• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.239-239
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• 2003

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.114-121
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• 2004

Recently, the finite element absolute nodal coordinate formulation (ANCF) was developed for the large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. In this paper, a computation method of dynamic stress in flexible multi-body dynamics using absolute nodal coordinate formulation is proposed. Numerical examples, based on an Euler-Bernoulli beam theory, are shown to verify the efficiency of the proposed method. This method can be applied for predicting the fatigue life of a mechanical system. Moreover, this study demonstrates that structural and multi-body dynamic models can be unified in one numerical system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.558-561
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• 2010

본 연구에서는 나노복합재의 탄소성 거동과 항복응력을 예측하기 위해 분자동역학 전산모사를 수행하였다. 나일론 기지와 실리카 나노입자가 포함된 단위 셀 구조로부터 나노입자의 체적분율 변화에 따른 응력-변형률 선도를 등변형률을 적용한 등온등압 앙상블 전산모사로부터 도출하였다. 4%의 변형률 범위에서 나노복합재의 탄성계수를 도출하였고, 이를 이용하여 2% 오프셋 방법으로 항복응력을 예측하였다. 나노입자의 유무에 따른 항복평면의 변화와 고분자 재료에서 나타나는 정수압 효과가 항복평면에 미치는 영향을 확인하기 위해 일축 인장/압축 그리고 이축 인장/압축을 수행하였고, 각각의 경우에 나타나는 나노복합재 내부의 자유체적 변화에 대한 분석을 통해 나노입자의 강화효과를 고찰하였다. 또한 고분자 기지로 인해 발생하는 정수압 효과를 반영한 von-Miss 항복평면을 도출하고, 입자의 체적분율 변화에 따른 항복응력의 예측이 가능하도록 정수압효과에 대한 파라메터를 체적분율의 함수로 근사하였다.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.702-707
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• 2000

Under the rapid change of a new vehicle model, it is necessary to develop a durability analysis technique using computer simulation. In order to do this. reliable dynamic stress-time history for the vehicle components must be calculated on various road conditions. In this paper, a full vehicle simulation model which is composed of flexible frame and chassis components is proposed and verified its reliability from the comparison with field test data. Finally, dynamic stress-time history on the rear chassis components is predicted with hybrid and modal superposition method.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.236.1-236.1
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• 2005

• 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.

• The Journal of the Petrological Society of Korea
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• v.25 no.3
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• pp.169-193
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• 2016

In order to characterize the Neotectonic crustal deformation and current stress field in and around the Korean Peninsula and to interpret their tectonic implications, this paper synthetically analyzes the previous Quaternary fault and focal mechanism solution data and recent geotechnical in-situ stress data and examines the characteristics of crustal deformations and tectonic settings in and around East Asia after the Miocene. Most of the Quaternary fault outcrops in SE Korea occur along major inherited fault zones and show a NS-striking top-to-the-west thrust geometry, indicating that the faults were produced by local reactivation of appropriately oriented preexisting weaknesses under EW-trending pure compressional stress field. The focal mechanism solutions in and around the Korean Peninsula disclose that strike-slip faulting containing some reverse-slip component and reverse-slip faulting are significantly dominant on land and in sea area, respectively. The P-axes are horizontally clustered in ENE-WSW direction, whereas the T-axes are girdle-distributed in NNW direction. The geotechnical in-situ stress data in South Korea also indicate the ENE-trending maximum horizontal stress. The current crustal deformation in the Korean Peninsula is thus characterized by crustal contraction under regional ENE-WSW or E-W compression stress field. Based on the regional stress trajectories in and around East Asia, the current stress regime is interpreted to have resulted from the cooperation of westward shallow subduction of the Pacific Plate and collision of Indian and Eurasian continents, whereas the Philippine Sea plate have not a decisive effect on the stress-regime in the Korean Peninsula due to its high-angle subduction that resulted in dominant crust extension of the back-arc region. It is also interpreted that the Neotectonic crustal deformation and present-day tectonic setting of East Asia commenced with the change of the Pacific Plate motion during 5~3.2 Ma.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.52-60
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• 2000

In order to design a reliable machine component efficiently, it is necessary to set up the process of durability analysis using computer simulation technique. In this paper, two methods for dynamic stress calculation, which are basis of durability analysis, are reviewed. Then, a user-oriented dynamic stress analysis program is developed from these two algorithms together with a general-purpose flexible body dynamic analysis and structural analysis programs. Finally, a slider-crank mechanism which has a flexible connecting-rod is chosen to show the special characteristics of these two dynamic stress calculation methods.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.1-6
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• 2013

A SIM card socket is used for a cell phone to fix an USIM card and a push-push mechanism is typically employed in the SIM card socket for a user convenience. A SIM card is inserted with locking when a user pushes the card once and a SIM card is removed with unlocking when a user pushes the card again. A push-push mechanism is operated by a heart-cam structure and a main spring. A cam slider and a cam stick consisting a push-push mechanism may be broken because of the main spring. So, dynamic stress at a cam slider and a cam stick which is generated by a main spring during operating should be analyzed and considered in the push-push mechanism design. In this paper, a flexible multibody model of a push-push mechanism was developed to analyze dynamic stress at a cam slider and a cam stick.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.180.2-181
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• 2003

벼는 미립내부의 온도 및 함수율의 차이에 의해 열응력 및 수분차에 의한 응력이 발생하게 되며, 응력이 과대하게 발생되면 낟알이 금이 가는 동할이 발생하게 된다. 동할은 주로 건조과정 또는 건조후에 주로 발생하게 되는데 벼의 품질에 가장 중요한 지표로서 동할이 발생되면 저장성이 저하되며, 도정시 싸라기가 증가하여 도정수율에도 많은 손실을 가져오게 된다. 본 연구는 함수율 20.01, 21.80 및 22.80%(w.b.) 3수준에 대하여 40.4, 50.0 및 60.9$^{\circ}C$ 3수준의 건조온도와 노출시간 5 ~ 120분 동안에 벼의 동할에 미치는 영향을 구명하고, 동할 예측모델을 개발하는데 목적이 있다. 초기 함수율이 낮고 건조온도가 높을수록 노출시간이 경과할수록 동할은 증가하는 것으로 나타났다. 건조온도 40.4$^{\circ}C$에서는 노출 100분전까지는 동할율이 2%이상 발생하지 않는 것으로 나타났으며, 건조온도 50.$0^{\circ}C$와 60.9$^{\circ}C$에서는 함수율 20.0%(w.b.)의 경우 27분 및 11분 노출했을 때 동할율이 2%이상 발생하였다. 동할 실험치를 실험모델에 적합시켜 다중회귀분석 프로그램을 이용하여 실험상수를 결정하였다. 실험모델의 결정계수는 모든 온도에서 0.9이상으로 높게 나타났으며, RMSE는 40.4$^{\circ}C$에서는 0.2230, 50.$0^{\circ}C$에서는 2.4975로 나타났다. 또한, 60.9$^{\circ}C$에서는 77813로 이는 동할 실험치가 0 ~ 100 사이의 값임을 고려할 때 허용 가능한 수준으로 판단된다.