Thermal stress problems ın FGMS

Akdoğan, Esra Nur
In this thesis transient temperature distribution, thermal stresses and thermal stress intensity factors (TSIFs) of an infinitely long functionally graded material (FGM) strip containing periodic cracks under thermal shock are studied. Thermal shock is applied by imposing a sudden change in the boundary temperatures. Solution of the present thermoelasticity problem is considered in three successive steps. First the thermal (conduction) problem is solved and the transient temperature distribution is determined. This is followed by the determination of thermal stresses by solving quasi-static elasticity problem. In the last step thermal stress intensity factors (TSIFs) are calculated. In this work, the main focus is the calculation of the transient temperature distribution and the resulting thermal stresses. Since the thermomechanical properties are considered to be functions of a spatial variable, a perturbation technique developed in [1] and [2] is adopted to find an analytical solution of transient heat conduction equation in Laplace domain. Inverse Laplace transformation is achieved by using "residue theorem". After numerically calculating the transient temperature distribution, thermal stresses are computed in the absence of any cracks for the FGM strip subjected to thermal shock. Then, by introducing the thermal stresses as the crack surface tractions in the singular integral equation which is derived in an earlier thesis [3], the TSIFs are determined.


Computational Methods for Inclined Cracks in Orthotropic Functionally Graded Materials Under Thermal Stresses
Dağ, Serkan; TOPAL, SERRA (2013-10-03)
This article sets forth two different computational methods developed to evaluate fracture parameters for inclined cracks lying in orthotropic functionally graded materials, that are under the effect of thermal stresses. The first method is based on the J(k)-integral, whereas the second entails the use of the J(1)-integral and the asymptotic displacement fields. The procedures introduced are implemented by means of the finite element method and integrated into a general purpose finite element analysis softw...
Thermal fracture analysis of orthotropic functionally graded materials using an equivalent domain integral approach
Dağ, Serkan (2006-12-01)
A new computational method based on the equivalent domain integral (EDI) is developed for mode I fracture analysis of orthotropic functionally graded materials (FGMs) subjected to thermal stresses. By using the constitutive relations of plane orthotropic thermoelasticity, generalized definition of the J-integral is converted to an equivalent domain integral to calculate the thermal stress intensity factor. In the formulation of the EDI approach, all the required thermomechanical properties are assumed to ha...
Thermal degradation of polysiloxane and polyetherester containing benzoxazine moieties in the main chain
Bagherifam, Shahla; Kışkan, Barış; Aydogan, Binnur; Yagci, Yusuf; Hacaloğlu, Jale (2011-01-01)
In this study investigation of thermal characteristics of polysiloxane and polyetherester containing benzoxazine moieties in the main chain was performed via pyrolysis mass spectrometry. Pyrolysis mass spectrometry analyses revealed that the thermal stability and the extent of cross-linking enhanced when the benzoxazine moieties were separated by thermally more stable units such as siloxanes. However, when the siloxane chain units were long, possibility of polybenzoxazine growth decreased significantly and ...
Circumferential crack problem for an fgm cylinder under thermal stresses
Dağ, Serkan; Kadıoğlu, Fevzi Suat (1999-01-01)
The main objective of this study is to determine the stress intensity factors associated with a circumferential crack in a thin-walled cylinder subjected to quasi-static thermal loading. The cylinder is assumed to be a functionally graded material In order to make the problem analytically tractable, the thin-walled cylinder is modeled as a layer on an elastic foundation whose thermal and mechanical properties are exponential functions of the thickness coordinate. Hence a plane strain crack problem is obtain...
Thermal stresses in elastic-plastic tubes with temperature-dependent mechanical and thermal properties
Orcan, Y; Eraslan, Ahmet Nedim (2001-11-01)
The thermoelastic-plastic deformations of internal heat-generating tubes are investigated by considering the temperature dependence of the thermal conductivity coefficient, Young's modulus, the coefficient of thermal expansion, and the yield limit of the material. A model describing the elastic-plastic behavior of the tube is developed. The model consists of a system of two second-order ordinary differential equations and a first-order ordinary differential equation involving nonlinear temperature-dependent...
Citation Formats
E. N. Akdoğan, “Thermal stress problems ın FGMS,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Mechanical Engineering., Middle East Technical University, 2019.