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EKİCİ, BÜLENT

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Mühendislik Fakültesi

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EKİCİ

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BÜLENT

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Now showing 1 - 8 of 8

Open Access
The similar and dissimilar spot welding of 304 and 316l austenitic stainless steels
(2017-11-01) ÇINAR, ÖZGÜR; ÇETİNER, BURCU NİLGÜN; GÜLLÜOĞLU, ARİF NİHAT; EKİCİ, BÜLENT; ÇINAR Ö., ÇETİNER B. N., TOPCU İ., GÜLLÜOĞLU A. N., EKİCİ B.
Open Access
Ballistic behavior of high hardness perforated armor plates against 7.62 mm armor piercing projectile
(ELSEVIER SCI LTD, 2014-11) EKİCİ, BÜLENT; Kilic, Namik; Bedir, Said; Erdik, Atil; Ekici, Bulent; Tasdemirci, Alper; Guden, Mustafa
In this paper, some of the important defeating mechanisms of the high hardness perforated plates against 7.62 x 54 armor piercing ammunition were investigated. The experimental and numerical results identified three defeating mechanisms effective on perforated armor plates which are the asymmetric forces deviates the bullet from its incident trajectory, the bullet core fracture and the bullet core nose erosion. The initial tests were performed on the monolithic armor plates of 9 and 20 mm thickness to verify the fidelity of the simulation and material model parameters. The stochastic nature of the ballistic tests on perforated armor plates was analyzed based on the bullet impact zone with respect to holes. Various scenarios including without and with bullet failure models were further investigated to determine the mechanisms of the bullet failure. The agreement between numerical and experimental results had significantly increased with including the bullet failure criterion and the bullet nose erosion threshold into the simulation. As shown in results, good agreement between Ls-Dyna simulations and experimental data was achieved and the defeating mechanism of perforated plates was clearly demonstrated. (C) 2014 Elsevier Ltd. All rights reserved.
Open Access
Effect of air pressure on nanofiber production in solution blowing method
(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2020-07-21) EKİCİ, BÜLENT; Polat, Yusuf; Yangaz, Murat Umut; Calisir, Mehmet Durmus; Gul, Mehmet Zafer; Demir, Ali; Ekici, Bulent; Kilic, Ali
In this study, effect of air pressure on nanofiber diameter and morphology was studied for solution blowing technique. A computational fluid dynamics (CFD) analysis was realized via ANSYS (R) Fluent software, and the results were compared with experimental solutions. The results showed that an increase in air inlet pressure from 100 kPa to 300 kPa has significant effect on nanofiber diameter and morphology. In contrast, as the air inlet pressure increases above 300 kPa to 600 kPa, both nanofiber diameter increases, and the fiber agglomerations are observed due to high turbulence intensity. The droplets were observed at 100 kPa air inlet pressure due to low driving force applied to the polymer solution. The effects of air pressure on nanofiber diameter and morphology have been investigated by using finite volume method, and the results are compared with the experimental results.
Open Access
Sustainable machining of the magnesium alloy materials in the CNC lathe machine and optimization of the cutting conditions
(KAUNAS UNIV TECHNOL, 2014-06-25) BAKIR, BARKIN; Eker, Beni; Ekici, Bulent; Kurt, Mustafa; Bakur, Barkin
In this study, MQL turning performance was compared to dry conditions. The magnesium based material will be formed by applying the orthogonal cutting. The CNC Lathe shall be used for both cutting processes. The experiment used MINITAB 16 software to establish the experiment plan. In this study, workpiece was turned at cutting speeds of 230, 330 and 430 m/min, feed rates of 0.20, 0.35 and 0.50 mm/rev and cutting depth of 1, 2 and 3 mm. Taguchi experimental design method was used for determining the settings of turning parameters. Orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA) were carried out to determine the optimum levels and to analyze the influence of cutting speed, feed rate, cutting depth on surface roughness, temperature and cutting forces during dry and MQL turning.
Open Access
Finite element analysis on the optimal material choice and cavity design parameters for MOD inlays exposed to different force vectors and magnitudes
(TAYLOR & FRANCIS LTD, 2017-01-02) EKİCİ, BÜLENT; Sener-Yamaner, Isil Damla; Ekici, Bulent; Sertgoz, Atilla; Yuzbasioglu, Emir; Ozcan, Mutlu
