Makina Fakültesi

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http://hdl.handle.net/11527/25301

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  • Öge
    Optimization of laser direct structuring process parameters for material extrusion of polycarbonate
    (Wiley, 2023) Akagündüz, Cansu Gizem ; Soylemez, Emrecan ; orcid.org/0000-0003-4827-2606 ; Makina Mühendisliği
    Laser direct structuring (LDS) is critical in the integration of circuits onto 3D-shaped plastic parts, such as antennas and radio frequency components. The LDS process encompasses three stages: deposition of 3D parts, laser structuring, and metallization. While laser-direct structurable parts have been manufactured through plastic injection molding, material extrusion (MEX) is a favored additive manufacturing process for economic low-volume production and fast prototyping advantages. Although injection-molded LDS literature is available, 3D-printed laser-direct structured components merit further investigation. This study focuses on the MEX of catalyst-loaded polycarbonate (PC) parts and its LDS process. The parameters from the nanosecond fiber laser, including scan speed, power, and frequency, are thoroughly analyzed to understand the surface property changes and metallization performance of the printed PC parts. The single scan track width, which corresponds to the accuracy of conductive path width and metallization thickness, is employed to elucidate the findings. A process map is built to keep the track width constant aimed at enhancing the uniform metallization of intricate components. Thresholds are established, identifying a minimum track width of 22.1 μm and metallization thickness of 2.5 μm. These delineate clusters of process parameters that yield conductivity levels suitable for various applications.
  • Öge
    Evaluation of mechanical properties of additively manufactured beams with lattice structures
    (American Society of Mechanical Engineers, 2024) Pir, İnci ; Şahin, Serhat Arda ; Tüfekci, Mertol ; Tufekci, Ekrem ; Makina Mühendisliği
    The use of lattice structurses is becoming more common day by day. Limitations such as being expensive and time-consuming have led to a search for new solutions in the industry. In light of these limitations, the widespread use of 3D printing technology methods is evaluated. 3D printing technology has advantages in terms of design flexibility, quick prototyping, lightness and the ability to produce complex shapes. 3D printing is used to systematically investigate different geometries in line with the requirements of sustainable product development, leading to the production of auxiliary structures that are both strong and lightweight. This research investigates the mechanical properties of various lattice structures that were previously modelled and analysed through analytical methods in the literature. The samples with five different auxetic structures are manufactured using the Fused Deposition Modelling (FDM) 3D printing technique, with Acrylonitrile Butadiene Styrene (ABS) as the selected material. The manufactured samples are subjected to a three-point bending test to assess their mechanical characteristics, including the flexural modulus, flexural strength, and elongation at break, and the effect of the in-plane geometry on the mechanical behaviour is evaluated.
  • Öge
    Effects of particle damper design parameters on the damping performance of laser powder bed fused structures
    (Springer, 2024) Özçevik, Birol ; Söylemez, Emrecan ; Bediz, Bekir ; Şimşek, Uğur ; 0000-0003-4003-9287 ; 0000-0003-4827-2606 ; 0000-0002-7925-8228 ; 0000-0002-4405-5420 ; Mechanical Engineering
    Particle dampers (PD), a passive damping technology, absorb energy from particle-particle and particle-cell wall interactions originating from friction and collision. PDs offer advantages such as design simplicity, low cost, applicability in harsh conditions, and flexibility to be used in a wide frequency band range. Additive manufacturing, specifically the powder bed fusion process, can fabricate structures with integrated PDs in a single printing process, eliminating the need to implement external dampers. However, the dynamic behavior of PDs must be determined to utilize their full potential. In this study, we examined 16 cases of integrated PDs by varying specific parameters including size, number, and locations on the structure to understand the effects of these parameters on the dynamic behavior of the first and second modes of the structure. Modal tests were conducted on additively manufactured samples to extract frequency response functions and calculate modal parameters (natural frequency and damping ratio) using the rational fraction polynomial method, studying the effects of PDs. The results showed that the damping performance of the parts was increased by a factor of up to 10 using body-integrated PDs compared with the fully fused specimen. The effectiveness of body-integrated PDs was shown to be strongly dependent on their volume and location. For instance, the damping generally increased as the volume fraction increased, which also reduced the total weight of the specimens by up to 60 g. Furthermore, the damping performance significantly increased for a specific mode when the PDs were located near the maximum displacement regions.
