Person: KARPAT, ESİN
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KARPAT
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ESİN
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Publication Effects of drive side pressure angle on gear fatigue crack propagation life for spur gears with symmetric and asymmetric teeth(Amer Soc Mechanical Engineers, 2020-01-01) KARPAT, FATİH; DOĞAN, OĞUZ; Yılmaz, Tufan; YILMAZ, TUFAN GÜRKAN; Yüce, Celalettin; YÜCE, CELALETTİN; KARPAT, ESİN; KOPMAZ, OSMAN; Kalay, Onur Can; Mühendislik Fakültesi; Mekatronik Mühendisliği BölümüToday gears are one of the most crucial machine elements in the industry. They are used in every area of the industry. Due to the high performances of the gears, they are also used in aerospace and wind applications. In these areas due to the high torques, unstable conditions, high impact forces, etc. cracks can be seen on the gear surface. During the service life, these cracks can be propagated and gear damages can be seen due to the initial cracks. The aim of this study is to increase the fatigue crack propagation life of the spur gears by using asymmetric tooth profile.Nowadays asymmetric gears have a very important and huge usage area in the industry. In this study, the effects of drive side pressure angle on the fatigue crack propagation life are studied by using the finite element method. The initial starting points of the cracks are defined by static stress analysis. The starting angles of the cracks are defined constant at 45 degrees. The crack propagation analyses are performed in ANSYS SMART Crack-Growth module by using Paris Law. Four different drive side pressure angles (20 degrees-20 degrees, 20 degrees-25 degrees, 20 degrees-30 degrees and 20 degrees-35 degrees) are investigated in this study. As a result of the study the fatigue crack propagation life of the gears is increased dramatically when the drive side pressure angle increase. This results show that the asymmetric tooth profile not only decrease the bending stress but also increase the fatigue crack propagation life strongly.Publication A comparative 3d finite element computational study of stress distribution and stress transfer in small-diameter conical dental implants(Univ Osijek, Tech Fac, 2021-12-01) Doğan, Oğuz; Dhanasekaran, Lokesh; Khandaker, Morshed; Kalay, Onur Can; Karaman, Hasan; Karpat, Fatih; KARPAT, FATİH; Doğan, Oguz; DOĞAN, OĞUZ; Yuce, Celalettin; YÜCE, CELALETTİN; Karpat, Esin; KARPAT, ESİN; Dhanasekaran, Lokesh; Khandaker, Morshed; Mühendislik Fakültesi; Elektrik Elektronik Mühendisliği; 0000-0001-8643-6910; 0000-0001-8474-7328; 0000-0003-1387-907X; 0000-0001-5985-7402; A-5259-2018; GXH-1702-2022; AAV-7897-2020; R-3733-2017The implant design is one of the main factors in implant stability because it affects the contact area between the bone and the implant surface and the stressstrain distribution at the bone-implant interface. In this study, the effect of different groove geometries on stress-strain distributions in small-diameter conical implants is investigated using the finite element method (FEM). Four different thread models (rectangular, buttressed, reverse buttressed, and symmetrical profile) are created by changing the groove geometry on the one-piece implants, and the obtained results are compared. The stress shielding effect is investigated through the dimensionless numbers that characterize the load-sharing between the bone-implant. It is determined that the lowest stress distribution is observed with rectangular profiled groove geometry. Besides, it is obtained that the buttressed groove geometry minimizes the stress effects transmitted to the periphery of the implant. The symmetrical profiles had better performance than rectangular profiles in stress transfer.Publication A deep learning- based method for early crack diagnosis in non-standard spur gear pairs(Amer Soc Mechanical Engineers, 2023-01-01) Ekwaro-Osire, Stephen; Dirik, Ahmet Emir; DİRİK, AHMET EMİR; Kalay, Onur Can; Karpat, Fatih; KARPAT, FATİH; Karpat, Esin; KARPAT, ESİN; Dirik, Ahmet Emir; Mühendislik Fakültesi; Elektrik ve Elektronik Mühendisliği Bölümü; 0000-0001-8643-6910; 0000-0001-8474-7328; 0000-0002-9548-8648; KIK-4851-2024; A-5259-2018Gears are the key components of modern industry and have been widely employed in the automotive, wind turbine, and aviation fields. From the engineering point of view, an intelligent method that can automatically extract fault features from the vibration signals would be precious since failing in early diagnosis of root cracks may result in a tooth broken rapidly. In this regard, deep learning (DL) is increasingly popular in achieving early fault diagnostics tasks in geared systems with the wide availability of sensors and ever-increasing computation power. With this in mind, the asymmetric tooth concept offers higher load-carrying capacity, long fatigue propagation life, and the ability to lessen vibration and noise than the standard (symmetric) involute profile spur gears. From this standpoint, this study aims to determine the tooth root crack and its degree for both symmetric (20 degrees/20 degrees) and asymmetric (20 degrees/30 degrees) involute spur gears with a DL-based approach using vibration data. To this end, the single tooth stiffness values of the designed gears were obtained with ANSYS software for healthy and cracked gears (50%-100%), and then the time-varying mesh stiffness was calculated. Besides, a six-degree-of-freedom dynamic model was developed by deriving the equations of motion of a one-stage spur gear transmission. The vibration responses were collected for the healthy state, 50%, and 100% crack degrees for symmetric and asymmetric tooth profiles. Three different signalto-noise ratios were considered to complicate the early crack diagnosis task and evaluate its influence on the DL algorithm's classification performance. The obtained findings were then evaluated and interpreted in time and frequency