Filtreler

2005 - 20083
Filtreleri Sıfırla

Ayarlar

Yazar: İnan, Esin × Bölüm: Işık Üniversitesi, Fen Edebiyat Fakültesi, Enformasyon Teknolojileri Bölümü ×

Arama Sonuçları

Listeleniyor 1 - 3 / 3
  • Küçük Resim
    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, Esin
    In 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.
  • Küçük Resim
    Yayın
    Estimation of microstretch elastic moduli by the use of vibrational data
    (Springer, 2007) Kırış, Ahmet; İnan, Esin
    In 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.
  • Küçük Resim
    Yayın
    Eshelby tensors for a spherical inclusion in microelongated elastic fields
    (Pergamon-Elsevier Science ltd, 2005-01) Kırış, Ahmet; İnan, Esin
    Eshelby 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.