• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.122-126
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• 2000

In particle or short-fiber reinforced composites cracking of the reinforcements is a significant damage mode because the broken reinformcements lose load carrying capacity . The average stress in the inhomogeneity represents its load carrying capacity and the difference between the average stresses of the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix, An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. influence of the cracking damage on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.287-292
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• 1998

In particle or short-fiber reinforced composites. cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with the load carrying capacity of intact and broken ellipsoidal inhomogeneities embedded in an infinite body and a damage theory of particle or short-fiber reinforce composites. The average stress in the inhomogeneity represents its load carrying capacity. and the difference between the average stresses of the intact t and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix. An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori and Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.206-211
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• 2000

The accelerated testing technique using the equivalent load condition plays an important part in development process. However, in the industrial field, the theoretical background and advantages of this accelerated testing technique have been lack of understanding. Because the environmental durability condition forms the foundation of the accelerated testing technique, it is important to analyze the loading components and damage in service environment. In this work, we present the theoretical background and process for accelerated testing, and introduce our accelerated equivalent load analysis program. We developed the GUI program, and the user can easily obtain the result by selecting the program module.

• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.192-202
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• 2002

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the cracked reinforcements lose load carrying capacity. This paper deals with an incremental damage theory of particle or short-fiber reinforced composites. The composite undergoing damage process contains intact and broken reinforcements in a matrix. To describe the load carrying capacity of cracked reinforcement, the average stress of cracked ellipsoidal inhomogeneity in an infinite body as proposed in the previous paper is introduced. An incremental constitutive relation on particle or short-fiber reinforced composites including progressive cracking of the reinforcements is developed based on Eshelby's (1957) equivalent inclusion method and Mori and Tanaka\`s (1973) mean field concept. Influence of the cracking damage on the stress-strain response of composites is demonstrated.

• International Journal of Automotive Technology
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• 제6권3호
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• pp.285-291
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• 2005

In this paper, the author proposes a fatigue damage parameter of spot welded joints under proportional loading. The proposed fatigue damage parameter is developed based on von Mises' equivalent stress and local structural stress at the edge of spot weld nugget. The structural stress at the edges of the weld nugget in each sheet is calculated using the forces and moments that are determined by finite element analysis. A structural equivalent stress is then calculated by von Mises' equivalent stress equation. The structural equivalent stresses are correlated to experimental fatigue life of the spot welded joints. The proposed parameter is evaluated with fatigue test data of spot welds subjected to multi axial and tensile-shear loads. Sheppard's parameter and Rupp and co-workers' parameter are also evaluated with the same test data to compare with the author's parameter. This proposed parameter presents a better correlation with experimental fatigue data than those of Sheppard's and Rupp and co-workers' parameter. The proposed parameter should be very effective for durability calculations during the early design phase since coarsely meshed finite element models can be employed.

• 한국구조물진단유지관리공학회 논문집
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• 제8권4호
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• pp.239-246
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• 2004

충격하중에 대한 양단 고정보의 거동을 강 소성 모델을 이용하여 파악 하였다. 또한 손상을 발생시키는 정 역학적 붕괴하중과 이상임펄스에 대한 하중최대치 비와 임펄스 비를 이용하여 손상곡선을 작성하였다. 작성된 손상곡선으로부터 충격하중의 하중 최대치와 임펄스는 구조물의 안전에 중요 변수가 됨을 보였으며 또한 하중최대치 비와 임펄스 비로 작성된 손상곡선은 하중작용시간과 하중의 형태 그리고 구조물의 동적 특성이 함께 고려된 기준으로, 등가 동하중에 초점을 맞추어 일괄적으로 구조물의 안전성을 판단할 수 있는 방법이다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권1호
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• pp.157-164
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• 2004

강 소성 모델을 이용한 단순보의 손상곡선을 소성힌지를 발생시키는 정역학적 붕괴하중과 이상임펄스에 대한 하중최대치 비와 임펄스 비를 이용하여 작성하였다. 작성된 손상곡선으로부터 임펄스와 하중 최대치가 구조물의 안전에 중요 변수가 됨을 보였으며 또한, 하중최대치 비와 임펄스 비로 작성된 손상곡선은 하중작용시간과 하중의 형태 그리고 구조물의 동적 특성이 함께 고려된 기준으로, 등가 동하중에 초점을 맞추어 일괄적으로 구조물의 안전성을 판단할 수 있는 방법이다.

• 콘크리트학회지
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• 제6권2호
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• pp.148-158
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• 1994

본 논문은 실제 교량위를 통과하는 차량에 의하여 프리스트레스트 콘크리트 합성거다 교량에 발생하는 프로하중을 합리적으로 표현할 수 있는 등가프로하중모델을 도출하는데 그 목적을 두고 있다. 교량에 작용하는 피로하중은 그 크기와 지속시간이 불규칙피로하중과 같은 피로손상을 줄 수 있는 등가의 피로하중 모델을 제안하여 피로해석 및 설계를 간편하고 합리적으로 수행할 수 있도록 하였다. 또, 이 모델의 적용성을 검토하기 위하여 국내의 교통량조사 자료를 이용하여 교량을 통과하는 차량의 확률모델을 도출하고, 이 모델로부터 작용 모멘트의 확률특성을 결정하여 피로해석을 수행하였다.

• 한국공작기계학회논문집
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• 제13권4호
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• pp.106-112
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• 2004

In particle or short-fiber reinforced composites, cracking or debonding of the reinforcements cause a significant damage mode because the damaged reinforcements lose load carrying capacity. The average stress in the inhomogeneity represents its load carrying capacity, and the difference between the average stresses of the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix. An incremental constitutive relation of discontinuously-reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.693-697
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• 2005

This study was performed to develop accelerated life test method of the wind-turbine gearbox using accumulated damage theory that used to model the fatigue of parts that receive variable load. The accumulated damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of the gearbox was described. Life distribution of the wind-turbine gearbox was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 140,600 hours and 99% reliability for one test sample According to the accumulated damage theory, because test time can shorten in case increase test load, test time could be reduced by 1.2 years when we put the load 1.2 times of rated load than 0.93 times of rated load that is equivalent load calculated by load spectrum of the wind turbine. This time, acceleration coefficient was 21.3. This accelerated test method was used to develop accelerated test method of gear reducer, gear and bearing as well as the industrial gearbox and it is considered to be applied comprehensively to mechanical parts the fatigue of which is happened by load or pressure etc.