Browsing by Author "KARPAT, FATİH"

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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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; Bursa Uludağ Üniversitesi/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-3733-2017
The 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.
A comparative experimental study on the impact strength of standard and asymmetric involute spur gears
(Elsevier, 2021-01-06) Kalay, Onur Can; Doğan, Oğuz; Yılmaz, Tufan Gürkan; Yüce, Celalettin; Karpat, Fatih; Kalay, Onur Can; YILMAZ, TUFAN GÜRKAN; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8643-6910; 0000-0003-3772-7871; 0000-0001-8474-7328; GDQ-4936-2022; V-6153-2017; A-5259-2018
Gears are one of the main components of the power transmission systems and are used in various fields. Problems caused by sudden load changes in mobile systems are frequently encountered today. Gear dynamics have become more influential due to demands of high power transmission capability, long life, and low-cost. However, inertial forces caused by accelerated movements of gear can have unpredictable results. The impact loads must be calculated correctly. It is inconvenient to determine the impact strength of gear via standard drop-weight test rig due to inhomogeneity and complex geometries. This study investigates how the tooth profile affects the impact load on the involute spur gears. For this reason, a special test setup and experimental approach was proposed to examine the influence of the asymmetric profile on the impact strength. It was observed that the peak force values increased by approximately 15.3% when using 20/30 degrees asymmetric profile gears in comparison with the 20 degrees/20 degrees standard design. This improvement can reach up to 25.8% in terms of peak force energy. The results indicate that the proposed novel test setup and the experimental method can be used for measuring the impact strength of asymmetric involute gears.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; 0000-0001-8643-6910; 0000-0001-8474-7328; 0000-0002-9548-8648; KIK-4851-2024; A-5259-2018
Gears 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.
A numerical analysis of hybrid spur gears with asymmetric teeth: Stress and dynamic behavior
(Mdpi, 2022-11-01) KARADERE, GÜLTEKİN; KARPAT, FATİH; Karpat, Fatih; Karadere, Gültekin; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; 0000-0003-3772-7871; 0000-0001-8474-7328; V-6153-2017; A-5259-2018
Hybrid gears are composed of high-strength steel, carbon fiber reinforced plastic (CFRP), and adhesive bond to join these materials. In this study, the effect of rack tip radius (TR), drive side pressure angle (DSPA), and rim thickness (RT) on the stress of hybrid gears is investigated numerically. In addition, the stress results of hybrid gears are compared with steel gears that are used for validation of the numerical results. Single tooth stiffness (STS) values are calculated based on tooth deformations obtained from numerical analyses. The 2-DOF model is used to observe the influence of DSPA and RT on the dynamic factor (DF) and static transmission error (STE). According to the results, increasing RT has a positive effect on stress, STS, and STE, while DSPA is effective on the dynamic factor at most.
An investigation on the design of formate and generate face milled hypoid gears
(Amer Soc Mechanical Engineers, 2020-01-01) Doğanlı, Mert; Altıntaş, Elif; Yılmaz, Tufan Gürkan; YILMAZ, TUFAN GÜRKAN; Kalay, Onur Can; Karpat, Fatih; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0003-3772-7871; 0000-0001-8643-6910; 0000-0001-8474-7328; A-5259-2018
Hypoid gears are transmission elements that transfer power and moment between shafts whose axes do not intersect. They are similar in structure to spiral bevel gears. However, there are many advantages compared to spiral bevel gears in terms of load carrying capacity and rigidity. Hypoid gear pairs are mostly used as powertrain on the rear axles of cars and trucks. Hypoid gears are manufactured by two essential methods called face-milling and face-hobbing, and there are mainly two relative kinematic movements (Formate (R) and Generate). In this study, the gears produced with the Face-milling method are discussed. Face milled hypoid gears can be manufactured with both Formate (R) and Generate, while pinions can only be manufactured with the Generate method. The most crucial factor that determines the performance of hypoid gears is the geometry of hypoid gears. The gear and pinion geometry is directly dependent on the tool geometry, machine parameters, and relative motion between the cradle and the workpiece. The gear geometry determines the contact shape and pressure during power transmission. In this study, the mathematical equation of the cutting tool is set. After that, using differential geometry, coordinate transformation, and the gearing theory, the mathematical equation of hypoid gear is obtained.
