Yazar "Saglam, Ismail" seçeneğine göre listele

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    Complete flat cone metrics on punctured surfaces
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Saglam, Ismail
    We prove that each complete flat cone metric on a surface with regular or irregular punctures can be triangulated with finitely many types of triangles. We derive the Gauss-Bonnet formula for this kind of cone metrics. In addition, we prove that each free homotopy class of paths has a geodesic representative.
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    Fracture characterization and modeling of Gyroid filled 3D printed PLA structures
    (Walter De Gruyter Gmbh, 2021) Torun, Ahmet Refah; Dike, Ali Sinan; Yildiz, Ege Can; Saglam, Ismail; Choupani, Naghdali
    Polylactic acid (PLA) is a commonly used biodegradable material in medical and increasingly in industrial applications. These materials are often exposed to various flaws and faults due to working and production conditions, and increasing the demand for PLA for various applications requires a full understanding of its fracture behavior. In addition to ABS, PLA is a widely used polymeric material in 3D printing. The gyroid type of filling is advantageous for overcoming the relatively higher brittleness of PLA in comparison with conventional thermoplastic polymers. In this study, the effects of various filling ratios on the fracture toughness of 3D printed PLA samples with gyroid pattern were investigated numerically and experimentally for pure mode I, combined mode I/II, and pure mode II. Two-dimensional finite element modeling was created, and the two-dimensional functions of stress intensity coefficients were extracted in loading mode I, mode I/II, and mode II at varied filling ratios of the gyroid PLA samples. Mixed-mode fracture tests for 3D printed PLA samples with a gyroid pattern at various filling ratios were performed by using a specially developed fracture testing fixture. The results showed that the amount of fracture toughness of the samples under study in tensile mode was much higher than those values in shear mode. Also, as the percentages of the filling ratios in the samples increased, both tensile and shear fracture toughness improved.
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    From Euclidean triangles to the hyperbolic plane
    (Elsevier Gmbh, 2022) Saglam, Ismail
    We introduce a model of the hyperbolic plane which arises from Thurston's ideas on best Lipschitz maps between surfaces. More precisely, we apply Thurston's theory to the space of Euclidean triangles. We prove that the Lipschitz constant of the unique affine map between two Euclidean triangles induces a metric on the set of isometry classes of the triangles with area 1/2. We then prove that this space of triangles together with 2 times its natural metric is isometric to the hyperbolic plane. Our construction is simple and natural and it makes relations between several geometrical ideas. (C) 2021 Elsevier GmbH. All rights reserved.
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    Ideal triangulation and disc unfolding of a singular flat surface
    (Tubitak Scientific & Technological Research Council Turkey, 2021) Saglam, Ismail
    An ideal triangulation of a singular flat surface is a geodesic triangulation such that its vertex set is equal to the set of singular points of the surface. Using the fact that each pair of points in a surface has a finite number of geodesics having length <= L connecting them, where L is any positive number, we prove that each singular flat surface has an ideal triangulation provided that the surface has singular points when it has no boundary components, or each of its boundary components has a singular point. Also, we prove that such a surface contains a finite number of geodesics which connect its singular points so that when we cut the surface through these arcs we get a flat disc with a nonsingular interior.
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    Oblique impact behavior of Al-LDPE-Al sandwich plates
    (Walter De Gruyter Gmbh, 2020) Kaya, Seyma Helin; Karaoglu, Furkan Nuri; Saglam, Ismail; Choupani, Naghdali; Torun, Ahmet Refah
    Metal-polymer-metal hybrid sandwich panels are gaining importance in various industrial applications due to their light weight and damping properties. When compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled more easily. In addition to their applications in civil engineering, the aluminum-low density polyethylene-aluminum (Al-LDPE-Al) sandwich panels yield a potential use as light ballistic protection material. In this study, a standard hybrid panel of 3.2 mm polyethylene filling and 0.4 mm of two aluminum metal sheets was experimentally tested under ballistic impact. A finite element model was constructed via commercial software and validated through shooting experiments with a rifle under real conditions. The finite element model was used to simulate the oblique impact behavior of Al-LDPE-Al sandwich panels as a single layer, as 5 layers stacking and as a single layer equivalent of the stacked 5 layer. Results showed that the oblique impact does not have a significant effect on the single layer panel. Stacked layers, however, and the equivalent single layer of a stacked layer have the highest energy absorption under a 30 degrees hitting angle.
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    Thurston's asymmetric metric on the space of singular flat metrics with a fixed quadrangulation
    (European Mathematical Soc-Ems, 2024) Saglam, Ismail; Papadopoulos, Athanase
    Consider a compact surface equipped with a fixed quadrangulation. One may identify each quadrangle on the surface with a Euclidean rectangle to obtain a singular flat metric on the surface with conical singularities. We call such a singular flat metric a rectangular structure. We study a metric on the space of unit area rectangular structures which is analogous to Thurston's asymmetric metric on the Teichm & uuml;ller space of a surface of finite type. We prove that the distance between two rectangular structures is equal to the logarithm of the maximum of ratios of edges of these rectangular structures. We give a sufficient condition for a path between two points of the this Teichm & uuml;ller space to be geodesic and we prove that any two points of this space can be joined by a geodesic. We also prove that this metric is Finsler and give a formula for the infinitesimal weak norm on the tangent space of each point. We identify the space of unit area rectangular structures with a submanifold of a Euclidean space and we show that the subspace topology and the topology induced by the metric we introduced coincide. We show that the space of unit area rectangular structures on a surface with a fixed quadrangulation is in general not complete.