• 한국구조물진단유지관리공학회 논문집
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• 제13권1호통권53호
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• pp.88-96
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• 2009

본 연구에서는 FBG 센서 및 PDA를 이용하여 새로운 안전관리 시스템인 무선 계측 시스템을 개발하기 위해 FBG 센서를 이용하여 광섬유 변위(FBG-LVDT) 센서, 광섬유 변형률(FBG-STRAIN) 센서, 광섬유 온도(FBG-TEMP) 센서 그리고 광섬유 가속도(FBG-ACC) 센서를 특별 제작하였다. 또한, 신호처리 시스템에는 적용된 FBG 센서들의 무선송신 시스템이 가능하도록 신호처리 시스템을 구성하였으며, PDA를 이용하여 원격 거리에서도 display가 가능할 수 있도록 프로그램을 개발하였다. 개발된 FBG 센서들과 무선계측 모니터링 시스템의 현장 적용성, 정확성 및 활용 가능성을 검증하고자 현장 교량에서 정적, 동적 재하시험을 실시하였다. 또한, FBG-LVDT 센서, FBG-ACC 센서에 의하여 측정된 동적 데이터들은 Meister의 진동등감각 곡선에 적용시킴으로서 교량의 진동에 대한 사용성 평가를 실시하였고 교량의 진동 사용성을 고려하여 진동 제한 기준을 제시하여 대상 교량의 진동 평가를 위한 방법을 마련하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2090-2100
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• 2011

Railway rail fastening system is the critical device which gives big influences to not only the vehicle driving stability and the orbit's structural stability against the impulsive load, but also the noise vibration and the ride comfort. As a part of the low-carbon green growth, the importance of the railroad industry is getting highlights on its excellent energy-efficiency and eco-friendliness. However, so far the Korea's domestic rail fastening system technology is not so good and the technical reliance to abroad is very heavy. In this study, we conducted comparative analysis on the rail fastening system with new and used one of the same type. And those systems are imported by Seoul Metro and are being used by it. With this basis, we developed the components and the materials and then, established the durability assessment methods appropriate to the Korean domestic circumstances. And through the reliability qualification test on the 7 parts of the rail fastening system, we've improved the reliability and guaranteed the 15 years of service lifetime. ($B_{10}Life15$) Establishment and standardization of Reliability Standard on the parts of the rail fastening system such as anti-vibration pads, guide-plate, screw spike made it possible to perform the internationally fair assessment. And it is thought that we can satisfy the manufactures' and consumers' needs of cost-cutting and qualification security by shortening of assessment period on rail fastening system.

• 한국기계가공학회지
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• 제19권9호
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• pp.107-115
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• 2020

The rotation accuracy of the main spindle that determines the accuracy of CNC machine tools is closely related to the quality of production because it directly affects the shape error and surface roughness of the workpiece. Therefore, the main spindle requires high rotation accuracy, rigidity, and rotation technology. This rotation accuracy is greatly affected by the bearing, center alignment between rotating parts, assembly tolerance, and unbalance of the rotation mass. In this study, the effects of the unbalance of the rotation mass of the main spindle on the rotation accuracy were investigated experimentally. In particular, we tried to study the technical reasons for improving the unbalance of the main spindle and maintaining the rotation accuracy as we verified the correlation between the vibration characteristics of CNC machine tools due to the specifically set unbalance amount and the surface roughness of the workpiece.

• 한국소음진동공학회논문집
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• 제25권1호
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• pp.5-12
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• 2015

According to the analysis of special medical examination and work environment monitoring data, the rate of C1 and D1 on noise hazard exceeded 90 % among those of total hazardous factors. The rate of company exceeding noise exposure limit was also more than 90 %. The analysis result shows that main ages diagnosed with C1 and D1 was age of 50s. The majority scale company having workers diagnosed with C1 and D1 was the companies employing 5~49 workers. Types of industries which have a large number of companies exceeding noise exposure limit were automobile and trailer manufacturing, metal processing industry and primary metal manufacturing. A large number of work processes exceeding noise exposure limit were forming and processing work, cutting and bending work and grinding. To reduce the number of company exceeding noise exposure limit, the reduction counterplan should be focused on the type of industry and the work process which exceeded noise exposure limit frequently. However, the reduction counterplan is preemptively necessary to the type of industry and the work process which exceeded noise exposure limit consecutively if the purpose of reduction counterplan is not to merely reduce the number of company exceeding noise exposure limit but to abate workers' suffering from noise.