Design and analysis of internal gears with different rim thickness and shapes
(Amer Soc Mechanical Engineers, 2016-01-01) Karpat, F.; Ekwaro-Osire, S.; Yılmaz, T. G.; Doğan, O.; Yüce, C.; KARPAT, FATİH; YILMAZ, TUFAN GÜRKAN; DOĞAN, OĞUZ; YÜCE, CELALETTİN; Uludağ Üniversitesi/Mühendislik Fakültesi/Makina Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0003-4203-8237; 0000-0003-1387-907X; GXH-1702-2022; AAV-7897-2020; V-6153-2017; R-3733-2017; A-5259-2018
In recent years, thanks to their significant advantages such as compactness, large torque-to-weight ratio, large transmission ratios, reduced noise and vibrations, internal gears have been used in automotive and aerospace applications especially in planetary gear drives. Although internal gears have a number of advantages, they have not been studied sufficiently. Internal gears are manufactured by pinion type cutters which are nearly identical with pinion gear except the addendum factor which is 1.25 instead of 1. The tip geometry of a pinion type cutter which determines the fillet of internal gear tooth can be sharp or rounded. In this study, the design of internal gears were investigated by using a traditional approach. Mathematical equations of pinion type cutter were obtained by using differential geometry, then the equations of internal gear tooth were derived accurately by using coordinate transformations and relative motion between the pinion type cutter and internal gear blank. A computer program was generated to attain points of internal gear teeth and three dimensional design of complete gear. 20-20 were used as pressure angle. To find optimum internal gear geometry, different rim thicknesses and shapes are tried out for finite element analyses. There were several parameters that were shown to effect the performance of the internal gears, with tooth stiffness being the most significant parameter. Tooth stiffness was also vitally influence the dynamic analysis. In order to compute gear tooth stiffness of the internal gear with various rim thicknesses and shapes, finite element analysis was used. A static analysis was performed to assess the gear bending stress and tooth displacement. Tetrahedral element type was selected for meshing. The internal gear outer ring was fixed and the force of 2500 N was applied on the tooth. According to the displacement values from the analysis internal gear tooth stiffness were calculated individually. Additionally, the effect of root bending stress with varying rim thickness, shapes, and root radius were investigated. The bending stresses were calculated according to ISO 6336 and using finite element analysis were shown to be in good agreement. It was shown that when the rim thickness and fillet radius were increased, the maximum bending stresses decreased considerably. As rim thickness was increased, the maximum bending stress decreased nearly 23%. It was also shown that as the fillet radius decreased, the maximum bending stress increased, whereas the rim stresses slightly changed. As the fillet radius was decreased, the maximum bending stress increased nearly 10%. It was also observed that when rim thickness was increased, the stress on the rim was decreased, whereas tooth stiffness was increased. However, fillet radius had no visible effect both on rim stress and tooth stiffness. Furthermore, it was shown that the rim shape had significant effect on rim stress.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makina Mühendisliği Bölümü.; 0000-0001-8474-7328; IUG-4938-2023; GDQ-4936-2022; A-5259-2018
Bone 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.
Effect of micro-grooving on the stress shielding of titanium: Experimental and numerical investigations
(Amer, 2018-01-01) Jamadagni, Harsha G.; Karaman, Hasan; Karpat, Fatih; Williams, Wendy; Dhanasekaran, Lokesh; Khandaker, M.; ASME; Karaman, Hasan; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0001-8474-7328; A-5259-2018; HJS-9729-2023
Micron sizes grooves can control the cell settlement on the implant surface or be used to direct tissue generation at the implant/bone interface. The effect of shape, size and the type of material of the microgrooves on the mechanical stimulus transfer from the implant to bone at physiological loading is not known yet. Therefore, this study evaluated both experimentally and numerically the effect of surface modification on a titanium implant to the load transfer characteristics from implant to bone for examining stress shielding parameters. This study measured the effect of micron grooves on titanium to the mechanical stability of titanium using a rabbit model. This study also developed a finite element model based on the in vivo test model to examine the stress shielding parameters. The results showed that the mean values of fracture strength were significantly higher for grooved titanium samples (1.32 +/- 0.45 MPa, n = 3) compared to control samples (without any groove) (0.22 +/- 0.16 MPa, n=6) (P < 0.05). The load-displacement graph from the pull out tension tests was used to measure the frictional coefficient between Ti and bone from the FEA model. It was found from the FEA model that the average co-efficient of friction between titanium and bone was 0.50. Maximum equivalent stress along the interface of microgrooves on titanium was higher from groove area in compare to the non-groove area because of the change of the geometry along the groove. The microgrooves in the model have a significant effect on the stress transfer parameter between implant and adjoining bone. The unequal load sharing due to micro-grooving causes an increase in stiffness of the adjacent bone to the implant.
