• 한국소음진동공학회논문집
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• 제17권10호
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• pp.967-975
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• 2007

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modern semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element bearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300 rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through 3-D FE analysis and experimental modal analysis. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated by considering the generalized forces of the gear action as well as the rotor itself. Each resultant bearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of lateral and torsional critical speeds, and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, unbalance responses under various unbalance locations, and torsional interference diagram. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3197-3202
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• 2013

철도차량 차체 설계시 음압레벨에 따른 소음해석을 통한 차체 패널의 감쇠특성을 최적화하는 것이 필요하다. 본 논문은 철도차량 차체용 알루미늄 더블스킨 압출패널의 진동감쇠특성 해석을 통한 철도차량 차체의 구조소음 해석에 관한 연구이다. 주파수응답 가진시험을 통하여 측정된 기계적 모빌리티 값인 포인트 모빌리티, 트랜스퍼 모빌리티, 모달 모빌리티와 단순음원이론을 사용하여 정규화된 음압을 계산하였다. 도포용 감쇠재의 감쇠값을 라미네이티드 쉘요소에 사용하여 유한요소해석을 수행함으로써, 감쇠처리에 의한 소음감소수준 예측을 하였다. 또한 실제 차량 구조와 유사한 고정경계조건의 감쇠특성해석을 통하여 열차주행시 발생하는 진동의 영향을 크게 받는 언더프레임과 같은 부위에 일정 두께의 감쇠재 코팅이 진동 및 소음억제에 큰 효과가 있을 것으로 사료된다.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1437-1442
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• 2010

슬리퍼 메탈은 열간 압연 공정의 동력전달 부품이다. 슬리퍼 메탈은 스핀들과 커플링을 연결한다. 그러므로 슬리퍼 메탈이 심각하게 손상되면 스핀들과 커플링은 서로 충돌할 것이다. 슬리퍼 메탈의 파손을 방지하는 것은 기계적 수명을 연장하는 필수적인 요소이다. 본 연구에서는 슬리퍼 메탈의 수명 연장을 위하여 유한요소법을 사용하여 구조해석 및 형상 설계를 수행하였다. 수정된 슬리퍼 메탈과 스핀들 조립의 간섭을 검증하기 위해 다양한 체결 타입과 동적 경계 조건을 적용하여 동적 시뮬레이션을 수행하였다. 슬리퍼 메탈의 구조 해석과 형상 설계의 결과로써 수정된 슬리퍼 메탈의 최대응력은 초기 모델과 비교하여 22 % 감소하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.175-183
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• 2004

In hot strip rolling, a capability for precisely predicting roll force is crucial for sound process control. In the past, on-line prediction models have been developed mostly on the basis of Orowan's theory and its variation. However, the range of process conditions in which desired prediction accuracy could be achieved was rather limited, mainly due to many simplifying assumptions inherent to Orowan's theory. As far as the prediction accuracy is concerned, a rigorously formulated finite element(FE) process model is perhaps the best choice. However, a FE process model in general requires a large CPU time, rendering itself inadequate for on-line purpose. In this report, we present a FE-based on-line prediction model applicable to precision process control in a finishing mill(FM). Described was an integrated FE process model capable of revealing the detailed aspects of the thermo-mechanical behavior of the roll-strip system. Using the FE process model, a series of process simulation was conducted to investigate the effect of diverse process variables on some selected non-dimensional parameters characterizing the thermo-mechanical behavior of the strip. Then, it was shown that an on-line model for the prediction of roll force could be derived on the basis of these parameters. The prediction accuracy of the proposed model was examined through comparison with measurements from the hot strip mill.

• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.672-678
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• 2009

Acoustic Emission (AE) technique is a non-destructive testing method and widely used for the early detection of faults in rotating machines in these days, because the sensitivity of AE transducers is higher than normal accelerometers. So it can detect low energy vibration signals. The faults in the rotating machines are generally occurred at bearings and gearboxes which are the principal parts of the machines. It was studied to detect the bearing faults by envelop analysis in several decade years. And the researches showed that AE had a possibility of the application in condition monitoring system(CMS) using the envelope analysis for the rolling bearing. And peak ratio (PR) was developed for expression of the bearing condition in condition monitoring system using AE. Noise level is needed to reduce to take exact PR value because the PR is calculated from total root mean square (RMS) and the harmonics peak levels of the defect frequencies of the bearing. Therefore, in this paper, the discrete wavelet transform (DWT) was added in the envelope analysis to reduce the noise level in the AE signals. And then, the PR was calculated and compared with general envelope analysis result and the result of envelope analysis added the DWT. In the experiment result about inner fault of bearing, defect frequency was difficult to find about only envelop analysis. But it's easy to find defect frequency after wavelet transform. Therefore, Envelop analysis added wavelet transform was useful method for early detection of default in signal process.

