• 대한조선학회논문집
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• 제29권2호
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• pp.140-149
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• 1992

한 구조물을 제작 설계할 경우, 단번에 모든 설계 조건들을 다 만족시키기는 쉽지 않고 몇번의 설계 변경을 통하게 된다. 이 경우 만족스러운 기능을 위한 설계 변경 방향 설정이 필요하고 그 설계 변경량도 결정해 주어야 한다. 마찬가지로 구조물의 진동 등 동적 거동 변경을 위해서는 어느 부분의 미소 변화에 대한 동적 성능 변화량(동특성 민감도)을 쉽게 추출해 낼 수 있어야 한다. 이를 위해 본고에서는 부분 구조물들로 조합된 전체 구조물에 대하여 설계변수에 대한 동적성능의 민감도를 좀더 쉽게 계산할 수 있는 새로운 방법을 제시하였다. 이 방법은 부분 구조 진동형 합성법의 계산 이점을 충분히 이용하였으며 부분 구조 동특성 민감도 합성법이라고 일컬어진다. 본고의 주 내용으로, 전체 구조물의 진동 특성치 민감도가 부분 구조물의 진동 특성치 및 변경가능 부분 구조물의 내부 진동 민감도 등으로부터 합성되어 구해질 수 있음을 나타내 보였다. 예시 구조물로서 트러스 구조물이 선정되었고 통상적인 방법과 여기서 새로이 제시된 방법에 의한 해석결과 들을 비교하였으며, 결론적으로 새로운 방법이 정확도와 계산효율 면에서 충분한 이점이 있음을 보여 주었다.

• 한국공작기계학회논문집
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• 제14권3호
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• pp.122-127
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• 2005

The styling of automobile wheels and their effect on vehicle appearance has increased in importance in recent years. The wheel designer has been given the task of insuring that a wheel design meets its engineering objectives without affecting the styling theme. The wheel and tire system is considered as a vehicle component whose dynamic modal information of the tire/wheel system are employed in the modal synthesis model of the vehicle. The vibration characteristics of a automobile wheel play an important role to judge a ride comfort and quality for a automobile. In this paper, the vibration characteristics of a Al-alloy and steel wheel for automobile are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function method. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.

• Structural Engineering and Mechanics
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• 제44권3호
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• pp.305-323
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• 2012

Structural defects such as cracks are the source of local flexibilities and cause deficiencies in structural resistance. In the engineering constructions, structural elements sometimes are subjected to axial loading. Therefore, besides crack ratios and locations, influence of applied load on the stability and dynamical characteristics should also be explored. This study offers a numerical technique for the vibration and stability analysis of axially loaded cracked beams. The model merges finite element and component mode synthesis methods. Initially, stability analysis is completed and then dynamical characteristics of beams are found. Very good conformities between outcomes of the current study and those in literature, give the confidence that proposed method is reliable and effective.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.735-741
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• 2011

In the early phase of vehicle development, CAE is conducted as tool for vehicle performance assessment. To maintain acceptable road noise performance, solution for reduced vehicle sensitivity is required. Chassis interface dynamic stiffness characteristics are key component to isolating vibration and noise of road from the vehicle interior. This research provide how to set up the optimized dynamic characteristics under noise effect through DFSS study. CAE-based DOE is performed to build prediction math model, CMS process involves DOE to achieve very fast run times while giving results very comparable. Minimized $95^{th}$ percentile of performance distribution is applied to minimize vehicle sensitivity and road noise levels variation during the optimization process. Finally, the results of optimization were reviewed for performance and robustness.

• 한국소음진동공학회논문집
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• 제21권7호
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• pp.674-681
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• 2011

In the early phase of vehicle development, CAE is conducted as tool for vehicle performance assessment. To maintain acceptable road noise performance, solution for reduced vehicle sensitivity is required. Chassis interface dynamic stiffness characteristics are key component to isolating vibration and noise of road from the vehicle interior. This research provide how to set up the optimized dynamic characteristics under noise effect through DFSS study. CAE-based DOE is performed to build prediction math model, CMS process involves DOE to achieve very fast run times while giving results very comparable. Minimized 95th percentile of performance distribution is applied to minimize vehicle sensitivity and road noise levels variation during the optimization process. Finally, the results of optimization were reviewed for performance and robustness.

