• 한국기계가공학회지
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• 제1권1호
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• pp.89-100
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• 2002

The purpose if this research was to improve the pressure distribution on the disk brake pad Not uniform pressure distribution on the disk brake pad generate the unbalance wear of it and the unbalance wear of disk brake pad generate vibration, noise, heat and reduce the braking capacity. For improve the pressure distribution on the pad in this research, upper face of caliper housing finger was cut. Two kinds of caliper which uncut and cut of finger face were compared the stress distribution by FEM analysis and real experiment. Also natural frequency and deforming displacement ware calculated. It was understood that pressure distribution could Improve by cut inside upper face of caliper housing finger.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1387-1395
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• 2013

차륜 불평형은 차륜의 무게중심이 윤축의 기하학적 중심축에서 벗어나 있을 때 발생한다. 차륜 불평형을 수정하지 않고 주행하면 불평형에 의한 원심력이 차체의 진동을 발생시키게 되며 차륜의 마모를 촉진시키거나 차축 베어링에 손상을 주게 된다. 본 연구에서는 철도차량 동적해석을 통하여 차륜 불평형이 차량 임계속도와 차체 진동에 미치는 영향을 검토하였다. 차륜 불평형은 임계속도를 감소시키고 차체 공진을 유발할 수 있음을 알 수 있었다. 또한 차륜의 정적, 동적 불평형에 따른 차체진동을 해석함으로써 불평형 수정은 양면 밸런싱이 필요함을 밝혔다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.272-278
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• 1999

Tungsten Carbide(WC) Roll is widely used in finishing stands of wire rod mill. This report is about the manufacturing method of WC roll with excellent wear resistance. To enhance wear resistance, WC content has been increased to the maximum extent while binder content such as Co, Ni, Cr has been minimized. Part of WC is replaced with TiC having more wear resistant than WC. WTiC powder has been used to prevent weight unbalance resulting from the difference of specific weight when adding TiC. The roll manufactured by this method, is having more wear resistance than the existing rolls when applying to the final stand of the finishing mill. This report shows that WC is the critical factor of wear resistance in WC rolls and an approprite amount of TiC effects wear resistance and when adding TiC, using WTiC powder is better.

• 소음진동
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• 제7권6호
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• pp.1015-1023
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• 1997

Rotordynamic analysis of a multistage turbine pump using finite element method is performed to investigate the effects of seal wear on its system behavior. Stiffness and damping coefficents of the 2-axial grooved bearing are obtained as functions of rotating speed. Stiffness and damping coefficients of plane annuler seals are calculated as functions of rotating speed as well as seal clearance of seals become larger, these stiffness and damping coefficients decrease drastically so that there can be significant changes in whirl natural frequencies and damping characteristics of the pump rotor system. Although a pump is designed to operate with a sufficient seperation margin from the 1st critical speed, seal wear due to long operation may cause a sudden increase in vibration amplitude by resonance shift and reduce seal damping capability.

• 한국화재소방학회논문지
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• 제33권2호
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• pp.79-84
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• 2019

선박 운항 중 화재나 사고 시에 선박 내부의 복잡한 구조나 침수로 인해 갑판으로의 신속한 피난이 어려울 경우 유해가스나 산소 부족에 대응하기 위해서는 비상탈출용 호흡구난장비가 필수적이다. 최근 국내에서도 비상탈출호흡구가 개발 보급되고 있으나, 기본 성능만 만족할 뿐 실제 사용시의 착용성 및 활동성에 대한 평가 사례가 없어 그 효용성에 대해 의혹이 크다. 본 연구에서는 선박사고에 적합한 비상탈출호흡구에 대한 착용성 및 활동성 평가 항목을 제반 국제 기준으로부터 도출하였고, 개방식과 폐쇄식 각각의 국산 제품 샘플에 대한 평가를 수행하였다. 개방식은 시인성, 착용시간, 호흡저항 및 호스 걸림 부분에서, 폐쇄식은 정화통 방해, 무게 불균형, 호흡백 시야 가림 부분에서 개선이 필요한 것으로 평가되었다.

