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nvestigation of the Indentor’s Tip Radius in Contact with Half Plane with FGM Coating

Molavi Nojumi, Mohamad | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41085 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Adib Nazari, Saeed
  7. Abstract:
  8. In this research, the surface stress distribution function due to the contact between a rigid rounded apex wedge and a FG coating is investigated. This study is important, especially in the fracture mechanics point of view, because stresses due to the contact can be considered as a fine crack source which grows gradually and finally leads to the failure of the structure. The structure includes two components. The first is the FG coating and then, the homogeneous substrate which is connected to the FG coating. Usually, it is considered that the homogeneous substrate is a metal, and properties at the connection are metallic, then properties change gradually through the thickness of the FG coating, so that, the material at the surface of the structure is a ceramic. In the current research, the change of properties in the FG coating is exerted in three statuses 7, 1, and 1/7 times in comparison with the substrate property. It is assumed that, properties change exponentially and continuously through the FG coating. Beside, the Poisson’s ratio is constant. This assumption let to solve the problem with two dimensional elasticity theory. After extraction of the integral equation, by using Jacobi polynomials, it converts to a system of algebraic equations which can be solved by collocation method. The presented solution generally, includes sliding contact, and it is supposed that the conditions of Coulomb friction prevail. Numerical results are presented for normal frictionless contact, because it is more straightforward, and requires fewer attempts. The effect of the wedge tip radius, changes of the properties in the FG coating, and the effect of the (contact length / thickness of the FG coating) parameter which is latent in solution, is observed. Finally, the force-contact length relation is presented
  9. Keywords:
  10. Contact Mechanics ; Singular Integral Equations ; Functionally Graded Materials (FGM) ; Collocation Method ; Rounded Apex Edge

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