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Yayın Identification of the material properties of microisotropic materials(Springer Heidelberg, 2015-07) Kiriş, Ahmet; İnan, EsinThe vibration problem of a rectangular plate is considered in the present work. The main purpose here is to identify the upper bounds of the unknown material moduli of the microisotropic plate material. The frequency spectrum is obtained by extending Ritz Method to the present case. Three dimensional (3-D) vibration analysis is performed and some additional frequencies are observed among the classical frequencies as characterizing the microisotropic effects. These additional frequencies disappear by increasing values of microisotropic constants beyond some certain limits while the classical frequencies remain in the spectrum. The inverse problem is established for the identification of the upper bounds of the microisotropic constants as an optimization problem where an error function is minimized.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 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 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.
