에는 사고 발생률이 높아 질 수밖에 없다. 이러한 구조물의 파괴를 방지하기 위해서는 보다 정확한 응력 또는 변형률 해석, 각종 현상을 재현한 시뮬레이션 시험법의 개발, 비파괴 검사기술의 개발과 더불어 재료개발에 병행되어야 할 것이다. 아울러 구조물의 잔존수명 예측 기술이 더욱 개발되어야 할 것이다.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.112-121
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• 1995

Various CAE technologies are used in automobile industries for the purpose of design and analysis. In this paper, a fatigue life evaluation system FLEVA based on the local strain approach is developed and the system is applied for the fatigue strength design of the suspension knuckle, an automobile component. Various steps such as material test, finite element analysis and cumulative fatigue damage analysis of the suspension knuckle were taken. The usefulness of the approach was verified by the fatigue test on the suspension knuckle.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.52-57
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• 2012

This study presents sealing characteristics of multi-contact o-rings as functions of strain, compression stress, and contact normal stress using a FEM technique. The FEM results on the sealing characteristics show that the maximum strain, maximum compression stress, and maximum contact normal stress of multi-contact o-rings are approximately 1.7 times higher than those of conventional o-rings. This is due to a U-grooved cross section of multi-contact o-rings, and the multi-contact o-rings with a U-groove show more effective in sealing for high pressure vessels, valves, and gas equipments. And the extrusion failure in the multi- contact o-ring does not produce for an increased gas pressure due to a U-groove. This may extend sealing life compared to that of a conventional o-ring.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1163-1169
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• 2012

Rubber, a hyperelastic material, is the main material used in tires. During the operation of a car, the tire receives various types of loads. The accumulation of strain energy due to such loads induces tire failure. Generally, because rubber materials used for tires have stress softening characteristics, unlike metals, test methods used for metals cannot be applied to rubber. Therefore, in this study, for the evaluation of the fatigue properties of two types of specimens that have different material components, a tensile test and a fatigue test according to the extended strain range dissimilar to ASTM D4482 are performed, and fatigue life equations are proposed based on the test results.