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Yayın Eshelby tensors for a spherical inclusion in microstretch elastic fields(Elsevier Ltd, 2006-08) Kırış, Ahmet; İnan, EsinIn the present work, microelastic and macroelastic fields are presented for the case of spherical inclusions embedded in an infinite microstretch material using the concept of Green's functions. The Eshelby tensors are obtained for a spherical inclusion and it is shown that their forms for microelongated, micropolar and the classical cases are the proper limiting cases of the Eshelby tensors of microstretch materials.Yayın Thermo-microstretch elastic bodies and plane waves(IOP PUBLISHING LTD, 2011) İnan, Esin; Kırış, AhmetIn the present work, vibration problems of rectangular plates are considered for the determination of upper bounds to the unknown microstretch material properties. The frequencies are obtained by extending the Ritz method to this case. The analysis shows that some additional frequencies characterizing the microstretch effects appear among the classical frequencies. Furthermore, by the increasing values of the microstretch constants, the additional frequencies disappear and only the classical frequencies remain in the spectrum. Considering this phenomenon, an optimization problem is established for the identification of the upper bounds of microstretch elastic constants. In the second part of the work, thermal effects are considered and several theories are discussed. Finally, propagation of the plane waves is investigated.Yayın On the identification of microstretch elastic moduli of materials by using vibration data of plates(Pergamon-Elsevier Science LTD, 2008-06) Kırış, Ahmet; İnan, EsinIn the present work, the vibration problems of rectangular plates modeled by Eringen's microstretch theory are investigated for the identification of the upper bounds of the microstretch moduli of the plate material. The calculated frequencies of the plates are obtained by extending the Ritz method to the microstretch plates. The three dimensional (3D) vibration analysis of the plates shows that some additional frequencies occur among the classical frequencies as characterizing the microstretch effects. Then it is also observed that these additional frequencies disappear and only the classical frequencies remain with the increasing values of microstretch constants. The inverse problem is established for the identification of the upper bounds of the microstretch elastic constants as an optimization problem where an error function is minimized.Yayın Estimation of microstretch elastic moduli by the use of vibrational data(Springer, 2007) Kırış, Ahmet; İnan, EsinIn the present work, a nonlinear wave theory is used for the estimation of the material properties of a "microstretch" medium. For this purpose a thin plate is considered and triplicate Chebyshev polynomial series are used as admissible functions to ensure the satisfaction of geometric boundary conditions of the plate. The Ritz technique is applied to derive the frequency equation of the microstretch plate and an optimization procedure is performed by minimising the least square "distance" between computed natural frequencies from the energy method and measured natural frequencies. To realize the optimization procedure, a genetic algorithm is used to estimate the elastic moduli of microstretch medium.Yayın A hollow cylinder problem in microstretch theory(Springer-Verlag, 2011) İnan, Esin; Kırış, AhmetA hollow cylinder micro-damaged tube under pressure problem is discussed. Micro damage is modeled with Eringen's microstretch theory and the displacement and its comparison with classical result are given.Yayın Free vibration of composite sandwich beams with microstretch viscoelastic core(Springer Science and Business Media Deutschland GmbH, 2021) Aydınlık, Soner; Kırış, Ahmet; İnan, EsinIn the present work, we studied a sandwich beam which is made of two thin stiff layers on top and bottom and a microstretch viscoelastic core in the middle. Here, the top and the bottom stiff layers are considered as elastic, while the inner part is taken as microstretch viscoelastic material. The free vibration of this composite beam is investigated. Differential transform method is used for the solution. The values of the frequencies obtained for microstretch case are found greater than the classical ones, as it is expected. Besides, the minimum differences between the classical frequencies and deviated classical frequencies due to the microstretch core are getting bigger for the large loss factors.Yayın Eshelby tensors for a spherical inclusion in microelongated elastic fields(Pergamon-Elsevier Science ltd, 2005-01) Kırış, Ahmet; İnan, EsinEshelby tensors are found for a spherical inclusion in a microelongated elastic field. Here. a special micromorphic model is introduced to describe the damaged material which defines the damage as the formation and the growth of microcracks and microvoids occurred in the material at the microstructural level. To determine the new material coefficients of the model, an analogy is established between the damaged body and the composite materials and then Mori-Tanaka homogenization technique is considered to obtain overall material moduli. Following this idea, the determination of the Eshelby tensors which establish the relation between the strains of the matrix material and of the inclusion becomes the first task. Introducing the concept of eigenstrain and microeigenstrain, the general constitutive theory is given for a homogeneous isotropic centrosymmetric microelongated media with defects. Then by the use of Green's functions, micro and macro elastic fields are presented for the case of spherical inclusions embedded in an infinite microelongated material. Thus, the Eshelby tensors are obtained for a microelongated elastic field with a spherical inclusion and it is also shown that the classical Eshelby tensors can be obtained as a limit case of the microelongation.