Effect of the cooling process on the mechanical properties and microstructural behavior of extruded az31 and am50 mg alloys
(Walter De Gruyter Gmbh, 2021-07-01) Kurtulus, Enes; Sapmaz, Irem; Karpat, Faith; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; 0000-0001-8474-7328; A-5259-2018
During the extrusion of magnesium alloys, temperature change could have a significant effect on the outcome. When this effect is not considered, some commonly known defects might be observed, such as hot cracking. In this study, all samples consist of extruded AZ31 and AM50 magnesium alloys as a solid profile, but the methods by which they are cooled, such as air cooling and water quenching, vary. The effects of cooling methods on tensile-compression behavior and the microstructural properties of the samples were investigated. Test samples were obtained in extrusion direction and perpendicular to the extrusion direction separately for mechanical tests. The main purpose of this study was to investigate the effect of different cooling methods on the mechanical properties and microstructural behavior of AZ31 and AM50 magnesium alloys after extrusion, once different cooling methods were applied. According to the microstructural investigation results, an AM50 magnesium alloy has a finer grain structure as compared with an AZ31 alloy according to both cooling methods in the extrusion process. The average grain size values of both alloys were found to be higher for water cooling. Cooling methods have significant effects on the tensile properties of both alloys, depending on their extrusion directions.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi; 0000-0001-8474-7328; A-5259-2018
As 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%.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Mekatronik Mühendisliği Bölümü.
Today 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.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0001-8474-7328; A-5259-2018
Gears 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.
Effects of rim thickness on tooth root stress and mesh stiffness of internal gears
(Amer Soc Mechanical Engineers, 2015-01-01) Yilmaz, Tufan; YILMAZ, TUFAN GÜRKAN; Yüce, Celalettin; YÜCE, CELALETTİN; Karpat, Fatih; KARPAT, FATİH; Engin, B.; Doğan, O.; DOĞAN, OĞUZ; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0003-4203-8237; 0000-0003-1387-907X; 0000-0003-3772-7871; A-5259-2018; GXH-1702-2022; R-3733-2017; AAV-7897-2020; V-6153-2017
In recent years, internal gears are used commonly in a number of automotive and aerospace applications especially in planetary gear drives. Planetary gears have many advantages such as compactness, large torque-to-weight ratio, large transmission ratios, reduced noise and vibrations. Although internal gears have many advantages, there are not enough studies on it. Designing an internal gear mechanism includes two important parameters. The gear mesh stiffness which is the main excitation source of the system. In this paper, 2D gear models are developed in order to compute gear mesh stiffness for various rim thicknesses and different rim shapes of the internal gear design. Effects of root stress with varying rim thickness and some tooth parameters are investigated by using 2D gear models. The stress calculated according to ISO 6336 and the stresses calculated against FEM are compared. These results are well-matched. It is observed that when the rim thicknesses are increased, both the maximum bending stresses and gear mesh stiffness are decreased considerably.
Effects of tooth root cracks on vibration and dynamic transmission error responses of asymmetric gears: A comparative study
(Taylor & Francis Inc, 2023-03-03) Doğan, Oğuz; YÜCE, CELALETTİN; Kalay, Onur Can; Yüce, Celalettin; Karpat, Fatih; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makina Mühendisliği Bölümü.; 0000-0001-8643-6910; 0000-0003-4203-8237; 0000-0003-1387-907X; 0000-0001-8474-7328; R-3733-2017; AAV-7897-2020; A-5259-2018
Gears are significant machine elements used in various industrial applications. An undetected fault in a gear transmission system may lead to a fatal breakdown and, thus, severe economic losses or even human casualties. From this standpoint, the present study developed a numerical method to detect root crack damages in symmetric and asymmetric involute spur gears. To achieve this end, the single tooth stiffness values were calculated for healthy and cracked (25%-50%-75%-100%) gears, and then the time-varying mesh stiffness was obtained. A six-degree-of-freedom dynamic model of a single-stage gear mechanism was developed to collect vibration and Dynamic Transmission Error (DTE) signals. The efficacy of vibration and DTE responses in fault detection was compared through six statistical indicators. The results indicate that the vibration signals were more effective than DTE in detecting tooth root cracks. It was observed that the statistical indicator changes significantly increase with the increment of the drive side pressure angle from 20 degrees to 30 degrees for the backup ratios where the root crack propagates along the tooth, thus making fault detection easier. The findings could provide significant outputs for a better understanding of the influence of tooth asymmetry on gear dynamics characteristics and early fault diagnosis.
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; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0003-4203-8237; 0000-0001-8474-7328; AAV-7897-2020; A-5259-2018; GXH-1702-2022
A 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.
Evaluation of biomechanical performances of electrospun fiber anchored silicone disc as an intervertebral disc implant
(Amer Soc Mechanical Engineers, 2018-01-01) Tummala, Subhakar; Riahinezhad, Shahram; Khandaker, M.; Doğan, Oguz; DOĞAN, OĞUZ; Karpat, Fatih; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; 0000-0003-4203-8237; 0000-0001-8474-7328; 0000-0001-5985-7402; A-5259-2018; AAV-7897-2020; GXH-1702-2022
A 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.
