• Title, Summary, Keyword: 마모결함

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Study on NDT Fault Diagnosis of the Ball Bearing under Stage of Abrasion by Infrared Thermography (마모 단계의 볼 베어링에 대한 적외선 열화상 비파괴 결함 진단 연구)

  • Seo, Jin-Ju;Hong, Dong-Pyo;Kim, Won-Tae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.32 no.1
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    • pp.7-11
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    • 2012
  • For fault detection about the abrasion stage of rotational machineries under the dynamic loading conditions unlike the traditional diagnosis method used in the past decade, the infrared thermographic method with its distinctive advantages in non-contact, non-destructive, and visible aspects is proposed. In this paper, by applying a rotating deep-grooved ball bearing, passive thermographic experiments were conducted as an alternative way to proceeding the traditional fault monitoring on spectrum analyzer. As results, the thermographic experiment was compared with the traditional vibration spectrum analysis to evaluate the efficiency of the proposed method. Based on the results obtained as NDT, the temperature characteristics and abnormal fault detections of the ball bearing according to the abrasion stage were analyzed.

Structural Integrity Evaluation of SG Tube with Surface Wear-type Defects (표면 마모결함을 고려한 증기발생기 세관의 구조건전성 평가)

  • Kim, Jong-Min;Huh, Nam-Su;Chang, Yoon-Suk;Hwang, Seong-Sik;Kim, Joung-Soo;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12
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    • pp.1618-1625
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    • 2006
  • During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

Classification of Defects in Rotary Compressor by Neural Pattern Recognition of Acoustic Emission Signal (AE신호의 신경망 형상인식법에 의한 로터리 압축기의 결함 분류에 관한 연구)

  • Lee, K.Y.;Lee, C.M.;Hwang, I.B.;Kim, Y.W.;Hong, J.K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.18 no.1
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    • pp.17-26
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    • 1998
  • The specimen with the wear between a roller and a vane and a normal specimen are classified by AE signal pattern recognition method with a neural network classifier in airconditioning operation test. Also the specimen with the scoring between a shaft and a bearing and a normal specimen are classified by the same method. As the internal pressure increases, the wear between the roller and the vane increases. The different pairs of oils and refrigerants five the effect on the wear.

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Research on fault analysis and reliability improvement of APU start motor for Korea Utility Helicopter (한국형 기동헬기 APU 시동모터 결함원인 분석 및 신뢰성 개선)

  • Kang, Tae-Woo;Yeom, Hyo-Won;Lee, Hee-Rang;Ahn, Jong-Moo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.6
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    • pp.703-709
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    • 2017
  • Korea Utility Helicopter(KUH) is a project to replace the aging helicopter presently being operated by the military with a domestic helicopter. The auxiliary power unit is a device that supplies emergency power to the system by an alternator installed when the main generator fails and the start motor converts the electrical energy of the battery into mechanical rotational energy to rotate the auxiliary power unit engine. With continuing power and operation, defects of the starting motor were found and improvements were carried out to solve it. In the failure mode analysis, the causes of possible defects were classified into 5 categories. Analysis of the 5 factors revealed that the main cause of defects is mechanical wear, which was found to be related to spring pressure. 250 tests were conducted through the theoretically determined pressure and regression analysis was performed with 4 sampling.The results showed that pressure was related to wear rate. In conclusion, early wear and breakage due to wear can be controlled through spring force and test showed the prediction of wear and the validity of the result were confirmed.

타이어의 마모한계

  • Song, Yeong-Gi
    • The tire
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    • pp.6-7
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    • 1989
  • 과마모 타이어의 사용으로 인한 사고발생의 위험을 미연에 방지하기 위하여 미국, 일본 등에서는 오래 전부터 타이어의 마모한계를 법제화하여 이를 시행하고 있다. 우리나라에서도 자동차보유대수의 급증에 따라 타이어의 결함으로 인한 사고발생율이 높아지고 있는 현실을 감안, 교통부에서는 지난 4월 「자동차안전기준에 관한 규칙」개정시 이에 대한 대책의 일환으로 타이어 관계조항(규칙 제12조2항)을 개정, 타이어 트레드 홈깊이를 1.6mm 이상 유지하도록 규정하였으며, 이 개정된「자동차안전기준에 관한 규칙」의 시행을 눈앞에 두고 있다.<필자주>

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The Effect of Mn on the Elevated Temperature Sliding Wear Behavior of Fe-20Cr-1C-1Si Hardfacing Alloy (Fe-20Cr-1C-1Si 경면처리 합금의 고온 Sliding 마모거동에 미치는 Mn의 영향)

  • Kim, Geun-Mo;Kim, Jun-Gi;Yang, Yeong-Seok;Gang, Seong-Gun;Kim, Seon-Jin
    • Korean Journal of Materials Research
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    • v.9 no.9
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    • pp.937-942
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    • 1999
  • Fe계 합금의 적층결함에너지를 감소시키는 것으로 알려진 Mn이 Fe-20Cr-1C-Si 경면처리 합금의 변형유기 상변태거동과 상온 및 고온 마모저항성에 미치는 영향에 대하여 조사하였다. 15ksi의 접촉응력에 대하여 0~25wt.% Mn을 첨가한 시편은 모두 상온에서 마모손실량이 적은 우수한 마모저항성을 보였는데 Mn 첨가량이 5wt.% 이하인 시편의 경우 마모표면에서 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 반면 15wt.% 이상 Mn을 첨가한 시편에서는 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 발생하는 것으로 나타났다. 25$0^{\circ}C$까지 고온 마모시험결과 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 5wt.% 이하 Mn 첨가시편은 Mn 첨가량이 증가할수록 마모손실량이 증가하는 것으로 보아 Mn 첨가는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 있어서 고온 마모저항성을 저하시키는 것으로 생각되며 이는 Mn이 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태의 M(sub)d 온도를 감소시키기 때문으로 생각된다. 반면에 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 일어난 15wt.% 이상 Mn 첨가 시편의 경우 Mn 첨가량 증가에 따른 고온 마모손실량의 차이가 없는 것으로 보아 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 비해 온도의 존성이 적은 것으로 생각된다.

