Person: KARPAT, FATİH
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KARPAT
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FATİH
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Publication The effect of hamatum curvature angle on carpal tunnel volumetry: A mathematical simulation model(Hindawi Ltd, 2020-03-10) Akdağ, Gökhan; Alp, Nazmi Bülent; Kaleli, Tufan; KALELİ, HÜSEYİN TUFAN; Kalay, Onur Can; Karpat, Fatih; KARPAT, FATİH; Macunluoğlu, Aslı Ceren; Oral, Gamze Saygı; Mühendislik Fakültesi; Biyoistatistik Ana Bilim Dalı; 0000-0003-3656-0088; 0000-0003-1109-8958; 0000-0001-8643-6910; 0000-0001-8474-7328; 0000-0002-6802-5998; AAB-6136-2022; A-5259-2018In carpal tunnel volume measurements, the angle of the hamatum curvature is not considered a variable, and its effect on carpal tunnel volume has not been investigated. We hypothesize that a change in the anatomical angle of the hamatum curvature changes the carpal tunnel volume. To prove our hypothesis, we used a mathematical simulation model considering the carpal tunnel as a truncated cone. We reviewed the wrist CT scans of 91 adults (>18 years of age), including 51 men and 40 women. We measured the angle of the hamatum curvature in the CT scans. We measured cross-sectional areas at the outlet of the carpal tunnel at the level of the trapezium and hook of hamate (r1) and at the inlet at the level of the scaphoid and pisiform (r2) and the length (h) of the carpal tunnel. We attempted to calculate the effect of 2 degree by 2-degree changes in the angle of the hamatum curvature between the angles of 98 degrees and 140 degrees on the carpal tunnel volume. The mean angle of the hook of hamatum of the subjects was 122.55 degrees +/- 8.20 degrees (range, 97.20 degrees-139.31 degrees). No suitable cutoff point was found for the angle values. There was no difference between the gender groups according to the angle value. The data clearly show that there is a high correlation between carpal tunnel volume and the angle of hamatum curvature. The results of our study emphasize the importance of taking into account the anatomical features of the hamatum bone, especially the angle of curvature, which may play a predisposing role in idiopathic carpal tunnel syndrome.Publication Evaluation of biomechanical performances of electrospun fiber anchored silicone disc as an intervertebral disc implant(Amer Soc Mechanical Engineers, 2018-01-01) Tummala, Subhakar; Doğan, Oğuz; Karpat, Fatih; Riahinezhad, Shahram; Khandaker, M.; ASME; DOĞAN, OĞUZ; KARPAT, FATİH; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0003-4203-8237; 0000-0001-8474-7328; AAV-7897-2020; A-5259-2018; GXH-1702-2022A tissue engineered intervertebral disc (IVD) anchor the circumference and top/bottom sides of nucleus pulposus (NP) implants with annulus fibrosus and endplates. The proper anchorage of a NP implant to annulus fibrosus and endplates is possible by enclosing the NP by electrospun fiber mesh that mimics the surrounding structures. The biomechanical performance of silicone based NP can be improved if electrospun fiber mesh can secure all sides of silicone NP. However, it is unknown whether silicone surrounded by an electrospun nanofiber matrix can better restore the biomechanical functions of the disc in compare to intact, IVD made with silicone only, and, IVD made with silicone anchored all sides by nanofiber. This study compared the compressive and viscoelastic properties of a silicone and electrospun nanofiber anchored silicone discs (ENAS) under compression and shear with the same properties of human NP. This study developed a nonlinear finite element model (FEM) for the intact and ENAS implanted human lumbar vertebra segments. The compression test results show that ENAS disc compressive modulus (87.47 +/- 7.56 kPa, n = 3) is significantly higher in compare to silicone gel (38.75 +/- 2.15 kPa, n = 3) and the value is within the range of the compressive modulus of human NP (64.9 +/- 44.1 kPa). The rheological test results show that ENAS disc compressive modulus (16 similar to 40 kPa) is significantly higher in compare to silicone gel (0.10 similar to 0.16 kPa) and the value is within the range of the compressive modulus of human NP (7 similar to 20 kPa). These results confirm the suitability of ENAS disc over silicone as NP implant. A finite element model has been developed based on the ENAS properties. The FEA results showed that ENAS can restore better the biomechanical motions of a lumbar vertebra segments in compare to silicone NP.Publication Vibration-based early crack diagnosis with machine learning for spur gears(Amer Soc Mechanical Engineers, 2020-01-01) Karpat, Fatih; KARPAT, FATİH; Dirik, Ahmet Emir; DOĞAN, OĞUZ; DİRİK, AHMET EMİR; Kalay, Onur Can; Korcuklu, Burak; KORCUKLU, BURAK; Doğan, Oğuz; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0001-8474-7328; 0000-0001-8643-6910; KIK-4851-2024; A-5259-2018Gear mechanisms are one of the most significant components of the power transmission systems. Due to increasing emphasis on the high-speed, longer working life, high torques, etc. cracks may be observed on the gear surface. Recently, Machine Learning (ML) algorithms have started to be used frequently in fault diagnosis with developing technology. The aim of this study is to determine