Dynamic frictional contact problems involving functionally graded materials

Balcı, Mehmet Nurullah
The main aim of this study is to analyze the dynamic frictional contact problem of layered and functionally graded materials. Investigating contact problems including dynamic effects has a significant importance in mechanical engineering applications since many contact problems arise between moving structures. In moving contact problems, speed of the punch may not be so small to ignore dynamic effects. Hence, contact problem should be examined using elastodynamics theory. In this study, both frictional moving contact problems of homogenous elastic coatings and functionally graded coatings pressed by a moving rigid punch with various punch profiles are considered. The rigid punch is pressed against the coating and it moves at a constant subsonic speed. Governing partial differential equations are solved analytically using Galilean and Fourier transformation techniques. Displacement fields in both coating and the substrate are found by applying boundary and interface continuity conditions. Equations for the mixed boundary value problem is reduced to a singular integral equation of the second kind including unknown normal contact stress. The singular integral equation is solved numerically using a suitable expansion-collocation technique and normal contact stress is found. A verification study for elastostatic contact analysis is carried out using computational results generated by the use of finite element method. A verification study for elastodynamic contact analysis is conducted by utilizing available results in the literature. Consequently, the influences of punch profile, punch sliding speed, material inhomogeneity, coefficient of friction and coating thickness on contact stresses and punch stress intensity factors are investigated.


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The main objective of this study is to evaluate mixed mode stress intensity factors for inclined embedded cracks in functionally graded materials. Fracture analysis of inclined cracks requires the calculation of both Mode I and Mode II stress intensity factors ( I K , II K ). In this study, k J -integral is used to calculate I K and II K . Equivalent domain integral approach is utilized to evaluate the k J - integral around the crack tip. The present study aims at developing a finite element model to study ...
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In this study, it is aimed to investigate the mixed-mode fracture behavior of orthotropic functionally graded material (FGM) coatings bonded to a homogeneous substrate through a homogeneous bond-coat. Analytical and computational methods are used to solve the embedded cracking problems under mechanical or thermal loading conditions. It is assumed that the material property gradation of the FGM coating is in the thickness direction and cracks are parallel to the boundaries. The principal axes of orthotropy a...
Citation Formats
M. N. Balcı, “Dynamic frictional contact problems involving functionally graded materials,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.