Mixed-mode fracture analysis of orthotropic FGM coatings under mechanical and thermal loads

İlhan, Küçük Ayşe
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 are parallel and perpendicular to the boundaries. A single embedded crack in the orthotropic FGM coating is investigated analytically assuming that crack surfaces are subjected to either uniform normal or uniform shear stresses. Using Fourier transformations, the problem is reduced to a couple of singular integral equations that are solved numerically to obtain the mixed-mode stress intensity factors, energy release rate and crack opening displacements. To investigate the analytically untractable problems without restrictive assumptions, a computational approach is employed. The adopted computational approach is based on finite element method and displacement correlation technique. Using the computational approach, fracture parameters are obtained considering single and periodic embedded cracking conditions in the orthotropic FGM coatings under mechanical or thermal loads. The results obtained in this study show the effects of material nonhomogeneity, material orthotropy and geometric variables on the fracture behavior of the structure.


Contact mechanics of graded orthotropic coatings
Arslan, Onur; Aksel, Mehmet Haluk; Dağ, Serkan; Department of Mechanical Engineering (2015)
Analytic and computational studies are performed for contact problems of orthotropic functionally graded material (FGM) coatings which are bonded to isotropic homogeneous substrates without any interfacial defects. The orthotropic FGM coatings possess orhotrophic stiffness gradations through the coating thickness direction. The variations of each orthotropic stiffness constants are assumed to behave as exponential functions. In the analytical procedure, the problems of orthotropic graded coatings which are ...
Analytical Solution of a Crack Problem in a Radially Graded FGM
Cetin, Suat; Kadıoğlu, Fevzi Suat (2008-09-25)
The objective of this study is to determine stress intensity factors (SIFs) for a crack in a functionally graded layer bonded to a homogeneous substrate. Functionally graded coating contains an edge crack perpendicular to the interface. It is assumed that plane strain conditions prevail and the crack is subjected to mode I loading. By introducing an elastic foundation underneath the homogeneous layer, the plane strain problem under consideration is used as an approximate model for an FGM coating with radial...
Three dimensional fracture analysis of FGM coatings
İnan, Özgür; Dağ, Serkan; Department of Mechanical Engineering (2004)
The main objective of this study is to model the three dimensional surface cracking problem in Functionally Graded Material (FGM) coatings bonded to homogeneous substrates. The FGM coating is assumed to be a (ZrO2) ا (Ti-6Al-4V) layer. Homogeneous ceramic, metal ا rich, ceramic ا rich and linear variation material compositions are considered in the analyses. The surface crack is assumed to have a semi ا circular crack front profile. The surface crack problem in the FGM coating ا substrate system is examined...
Güler, Baran; Efe, Mert (2018-06-22)
Materials with deformation behavior sensitive to their microstructure may need deformation analysis at multiple scales to establish the relationship between the microstructure and response to deformation processing. In this work, we use in-plane biaxial test (cruciform) to measure the macro- and microstructure-scale mechanical behavior of a 6061-T6 aluminum alloy at various strain paths. We report flow curves, forming and fracture limits as examples to the macromechanical behavior. As an alternative to the ...
Mechanical modeling of Thin Films Bonded to Functionally Graded Materials
GÜLER, MEHMET ALİ; Gulver, Yusuf Fuat; Dağ, Serkan (2008-09-25)
In this study the contact problems of thin films bonded to Functionally Graded Materials (FGM) are considered. In these problems the loading consists of any one or combination of stresses caused by uniform temperature changes and temperature excursions, far field mechanical loading, and residual stresses resulting from film processing or in the manufacturing process of the graded coating. The primary interest in this study is in examining stress concentrations or singularities near the film ends for the pur...
Citation Formats
K. A. İlhan, “Mixed-mode fracture analysis of orthotropic FGM coatings under mechanical and thermal loads,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.