the gear root crack and its degree with vibration-based diagnostics approach using ML algorithms.To perform early crack detection, the single tooth stiffness and the mesh stiffness calculated via ANSYS for both healthy and faulty (25-50-75-100%) teeth. The calculated data transferred to the 6-DOF dynamic model of a one-stage gearbox, and vibration responses was collected. The data gathered for healthy and faulty cases were evaluated for the feature extraction with five statistical indicators. Besides, white Gaussian noise was added to the data obtained from the 6-DOF model, and it was aimed at early fault diagnosis and condition monitoring with ML algorithms.In this study, the gear root crack and its degree analyzed for both healthy and four different crack sizes (25%-50%-75%-100%) for the gear crack detection. Thereby, a method was presented for early fault diagnosis without the need for a big experimental dataset. The proposed vibration-based approach can eliminate the high test rig construction costs and can potentially be used for the evaluation of different working conditions and gear design parameters. Therefore, catastrophic failures can be prevented, and maintenance costs can be optimized by early crack detection.Publication Design and analysis of lattice structure applied humerus semi-prosthesis(Walter De Gruyter Gmbh, 2023-06-05) Savran, Efe; Kalay, Onur Can; Alp, Nazmi Bülent; Karpat, Fatih; Savran, Efe; Kalay, Onur Can; KARPAT, FATİH; Mühendislik Fakültesi; Makina Mühendisliği Bölümü; 0000-0001-8474-7328; IUG-4938-2023; GDQ-4936-2022; A-5259-2018Bone tissue loss may occur in bone structures, which are one of the elements that provide the body's endurance and movement of living things, due to situations such as falling, hitting, or cancer formation. In bad scenarios, applications such as an external plate or internal rod addition are made to regain the old durability of the structure. At the same time, full or semi-prosthesis applications can be made in cases where the original bone structure cannot be preserved. With today's advanced possibilities, lattice structures can be produced effortlessly with the additive manufacturing (AM) method. Here, the formation of the structure that can show anisotropic behavior depending on the production and the effect of the roughness caused by the production quality should also be seen in the process plan. In this study, it was aimed to compare the durability of titanium (Ti-6Al-4V) and magnesium (ZK60) materials for humeral half prosthesis using cubic-based lattice structure and to show their differences compared to the original bone structure. Maximum stress and deformation values were obtained by performing analyses with the finite element method on the lattice semi-humerus prosthesis obtained with this aim. Reliability analysis was made on the data obtained, and parameter optimization of the lattice structure was aimed. As a result of the study, it was seen that the lattice structure with 65% porosity compared to the reference values is reliable and with the same reliability rate, magnesium provides approximately 60% lightness compared to titanium.Publication Investigation of infectious droplet dispersion in a hospital examination room cooled by split-type air conditioner(Springer, 2024-05-08) Yüce, Bahadir Erman; Kalay, Onur Can; Karpat, Fatih; Alemdar, Adem; Temel, Şehime Gülsün; Dilektaşlı, Aslı Görek; Başkan, Emel Bülbül; Özakın, Cüneyt; Coşkun, Burhan; YÜCE, BAHADIR ERMAN; Kalay, Onur Can; KARPAT, FATİH; ALEMDAR, ADEM; TEMEL, ŞEHİME GÜLSÜN; GÖREK DİLEKTAŞLI, ASLI; BÜLBÜL BAŞKAN, EMEL; ÖZAKIN, CÜNEYT; COŞKUN, BURHAN; Tıp Fakültesi; Histoloji ve Embriyoloji Ana Bilim DalıThe novel coronavirus (SARS-CoV-2) outbreak has spread worldwide, and the World Health Organization (WHO) declared a global pandemic in March 2020. The transmission mechanism of SARS-CoV-2 in indoor environments has begun to be investigated in all aspects. In this regard, many numerical studies on social distancing and the protection of surgical masks against infection risk have neglected the evaporation of the particles. Meanwhile, a 1.83 m (6 feet) social distancing rule has been recommended to reduce the infection risk. However, it should be noted that most of the studies were conducted in static air conditions. Air movement in indoor environments is chaotic, and it is not easy to track all droplets in a ventilated room experimentally. Computational Fluid Dynamics (CFD) enables the tracking of all particles in a ventilated environment. This study numerically investigated the airborne transmission of infectious droplets in a hospital examination room cooled by a split-type air conditioner with the CFD method. Different inlet velocities (1, 2, 3 m/s) were considered and investigated separately. Besides, the hospital examination room is a model of one of the Bursa Uludag University Hospital examination rooms. The patient, doctor, and some furniture are modeled in the room. Particle diameters considered ranged from 2 to 2000 mu m. The evaporation of the droplets is not neglected, and the predictions of particle tracks are shown. As a result, locations with a high infection risk were identified, and the findings that could guide the design/redesign of the hospital examination rooms were evaluated.Publication