• Title, Summary, Keyword: Wear Type Defects

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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.

Fatigue wear of polyamides with surface defects under different loading conditions

  • Abdelbary, Ahmed;Nasr, Mohamed N.A.
    • Advances in materials Research
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    • v.5 no.3
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    • pp.193-203
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    • 2016
  • Compared to metal-to-metal tribology, polymer tribology presents further complexity as it is more prone to be influenced by operating conditions. Over the past two decades, progress in the field of wear of polymers has led to the establishment of more refined wear mechanisms. The current paper establishes the link between different load parameters and the wear rate of polymers, based on experimental investigations. A pin-on-plate reciprocating tribometer was used to examine the wear behaviour of polyamide sliding against a steel counterface, under constant and fluctuating loads, in dry conditions. In addition, the influence of controlled imperfections in the polymer surface upon its wear rate were examined, under cyclic and steady loading, in order to better understand surface fatigue wear of polymers. The imposed imperfections consisted of vertical artificial deep crack (slit) perpendicular or parallel to the direction of sliding. The study concludes with the followings findings; in general, wear of polymers shows a significant tendency to the type of applied load. Under cyclic loads, polymers show an increase in wear rate compared to those tested under static loads. Such increase was found to increase with the increase in cyclic load frequency. It is also demonstrated that surface cracks results in higher wear rates, particularly under cyclic loads.

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.

Development of Rheology Forming Technology of Wear Resistance Al-Si Materials (I);Filling Behavior and Defect Evaluation (내마모계 Al-Si 재료의 레오로지 성형기술 개발 (I);충진거동 및 결함분석)

  • Jung, Hong-Kyu;Kang, Sung-Soo;Moon, Young-Hoon;Kang, Chung-Gil
    • Journal of Korea Foundry Society
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    • v.20 no.6
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    • pp.368-376
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    • 2000
  • Rheology forming technology has been accepted as a new method for fabricating near net shaped products with lightweight aluminum alloys. The rheology forming process consists of reheating process of billet, billet handling, filling into the die cavity and solidification of rheology formed part. The rheology forming experiments are performed with two different die temperatures ($T_d$ = $200^{\circ}C$, $300^{\circ}C$) and orifice gate type. The filling behavior and various defects of Al-Si materials with wear resistance (A357, A390 and ALTHIX 86S) fabricated in rheology forming process are evaluated in terms of alloying elements and surface non-uniformity. Finally, the methods to obtain the rheology formed products with high quality are described by solutions for avoiding the surface and internal defects.

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Study on the efficient maintenance of wheel for High Speed Train (고속철도 차륜의 효율적인 관리에 관한 연구)

  • Kim Myeong-Soo;Koo Jeong-Seo;Lee Hi-sung;Kwon Seok-Jin
    • Proceedings of the KSR Conference
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    • pp.318-325
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    • 2005
  • In present, KTX's wheel is worn inevitably according to the interaction with rail in service. It was analyzed by wearing type, damage type and wheel reprofiling cycle on the running surface. As a result, damage on the running surface is main cause to reprofile the wheel. Wearing type of wheel is normal and it hasn't reprofiled according to normal wheel wear. As a follow-up result of the whee] defects on the running surface, if the defects size is well managed by periodical inspection, it would be efficient to increase the wheel life.

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Friction and Wear Characteristics of Gray Cast Iron Surface Processed by Broaching Method (브로칭 가공된 회주철 소재 표면의 마찰 및 마모 특성)

  • Kwon, Mun-Seong;Kang, Kyeong-Hee;Kim, Dae-Eun
    • Tribology and Lubricants
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    • v.34 no.6
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    • pp.262-269
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    • 2018
  • In this work the friction and wear characteristics of the gray cast iron surface processed by broaching method, which is widely used in the machinery industry, were investigated. The broaching process is mainly used for mass production because it has high dimensional accuracy and processing speed, but the defects on surface can be easily generated. In order to improve the tribological characteristics, the approach was to reduce the roughness and hardness of the surface by adding a machining process to the broaching specimen. The secondary machining process using abrasive grains produces low roughness and hardness than broaching because it has high tool accuracy and removes the work hardened surface. The friction coefficient and the wear rate were assessed using a reciprocating-type tribotester to analyze the effects of surface finishing on the tribological properties. The friction tests were conducted under dry and lubricated conditions. The test results showed that the reduction of surface roughness and hardness through secondary machining process in lubricated condition improved the friction and wear characteristics. The reason why the same results did not appear in a dry condition was that wear occurred more rapidly than in lubricated condition. Thus, the positive effect of roughness and hardness of the surface obtained through the secondary machining process was not observed.

