• Title, Summary, Keyword: Wear

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The Relationship between a Wear Depth :and a Decrease of the Contacting Force in the Nuclear Fuel Fretting (핵연료봉 프레팅마멸에서 마멸깊이와 접촉하중 감소사이의 관계)

  • Lee Young-Ho;Kim Hyung-Kyu
    • Tribology and Lubricants
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    • v.22 no.1
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    • pp.8-13
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    • 2006
  • Sliding wear tests have been performed to evaluate the effect of normal load decrease on the wear depth of nuclear fuel rods in room temperature air. The objectives of this study are to quantitatively evaluate the supporting ability of spacer grid springs, to estimate the wear depth by using the contacting force decrease and to compare the wear behavior with increasing test cycles (up to $10^7$) at each spring condition. The result showed that the contacting load decrease depends on the spring shape and the applied slip amplitude. The estimated wear depth is smaller when compared with measured wear depth. Based on the test results, the wear mechanism, the role of wear debris layer and the spring shape effect were discussed.

A Study on the Variation of the Fretting Wear Mechanisms under Elastically Deformable Contacts

  • Lee, Young-Ho;Kim, Hyung-Kyu
    • KSTLE International Journal
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    • v.10 no.1_2
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    • pp.27-32
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    • 2009
  • In this study, fretting wear tests of nuclear fuel rods have been performed by using two kinds of spacer grid springs with a concave and a convex shape in room temperature dry and distilled water conditions. The objectives were to examine the variation of the wear mechanism with increasing fretting cycles and to evaluate the difference of the wear debris detachment behavior at each test environment. From the test results, the wear volume of each spring condition increased with increasing fretting cycles regardless of the test environments. However, the wear rate did not show a regular tendency and apparently changed with increasing fretting cycles. This is because the formation of the wear particle layer and/or the variation of the contact condition between the fuel rod and spring surfaces could affect a critical plastic deformation for detaching the wear debris. Based on the test results, the relationship between the wear behavior of each spring shape and test environment condition, and the variation of the surface characteristics are discussed in detail.

Measurement of Wear and Friction Coefficients for the Prediction of Fretting Wear (프레팅 마멸계수 및 마찰계수 측정에 관한 연구)

  • Cho, Yong Joo;Kim, Tae Wan
    • Tribology and Lubricants
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    • v.28 no.3
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    • pp.124-129
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    • 2012
  • The prediction of fretting wear is a significant issue for the design of contacting mechanical components such as flexible couplings and splines, jointed structures and so on. In our earlier study, we developed a numerical model to predict the fretting wear using boundary element method. The developed algorithm needs experimental fretting wear coefficients and friction coefficients between two moving materials to get more reliable results. In this study, therefore, we demonstrated the measurement method of the fretting wear coefficients and friction coefficients using disk on plate tribometer with piazo actuator and gap sensor. For four different material combinations, the fretting wear coefficients and friction coefficients are acquired through the fretting wear experiment and the analysis of the measured values. Thess results are useful to predict the quantative fretting wear rate in the developed algorithm.

Effect of Different Golf Shoe treads on Wear and Ball Speed of Putting Green (퍼팅그린의 마모와 골프공의 구름에 미치는 골프화의 영향)

  • 심포룡;심규열
    • Asian Journal of Turfgrass Science
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    • v.11 no.3
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    • pp.205-210
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    • 1997
  • The metal spikes evaluated in this study significantly affected more negative on the turf wear and ball speed of putting green than alternative plastic spikes. 1.The metal spikes caused the most amount of wear compared with plastic spikes, athletic shoes and mountain-climbing shoes. On the other hand, athletic shoes caused the least amount of wear. Plastic spikes caused wear more than athletic shoes, hut apparently wear less than metal spikes. The wear from metal spike repaired later than any other tread types. 2.The wear from all kinds of shoe treads in wetcondition green were higher than in dry-condition green and the wear from metal spikes was more severe compared with plastic spikes in both green condition. 3. Ball speed of heavy compaction area by metal spike was reduced about 9% compared with that of light compaction area, hecause metal spikes made many holes in the putting green surface. On the other hand, plastic spikes did not affect hall speed of heavy and light compaction area in the putting green. Key words: Metal spike, Plastic spike, Wear, Ball speed.

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A Study on Automatic wear Debris Recognition by using Particle Feature Extraction (입자 유형별 형상추출에 의한 마모입자 자동인식에 관한 연구)

  • ;;;A. Y. Grigoriev
    • Tribology and Lubricants
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    • v.15 no.2
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    • pp.206-211
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    • 1999
  • Wear debris morphology is closely related to the wear mode and mechanism occured. Image recognition of wear debris is, therefore, a powerful tool in wear monitoring. But it has usually required expert's experience and the results could be too subjective. Development of automatic tools for wear debris recognition is needed to solve this problem. In this work, an algorithm for automatic wear debris recognition was suggested and implemented by PC base software. The presented method defined a characteristic 3-dimensional feature space where typical types of wear debris were separately located by the knowledge-based system and compared the similarity of object wear debris concerned. The 3-dimensional feature space was obtained from multiple feature vectors by using a multi-dimensional scaling technique. The results showed that the presented automatic wear debris recognition was satisfactory in many cases application.