Effects of asymmetric tooth profile on single-tooth stiffness of polymer gears(Walter De Gruyter Gmbh, 2022-04-26) Yüce, Celalettin; Doğan, Oğuz; Karpat, Fatih; KARPAT, FATİH; Mühendislik Fakültesi; 0000-0001-8474-7328; A-5259-2018As a result of polymer materials development and the use of additive manufacturing technologies, gear wheels made of polymer materials are becoming widespread in many areas of the industry. In recent years, determining the dynamic behavior of polymer gears has gained significant importance because it is desired to carry more loads and operate at higher speeds. Since it is one of the most critical factors affecting dynamic behavior, tooth stiffness should also be determined. In this study, the single-tooth stiffness (STS) of polymer gears with symmetrical and asymmetrical profile was measured experimentally with a unique test setup. Force was applied to three different points on the tooth, and the resulting deflection was measured with the help of linear variable differential transformer and a high-speed camera. Using the obtained deflection values, STS of the polymer tooth was calculated depending on the pressure angle. The experimental results are also compared with the finite element model created, and it is found that the results are matched well. As a result of the study, it is determined that the drive-side pressure angle of the polymer gear increased from 20 degrees to 32 degrees, and the tooth stiffness increased by approximately 10.8%.Publication Effects of rim thickness and drive side pressure angle on gear tooth root stress and fatigue crack propagation life(Elsevier, 2021-02-12) Doğan, Oguz; Yüce, Celalettin; Karpat, Fatih; KARPAT, FATİH; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0001-8474-7328; A-5259-2018Gears are the most significant machine elements in power transmission systems. They are used in almost every area of the industry, such as small watches to wind turbines. During the power transmission, gears are subjected to high loads, even unstable conditions, high impact force can be seen. Due to these unexpected conditions, cracks can be seen on the gear surfaces. Moreover, these cracks can propagate, and tooth or body failures can be seen. The fatigue propagation life is related to the gear tooth root stress. If the root stresses decrease, the fatigue life of the gears will increase. In this study, standard and non-standard (asymmetric) gear geometries are formed for four different rim thicknesses and four different pressure angles to examine fatigue crack prop-agation life. Moreover, the effects of the rim thickness and drive side pressure angle on the root stress are investigated. The static stress analyses are carried out to determine the starting points of the cracks, and the maximum point of the stress is defined as the starting point of the cracks. Fatigue crack propagation analyzes are performed for gears whose crack starting points are determined. The static stress analyses are conducted in ANSYS Workbench; similarly, the fatigue propagation analysis is performed in ANSYS smart crack growth. In this way, the directions of the cracks are determined for different rim thicknesses and drive side pressure angles. Besides, the number of cycles and da/dN graphs is obtained for all cases depending on crack propagation. As a result of the study, maximum stress values were decreased by 66%. The fatigue propagation life was increased approximately fifteen times by using the maximum drive side pressure angle and optimum rim thickness.Publication Experimental model development using an animal brain phantom to study neural damage from traumatic brain injury(Amer Soc Mechanical Engineers, 2022-01-01) Khandaker, Morshed; Giri, Amir; Nayak, Pramod; Jarshaw, Catherine; Kalay, Onur Can; Karpat, Fatih; Wolf, Roman F.; Kalay, Onur Can; KARPAT, FATİH; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; A-5259-2018; GDQ-4936-2022This study aims to conduct shock tube experiments to determine neural damage from realistic non-impact blast loading using an in vitro animal test model (ellipsoid filled with simulated tissue). Traumatic Brain Injury (TBI) is caused by a sudden impact on the head that leads to the disruption of the brain's normal function. Specific to war-related traumatic brain injuries include those which are blast-induced. Microbubbles measured in microns can form in the Cerebral Spinal Fluid (CSF) inside the skull during the blast. The "formation and dramatic collapse" of these microbubbles, a process known as cavitation, could be responsible for neural tissue damage. As a pressure wave comes into contact with a head, a shock wave is transmitted through the skull, cerebrospinal fluid, and brain tissue and causes a negative difference in pressure observed at the opposite side of impact. An event that causes a quick difference in pressure within the CSF, and comes with a directional force, may result in gas bubbles forming opposite the site of impact along with the brain-skull interface and accusing damage to the surrounding tissues. Using a rabbit brain phantom model, this research measured the impact of different ranges of shock on brain tissue. Our simplified surrogate model of the head consisted of a transparent and shatterproof spherical dummy, and a simplified