• Title/Summary/Keyword: ball-on-flat contact

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Contact analysis of spherical ball and a deformable flat model with the effect of tangent modulus

  • Sathish Gandhi, V.C.;Ramesh, S.;Kumaravelan, R.;Thanmanaselvi, M.
    • Structural Engineering and Mechanics
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    • v.44 no.1
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    • pp.61-72
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    • 2012
  • The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

Frictional Behavior and Film Thickness of Some Liquid Crystals in Elastohydrodynamic Lubrication (탄성 유체 윤활에서의 액정의 마찰 특성 및 유막두께)

  • 이희성
    • Tribology and Lubricants
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    • v.18 no.4
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    • pp.255-259
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    • 2002
  • The tribological properties of eight different liquid crystals were investigated in a concentrated point contact device and a ball-on-flat contact. For comparison, the same tests were also performed with commercial greases and the corresponding base oils. Under the fully flooded conditions studied, liquid crystals in a concentrated point contact showed lower friction than commercial greases and greater film thickness dependence on rolling speed than grease base oils or greases. Test results also showed that the film thickness and friction were little influenced by the composition of the examined liquid crystals.

A Study on Rolling Contact Behaviors of a Flat Rough Surface with a Smooth Ball (구와 평면간의 구름접촉거동에 관한 연구)

  • 김경모;정인성
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.3
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    • pp.554-570
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    • 1990
  • he rolling contact behaviors between a smooth ball and a flat rough surface under dynamic load are intricately affected by many factors, such as the diameter of a ball, normal load and the roughness of a flat surface etc. Accordingly, the experimental study is done to find them on the base of elastic hysteresis loss as theoretical approach is very difficult. The experimental apparatus composed of damped-free vibration system is used. This paper investigates the damping characteristics on the rolling contact area through rolling friction force and logarithmic decrement versus displacement obtained in accordance with the variations of those factors, and presents a new experimental method to find out contact width using the relations of logarithmic decrement and rolling friction force with displacement.

Fitting of Soft Contact Lenses (소프트 콘택트 렌즈의 피팅)

  • Lee, Eun-Hee;Kim, Dae-Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.5 no.1
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    • pp.173-180
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    • 2000
  • To determine the effect of base curve and diameter of soft contact lenses on the fitting under the various corneal curvature, the model eyes which was made of either stainless steel or ordinary wood, were used as the substitutes for human eyes. The evaluations of fit of the soft contact lenses on both wood model eyes and human eyes were found to be very similar to each other. All the contact lenses except very thin ones became flat after fit on the stainless steel model eyes because the model eye could not preserve enough moisture to hold the edge of contact lenses on the steel ball's surface. The relationships between the base curves of contact lenses and radii of cornea for the optimum (normal) fit were measured as follows : corneal curvature (C.C)<7.6 mm : base curve(B.C) 8.4 mm, C.C 7.6~7.8 mm : B.C 8.4~8.5 mm. C.C 7.8~8.1 mm : B.C 8.6 mm. It is concluded that larger base curve is required for the eyes which have abnormal bulge on its cornea. It is found that very thin soft contact lenses can be easily twisted or folded regardless of moisture content when they were fit on the relatively dry eyes(corneas).

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Estimation of Real Area of Contact and Lubrication Regimes using Electric Contact Resistance (전기 저항을 이용한 실접촉 면적과 윤활 영역의 예측)

  • 이홍철;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.11a
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    • pp.11-17
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    • 2000
  • The electric contact resistance between ball and disk was measured to estimate the real area of contact under dry and lubrication conditions. The results from the measured constriction resistance using the hypothesis of a single circular contact was compared with those of Hertzian contact theory and hardness. The resistance correlated well with the asperity contact area and friction when the ball slides on the flat disk spreaded with lubricant film. Therefore, the constriction resistance method was useful to identify the lubrication regimes with respect to various loads and speeds. The results of this work will aid in better prediction of lubrication regimes with respect to the operating conditions.

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Nano/Micro Friction with the Contact Area (접촉 면적에 따른 나노/마이크로 마찰 특성)

