• Title/Summary/Keyword: circular contact

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Investigation and Analysis of the Occurrence of Rail Head Checks

  • Jin, Ying;Aoki, Fusayoshi;Ishida, Makoto;Namura, Akira
    • International Journal of Railway
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    • v.2 no.2
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    • pp.43-49
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    • 2009
  • Wear and rolling contact fatigue (RCF) defects are most important causes of rail damage, and often interaction competitive at present railway track. Head check is one of rolling contact fatigue (RCF) defects, and generally occurs in mild circular curves and transition curves that are set at both ends of sharp circular curves. Wear tends to limit the crack growth of head checks by removing the material from the RCF surface. In order to clarify the conditions of the occurrence and growth of head checks, the authors measured the interacting forces between wheels and rails and the angle of attack of wheelset, and carried out contact analyses using the actual profile data of wheels and rails. The effects of the lateral force, the contact geometry, and the wear rate at rail gauge comer on the formation of head checks were also analyzed by using the worn profiles of actual wheels and rails and the data obtained by a track inspection car. Some specific range of wear rate at the gauge comer was identified as having close relation with occurrence of head checks.

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Application of L Integral to Interface Crack Problems (계면균열 문제에 대한 L적분의 응용)

  • 박재학;엄윤용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.1
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    • pp.34-42
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    • 1986
  • An interface of a circular arc formed by two isotropic, homogeneous elastic materials is investigated. It is shown that L integral satisfies the conservation law for the interface if it is perfectly bonded, in frictionless contact or separated such as in a crack with the origin of the coordinate system being located at the center of the circular arc. The property of path independence of the L integral is applied to an interfacial crack problem, to obtain the stress intensity factors, where the interfacial crack is located along the arc of the circular inclusion embedded in infinite matrix. It is assumed here that the contact zone exist as in the model proposed by Comninou, thus removing the overlapping of the materials along the interface. Another example is shown for case of a circular interfacial crack in the matrix of finite size, where the stress intensity factors are determined by computing a value of the L integral numerically along the path far from the crack tip.

Natural vibration characteristics of a clamped circular plate in contact with fluid

  • Jhung, Myung Jo;Choi, Young Hwan;Kim, Hho Jung;Jeong, Kyeong Hoon
    • Structural Engineering and Mechanics
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    • v.21 no.2
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    • pp.169-184
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    • 2005
  • This study deals with the free vibration of a circular plate in contact with a fluid; submerged in fluid, beneath fluid or on fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. The proposed method is verified by the finite element analysis using commercial program with a good accuracy. The normalized natural frequencies are obtained in order to estimate the relative added mass effect of fluid on each vibration mode of the plate. Also, the location of plate coupled with fluid and the cases of free and bounded fluid surface are studied for the effect on the vibration characteristics.

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.

Comparison of Contact Resistivity Measurements of Silver Paste for a Silicon Solar Cell Using TLM and CTLM (TLM 및 CTLM을 이용한 실리콘 태양전지 전면전극소재의 접촉 비저항 측정 비교연구)

  • Shin, Dong-Youn;Kim, Yu-Ri
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.6
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    • pp.539-545
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    • 2014
  • Contact resistivity between silver electrodes and the emitter layer of a silicon solar cell wafer has been measured using either the circular transmission line method or the linear transmission line method. The circular transmission line method has an advantage over the linear transmission line method, in that it does not require an additional process for mesa etching to eliminate the leakage current. In contrast, the linear transmission line method has the advantage that its specimen can be acquired directly from a silicon solar cell. In this study, measured resistance data for the calculation of contact resistivity is compared for these two methods, and the mechanism by which the linear transmission line method can more realistically reflect the impact of the width and thickness of a silver electrode on contact resistivity is investigated.

