• 한국산학기술학회논문지
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• 제18권11호
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• pp.697-704
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• 2017

본 연구는 영업운행 중인 고속열차의 진동 문제를 고찰하고, 이를 개선하기 위하여 진행되었다. 먼저 고속열차의 진동 수준을 알기 위하여 차체 진동가속도에 대한 측정이 수행되었다. 측정결과 운전실이 객차보다 진동이 크며, 열차 후미로 갈수록 진동이 더 커졌다. 운전실 및 객차 모두 수직방향 진동이 횡방향 진동에 비해서 크며, 콘크리트 구간에 비해 자갈궤도에서 진동의 최대값이 크다. KTX-산천 진동 경향과 개선점을 도출하기 위하여 동역학 해석을 수행하였다. 해석결과는 시험 결과와 유사하였으며, 객차 양 끝단의 단부객차 상부와 동력차량의 진동을 저감시킬 필요가 있었다. 객차의 진동을 저감하기 위하여 KTX-호남(200호대) 차량은 4가지 개선 설계를 수행하였고, 이 중 KTX-산천에 적용할 수 있는 방법을 해석에 적용하였을 때, 정상구간에서는 2.2%, 분기기구간에서는 11% 정도 진동이 감소할 것으로 예상되었다. 동력차량의 진동 저감을 위해 2차 코일스프링의 강성을 감소시키고, 2차 수직댐퍼의 댐핑계수를 증가시키는 방안을 제안하였다. 현가장치의 불량, 오조립 등 성능저하가 차체 및 대차의 진동을 증가시키는 것을 시운전 결과와 해석결과를 통하여 살펴보았으며, 현가장치 올바른 유지보수가 차량 진동을 저감시킴을 알 수 있었다. 차륜 마모에 대한 적절한 관리는 운행 효율 및 차체 진동저감에 중요한 역할을 하며, 현재 차륜 프로파일을 변경하여 차륜 삭정간의 주행거리를 늘리려는 연구가 진행 중이다.

• 한국소음진동공학회논문집
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• 제24권11호
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• pp.883-889
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• 2014

Mufflers have been widely used in the exhaust system to reduce the noise. However, installing muffler may deteriorate the efficiency due to the increase of back pressure. Mufflers usually consist of partition plates and perforated holes in a expansion chamber. In this paper, the influences of the location of the partition and hole on the acoustic TL and back pressure were examined. The acoustic TL was predicted using virtual lab commercial software, while the back pressure were predicted using CFX commercial software. The results were used to set up a database for finding their trends. The optimal muffler model in user-interested frequency range could be selected by analyzing this database.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall
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• pp.244-250
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• 1999

Active vibration control method for the reduction of vibration of structures have been developed. For the application of real structures active control system that has robustness must be designed because the mathematical model incompletely described has intrinsically modeling error. In this research we propose LQG/LTR method in designing control system with robustness. A combination of acceleration feedback and model-order reduction technique is used for the application of real structures and the computation efficiency. In case of such structures as the building and the tower the inter-story relative displacements represent an important constraint in seismic design. Therefore selection method of design parameters is also proposed in order to reduce the inter-story relative displacements.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.51-58
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• 2017

The characteristics and effectiveness of double tuned mass dampers (DTMD) have been studied by many researchers. DTMD usually consists of one larger mass block and one smaller mass block. In this study, DTMD was proposed to reduce the vibration of vertical pumps in industrial plants. In order to assess the efficiency of the proposed method, numerical analysis for the simplified vertical pump model with single and double TMDs was carried out. It was also investigated that the effects of optimal TMD parameters such as frequency ratio and damping ratio on dynamic responses of the main structure. According to analysis results, DTMD are more effective to control the vibration of the vertical pump and show good robustness to the change in the stiffness of TMD.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 1998년도 추계 학술논문발표회 논문집
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• pp.353-358
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• 1998

Vibrations exposured to human whole-body are transmitted through the contact area of a human body, such as feet, hip and back directly in contact with vibrating surface. they apparently leads to the decrease of human comfort, the reduction of working efficiency or normal activities, and, furthermore, causes the loss of health and safety. In this study, UH-1 vibration has been measured to produce the flight-time limitation at each mission Results of this study show that the most significant peaks appear at a main rotor blade-passage frequency and that the vibration level in ground is higher than that in airborne In addition, it is shown that the most affective aspect for the flight-time limitation is ground vibration level

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.757-761
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• 2001

In order to study noise barriers of complex shapes and to assess their efficiency, precise prediction model is required. For instance, geometrical approaches cannot deal with complex diffraction effects. So that in this paper, the time domain numerical computation method(Computational Aeroacoustics method) is applied to estimate noise reduction by diffraction and finite impedance condition. The CAA method can be used to calculate exactly the pressure of complex barrier shape with different impedance condition, such as T-shape, cylindrical edge and multi-edge noise barriers.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.872-876
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• 1996

Most studies of rotary machinery design have been performed to establsih a new mechanism or a dramatic combination of machine elements for the power transmission. Although the rotary machine is worked very efficiently, that still has a major work to better performance which is the optimization of the selected mechanism for the mechanical efficiency, low vibration and noise, or customer interest. This work presents a practical approach used for washer's efficiency and machinery vibration and noise reduction along with a systematic procedure. Also for the confirming the study, a computer simulation program and a real working mock-up are developed and used to show very good agreement with the analytical result.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.771-772
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• 2014

In this paper, the integrated design method of suction muffler in compressor was studied. There are three things to consider when designing this. First, the transmission loss was maximized to consider the noise reduction. Second, dissipation energy of fluid flow was minimized for energy efficiency. Finally, acoustical resonance frequency of suction muffler was controlled because energy efficiency can be increased by supercharging of refrigerant. Therefore, suction muffler was designed to have the specific resonance frequency. The input impedance was used for designing target acoustical resonance frequency. Topology optimization was used for optimization method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.687-689
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• 2014

This paper deals with the optimal muffler model by using acoustic analysis and CFD(computational fluid dynamics) analysis. The complicated muffler model could be better noise reduction performance. However, it could be worse affected to back-pressure performance by pressure drop in working fluid. High back-pressure is caused to low system efficiency. Therefore, it is important for the muffler design to consider the pressure drop. The muffler models are changed their partition plate position. Acoustic power transmission loss(TL) and pressure drop of working fluid are calculated by using computational analysis and used to build database for finding their trends. The optimal muffler model in user-interested frequency range could be selected by analyzing this database.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.21-27
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• 2014

In this paper, an approximate formula for radiation efficiency of the plate surround by an infinite rigid baffle is studied. The plate is simply supported and one side is in contact with air, while other side with water. By assuming an infinite plate, the fluid loading effect is derived in terms of an effective mass. Based on the observation that the fluid loading effect decreases as frequency increases, the radiation efficiency formula at high frequency, which was originally derived for a plate vibrating in the air, is modified as the approximate formula for a submerged plate. The fluid loading effect is taken into account in the wavenumber of the plate. Comparisons of the approximate formula with the numerical results shows that they match well except the mid-frequency range in which numerical results show many oscillations. In numerically solving the fully coupled equations of motion, fourfold integrals of the impedance coefficients are reduced to single nonsingular integrals, which results in substantial reduction in computing time.