Browsing by Author "Özer, Zafer"

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    Band structures of metacomposite based phononic crystals in quasi-Sierpinski fractals
    (Scientific Society of the Silicate Industry, 2021-05-29) Oltulu, Oral; Özer, Zafer; Mamedov, Amirullah M.; Özbay, Ekmel
    In this paper, we investigated the bandgaps of two-dimensional phononic crystals with quasiSierpinski carpet unit cells in a metacomposite based solid–solid phononic crystal. Finite element method was used to analyze the properties of two-dimensional phononic bandgaps (2D PBGs) in a quasi-fractal structure. Two new types of quasi-Sierpinski fractal unit cells whose constituents are homogeneous and isotropic were proposed to obtain larger full bandgaps. The results show that the PBGs of the proposed quasi-Sierpinski fractals are suitable to tune the PBG’s without changing the size of the phonic crystal. The new quasi-Sierpinski fractals also retain the selfsimilarity as in the third-order Sierpinski fractal unit cell. The investigated quasi-fractals can be easily modified to increase the filling fraction of the constituents, which can be effectively used to enlarge existing PBG by preserving degree of self-similarity structure.
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    Observation of elastic Weyl points in ferroelectric basedsonic metamaterials
    (Taylor & Francis Inc., 2024-02-20) Özer, Zafer; Palaz, Selami; Mamedov, Amirullah M.; Özbay, Ekmel
    The study of Weyl points in electronic systems has recently inspired extensive research in classical systems, such as photonic and acoustic lattices. We construct a single-phase three-dimensional structure, an analog of the honeycomb lattice, and then predict the existence of Weyl points with opposite topological charges (±1) as well as the associated gapless topologically protected surface states. We apply full-scale numerical simulations on the elastic three-dimensional structure and present a clear visualization of the topological surface states that are directional and robust. Such designed lattices can pave the way for novel vibration control and energy harvesting on structures that are ubiquitous in many engineering applications.
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    Observation of shear bond strength between zirconia core and silica based composite material; a finite element analysis
    (Scientific Society of the Silicate Industry, 2021-05-21) Soygun, Koray; Özer, Zafer; Kurtoğlu, Cem; Amirullah, M. Mame; Özbay, Ekmel
    The strength of all-ceramic restorations depends on not only properties of basic material but also used ceramic material, substructure and upper structure connection, the thickness of crown, design, and bonding technique of restoration. The purpose of this study is to analyze the shear stress between the zirconia core and silica-based ceramic by using the finite element method. Using 20-node structural solid elements, the shear stresses were calculated with the methods of shear test and Schmitz-Schulmeyer test through 3-dimensional finite element method. The commercial software Ansys (Ansys Version 11.0, ANSYS, Inc., Canonsburg, PA 15317, USA) was used to create a three-dimensional mesh. There is no significant difference between the test methods as a result of the force applied close to the bond interface. However, when moving away from the bond interface, it is understood that there is a failure in higher tensile forces. It was determined that there was no significant difference in the results when the force to be applied in both the Shear bond Test and Schmitz-Schulmeyer tests was performed the near interface of Zirconia core-Silica based veneer ceramic