• 한국정밀공학회지
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• 제18권11호
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• pp.107-115
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• 2001

Most of rotating machineries supported by contact bearing accompany lowering efficiency, vibration and wear. Moreover, because of vibration, which is occurred in rotating shaft, they have the limits of driving speed and precision. The rotor system has parametric variations or external disturbances such as mass unbalance variations in long operation. Therefore, it is necessary to research about magnetic bearing, which is able to support the shaft without mechanical contact and to control rotor vibration without being affected by external disturbances or parametric changes. Magnetic bearing system in the paper is composed of position sensor, digital controller, actuating amplifier and electromagnet. This paper applied the robust control method using quantitative feedback theory (QFT) to control the magnetic bearing. It also proposed design skill of optimal controller, in case the system has structured uncertainty, unstructured uncertainty and disturbance. Reduction of vibration is verified at critical rotating speed even external disturbance exists. Unbalance response, a serious problem in rotating machinery, is improved by magnetic bearing using QFT algorithm.

• 대한기계학회논문집A
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• 제28권5호
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• pp.586-592
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• 2004

In this study, the failure analysis of a decanter is carried out and the methods of performance improvement are presented. The decanter is a centrifugal separator that is used to separate water and solids from municipal and industrial sludge. Therefore, the decanter should be designed to improve the dewatering of sludge. Besides high performance, the decanter should guarantee its life time under a severe using condition. For theses reasons, the failure analysis and performance improvement of the decanter are studied. It is found from this study that the failure is caused by mass unbalance, wear, clogging or crack. If these failure causes are prevented, the life time as well as the performance is expected to be improved.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 춘계학술발표회 초록집
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• pp.38-39
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• 2007

Chromium nitrids(Cr-N)박막은 경질박막재료이며 특히 PVD법을 제조한 CrN 박막은 다른 이원계 박막에 비해 높은 내마모성을 갖는다고 알려져 있다. 본 실험에서는 CrN박막에 Zr을 첨가하여 3원계의 CrZrN 박막을 합성하여 박막의 Zr 함량에 따른 표면경도 및 조도를 측정하고 Ball-on-disk type의 마모실험과 습도제어 하에서의 마모실험을 실시하였다. 박막의 Zr 함량이 증가함에 따라 박막의 표면경도가 증가하고 표면조도는 낮아지는 것을 알수 있었고, 그에 따라 마찰계수 값 또한 낮게 측정되었다. 습도제어하에서는 마찰계수 값은 비슷한 경향을 보였으나 습도가 매우 낮은 건조한 환경에서는 박막의 마찰계수 값이 높게 나타나는 경향을 보였다.

• 한국정밀공학회지
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• 제15권10호
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• pp.65-72
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• 1998

The BTA drilling chip is better for deep hole drilling than other self-piloting with pad drilling chips because the large length to diameter ratio allows a unique cutting force dispersion and better supplies the high pressure fluid. Therefore the BTA is useful for many tasks, such as coolant hole drilling of large scale dies, as well as tube seat drilling, which is essential for the heat exchanger, and variable component drilling for automobiles. Deep hole drilling has several significant problems, such as hole deviation, hole over-size, circularity, straightness, and surface roughness. The reasons for these problems, which often result in quality short comings, are an alignment of the BTA drilling system and the unbalance of cutting force by work piece and tool shape. This paper analyzes the properties through an experiment which com¬pared single-edge BTA drills with multiple-edge BTA drills, as well as the shapes of the tools to cause an unbalance of cutting force, and its effect on the precision of the worked hole. Conclusions are as follows. 1) In SMSSC drilling, 60m/min of BTA with single and multi-edged tools proved the best cutting condition and the lowest wear character. 2) The roundness got a little worse as cutting speed was increased, but surface roughness was hot affected. 3) It was proved that the burnishing torque of both drills approached 26%. which is almost the same as the 24% insisted on by Griffiths, and the dispersion characteristic of the multi-edged BTA drill proved better than the single-edge BTA drill.

• 한국소음진동공학회논문집
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• 제14권4호
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• pp.344-351
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• 2004

Tilling pad journal bearings have been widely used to support the rotors of the high rotating machinery such as steam and gas turbines owing to their inherent dynamic stability characteristics. However, serious bearing problems such as fatigue damage in the upper unloaded pad, the break of locking pins and the wear of pinholes etc. by pad fluttering are frequently taken place in the actual steam turbines. The purpose of this paper is to investigate the mechanism of pad fluttering and to suggest the useful design guideline(application of preload, m) for the purpose of preventing bearing problems by pad fluttering in a tilting pad journal bearing. It is estimated that upper pad is easy to flutter because the film shape of the upper pad is diverged by moment acting on pivot point. This paper suggests that effective preload range(m $\geq$ 0.5) in order to be statically loaded pad under all operating conditions. Also, design modified bearing is suggested for the adjustment in actual steam turbines. And bearing and rotor dynamic analysis are performed to identify bearing characteristics and to verify the reliability of rotor-bearing system.