J-integral for subsurface crack in circular plate with inner hole under rolling and sliding contact (구름 및 미끄럼 접촉하의 중공원판의 표면하층균열에 대한 J-적분)

  • Lee, Kang-Yong;Kim, June-Yeop
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.7
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    • pp.1149-1155
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    • 1997
  • J-integral for a subsurface horizontal crack in a circular plate with an inner hole under rolling line contact is evaluated according to loading positions with various load conditions, crack length and crack location. Two-dimensional crack is modeled, and the relation between Tresca stress for uncracked model and J-integral is discussed. The loading location which gives the maximum J-integral depends on load condition and crack location, and the presence of friction force increases Tresca stress and J-integral near the surface. Regardless of friction force, crack location that gives maximum J-integral is the same as that of maximum Tresca stress in an uncracked model, and the value of J-integral is propotional to crack length. It is also showed that the variation of an inner radius of a disk does not effect J-integral value.

The Study on the Determination of the Contact Area of the Circular Plate Resting on Elastic Half-space under Axisymmetric Loading (탄성지반 위의 축대칭 하중을 받는 원판의 접촉응력 해석에 관한 연구)

  • 조현영;정진환;김성철
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1997.10a
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    • pp.87-94
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    • 1997
  • The circular plate resting on Boussinesq's half-space model under axisymmetric loading is studied by a finite element procedure to evaluate the distribution of contact pressure between plate and elastic half-space. The displacement of half-space due to axisymmetric surface loading can be evaluated by double integration of Boussinesq's solution. On that case the analytical integration can be executed for the radial direction but the analytical integration for the circumferential direction is impossible and the numerical integration should be considered. With the radial integration we can get non-dimensional function. Then the numerical integration for the formula is executed for the circumferential direction and the results are approximated 5th order Polynomials by using the least square method. With these 5th order approximate formula, the flexibility matrix of half-space is constructed as the coefficient matrix of nodal contact pressure by the finite element procedures. Iteration procedures are attempted by using this method to determine the separated region.

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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.

Dynamic response of functionally graded annular/circular plate in contact with bounded fluid under harmonic load

  • Yousefzadeh, Sh.;Jafari, A.A.;Mohammadzadeh, A.;Najafi, M.
    • Structural Engineering and Mechanics
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    • v.65 no.5
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    • pp.523-533
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    • 2018
  • In this study, the dynamic response of a functionally graded material (FGM) circular plate in contact with incompressible fluid under the harmonic load is investigated. Analysis of the plate is based on First-order Shear Deformation Plate Theory (FSDT). The governing equation of the oscillatory behavior of the fluid is obtained by solving Laplace equation and satisfying its boundary conditions. A new set of admissible functions, which satisfy both geometrical and natural boundary conditions, are developed for the free vibration analysis of moderately thick circular plate. The Chebyshev-Ritz Method is employed together with this set of admissible functions to determine the vibrational behaviors. The modal superposition approach is used to determine the dynamic response of the plate exposed to harmonic loading. Numerical results of the force vibrations and the effects of the different geometrical parameters on the dynamic response of the plate are investigated. Finally, the results of this research in the limit case are compared and validated with the results of other researches and finite element model (FEM).

An Experimental Study on Close-Contact Melting in Horizontal Capsules with Circular or Rectangular Cross Sections (원형 및 사각단면을 가지는 수평캡슐에서의 접촉용해에 관한 실험적 연구)

  • Kim, Si-Pom;Lee, Chi-Woo
    • Solar Energy
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    • v.13 no.1
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    • pp.39-48
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    • 1993
  • This empirical paper addresses the phenomena of the contact melting of PCM in horizontal capsules of circular and rectangular cross sections with various aspect ratio. The melting-rate tends to increase as the Stefan number increases. The case of rectangular tube displays larger melting-rate than that of circular tube, and the melting-rate increases as the aspect ratio decreasws for rectangular tubes. In case of circular tube, the effect of natural convection on the melting-rate is 6.1%, 8.6% and 11.2% according to Stefan number 0.0772, 0.1287 and 0.1802 respectively.

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