  • Öge
    From material to field test : an improved under sleeper pad model
    (Springer, 2024) Ulu, Arif ; Metin, Muzaffer ; Arıkoğlu, Aytaç ; Demir, Özgür ; 0000-0003-3000-3731 ; 0000-0002-9724-3433 ; 0000-0003-0058-3982 ; 0000-0003-0865-0684 ; Makina Mühendisliği
    This study aims to determine the stiffness values of under sleeper pad (USP) and rail pad (RP) components to reduce the high-amplitude vibrations that occur in the transition zones of some specific structures such as viaducts in ballasted railways. The conventional method of simulating USPs and RPs as spring–dashpot elements in the Kelvin–Voigt model is inadequate due to the absence of frequency and temperature dependencies in the model. The study proposes a new analytical model that considers USPs and RPs as viscoelastic (VE) materials and integrates them into the ballasted railway superstructure model by adding unit masses avoiding mathematical singularity. The process includes material testing, field measurements, and validation of the proposed model with finite element model analysis. The effect of ambient temperature and material modelling on the superstructure’s dynamic response in the frequency domain is analysed in detail. To account for VE behaviours of the resilient elements, the generalised Maxwell model (GMM) is chosen via unit mass implementation compared to other VE models. The obtained results show that the dynamic response of the railway superstructure is 8–10 times sensitive to temperature variation. This demonstrates how important it is to include the temperature-dependent dynamics of the elastomer material in the model. According to the other results that were obtained, the use of USP in transition zones does not solve the vibration problem radically. Bridge dynamic responses are also sensitive to the mass of the bridge rather than its stiffness.
  • Öge
    Production, characterization and mechanical behaviors of electrolytic metal-coated light polymeric cylinders for photogravure press applications
    (Springer, 2024) Yakışan, Kadir İlker ; Türkel, Veysel ; Çelik, Erdal ; 0000-0002-5922-5488 ; Makina Mühendisliği
    Since precision engraving is essential for almost any product or application, it is important that the printing system produces smooth and clear prints. In this regard, the rollers are made of steel and polymeric materials. However, light cylinder production is economical, transportation costs are very low, and it provides ease of transportation and distribution for printing houses. However, regional chain orientations and cracks occur in the polymeric material on the conical surfaces of the cylinders with shafts longer than 1 m. Therefore, it is necessary to improve the surface properties of polymeric cylinder. In this study, electrolytic hard chromium (Cr) and soft copper (Cu) metal layers, conductive (Ni and Ag) paint and polyester coating were successfully fabricated on polymeric lightweight cylinders via electroplating, spraying and hand brushing techniques for photogravure press application. At the fabrication stage on the steel base cylinders, polyurethane has been molded by using an injection molding machine. In order to eliminate the porosities, where polyurethane takes place, polyester has been coated on the polymeric cylinder and consequently polyester has been painted with conductive dye to obtain the conductivity. Then Cu and Cr have been coated by using the electroplating method and gravured. At the end of final stage, the process has been completed with coating of Cr on the Cu layer/conductive paint/polyester coating/polyurethane substrate. Phase analysis, microstructures and mechanical properties of the obtained samples have been examined through XRD, SEM–EDS, surface roughness, microhardness, tensile, three-point bending, scratch and wear machines. As a remarkable result of these studies, correlations were established between the quality of the layers and the mechanical properties as innovative scientific approaches, and between the layers produced on an experimental basis and the samples produced on a fabrication basis, they were produced and used in high-quality multilayered architecture to engraving technology and then to the society because of its effectiveness.
  • Öge
    Analytical and numerical modeling on strengths of aluminum and magnesium micro-lattice structures fabricated via additive manufacturing
    (Springer, 2024) Sun, Yeting ; Akçay, Fuzuli Ağrı ; Wu, Dazhong ; Bai, Yuanli ; 0000-0002-5116-0069 ; Makina Mühendisliği
    Bioinspired lattice structures have a wide range of applications in aerospace, automotive, energy, and medical device industries due to their high strength-to-weight ratio. Although experimental and numerical modeling methods have been extensively used to characterize the compressive behavior of lattice structures, an accurate analytical model has great values in material/structure designs and applications. In this study, a new analytical model is developed for two configurations based on limit analysis in the plasticity theory to predict the compressive strengths of micro-lattice structures (MLS). The model is also discussed for determining the amounts of stretching-dominated deformation and bending-dominated deformation. A comparative study is performed between analytical solutions and experimental results of AlSi10Mg (aluminum alloy) and WE43 (magnesium alloy) MLS additively manufactured via selective laser melting (SLM). Finite element simulations using beam elements are conducted to evaluate the accuracy of the analytical solution. Analytical results, finite element simulation results, and the experimental results are in a good agreement with both AlSi10Mg and WE43 MLS. The shear band formation, as a main failure mode of MLS, is also studied and evaluated using the classical Rudnicki–Rice’s criterion, for which a reasonably good accuracy is demonstrated.
