• Smart Structures and Systems
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• 제5권4호
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• pp.357-367
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• 2009

Structural Health Monitoring (SHM), particularly remote monitoring, is an emerging field with great potential to help infrastructure owners obtain more and up-to-date knowledge of their structures. The methodology could provide supplemental information to guide the frequency and extent of visual inspections, and the possible need for maintenance. The instrumentation for a SHM system needs to be developed with longevity and the objectives for the system in mind. Sensors need to be selected for reliability and durability, sited where they provide the maximum information for the objectives, and where they can be accessed and replaced should the need arise over the monitoring period. With the rapid changes now occurring with sensors and software, flexibility needs to be in place to allow the system to be upgraded over time. Damage detection needs to be considered in terms of the type of damage that needs to be detected, informing maintenance requirements, and how detection can be achieved. Current vibration analysis techniques appear not yet to have achieved the necessary sensitivity for that purpose. Societal factors will influence the design of a SHM system in terms of the sophistication of the instrumentation and methodology employed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• Elastomers and Composites
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• 제39권2호
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• pp.121-130
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• 2004

고무부싱은 차량부품들을 서로 연결하고 차체로 전달되는 진동을 줄여주는 역할을 하는 중요한 요소로써 가진변위와 주파수에 대해서 모두 비선형 특성을 보이며, 특히 주기적인 가진에 대해 히스테리시스 현상을 나타낸다. 본 논문에서는 1축 내구시험기를 이용하여 차량 현가 장치에 사용되는 부싱을 축 방향과 반경 방향에 대해 사인가진과 랜덤가진을 주어 특성을 살펴보았고 이러한 특성을 반영할 수 있는 동역학적 모델을 인공신경망을 이용하여 개발하였다. 실험결과는 신경망의 입력자료로 활용되었고, 오차역전파 알고리즘을 이용하여 실험적 부싱모델을 개발하였다. 개발된 실험적 부싱모델을 차량 시뮬레이션에 적용하여 유용성을 살펴보았다.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.190-198
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• 2002

Full scale durability test in the laboratory is an essential of any fatigue life evaluation of components or structures of the automotive vehicle. Component testing is particularly important in today's highly competitive industries where the design to reduce weight and production costs must be balanced with the necessity to avoid expensive service failure. Generally, hydraulic road simulator is used to carry out the fatigue test and the vibration test. In this paper, the algorithm and software to realize the real road profile are developed. The operation software for simultaneously controlled multi-axial road simulator is developed and the input and output data are displayed window based PC controller in the real time. Futhermore, the software to generate the real road profile are developed. The validity of the software are verified by applying the belgian road, the city road, the highway, and the gravel road. The results of the above experiment show that the real road profiles are realized well after 10th iteration.

• 한국정밀공학회지
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• 제33권8호
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• pp.617-622
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• 2016

The article describes the determination of the dynamic stability for an observation antenna, considering the rotational speed by the payload driving motor. A finite element model of the observation antenna was made using the solid and beam elements. The connecting parts between the solid and the beam was adequately coupled. The boundary conditions were made by restriction of the degree of freedoms in the supporting points. With the comparison between the modal analysis results and the rotating speed of the payload driving motor, no resonance for the structure of antenna was identified and first natural frequency was determined under 33 Hz (Seismic Cut-Off Frequency). Therefore, the dynamic stability of the antenna was confirmed by the comparism between the seismic safety criterion and the stress results of the dynamic analysis applied the loading conditions and required response spectrum (RRS).

• 한국지능시스템학회논문지
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• 제16권2호
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• pp.209-214
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• 2006

회전 기기에서 회전체의 편심은 언밸런스를 유발하는데 이를 보정하는 밸런싱은 회전 기기에서의 방진 및 저소음 설계에 중요한 항목일 뿐 아니라 회전기기의 안정성과 사용수명에 큰 영향을 미치기 때문에 매우 중요하다. 이러한 밸런싱 머신을 구현하기 위하여 편심을 정확히 측정하여야 하는데, 본 논문에서는 기존의 밸런싱 기기에 일반적으로 사용되고 있는 계측 원리와는 다르게 홀-이펙트 센서를 이용하여 편심을 측정하는 방식을 제안함으로써 저가의 계측 시스템 구성이 가능함을 보이고, 밸런싱 머신의 편심 측정부를 PC통신을 이용하여 제어하고자 한다.