Development of Wear Model concerning the Depth Behaviour

  • Kim, Hyung-Kyu;Lee, Young-Ho
    • KSTLE International Journal
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    • v.6 no.1
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    • pp.1-7
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    • 2005
  • Wear model for predicting the vehaviour of a depth is considered in this paper. It is deduced from the energy and volume based wear models such as the Archard equation and the workrate model. A new parameter of the equivalent depth ($D_e$= wear volume /worn area) is considered for the wear model of a depth prediction. A concenpt of a dissipated shear energy density is accommodated for in the suggested models. It is found that $D_e$ can distinguish the worn area shape. A cubic of $D_e$($D_e^3$) gives a better linear regression with the volume than that of the maximmum depth $D_{max}e$($D_{max}^3$) does. Both $D_{max}$ and $D_e$ are used for the presently suggested depth-based wear model. As a result, a wear depth profile can be simulated by a model using $D_{max}$. Wear resistance from the concern of an overall depth can be identified by the wear coefficient of the model using $D_e$.

Study on Wear of Journal Bearings during Start-up and Coast-down Cycles of a Motoring Engine - II. Analysis Results (모터링 엔진의 시동 사이클 및 시동 정지 사이클에서 저어널베어링의 마모 연구 - II. 해석 결과)

  • Chun, Sang Myung
    • Tribology and Lubricants
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    • v.31 no.3
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    • pp.125-140
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    • 2015
  • In this paper, we present the results of the wear analysis of journal bearings on a stripped-down single-cylinder engine during start-up and coast-down by motoring. We calculate journal bearing wear by using a modified specific wear rate considering the fractional film defect coefficient and load-sharing ratio for the asperity portion of a mixed elastohydrodynamic lubrication (EHL) regime coupled with previously presented graphical data of experimental lifetime linear wear in radial journal bearings. Based on the calculated wear depth, we obtain a new oil film thickness for every crank angle. By examination of the oil film thickness, we determine whether the oil film thickness at the wear scar region is in a mixed lubrication regime by comparing dimensionless oil film thickness, h/σ, to 3.0 at every crank angle. We present the lift-off speed and the crank angles involved with the wear calculation for bearings #1 and #2. The dimensionless oil film thickness, h/σ, illustrates whether the lubrication region between the two surfaces is still within the bounds of the mixed lubrication regime after scarring of the surface by wear. In addition, we present in tables the asperity contact pressure, the real minimum film thickness at the wear scar region, the modified specific wear rate, and the wear angle, α, for bearings #1 & #2. To show the real shape of the oil film at wear scar region, we depict the actual oil film thickness in graphs. We also tabulated the ranges of bearing angles related with wear scar. We present the wear volume for bearings #1 and #2 after one turn-on and turn-off of the engine ignition switch for five kinds of equivalent surface roughness. We show that the accumulated wear volume after a single turn-on and turn-off of an ignition switch normally increases with increasing surface roughness, with a few exceptions.

Quantitative characteristics of particle size distribution by the wear mode transition (마모유형 천이에 따른 입자크기분포의 정량적 특성)

  • 공호성;권오관
    • Tribology and Lubricants
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    • v.2 no.1
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    • pp.39-45
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    • 1986
  • Wear simulation test have been conducted in mild, severe and transient wear regions by a four-ball wear tester. Wear particles are separatively deposited by the RPD technique, and quantitatively analysed in terms of wear particles size distribution. Characteristics of the wear particle size distribution are compare to the results of wear tests through both weibull parameters and center moment method of the weibull distribution function.

Characteristics of rubber friction and wear (고무의 마찰과 마모 특성에 대한 고찰)

  • Kim, Hyun-Jae;Kim, Se-Nyung;Kim, Su-Hyung;Kim, Doo-Man
    • Journal of Aerospace System Engineering
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    • v.4 no.4
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    • pp.1-10
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    • 2010
  • The basic factor that affect wear performance is the wear characteristics, which come from sliding friction between rubber compound and road. Thus, this study focused on friction and wear of rubber. This paper briefly explain some characteristics of friction and wear referring to the papers on wear of rubber that scholars researched on. Research activities to predict the performance of the rubber wear is also explained.

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A Comparative Study on the Evaluation of the Wear Resistance in Zr-xNb-xSn Alloys

  • Lee, Young-Ho;Kim, Hyung-Kyu;Jung, Youn-Ho
    • KSTLE International Journal
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    • v.4 no.2
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    • pp.47-51
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    • 2003
  • Sliding wear tests have been carried out in room temperature air and water in order to compare the wear resistance of Zr-xNb-xSn alloys of various alloying elements (Nb and Sn). The main focus was to quantitatively compare the wear properties of the recently developed Zr-xNb-xSn alloys with the commercial ones using the evaluation parameters of the wear resistance with the consideration of the worn area. As a result, the recently developed alloys had a similar wear resistance compared with the commercial ones. The dominant factor governing the wear resistance was the protruded volume of the wear debris that was formed on the worn area in the air condition, but the accommodation of the plastic deformation on the contact area in water. In addition, the worn area size appeared to be very different depending on the tested alloys. To evaluate the wear resistance of each test specimen, the ratio of the wear volume or the protruded volume to the worn area ($D_e$ or $D_p$) is investigated and proposed as the evaluation parameters of the wear resistance.