• 항공우주시스템공학회지
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• 제12권4호
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• pp.18-25
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• 2018

가공의 정밀도와 난삭재 가공이 요구되는 항공기부품용 공작기계의 헤드프레임 구조는 정밀 고속가공을 위해 경량화 및 절삭력에 의한 변형최소화가 필요하다. 본 논문에서는 고강성 경량화 구조 최적설계를 위해 유한요소해석을 수행하여 초기형상을 설계하였고, 컴플라이언스를 최소화하여 경량, 고강성 및 저진동 구조의 위상 최적화 설계를 수행하였다. 최적화 설계결과 프레임 중량은 17.3% 감소되었고, 최대 처짐량은 0.007 mm 이하, 고유진동수는 30.6% 증가되었다. 구조 정강성은 각 축 방향으로 증가되었고, 동강성은 축에 따라 상반된 결과를 나타내었다. 위상 최적화 설계 구조에서 저진동의 고강성을 갖는 최적화된 구조를 확인하였다.

• 한국정밀공학회지
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• 제27권8호
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• 대한기계학회논문집A
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• 제41권3호
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• pp.199-204
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• 2017

현재 진동이 심한 산업현장에서 많은 종류의 풀림방지 너트가 사용되고 있다. 왜냐하면 진동의 풀림은 큰 사고를 유발할 수 있기 때문이다. 하지만 대부분의 풀림방지너트는 복잡한 가공과정을 거치기 때문에 가격 경쟁력에서 불리하다. 때문에 본 연구에서는 가공이 쉬운 새로운 유형의 커브드 너트를 개발 하고자 한다. 탄성에너지와 너트의 풀림메커니즘 사이의 탄성에너지를 연구하고 분석한 뒤, 나사의 풀림테스트를 한다. 커브드 너트는 기존너트에 밀링 공구를 이용하여 수직으로 한번 또는 두 번 너트의 밑면을 가공한다. 결과적으로 너트의 탄성에너지가 클수록 너트의 풀림을 막게 된다. 본 연구에서는 NAS3350의 진동테스트 장비를 이용하여 시험을 하고 결과를 분석한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.89-101
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• 2006

This study is a part of ???A study of the community noise:new guideline and policy' which have three main topics and ten sub-topics. Accordingly this part deals with a transpotation noise specifying road traffic ,railroad and aircraft noise, respectively. At first, the ,roadside traffic noise of whole country in 2004 ,22 major cities of total 29 was exceeded the envionmetal noise standards, 55dB(A) at night time ,therefore 24 milion people ,52.4% of korean, who reside at roadside estimates to be exposured the basic problems of this serious noise polluation comes from:: i)It's very limited noise mitigation measures against to continuously increase the number of automobile yearly. ii) and at beginning of road design, It has been neglect to introduce the anti-noise design and layout of road structural scheme as gadient,cutting and viaduct,embankment and zonning of roadside land-buffer area and also re-designation of noise sensitive areas,etc. Secondly ,concerned with the railroad trafffic noise, a inhabitants who are over the envionmetal noise limits,70dB(A), 65 dB(A) in day and night for 34 locations of mayor cities was exposured of 167,000 and 329,000 respectively. With the development of noise mitigation schemes in line with this study it is likely that noise monitoring system needs new installation as well as common use of noise assessment index with $L_{MAX}\;and\;L_{EQ}$. Lastly,noise complaints of millitary aircraft has been rapidly increasing ,so 2.9%(1.4 minion) person demands a compansation of \2,133 billion complying with their requirements we suggest to minimise the airport noise that is to develop of noise abatement procedure ,to make new noise index, to increase budget for house insulations and also to more increase of those the noise monitoring system and to unify the management etc.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.319-324
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• 2003

In general industrial rotating machinery is operated under 3,600 rpm as rotating speed and designed to have critical speed that is above operating speed. So, there was no problem to operate rotating machine under critical speed. But nowadays, they should be operated more than the frist critical speed as usual with the trend of high speed, large scale and hish precision in industries. In case of the large rotor assembly as the trend of large scale, using fitting method of disk or cylinder on shaft is rising for the convenience of assembly and cutting down of manufacturing cost. The shrink fitting is used to assemble lamination part on shaft for manufacturing of rotor of motor or generator in many cases and also is widely used for other machinery. In rotating system, which is compose of rotor and bearing, the critical speed is determined from inertia and stiffness for the rotor and bearings. In case of fitting assembly, analysis and design of the rotor is not easy because the rotor stiffness is determined depend on a lot of factors such as shaft material/dimension, disk material/dimension and assembled interference etc. Therefore designer who makes a plan for hish-speed rotating machine should design that the critical speed is located out of operating range, as dangerous factors exist in it. In order to appropriate design, an accurate estimation of stiffness and damping is very important. The stiffness variation depend on fitting interference is a factor that changes critical speed and if it's possible to estimate it, that Is very useful to design rotor-bearing system. In this paper, the natural frequency variation of the rotor depends on fitting interference between basic shaft and cylinder is examined by experimentation. From the result, their correlation is evaluated quantitatively using numerical analysis that is introduced equivalent diameter end the calculation criteria is presented for designer who design fitting assembly to apply with ease for determination of appropriate interference.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.788-791
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• 2005

Nodal displacements are referred to the Initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid fer structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.