• 열처리공학회지
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• 제22권4호
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• pp.203-209
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• 2009

Dual mass flywheel is the newly developed flywheel system which reduces the noise and vibration and make a better and comfortable ride of cars by adding inertia mass and damping device. However, verification of performance for this system should be carried out since this system is under developing status in our country. Especially, the durability for each part of this system should be guaranteed. Durable properties of driver plate which is the key component of dual mass flywheel were first investigated both in the raw (SCM435 in JIS) and heat-treated material. In addition, fatigue life analysis of driver plate was preformed in the real condition and the results were verified by comparison with the results of rig test.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.133-151
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• 2016

Self-Compacting Concrete (SCC) has been originally developed in Japan to offset a growing shortage of skilled labors, is a highly workable concrete, which is not needed to any vibration or impact during casting. The utilizing of fibers in SCC improves the mechanical properties and durability of hardened concrete such as impact strength, flexural strength, and vulnerability to cracking. The purpose of this investigation is to determine the effect of steel fibers on mechanical performance of traditionally reinforced Self-Competing Concrete beams. In this study, two mixes Mix 1% and Mix 2% containing 1% and 2% volume friction of superplasticizer are considered. For each type of mixture, four different volume percentages of 60/30 (length/diameter) fibers of 0.0%, 1.0%, 1.5% and 2% were used. The mechanical properties were determined through compressive and flexural tests. According to the experimental test results, an increase in the steel fibers volume fraction in Mix 1% and Mix 2% improves compressive strength slightly but decreases the workability and other rheological properties of SCC. On the other hand, results revealed that flexural strength, energy absorption capacity and toughness are increased by increasing the steel fiber volume fraction. The results clearly show that the use of fibers improves the post-cracking behavior. The average spacing of between cracks decrease by increasing the fiber volume fraction. Furthermore, fibers increase the tensile strength by bridging actions through the cracks. Therefore, steel fibers increase the ductility and energy absorption capacity of RC elements subjected to flexure.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1776-1781
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• 2008

To reduce interior noise of running vehicles, a floating floor construction has been widely used in recent railway industry. Among the key factors of the floating floor design, dynamic stiffness is of most important in acoustical point of view. Sometimes hard rubber type supports have often been selected due to the other design constraints such as heavy load condition, durability of rubber element and its cost etc., even though it seems like the softer support, the better isolation of noise and vibration. In this paper two representative floor supports have been considered to evaluate their effectiveness in interior noise contribution: one is a soft rubber and another is a relatively hard one. From the measured dynamic stiffness of the specimens, equivalent stiffness of actual floating floor has been derived to use in the analytical models. Calculated air-borne and structure-borne noise insulation properties of the floating floors have been compared with experiments in prototype car. In full car model interior noise levels of running vehicles have been predicted to quantify the effectiveness of the two different floating support materials and verified through the measured inside noise levels of actual train as well. By comparison with difference of running noise levels two materials for floor support can be investigated quantitatively so that it could be applied in floating floor design.

• Elastomers and Composites
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• 제45권4호
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• pp.291-297
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• 2010

차량에서 스트러트 인슐레이터는 도로노면으로부터 발생하는 소음과 진동을 방지하는 역할을 한다. 대부분의 점탄성 마운트들은 고무로 되어있으며 천연고무가 주성분이다. 이러한 고무 부품들은 초기에는 제 역할을 하지만 오랜 시간 고온과 반복하중에 노출되면 성능저하가 일어난다. 고무성능 변화는 NVH를 떨어뜨리고 승차감을 저하시킨다. 본 연구에서는 차량실험을 통해 스프링 변위를 측정하였고, 재현실험에서 가속도 센서를 이용하여 운행거리와 차량연식에 따른 인슐레이터 고무성능을 가속도 값, 고무 영구 변형량, 경도를 나타내었다.