• 한국철도학회논문집
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• 제18권3호
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• pp.212-222
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• 2015

도심 내의 트램 노선 설계 및 건설에서 환경 소음 문제를 해결하기 위해서는 트램 시스템의 소음 방사특성을 파악하여야 한다. 본 논문에서는 트램 시험 차량에 대한 전동 소음 특성을 연구하였으며, 전동 소음 관점에서의 레일 지지 구조의 적절한 강성을 검토하였다. 매립형 궤도와 탄성차륜의 모빌리티를 Timoshenko 보 모델과 유한 요소 모델을 각각 이용하여 구하였고, 측정값과 비교하였다. 선로변 방출 소음도에 대한 계산값을 측정값과 비교한 결과 300Hz 이상의 주파수 대역에서 작은 오차를 내었다. 레일 및 슬라브 지지 강성을 변화시켜가면서 레일 및 차륜의 소음원 강도를 분석하였으며, 지반 진동을 과다하게 유발하지 않으면서 레일 및 차륜으로부터 방사되는 소음이 감소될 수 있는 적정 지지 강성을 검토하였다.

• 수산해양기술연구
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• 제59권4호
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• pp.328-335
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• 2023

In this paper, among the various facilities used in marine farming, young bivalves of the Mytilus galloprovincialis of marine farming was placed on the deck of the fishing vessel to evaluate the environment conditions and drive shaft movement by rolling affecting the separator for the young bivalves and a clean process. There were a few studies on stress analysis of development facilities because it was difficult to access the fishing site due to the use of imported equipment and the lack of development of domestic equipment. In this study, stress analysis of the fixed part of separator for young bivalves and its adjacent part was performed on various phases when the vessel was tilted by rolling using the finite element method. In addition, the structural safety of the internal blade under the driving conditions according to the movement of the drive shaft by the hydraulic motor was confirmed through structural analysis. As a result, the connection part between the deck and the separator by rolling was confirmed to have higher stress than that of other parts due to stress concentration. In addition, it was confirmed that the maximum stress occurred on the connection part between blades. Even though the safety of the separator for marine farming was confirmed by structural analysis, it is necessary to comprehensively consider the age of vessels, the material of the deck, and the corrosion of the deck.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.71-75
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• 2003

The conduit fer superconducting cable is welded and plastically deformed during the jacketing process to make the CICC (Cable-in-Conduit-Conductors) fer a fusion magnet. The jacketing process of KSTAR (Korea Superconducting Tokamak Advanced Research) conductors is composed of several sequential steps such as rounding, welding, sizing, and square-rolling. Since the welded zone in Incoloy 908 conduit is brittle and easy to have flaws, there may be a possibility of stress corrosion cracking during the heat treatment of coil when both the induced tensile residual stress and the concentration of oxygen in the furnace are sufficiently high. The steps of the jacketing process were simulated using the finite element method of the commercial ABAQUS code, and the stress distribution in the conduit in each step was calculated, respectively. Furthermore, the variations of residual welding stresses through the steps of the jacketing process were calculated and analyzed to anticipate the possibility of the stress corrosion cracking in the conduit. The concentrated high tensile residual welding stresses along the welding bead decrease by the plastic deformation of the following sizing step. The distribution in residual stresses in the conductor for magnet coil is mainly governed by the last step of square-rolling.

• 한국자동차공학회논문집
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• 제17권5호
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• pp.115-126
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• 2009

This paper studied on the application of the crashworthiness regulations of Korean Railway Safety Law and Urban Transit Safety Law to the urban Maglev vehicle of KIMM. The Urban Maglev vehicle has to comply with the crashworthiness regulations for urban transit vehicles. The collision load cases have been simulated by using explicit finite element analysis. From the numerical results, the crashworthiness regulations of the Urban Transit Safety Law were completely satisfied, but maximum crash pulse requirement in 25 km/h crash event and no plastic deformation requirement in 10 km/h crash event in the Korean Railway Safety Law were not. If a commercial urban Maglev vehicle is developed in the near future, it is necessary that some soft buffing and energy absorbing devices are adopted in its front end so as to satisfy the crashworthiness regulations of the Korean Railway Safety Law.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.785-798
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• 2002

A reliable analytic model that predicts the surface profile of the exit cross section of workpiece in round-oval (or oval-round) pass sequence is established. The presented model does not require any plasticity theory but needs the only geometric information on workpiece and roll groove. Formulation is based on the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove in the roll axis direction when the maximum spread of workpiece is known beforehand. The validity of the analytic model is examined by hot rod rolling experiment with the roll gap, specimen size, design parameter of oval groove and steel grade changed. Results revealed that the cross sectional shapes predicted by the model were in good agreement with those obtained experimentally. We found that the analytic model not only has simplicity and accuracy for practical usage but also saves a large amount of computational time in comparison with finite element method.