  • Öge
    Comparative assessment of material homogenisation techniques
    (Institute for Materials, Technologies and Mechanics, 2024) Tüfekci, Mertol ; Pir, İnci ; Tüfekci, Ekrem ; https://orcid.org/0000-0002-0540-5387 ; https://orcid.org/0000-0003-3991-4005 ; Makina Mühendisliği
    This study evaluates the accuracy and computational demands of Mean Field Homogenisation (MFH) and Finite Element Method-Based Homogenisation (FEMBH) for composites. FEMBH requires generating a Representative Volume Element (RVE) to capture the essential microstructural characteristics. The focus is on nanoparticle-reinforced composites, considering the distinct mechanical properties of matrix and inclusion phases, as well as the influence of inclusion geometry, such as aspect ratio and reinforcement orientation. A comparative numerical analysis of various homogenisation techniques is conducted, assuming linear and elastic behaviour for both phases. Also, different FEMBH implementations are examined, including voxel and tetrahedral meshes, to assess their precision and computational efficiency. To represent the effect of the RVE size choice on the accuracy of the results, different RVE sizes are evaluated during the homogenisation process. The Mori-Tanaka method, representing MFH, demonstrates good accuracy in predicting macroscopic behaviour, while FEMBH, particularly with detailed meshing, yields precise results. However, FEMBH requires significant computational resources, especially with increasing aspect ratios and volume fractions of reinforcing particles, which demand higher mesh densities for accurate analysis.
  • Öge
    Numerical evaluation of mechanical behaviour of lattice structures for rotating blades
    (Institute for Materials, Technologies and Mechanics, 2024) Pir, İnci ; Şahin, Serhat Arda ; Tüfekci, Mertol ; Tüfekci, Ekrem ; https://orcid.org/0000-0002-0540-5387 ; https://orcid.org/0009-0002-8195-7543 ; https://orcid.org/0000-0002-5530-1471 ; https://orcid.org/0000-0003-3991-4005 ; Makina Mühendisliği
    Lattice structures have significant potential in engineering, allowing for material and weight reduction while maintaining desired mechanical properties. This versatility is crucial in applications ranging from aerospace to medical implants, where customisability and efficiency are essential. This study investigates the mechanical performance of four lattice structures with multiple and single-cell model approaches. The aim is to elucidate the impact of lattice design parameters on the structural integrity and performance of components subjected to dynamic loads typical of rotating blades in aerospace applications. Utilising Finite Element Analysis (FEA), this research is conducted to characterise the overall mechanical behaviour and to simulate the behaviour of these structures under conditions that represent real-world operational conditions for rotating blades. The loading conditions considered are tension, compression, shear and periodic boundary conditions are applied. By comparing the mechanical behaviour of these lattice structures against each other, this research aims to identify optimised lattice designs that enhance the performance and durability of rotating blades. This study is expected to contribute to the broader field of materials science and engineering by providing guidelines for designing more efficient, lightweight, high-performance components in various industrial applications.
  • Öge
    Tribologically enhanced self-healing hybrid laminates for wind turbine applications
    (Wiley, 2024) Hasırcı, Kemal ; Ergene, Berkay ; Irez, Alaeddin Burak ; orcid.org/0009-0004-8370-515X ; orcid.org/0000-0001-6145-1970 ; orcid.org/0000-0001-7316-7694 ; Mechanical Engineering
    Wind turbines are subjected to extreme weather and load conditions; hence, high strength and impact resistance are required. Furthermore, wind turbine blades can be subjected to impact loads such as bird strikes, resulting in the formation of microcracks. Self-healing capsules can be used to mend turbine blades for microscale damage. The incorporation of self-healing capsules may cause a decrease in the mechanical characteristics of the composites prior to impact resistance, which can be compensated for with efficient fillers such as silicon carbide whiskers (SiCw). Thus, a novel hybrid composite structure is examined with the advantage of using a self-healing mechanism and SiCw reinforcement. Tensile, tribological, and Charpy impact tests were performed to characterize the mechanical and tribological properties, which were supported with microscopic observations. Multiple experimental characterizations were performed to investigate the impact, and the ultimate tensile strength (UTS) and energy absorption capacity of the structure were shown to increase by 32% and 45%, respectively, with the addition of SiCw. The presence of self-healing agents provides a 5% rise in UTS after enough time for healing following the collision. The structure's tribological performance is improved by 10% in wear resistance and 20% in friction coefficient. Highlights Hybrid laminated composite structure with silicon carbide whisker and self-healing capsules. Tensile and Charpy impact tests conducted with microscopic observations Increased ultimate tensile strength and energy absorption capacity by 32% and 45%. Tribological improvement by 10% in wear resistance and 20% in friction coefficient.