Tribological Behaviors of DLC Thin Films Deposited using Precursor Gas diluted by Hydrogen under Aqueous Environment (수중 환경에서 수소로 희석된 반응 가스를 이용하여 증착된 DLC 박막의 트라이볼로지 거동)

  • Lee, Jin-U;Mun, Myeong-Un;Lee, Gwang-Ryeol
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.338-339
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    • 2012
  • This study examined the friction and wear behavior of diamond-like carbon (DLC) films deposited from a radio frequency glow discharge using a hydrogen diluted benzene gas mixture. The DLC films were deposited on Si (100) and polished stainless steel substrates by r.f.-PACVD at hydrogen to benzene ratios, or the hydrogen dilution ratio, ranging from 0 to 2.0. The wear test was carried out in both ambient and aqueous environments using a home-made ball-on-disk type wear rig. The stability of the DLC coating in an aqueous environment was improved by diluting the benzene precursor gas with hydrogen, suggesting that hydrogen dilution during the deposition of DLC films suppress the initiation of defects in the film and improved the adhesion of the coating to the interface.

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Utilizing Advanced Pad Conditioning and Pad Motion in WCMP

  • Kim, Sang-Yong;Chung, Hun-Sang;Park, Min-Woo;Kim, Chang-Il;Chang, Eui-Goo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.171-175
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    • 2001
  • Chemical mechanical polishing(CMP) process has been widely used to planarize dielectrics and metal, which can apply to employed in integrated circuits for sub-micron technology. Despite the increased use of CMP process, it is difficult to accomplish the global planarization of free-defects in inter level dielectrics and metal. Especially, defects like (micro-scratch) lead to severe circuit failure, and affects yield. Current conditioning method - bladder type, orbital pad motion- usually provides unsuitable pad profile during ex-situ conditioning near the end of pad life. Since much of the pad wear occurs by the mechanism of bladder type conditioning and its orbital motion without rotation, we need to implement new ex-situ conditioner which can prevent abnormal regional force on pad caused by bladder-type and also need to rotate the pad during conditioning. Another important study of ADPC is related to the orbital scratch of which source is assumed as diamond grit dropped from the strip during ex-situ conditioning. Scratch from diamond grit damaged wafer severely so usually scraped. Figure 1 shows the typical shape of scratch damaged from diamond. e suspected that intensive forces to the edge area of bladder type stripper accelerated the drop of Diamond grit during conditioning. so new designed Flat stripper was introduced.

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A Study on the Removal of CFRP Machining Defects by Various Tool Geometries (공구 형상에 따른 CFRP의 가공결함 제거에 관한 연구)

  • Park, Ki Moon;Ko, Tae Jo;Yu, Zhen;Kumaran S, Thirumalai
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.16 no.4
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    • pp.16-23
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    • 2017
  • CFRP(Carbon Fiber Reinforced Plastics) has many industrial applications due to its low weight and high strength properties. Due to its superior properties, for example, excellent resistance to fatigue wear, corrosion, and breakage from fatigue, it has been widely applicable to aircraft, automotive, and medical industries and so on. The main machining for CFRP is drilling, and route milling. In case of drilling, the machining defects such as the delamination of each layer, uncut fiber, resin burning, spalling, and exit burrs are inevitable. The issue to remove such kind of defects is necessary to make CFRP parts successful. From this point of view, this paper investigates the removal effectiveness of machining defects existing at exit region with different type of tool geometries. Consequently, based on the experiments, the tool geometry is most impact factor to remove uncut fiber or resin.

A Stud on the Fabrication and Characteristics of Al-Sn Alloy Strips by Twin-Roll Process (쌍롤법에 의한 Al-Sn합금 Strip의 제조 및 특성에 관한 연구)

  • Lee, Jeong-Keun;Joo, Dae-Heon;Kim, Myung-Ho
    • Journal of Korea Foundry Society
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    • v.22 no.4
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    • pp.174-183
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    • 2002
  • Twin-roll process is a relatively new continuous casting process which can produce high-quality strip products directly, and solidification rate can reach $10^3$ to $10^4$ K/s, leading to fine and uniform microstructures with enhanced mechanical properties. The strip casting condition for producing fine Al-Sn alloy strip was obtained experimentally, and defects appearing on the strip was examined. Crack formation and surface quality of the strip was found to depend mainly on process parameters such as melt temperature, roller gap and rolling speed. Sn structure of network type was observed in Al-20Sn and Al-40Sn alloy strips, and cell spacing of Al-40Sn alloy was smaller than that of Al-20Sn. Banding strength of the heat treated specimens increased with increasing of soaking time and temperature, and bonding strength of Al-20Sn alloy was more superior than that of Al-40Sn alloy. However wear resistance of Al-40Sn alloy contained large amount of soft Sn which possess good anti-friction characteristics was superior than that of Al-20Sn alloy.