phantom model of the head consists of a transparent ellipsoid with dimensions of a rabbit skull. This study made a custom design 3D printed multi-directional shock device for the blast on the brain. The first test group conducted on a simplified surrogate filled with degassed water to simulate CSF and tissue altogether. A second test group included the rabbit phantom model that was filled with degassed water. In the third blast tests, the phantom contained Sylgard gel, surrounded by a layer of degassed water, to represent brain tissue and the CSF, respectively. Blast pressure in the shock-wave tests conducted at 10-20 pounds per square inch (psi; 69-138 kPa). Pressure in the modeled CSF was determined by a pressure sensors placed at 5, 10, 15 and 20 cm distances from the shock tube film. In all tests, the pressure difference at the countercoup before and after the blast was measured using an impact sensor. This study successfully found microbubbles from the first group of test. In addition, we found decreasing pressure, impact and strain on the model in relation to distance from the blast source. The results of this study will be used in our finite element model to predict the occurrence of acute subdural hematoma due to the blast inside along the interface between various brain tissue in future study.Publication Multi-response optimization for laser transmission welding of pmma to abs using taguchi-based topsis method(Sage Publications Ltd, 2023-08-01) Küçükoğlu, Ayça; Yüce, Celalettin; Sözer, İbrahim Emrah; Karpat, Fatih; Küçükoğlu, Ayça; YÜCE, CELALETTİN; KARPAT, FATİH; Mühendislik Fakültesi; 0000-0003-1387-907X; 0000-0001-8474-7328; R-3733-2017; A-5259-2018; FJI-7166-2022Recently, the usage of laser transmission welding (LTW) technology in the automotive industry has been rising for joining thermoplastic parts regarding its superior properties in comparison to other welding technologies. However, specifying the process parameters is a crucial step to obtain satisfactory welding quality for the vehicle parts. In this context, this paper addresses the LTW process of Polimetil metakrilat (PMMA) to Akrilonitril butadien stiren (ABS) materials for the production of taillights in an automotive company and proposes a new multi-response Taguchi-Based TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) method to optimize machining parameters in the laser welding process. In the proposed solution methodology, the main effects of the parameters on different outputs are identified by using the L-16 orthogonal array of the Taguchi method. Regarding the best parameter set for each output, the best parameter set for multi-response is identified by using the TOPSIS method, in which alternatives are evaluated through the interrelated quality measures. To optimize welding process in taillight production, PMMA and ABS samples with the dimensions of 40 mm in width, 85 mm in length, and 2 . 7 mm in thickness are used in the experiments. The samples are welded by using LPKF Twinweld 3D 6000 (R) laser welding machine. For the welding process, laser power, welding speed, and pressure force are taken into account as the input parameters to optimize three responses: weld strength, breaking strain, and weld width. To identify the best process parameter values, the Taguchi Method is initially employed to calculate the main effects of LTW parameters for each output. Then, the TOPSIS method is carried out to evaluate a number of alternative parameter sets generated through the Taguchi results. As a consequence of the TOPSIS ranking scores, the best parameter set that jointly optimizes three outputs of the LTW process is identified for the taillight production as 60 W power, 100 mm / s speed, and 150 N pressure force. Based on the conducted experiments, this parameter setting achieves the highest weld strength, breaking strain level, and above-average weld width. The results of the experiments show that the proposed methodology is capable of optimizing LTW parameters for a multi-response with fewer experiments in the joining of plastic vehicle parts.Publication Experimental verification and finite element analysis of automotive door hinge(Amer, 2015-01-01) Doğan, S.; Güven, C.; Karpat, Fatih; Yılmaz, Tufan Gürkan; Doğan, Oğuz; ASME; KARPAT, FATİH; YILMAZ, TUFAN GÜRKAN; DOĞAN, OĞUZ; Mühendislik Fakültesi; Makine Mühendisliği; 0000-0001-8474-7328; 0000-0003-3772-7871; 0000-0003-4203-8237; V-6153-2017; A-5259-2018; GXH-1702-2022; AAV-7897-2020; CTF-4189-2022; EVY-7464-2022In automotive industry, achieving lightweight, low-cost, reliable and more accurate product design are the most important goal. Using Finite Element Analysis (FEA) is an important tool for achieving this since it decreases prototyping cost and time. Cars have different door system and one of the important part of them is door hinge. An automotive door hinge is mainly composed of three elements, fixed part, mobile part and hinge pin that fasten fixed part and mobile parts. Manufacturers have to perform tests and analysis for ensuring international and customer requirements.In this study, FEA results are compared with static and dynamic test results of front door hinge of automotive according to International specifications. The agreement between the computed and measured values is shown.