• 한국기계가공학회지
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• 제18권8호
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• pp.8-17
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• 2019

In this study, a model reduction technique was used to develop a precise noise and vibration prediction model for the individual components of a driveline system. The dynamic reduced-order model generated by the Craig-Bampton method was applied to perform dynamic analysis of an electric agricultural power cart. The natural frequency and acceleration response results were analyzed according to the different number of dominant sub-structural modes contained in the reduced-order models. Through the analysis results, it was confirmed that a sufficient number of dominant sub-structures to satisfy the operating conditions should be selected to construct an optimal reduced-order model.

• 한국항공우주학회지
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• 제31권4호
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• pp.53-59
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• 2003

다목적실용위성(KOMPASA) 태양전지판을 전개하기 위해 사용되는 Strain Energy Hinge(SEH)는 신뢰성 있는 전개를 보장하지만, 태양전지판이 완전 전개되는 순간, 큰 좌굴충격력을 유발하여 위성의 구조적 안정성이나 자세제어에 심각한 영향을 미칠 수 있으므로 전개장치의 설계단계에서부터 동역학적인 평가가 필요하다. 더욱이 위성의 임무가 다양해짐에 따라 태양전지판의 면적이 커지면서 보다 실제적이고 정확한 해석을 위해서는 태양전지판의 탄성변형 효과도 고려되어야 한다. 본 연구에서는 SE H를 이용하여 탄성효과가 큰 태양전지판을 전개할 때 발생하는 동적 특성들을 예측할 수 있도록 동력학 해석절차를 제시하였으며 다목적실용위성 2호의 태양전지판 전개시험을 통하여 해석결과의 신뢰성을 검증하였다.

• 한국전산구조공학회논문집
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• 제35권3호
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• pp.175-182
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• 2022

부분구조화 기법은 자유도가 많고 복잡한 구조물의 유한요소 해석 모델 단순화에 효율적으로 적용될 수 있는 기법이다. 대표적으로 선형 문제에 대해서는 Craig-Bampton method 등이 있다. Craig-Bampton method는 경계 요소를 제외한 나머지 요소의 불필요한 자유도를 제거함으로써 선형 구조물의 축소를 수행한다. 최근에는 부분구조화 기법과 더불어 구조물의 최적설계를 위해 멀티레벨 최적화 기법이 많이 활용되고 있다. 시스템의 목표를 달성하기 위해 각 부구조에 새로운 목표를 할당하는 기법이다. 본 연구에서는 유전자 알고리즘을 이용하여 시스템 목표 달성을 위한 각 부구조별 내부 자유도 개수를 새로운 목표로 할당하고 최적화를 수행하였다. 최적화 절차로부터 도출된 부구조별 내부 자유도 개수를 이용하여 시스템의 축소를 수행하였다. 다양한 수치예제들을 통해 축소 모델에 대한 결과를 확인하였으며, 90% 이상의 정확도를 가지는 것을 확인하였다.

• Tribology and Lubricants
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• 제36권2호
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• pp.105-115
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• 2020

This paper presents a numerical study on the rotordynamic analysis of a dual-spool turbofan engine in the context of blade defect events. The blades of an axial-type aeroengine are typically well aligned during the compressor and turbine stages. However, they are sometimes exposed to damage, partially or entirely, for several operational reasons, such as cracks due to foreign objects, burns from the combustion gas, and corrosion due to oxygen in the air. Herein, we designed a dual-spool rotor using the commercial 3D modeling software CATIA to simulate blade defects in the turbofan engine. We utilized the rotordynamic parameters to create two finite element Euler-Bernoulli beam models connected by means of an inter-rotor bearing. We then applied the unbalanced forces induced by the mass eccentricities of the blades to the following selected scenarios: 1) fully balanced, 2) crack in the low-pressure compressor (LPC) and high pressure compressor (HPC), 3) burn on the high-pressure turbine (HPT) and low pressure compressor, 4) corrosion of the LPC, and 5) corrosion of the HPC. Additionally, we obtained the transient and steady-state responses of the overall rotor nodes using the Runge-Kutta numerical integration method, and employed model reduction techniques such as component mode synthesis to enhance the computational efficiency of the process. The simulation results indicate that the high-vibration status of the rotor commences beyond 10,000 rpm, which is identified as the first critical speed of the lower speed rotor. Moreover, we monitored the unbalanced stages near the inter-rotor bearing, which prominently influences the overall rotordynamic status, and the corrosion of the HPC to prevent further instability. The high-speed range operation (>13,000 rpm) coupled with HPC/HPT blade defects possibly presents a rotor-case contact problem that can lead to catastrophic failure.