• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.13-13
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• 2017

선회시스템의 수명을 정확히 예측하기 위해서는 굴삭기의 상부회전체 및 선회시스템의 모든 구성요소들의 질량관성모멘트를 고려하여 선회감속기의 수명 평가를 수행해야 한다. 선회감속기의 수명 평가방법은 주로 실험실 시험으로 수행이 되며, 시험 장비는 장비 구축 편의성과 비용 등의 이유로 증속기와 굴삭기 상부회전체의 등가 관성체 등으로 구성된다. 굴삭기 선회시스템의 정확한 등가 실험실 시험을 위해서는 시험에 사용되는 등가 관성체의 관성모멘트를 정확히 결정하는 것이 매우 중요하다. 본 연구는 굴삭기 선회시스템의 등가 실험실 시험을 위해 굴삭기 상부회전체의 관성모멘트를 결정하기 위하여 수행되었다. 굴삭기 선회 시험을 통하여 선회감속기 입력 속도 및 토크를 측정하였고, 반복계산법을 이용하여 굴삭기 상부 회전체의 등가관성모멘트를 계산하였다. 굴삭기 상부회전체의 시뮬레이션 모델을 개발하여 선회 시험 결과와 시뮬레이션 모델 비교 분석을 통해 굴삭기 시뮬레이션 모델을 검증하고, 검증된 모델을 이용하여 상부회전체의 관성모멘트가 반영된 등가 실험실 시험 시뮬레이션 모델을 개발하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.271-277
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• 2017

In this paper, the amplitude and frequency dependent dynamic characteristics of the equivalent stiffness of a rubber bushing are investigated. A new mathematical model is proposed to explain the large deformation and size effect of a rubber bushing. The proposed model consists of elastic, viscous, and frictional stress components and the equivalent strain. The proposed model is verified using experimental results. The comparison shows that the proposed model can accurately predict the equivalent stiffness values of a rubber bushing under various magnitudes and frequencies. The developed model could be used to predict the dynamic equivalent stiffness of a rubber bushing in automotive engineering.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.608-614
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• 1995

공작기계 등과 같이 복잡한 대형 구조물의 구조해석에 있어서 결합부요소의 강성과 질량특성을 모델링하는 일반적 인 방법이 없는 실정이므로 어려움이많다. 본 연구에서는 공작기계에서 흔히 쓰이는 Slide-way contact joint 결 합부를 등가의 강성행렬 요소(Generalized stiffness matrix element)로 모델링하는 방법을 제안하였다.. 기존의 유 한용소 해석법 프로그램을 이용하여 결합부 유한요소 모델의 유연도계수(Flexibility influence coefficients)를 계산하고 Guyan의 정축약이론을 이용하여 등가의 강성행렬요소로 축약시키는 방법이다. 제안된 방법을 대형 평면연 삭기 구조해석에 적용하고, 그 결과를 강결합 모델의 결과 및 Yoshimura의 등가스프링결합부 모델을 사용한 경우의 결과와 비교하므로써 본 연구에서 제안한 결합부 모델링 방법의 유용성을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.961-966
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• 2013

A coupled governing equation of thermoelectric materials can be converted into an uncoupled form to predict the effective Seebeck coefficient of thermoelectric composites, where modified Eshelby model is adopted. The predicted results by the present approach for serial- and parallel-connected composites and composite with spherical inclusions are compared with theoretical and experimental results from literatures to be justified. It is shown that the predictions by the theoretical approaches coincide exactly and show in good agreement with the experiments.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.290-291
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• 2011

본 논문에서는 열-전기-기계 하중 하의 지능형 복합재료 보 모델을 전산점근해석기법에 기초하여 개발하였다. 열-전기-기계 하중 하의 구조물은 지난 십년간 많은 연구가 있어왔으나, 주로 고전적 보 모델에 기반을 두어 진행되어져 왔다. 멀티피직스 환경하의 구조물은 여러 가지 하중의 조합과 이에 따른 연성효과의 고려가 필수적이다. 따라서 공학적인 가정이 없는 점근해석기법은 보다 정확한 등가 보 모델을 개발하는데 있어 기반요소가 될 수 있다. 본 연구에서는 3차원 멀티피직스 구성방정식으로부터 출발하여 점근기법을 적용 체계적으로 등가 보 모델을 유도하고 그 해석 결과를 고찰하고자 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.111-118
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• 2022

An electro-mechanical actuator (EMA) is an actuator that combines an electric motor with a mechanical power transmission elements, and it is suitable for urban air mobility (UAM) in terms of design freedom and maintenance. In this paper, the author presents the research results of the EMA that controls the rotor blade pitch angle of UAM. The actuator is based on an inverted roller screw and controls the blade pitch angle through a two-bar linkage. The dynamic equations for the actuator alone and the blade pitching motion with actuator were derived. For the latter, the equivalent moment of inertia is variable depending on the link angle due to the two-bar linkage. The variations of the equivalent moments of inertia are analyzed and compared in terms of the nut motion and the blade pitch motion. For an example model, the variation of the equivalent moment of inertia of the former is smaller than the latter, so it is judged that the dynamic equations derived from the point of view of the nut motion is suitable for the controller design.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.323-324
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• 2017

본 연구는 기계적 특성을 갖는 소나(SONAR, Sound Navigation and Ranging) 트랜스듀서(Transducer)를 BVD(Butterworth Van-Dyke)모델을 기반으로 하는 전기적 등가 회로로 모델링하며 PSO(Particle Swarm Optimization) 알고리즘을 활용하여 상기 등가 모델에 사용되는 전기적 소자들의 소자값을 추출한다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.82-90
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• 2019

We propose an equivalent model of a sintered metal mesh filter calculated by Ergun's equation and polynomial regression for the CFD analysis of breakaway devices at a hydrogen fueling station. CFD analysis of filters that cause high pressure loss is essential because breakaway devices in high-pressure hydrogen conditions require low pressure loss. A differential pressure experiment with a filter was performed in a low-pressure air condition considering similarities. An equivalent model was developed by deriving the resistance value by the polynomial regression using the experimental results. The results of CFD analysis using the equivalent model show that there was almost no error in the operating condition of the breakaway device compared to the experimental results. Through this work, we believe that the proposed equivalent model of a filter can be applied to the analysis of breakaway devices in hydrogen fueling stations. We will study how to optimize the shape and position of the filter in breakaway devices using the developed equivalent model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.45-50
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• 2014

A vibration test coupon is prepared with nine plastic ball grid array packages on a printed circuit board using SnPb solders, and a random vibration test is conducted on the coupon. Life data from the test are analyzed, and it is shown that over the board, life data is location-dependent. For investigating this location dependency, a finite element model is developed and the equivalent stresses, which are defined based on the stress response functions at each node, are investigated. It is shown that one of the corner solder balls has the maximum equivalent stress at a package during the test. Finally, it is demonstrated that the maximum equivalent stress and durability life are inversely proportional.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1361-1370
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• 2012

A shape optimization is proposed to obtain the desired final shape of forming and forging products in the manufacturing process. The final shape of a forming product depends on the shape parameters of the initial blank shape. The final shape of a forging product depends on the shape parameters of the billet shape. Shape optimization can be used to determine the shape of the blank and billet to obtain the appropriate final forming and forging products. The equivalent static loads method for non linear static response structural optimization (ESLSO) is used to perform metal forming and forging optimization since nonlinear dynamic analysis is required. Stress equivalent static loads (stress ESLs) are newly defined using a virtual model by redefining the value of the material properties. The examples in this paper show that optimization using the stress ESLs is quite useful and the final shapes of a forming and forging products are identical to the desired shapes.