This simulation study evaluated the effect of three different inlay materials (composite, glass ceramic, zirconia), cavity design parameters (isthmus width and depth) and different force vectors and magnitudes on the stress distribution within mesio-occlusal-distal (MOD) inlays and the remaining enamel and dentin. The mechanical performance of inlays was evaluated using 3-D finite element analysis (FEA) method. Three different restoration materials and hard tissues of the restored tooth with different cavity depth (2-5mm) and width (2-4mm) were exposed to occlusal loading with different magnitudes from 10 to 130kg at varying angles between 0 degrees and 15 degrees. The maximum von Mises stresses were calculated for the inlays, tooth structure and bonded surfaces. Response Surface Optimization method was implemented into the finite element software package in order to design cavity shapes with more favourable interfacial stresses for bonded restorations under occlusal loading. Teeth restored with resin composite exhibited the highest von Mises Stress, followed by glass ceramic and zirconia. The increase in isthmus width decreased interfacial shear stresses in zirconia MOD inlay but the increase in cavity depth did not change the stress levels for all three materials. According to mechanical safety factor, inlay and tooth structure remained within the mechanical limits in three parameters (material, magnitude of force, cavity shape) but negatively affected by the force vector.
Open Access
Mechanical performance of carbon - aramid fiber-reinforced laminated composites under impact and shear loading
(2021-11-01) EKİCİ, BÜLENT; ATMACA B. N., ORUÇ R., AŞÇI G., YİĞİT K., YÜZER S., POLAT Y., EKİCİ B.
In this study, the drop weight impact response and the interlaminar shear strength of hybrid carbon/aramid fiber-reinforced laminated composites with different stacking sequences were investigated. Seven different laminates including two types of sandwich-like interply hybrid, three types of interply hybrid, and two types of non-hybrid named carbon and aramid were produced using the vacuum-assisted resin transfer molding method. Drop weight impact and short-beam shear tests were applied to the laminates to calculate the low-velocity impact response and the interlaminar shear strength, respectively. It is observed that while the outer layer of the hybrid structure is carbon, the structure can carry less load but absorb more energy. Pure carbon and pure aramid composites cannot carry loads but can absorb energy as much as their hybrid versions can. Sandwich-like interply hybrid with central carbon showed the best results when load and energy values were compared. Also, sandwich-like interply hybrid with central carbon has higher ILSS among hybrid structures because its center region consists of carbon layers.
Open Access
Evaluation of reliability of zirconia materials to be used in implant-retained restoration on the atrophic bone of the posterior maxilla: A finite element study
(2019) EKİCİ, BÜLENT; Degirmenci, Kubra; Kocak-Buyukdere, Ayse; Ekici, Bulent
Open Access
Determination of penetration depth at high velocity impact using finite element method and artificial neural network tools
(ELSEVIER SCIENCE BV, 2015-06) EKİCİ, BÜLENT; Kilic, Namik; Ekici, Bulent; Hartomacioglu, Selim
Determination of ballistic performance of an armor solution is a complicated task and evolved significantly with the application of finite element methods (FEM) in this research field. The traditional armor design studies performed with FEM requires sophisticated procedures and intensive computational effort, therefore simpler and accurate numerical approaches are always worthwhile to decrease armor development time. This study aims to apply a hybrid method using FEM simulation and artificial neural network (ANN) analysis to approximate ballistic limit thickness for armor steels. To achieve this objective, a predictive model based on the artificial neural networks is developed to determine ballistic resistance of high hardness armor steels against 7.62 mm armor piercing ammunition. In this methodology, the FEM simulations are used to create training cases for Multilayer Perceptron (MLP) three layer networks. In order to validate FE simulation methodology, ballistic shot tests on 20 mm thickness target were performed according to standard Stanag 4569. Afterwards, the successfully trained ANN(s) is used to predict the ballistic limit thickness of 500 HB high hardness steel armor. Results show that even with limited number of data, FEM-ANN approach can be used to predict ballistic penetration depth with adequate accuracy. Copyright (C) 2015, China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.