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Rolling Contact Analysis of a Cylinder with a FGM Coated Half-Plane

Alinia, Yadolah | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43399 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Adibnazari, Saeed
  7. Abstract:
  8. This study focuses on the mathematical modeling of the rolling contact problem of an FGM coating-substrate system. The first part presents the uncoupled rolling contact problem of an FGM coated half-plane under the assumption of a central stick zone with two slip zones of the same sign. Considering all possible stick/slip scenarios, the fully coupled rolling contact problem of a graded coating is given in the second part. Finally, the rolling contact problem of two elastically similar cylinders with graded coatings will be discussed. Generally, all mentioned problems can be solved in three consecutive steps. First, the governing equations of the relevant rolling contact problem are constructed by means of the singular integral equations approach. Later, the Gauss-Chebyshev numerical integration method is utilized to discretize the governing equations into systems of algebraic equations. Finally, some numerical algorithms are proposed to solve these systems of algebraic equations. Comprehensive parametric study is carried out to examine the effects of the material properties, the coefficient of friction, the coating thickness and the external loads on the surface stress components, the stick/slip configurations, the creep ratio and the power loss. This study aimed to emphasize the capability of the graded materials in improving the rolling contact fatigue of tribological components, modifying the dynamic characteristics of railroad vehicle, decreasing the wear rate and increasing the efficiency of power transmitting systems. The results indicate that if the coefficient of friction is greater than 0.3 then the Goodman approximation is no longer valid. Hence, the fully coupled solution must be extracted for high coefficient of friction values. Moreover, gradual variation of the shear modulus significantly affects the tensile peak of the surface in-plane stress such that for a constant value of the external loads, the tensile peak of the softening coating is 60% less than that of the homogeneous coating. Also, if one leaves the surface up to 10% of the coating thickness then the effect of the surface disturbances vanish rapidly such that the value of Von Mises and Tresca parameters decrease about 20% to 50%.

  9. Keywords:
  10. Rolling Contact ; Functionally Graded Materials (FGM) ; Integral Equation ; Power Loss ; Contact Stresses ; Creep Ratio

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