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A Study on Wear-type Defects of Part and Materials in Wind Power Generation (풍력발전기 부품소재의 마모결함 검출에 관한 연구)

  • Kim, Sung-Hyun;Choi, Seung-Hyun;Jung, Na-Ra;Yoon, Cheon-Han;Kim, Jae-Yeol
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.22 no.6
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    • pp.989-995
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    • 2013
  • Unlike fossil-or nuclear fuel-based power generation, wind power generation using inexhaustible wind energy is a pollution-free, hazardless power generation method. In this study, ultrasound thermography is used for fabricating specimens of wind power generator bearings and wind power generator supplement flanges, and an optimally designed ultrasound horn and ultrasound excitation system are used for detecting damage to part materials of a wind power generation setup. In addition, thermal flow analysis and ultrasonic thermography imaging are comparatively analyzed for improving the detection reliability in terms of surface and internal defects of part materials and for verifying the developed system's field applicability and reliability.

대구경 사파이어 단결정 기판의 결함 평가를 위한 X-선 토포그래피 장비 구축

  • Jeon, Hyeon-Gu;Jeong, In-Yeong;Lee, Yu-Min;Kim, Chang-Su;Park, Hyeon-Min;O, Byeong-Seong
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.238-238
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    • 2013
  • 사파이어 단결정은 광학 투명도, 물리적 강도, 충격 저항, 마모 부식, 높은 압력 및 온도 내구성, 생체 호환성 등 다양한 특성을 가지고 있어 다양한 분야에서 사용되고 있으며, 특히 최근에는 백색 또는 청색 LED 소자 분야에서 기판으로 주로 활용되고 있다. 이러한 사파이어 단결정 기판은 공정에서 결정 성장 조건 및 기계적 연마 등의 다양한 요인으로 결정학적 결함이 발생한다. 이러한 결정학적 결함을 제어함으로서 좋은 품질의 단결정 기판을 생산할 수 있다. 이에 따라 각종 결함 제어를 위해서 X-선, EPD, 레이저 편광법 등 다양한 방법으로 결함들을 측정하고 있다. 그 중에서도 X-선 토포그래피는 시료를 비파괴적인 방법으로 단결정의 결함 밀도와 유형 등을 파악하는데 매우 유용한 측정법이며, Lang 토포그래피로 대표되는 X-선 회절 투과법은 기판과 같은 대구경의 시료를 우수한 분해능으로 내부 결함까지 관찰할 수 있는 장점을 지니고 있다. 본 연구에서는 대구경 사파이어 단결정 기판에 내재하는 결정 결함을 확인 및 분석하기 위해 X-선 Lang 토포그래피(X-ray Lang Topography) 장비를 구축하였다. 그리고 4, 6인치 c-면 사파이어 단결정 기판의 (110), (102) 회절면의 X-선 토포그래피 측정을 통해 전위(dislocation), 스크래치(scratch), 표면데미지(surface damage), 트윈(twin), 잔류 응력(strain) 등의 결함의 유형을 식별 및 분석하였으며, 각각의 결함들의 토포그래피 이미지 형성 메커니즘에 대해 분석하였다. 이를 통해 X-선 Lang 토포그래피(X-ray Lang Topography) 장비가 대구경 사파이어 단결정 기판의 결정 결함 평가에 폭넓은 활용이 가능할 것으로 예상된다.

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The Effect of Vandium on the microstructure and Elevated Temperature Sliding Wear Resistance of Fe-20Cr-1.7C-1Si-xV Hardfacing Alloy (Fe-20Cr-1.7C-1Si-xV 경면처리 합금의 미세조직과 고온 Sliding 마모저항성에 미치는 Vanadium의 영향)

  • Kim, Jun-Gi;Kim, Geun-Mo;Lee, Deok-Hyeon;Jang, Se-Gi;Gang, Seong-Gun;Kim, Seon-Jin
    • Korean Journal of Materials Research
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    • v.8 no.10
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    • pp.969-974
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    • 1998
  • The effect of vanadium, which is known to decrease the stacking fault energy of Fe-base alloys, on the microstructure and elevated temperature sliding wear resistance of Fe-20Cr- 1.7C- 1Si alloy was investigated. The maximum amount of vanadium maintaining the austenitic matrix seems to be about 3wt.% in Fe-20Cr- 1.7C-1Si-xV (x = 0, 1, 3, 6. lOwt.%) alloys and the austenitic alloys showed better wear resistance than ferritic alloys. It was considered to be due to the low stacking fault energy and $\gamma->\alpha$ strain-induced phase transformation at rmm temperature. It was shown from elevated temperature sliding tests up to .$225^{\circ}C$ that the addition of vanadium increases the temperature, at which the transition from oxidative wear to adhesive wear occur, and the amount of d formed at $225^{\circ}C$. Thus, it was considered that the addition of vanadium improves the elevated temperature sliding wear resistance of Fe-20Cr- 1.7C - 1Si by reducing the increasing rate of stacking fault energy with temperature and by increasing Ma temperature.

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