• Elastomers and Composites
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• 제42권4호
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• pp.209-216
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• 2007

가변진폭 하중에서 고무부품의 피로수명 예측방법에 대하여 연구하였다. 서로 다른 변위에서 변위제어 피로시험을 수행하였으며 피로손상변수로 최대 Green-Lagrange 변형률을 선정하였다. Green-Lagrange 변형률에 의한 고무의 피로수명 곡선은 3차원 덤벨시편의 비선형 유한요소법을 이용하여 결정하였다. 피로수명 예측을 위하여 가변진폭 하중이력으로 SAE의 하중이력을 이용하였다. 레이스트랙법과 단순화된 레인플로집계법을 이용하여 하중이력신호를 축약하였다. 누적손상피로를 계산하는 방법으로 수정Miner 법칙을 이용하였으며, 최종적으로 하중이력신호에서 최대 진폭의 30% 이하를 노이즈로 간주하여 예측하였을 경우의 피로수명은 실제 가변진폭 하중 하에서의 피로시험결과와 비교적 잘 일치하였다.

• 대한기계학회논문집
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• 제12권6호
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• pp.1350-1357
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• 1988

A computer software was developed for predictions of fatigue crack initiation life of notched members under variable loadings. The software was constructed based on a new fatigue life prediction method utilizing modified .epsilon.-N curves, which can account for the stress interaction effect. The effect of mean plastic strain on low-cycle fatigue life was also incorporated in the software. The software can be utilized for the first step approximation when fundamental data of material fatigue properties are not available.

• 한국산업정보학회논문지
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• 제27권5호
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• pp.73-82
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• 2022

고혈압과 같은 만성질환은 발병의 원인은 다양한 요인들이 복합적으로 작용하기 때문에 생애주기에 따라 차별화된 관리가 필요하다. 본 연구는 머신러닝을 이용해 고혈압 발병에 영향을 미치는 요인들의 생애주기별로 차이를 분석한다. 이를 위해, 질병관리청의 국민건강영양조사 데이터에 대한 전처리 및 변수 선택 과정을 거쳐 총 35개의 변수를 활용했다. 분석결과, 트리기반 머신러닝 모델 중 XGBoost가 중년과 노년 모두 예측 성능이 높은 모델로 나타났다. 변수중요도를 통해 도출된 생애주기별 고혈압 위험요인을 살펴보면 중년의 경우 개인특성 요인, 유전적 요인, 영양섭취 요인이 고혈압 위험요인으로 나타났고, 노년의 경우 영양섭취 요인, 식생활 요인, 생활습관 요인이 고혈압 위험요인으로 도출되었다. 본 연구 결과는 생애주기별 고혈압 관리에 유용한 기초자료로 사용될 수 있을 것으로 기대된다.

• Corrosion Science and Technology
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• 제20권4호
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• pp.169-174
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• 2021

In this study, performance tests, a field evaluation, and a life cycle cost (LCC) analysis for high performance coating systems were conducted to prepare a plan to reduce the cost of maintenance coating and contribute to the service life extension of steel bridges by applying high performance coatings to steel bridges that will be constructed in the future. From the deterioration models based on the field evaluation for chlorinated rubber and urethane topcoat systems, which have been applied often, the mean service lives were derived as 20.8 and 26.6 years, respectively. For the other coating systems that have not been applied in practice, the coordination factors were differentially applied with evaluation items. The most durable coating system was predicted to be thermal spray coating (TSC) primer/epoxy intermediate coat/fluoride resin topcoat, with a predicted value as long as 42.2 years. The LCC analysis indicates that partial application of high performance coating, such as TSC and fluoride resin, to specific parts vulnerable to corrosion and ultraviolet ray (UV) is more advantageous than the use of general coating systems.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.339-349
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• 2004

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with $L_{50}$ life of L-P model, Crossland criterion for the radial load increment is similar to $L_{50}$ life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact. there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• 한국정밀공학회지
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• 제24권5호
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• pp.44-55
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• 2007

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with L50 life of L-P model, Crossland criterion for the radial load increment is similar to L50 life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact, there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• 한국정밀공학회지
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• 제28권9호
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• pp.1062-1069
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• 2011

In electro-galvanizing line to manufacture the electro-galvanized steel sheet, polishing system is required to maintain clean surface of conductor roll and to secure the quality of the steel sheet. At the same time, prediction and decision of the replacement cycle for felt material and its brush installed in the polishing system is also important because the brush is directly contacted on the conductor roll surface. In this study, the polishing system has been designed which the brush is repetitive translating according to the longitudinal direction of the conductor roll. Furthermore, the prediction on the wear-life of the felt material used for the brush is performed using the contact pressure extracted by finite element analysis. And to verify the predicted wear-life of the felt material, the experimental study is also carried out. From the comparison result between the predicted and the measured wear-life of the felt material, it is presented that the wear-life and the replacement cycle of the felt material are well predicted by considering a wear compensation factor, and the wear compensation factor is useful and reasonable.

• International Journal of Ocean System Engineering
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• 제1권3호
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• pp.171-179
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• 2011

This paper presents the concept design procedure of a floating-type combined renewable energy platform based on hydrodynamic analyses and is focused on the fatigue design of taut-type mooring lines of the platform. Two types of combined renewable energy platforms are considered: a combination of wind turbine, wave turbine and photovoltaic energy plant and a combination of wind turbine, current turbine and photovoltaic energy plant. The basic configurations are conceptually determined from the understanding of floating offshore plants, while the main dimensions have been determined based on a hydrostatic calculation. Fully coupled hydrodynamic analyses have been carried out to identify the motion characteristics of the floating body and the tension histories of the mooring lines. The tension history is used for the fatigue life prediction based on the rain-flow cycle counting method. For the fatigue life prediction, tension life curves from API and the Palmgren-Miner rule are employed.

• Structural Engineering and Mechanics
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• 제28권4호
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• pp.387-410
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• 2008

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.281-284
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• 2006

The marine Transmission tower infrastructure erected in the SI-HWA lake is deteriorated and damaged by the various environment effect, and then, there is a possibility of going bad in the safety. The appropriate maintenance to ensure the security of the structure during life cycle is necessary. Specially the Jacket or the steel file foundation in the sea is apt to be corroded quickly. In this research, to establish life management system of 345kV Yonghung marine transmission tower structure, the actual durability research facility which can obtain the actual proof data is constructed. the maintenance guideline and procedure of the structure are established. Hereafter, there is a plan which will advance the research against the composition of the life prediction model, which is based on the data acquired from the actual durability research facility.