Experimental investigation of the impact resistance of involute spur gears
(IEEE, 2018-01-01) Doğan, Oğuz; Yüce, Celalettin; Karpat, Fatih; Kalay, Onur Can; IEEE; DOĞAN, OĞUZ; YÜCE, CELALETTİN; KARPAT, FATİH; Kalay, Onur Can; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi; 0000-0003-4203-8237; 0000-0003-1387-907X; 0000-0001-8474-7328; 0000-0001-8643-6910; A-5259-2018; GXH-1702-2022; R-3733-2017; GDQ-4936-2022
Gears are the most commonly used power transmission element in today's world. Due to their advantages, gears are widely used in many sectors such as aerospace, space, wind turbines, automotive, etc. In these sectors the moment, speed and power values that need to be transmitted are increasing day by day. Due to the increased power and moment values, gears are exposed to high dynamic, impact loads and they are subject to damage due to these loads. For this reason, the impact resistance of the gears must be determined carefully in the design phase of the gear. In this study, an experimental method for determining impact loads of the gears is developed. A special drop gear impact test setup is designed and manufactured to determine the impact loads on the gear. The test setup works by dropping the load on the gear tooth from a certain height. In this way, the teeth are broken and the impact load, acceleration and displacement values are measured by using special measurement instruments which are attached on the test setup. The effect of surface hardness on impact loads is investigated. Two different gear samples are used in the experiments. It is seen that the surface hardness has great effect on the impact loads of the gears. It has been found that surface hardened gears have much higher impact strength than unhardened gears.
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; Uludağ Üniversitesi/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-7464-2022
In 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.
Fatigue performances of helicopter gears
(Walter De Gruyter Gmbh, 2023-01-27) Doğan, Oğuz; Yılmaz, Tufan Gürkan; YÜCE, CELALETTİN; Kalay, Onur Can; Karpat, Esin; Kopmaz, Osman; KOPMAZ, OSMAN; Karpat, Fatih; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; 0000-0001-8643-6910; 0000-0003-1387-907X; 0000-0003-4203-8237; 0000-0003-3772-7871; 0000-0001-8474-7328; A-5259-2018; V-6153-2017; R-3733-2017
Gears are widely used machine elements to transmit power and motion in the industry. During the power transmission, the gears are subjected to cyclic loads. Thus the fatigue resistance of the gears should be deeply investigated. In particular, this issue is gaining much more importance in the space and aviation fields. In this study, the fatigue life of gears made of 9310-VIM-VAR steel used in the aviation field was determined experimentally, and the crack propagation paths obtained were numerically verified. To this end, the SAE J1619 standard single-tooth bending fatigue test apparatus was redesigned and manufactured in order to adapt it to the helicopter gears. Totally 28 single-tooth bending fatigue tests were carried out for various loading conditions. Accordingly, the S-N curves for the helicopter gears were created. The experimental results were verified by the finite element fatigue crack propagation analysis in terms of the initial crack location, crack initialization angle, and crack propagation paths. Conducted experiments and numerical studies are found as compatible with each other.
Fault diagnosis with deep learning for standard and asymmetric involute spur gears
(Amer Soc Mechanical Engineers, 2021-01-01) Yuce, Celalettin; Dogan, Oguz; Karpat, Fatih; Dirik, Ahmet Emir; KARPAT, FATİH; DİRİK, AHMET EMİR; Kalay, Onur Can; Korcuklu, Burak; KORCUKLU, BURAK; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi; 0000-0001-8474-7328; 0000-0002-6200-1717; 0000-0001-8643-6910; 0000-0003-1387-907X; A-5259-2018; R-3733-2017
Gears are critical power transmission elements used in various industries. However, varying working speeds and sudden load changes may cause root cracks, pitting, or missing tooth failures. The asymmetric tooth profile offers higher load-carrying capacity, long life, and the ability to lessen vibration than the standard (symmefric) profile spur gears. Gearbox faults that cannot be detected early may lead the entire system to stop or serious damage to the machine. In this regard, Deep Learning (DL) algorithms have started to be utilized for gear early fault diagnosis. This study aims to determine the root crack for both symmefric and asymmefric involute spur gears with a DL-based approach. To this end, single tooth stiffness of the gears was obtained with ANSYS software for healthy and cracked gears (50-100%), and then the time-varying mesh stiffness (TVMS) was calculated. A six-degrees-of-freedom dynamic model was developed by deriving the equations of motion of a single-stage spur gear mechanism. The vibration responses were collected for the healthy state, 50% and 100% crack degrees for both symmefric and asymmefric tooth profiles. Furthermore, the white Gaussian noise was added to the vibration data to complicate the early crack diagnosis task. The main contribution of this paper is that it adapts the DL-based approaches used for early fault diagnosis in standard profile involute spur gears to the asymmefric tooth concept for the first time. The proposed method can eliminate the need for large amounts of training data from costly physical experiments. Therefore, maintenance strategies can be improved by early crack detection.