domains. To this end, the Fourier transform was applied to the simulated timesequence acceleration data in the time domain. As a supplementary finding, the present research also benefited from three statistical indicators, namely, (1) root mean square, (2) kurtosis, and (3) crest factor, to investigate whether the configuration of tooth profiles would provide an advantage in detecting tooth- root cracks. The present study also evaluated the influence of residual signals on the proposed DL-based method's classification accuracy and further expanded the scope of research work. The findings indicated that the overall classification accuracy could be improved by 5.1% using asymmetric (20 degrees/30 degrees) gearing.Publication Optimization and comparative analysis of quarter-circular slotted microstrip patch antenna using particle swarm and fruit fly algorithms(Zarka Private Univ, 2023-07-01) Karpat, Esin; İmamoğlu, Fatih; KARPAT, ESİN; İmamoğlu, Fatih; Elektrik Elektronik Mühendisliği Bölümü; 0000-0002-2740-8183; AAH-3387-2021; JGK-2973-2023This paper proposes a parametric study of modified rectangular microstrip antenna in the frequency range between 1.4-2.65 GHz for wireless communication applications, incorporating with optimization methods Particle Swarm Optimization (PSO) and Fruit Fly Optimization (FOA). To design an antenna using optimization methods a fitness function of required parameters is needed. The resonance frequency of Microstrip Patch Antennas (MPAs) depends on various parameters and a standard frequency function does not exist for MPAs. In this study, a rectangular patch antenna is designed for the required resonance frequency and modified with circular quarter slots. The frequency-shift with the change of design variables, which are the substrate thickness and the radius of the slots, is observed. The resonance frequency is obtained as a function of the design variables and it is used in the optimization process to minimize the difference between the target frequency and the calculated one. The original algorithms FOA and PSO have been adapted for its application to a modified rectangular patch antenna design problem: resonance frequency and design of antenna. The design parameter values obtained via optimization and the performances of the optimization methods are presented. The results showed that both PSO and FOA find the dimensions correctly. It is also observed that the sensitivity of the FOA increases with the fruit fly population and the convergence gets faster. The outcomes of this paper show that the PSO algorithm gives better results when compared to the FOA for the proposed antenna.Publication Optimization of multilayer absorbers using the bald eagle optimization algorithm(MDPI, 2023-09-01) Kankılıç, Sueda; Karpat, Esin; KANKILIÇ, SUEDA; KARPAT, ESİN; Mühendislik Fakültesi; Elektrik Elektronik Mühendisliği Bölümü; 0000-0002-2740-8183; AAH-3387-2021; JIL-2783-2023Electromagnetic (EM) absorbers have several uses in today's military and civilian industries, and there is a growing demand for microwave absorbers with good absorption characteristics and thin layer structures over a broad frequency range (FR) within a specific EM spectrum band. This study aimed to find the most suitable design using different material sets, using the recently introduced Bald Eagle Search Optimization Algorithm (BESOA) to design a multilayer EM absorber for the required FR. An FR of 1 to 20 GHz was considered, and the multilayer absorbers were designed for 2-8 GHz, 12-18 GHz, 2-18 GHz, and 1-20 GHz FRs. For various incidence angles between 30 & DEG; and 75 & DEG; and polarizations (TE and TM) in chosen FRs, comparisons were made with the Improved Particle Swarm Optimization (PSO), Differential Evolution (DE), Central Force Optimization (CFO), Lightning Search Algorithm (LSA), Double Stage Ant Bee Colony (DS-ABC) and other optimization algorithms found in the literature. The optimization algorithms that were used to design MMAs in the literature aim to construct the absorber with the lowest maximum reflection coefficient (RC) in the given FR and the thinnest thickness by selecting suitable material layers from a predefined database. The numerical and visual comparisons show that the obtained designs have the lowest maximum RC with the thinnest overall thickness compared to those in the literature. Numerical best results are presented for each variation obtained as a result of the optimization.Publication Measurement and prediction of electromagnetic radiation exposure level in a university(Univ Osijek, Tech Fac, 2022-02-01) Karpat, Esin; KARPAT, ESİN; Bakcan, M. Rafet; Mühendislik Fakültesi; Elektrik ve Elektronik Mühendisliği BölümüThe importance of electromagnetic (EM) sources in human life has been increasing with the development of technology. EM radiation triggers some problems in our life such as EM interference and human health problems. EM radiation level which is emitted by the base station increases in proportion to the density of population in a region. EM exposure is higher in areas where people are highly concentrated such as hospitals, military barracks, schools, shopping malls, than in any other region. It is important to show sustained concern about the EM radiation intensity in these areas to keep the levels under the permissible limits. In this study, electric field values are measured statically at locations where the population density is too high, to examine the electric field intensity levels throughout the campus. Besides, two different artificial neural models (ANN) are developed to estimate the electric field values of random locations which are specific regions for electromagnetic exposure. Moreover, measurement results and estimated results are evaluated within the limits defined by national (ICTA) and international (ICNIRP) standards. Finally, the EM exposure map is constructed with data that is average electric field intensity versus measurement locations.