  • Yoon Eui-Sung;Singh R. Arvind;Kong Hosung
    • Tribology and Lubricants
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    • v.21 no.5
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    • pp.209-215
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    • 2005
  • Nano/micro friction with the contact area was studied on Si-wafer (100) and diamond-like carbon (DLC) film. Borosilicate balls of radii $0.32{\mu}m,\;0.5{\mu}m,\;1.25{\mu}m\;and\;2.5{\mu}m$ mounted on the top of AFM tip (NPS) were used for nano-scale contact and Soda Lime glass balls of radii 0.25mm, 0.5mm, 1mm were used for micro-scale contact. At nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at micro scale it was measured using ball-on flat type micro-tribotester. All the experiments were conducted at controlled conditions of temperature $(24\pm1^{\circ}C)$ and humidity $(45\pm5\%)$. Friction was measured as a function of applied normal load in the range of 0-160nN at nano scale and in the range of $1000{\mu}N,\; 1500{\mu}N,\;3000{\mu}N\;and\;4800{\mu}N$ at micro scale. Results showed that the friction at nano scale increased with the applied normal load and ball size for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for Si-wafer at micro scale. However, for DLC friction decreased with the ball size. This difference of in behavior of friction in DLC nano- and microscale was attribute to the difference in the operating mechanisms. The evidence of the operating mechanisms at micro-scale were observed using scanning electron microscope (SEM). At micro-scale, solid-solid adhesion was dominant in Silicon-wafer, while plowing in DLC. Contrary to the nano scale that shows almost a wear-less situation, wear was prominent at micro-scale. At nano- and micro-scale, effect of contact area on the friction was discussed with the different applied normal load and ball size.

Effect of Multiple Contact Spots Simulated by Array of Balls on Contact Resistance (볼군의 다수 접촉점이 접촉저항에 미치는 영향)

  • ;Myshkin,N.K.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.2967-2972
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    • 1994
  • The multiple character of the contact interaction and the collective behavior of elementary microcontacts play a significant role in all the processes occurring in the surface layers, including the failure due to friction and wear. The array of metal spheres compressed between flat plates has been used for simulation of the contact behavior of multiple contact of solids under normal loading. An experimental design has been made providing regular array of the spheres at the same size with different spatial order. Measurement of electrial contact resistance has been made using the equipment providing the adequate accuracy in the range of micro Ohms. The data on electrical contact resistance have been compared with theoretical predictions using the multiple contact model of constriction resistance. The effect of single spots number and array on conductivity of contact has been evaluated.

Analysis of Electrical Contact Resistance Model in Multi-Contact of Tribological Elements (트라이볼로지 기소의 멀티접촉에서 전기접촉저항 모델해석에 관한 연구)

  • 김청균
    • Tribology and Lubricants
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    • v.12 no.4
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    • pp.52-59
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    • 1996
  • The results of the electrical contact conductivity of multi-contact spots accounting the surface roughness and the non-conductive films of different origins such as air, water, cutting oil, and machining oil are presented. The array of metal spheres compressed between two flat plates has been used for simulation of the contact behavior of multiple contact of solids, under normal loading. Measurement of electrical contact resistance has been made using the equipment providing the adequate accuracy in the range of micro Ohms. The data on electrical contact resistance have been compared with theoretical predictions using the multiple contact model of constriction resistance. The effect of single spot number and array on conductivity of contact has been evaluated. The results of the experiments show that the contact resistance are closely related to the number of loading cycles, form of surface roughness, and presence of non-conductive films that reduce the size of the real electrical contact spots.

Performance analysis of spherical indentation process during loading and unloading - a contact mechanics approach

  • Gandhi, V.C. Sathish;Kumaravelan, R.;Ramesh, S.
    • Structural Engineering and Mechanics
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    • v.52 no.3
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    • pp.469-483
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    • 2014
  • In an indentation approach, the smooth rigid spherical ball penetrated into a deformable flat is considered for the study based on contact mechanics approach. The elastic-plastic frictionless spherical indentation analysis has been under taken in the finite element analysis using "ABAQUS" and experimental study. The spherical indentation has been studied for the materials like steel, aluminium, copper and brass with an identical spherical indenter for diverse indentation depths. The springback analysis is executed for studying the actual indentation depth after the indenter is unloaded. In the springback simulation, the material recovers its elastic deformation after the indenter is unloaded. The residual diameter and depth of an indentation for various materials are measured and compared with simulation results. It shows a good agreement between the simulation and an experimental studies.

ANTIWEAR FILM FORMATION BY COMPONENTS OF PASSENGER CAR MOTOR OILS

  • Yamaguchi, E.S.;Roby, S.H.;Francisco, M.M.;Ruelas, S.G.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.267-268
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    • 2002
  • Engine testing of new low-sulfur, low-phosphorus anti wear components is expensive and time consuming so bench testing of potential candidates is highly desirable as a first step evaluation. Electrical contact resistance (ECR) has been shown to be a convenient method to assess antiwear film formation in a ball-on-flat bench wear test. Correlation of the bench test to fired engines was demonstrated for lubricants varying only in the type of detergent. Previous papers have examined film formation by one and two component formulations of zinc dialkyldithiophosphate (ZnDTP) and detergents. In this study, the ECR technique is systematically extended to formulations including ZnDTP, detergent, and dispersant. Both type and level of components are considered and the implications for engine performance are discussed.

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