  • Öge
    The microstructural evolution of material extrusion based additive manufacturing of polyetheretherketone under different printing conditions and application in a spinal implant
    (Wiley, 2024) Irez, Alaeddin Burak ; Dogru, Alperen ; orcid.org/0000-0001-7316-7694 ; orcid.org/0000-0003-3730-3761 ; Makina Mühendisliği
    With the advances in additive manufacturing, polyetheretherketone (PEEK), a biocompatible polymer, can be used in biomedical applications such as spinal implants. This paper aims to investigate the evolution of the microstructure of PEEK parts manufactured by material extrusion (MEX)-based additive manufacturing with different printing parameters. The effect of layer thickness (LT) and nozzle diameter on mechanical properties was investigated using tensile, Charpy impact, and short beam strength (SBS) tests. Two different LTs, 0.1 and 0.2 mm, and two different nozzle diameters, 0.6 and 0.8 mm, were used as printing parameters. By increasing the LT, tensile strength dropped by around 24%, and impact strength by almost 55%. Moreover, altering the LT resulted in a 15% decrease in interlaminar shear strength (ILSS) from the SBS test. In addition, increasing the nozzle diameter also led to a significant reduction in all of the results as tensile strength, Charpy impact strength, and ILSS. The results were also consolidated by scanning electron microscopy. The main findings were that increasing LT leads to an increase in microstructural defects that act as stress concentrators. Following the tests, response surface methodology (RSM) was used to determine optimal printing parameters. In the end, using the optimum printing parameters from the RSM study, a structural analysis of a MEX-printed spinal implant was conducted through finite element method, considering the loading cases mimicking daily human body motions. Highlights As layer thickness increased, tensile and impact strength dropped. Tensile and impact strength dropped truly with increasing nozzle diameter. SEM revealed that increasing layer thickness causes more microstructural flaws. FEM analysis showed that PEEK-based implant provides structural integrity.
  • Öge
    Development of sunflower husk reinforced polypropylene based sustainable composites: an experimental investigation of mechanical and thermal performance
    (Wiley, 2024) Irez, Alaeddin Burak ; orcid.org/0000-0001-7316-7694 ; Makina Mühendisliği
    Climate change, shrinking resources, and rising raw material costs have pushed the industry to create more sustainable, and lightweight materials. Natural fiber composites are materials of interest for replacing conventional materials such as steel. Sunflower husks (SH), among many other natural fibers, are readily accessible as agricultural waste and have advantageous properties. In this study, sunflower husks were mixed with polypropylene (PP) matrix using a twin-screw extruder, and then tests specimens for experimental characterizations were manufactured through injection molding. The tensile tests revealed that the inclusion of SH into PP decreased the load-bearing capacity of the composites by around 20% and increased their impact resistance by over 200%, while reducing the ductility by about eight times. Moreover, magnesium hydroxide (Mg(OH)2) was incorporated into the composites as a flame retardant, and it has improved the stiffness and impact resistance of the composites. Besides, incorporation of SH and Mg(OH)2 elevated significantly the glass transition temperature of the composites. The use of Mg(OH)2 delayed 60% the flame retention of the composites observed from UL-94 HB flammability testing. In summary, they could be suitable for components such as spare wheel wells, seat backs, trunk floor, the acoustic panel behind the door, and airbag housing.
  • Öge
    Transformation of waste carbon fiber prepreg into sustainable composites: application in the automotive industry components
    (Wiley, 2024) Irez, Alaeddin Burak ; Yakar, Hasan ; orcid.org/0000-0001-7316-7694 ; Makina Mühendisliği
    Carbon fiber (CF) prepregs are employed in the manufacture of many different aeronautical structural and non-structural components. Following the cure of the prepregs in molds, trimming is generally used to give the final shape to the components. Considering the aircraft's vast surface area and the use of multiple prepreg layers in each component, an extensive amount of carbon fiber prepreg is discarded. The unique characteristics of carbon fibers render this CF waste highly valuable and requires its efficient recycling. Cured waste CF prepregs were milled and processed in this research to produce chopped carbon fibers for use in the novel composite development. The matrix material used in the composites was selected as recycled polypropylene sourced from old surgical masks, which highlighted the sustainability of the developed composites. To enhance the quality of the fiber-matrix interface and improve the impact resistance of the composites an anhydride-grafted polyethylene (Fusabond) was employed in small quantities. From mechanical characterizations, synergistic effects of the fillers were observed. Besides, compositions containing CF and Fusabond are found more impact resistant than neat matrix. In addition, the use of carbon fibers increased fracture toughness of the matrix through various mechanisms including fiber bridging, fiber pullout, and matrix plastic deformation identified by scanning electron microscopy fractography. Thermomechanical characterizations using dynamic mechanical analysis revealed that carbon fiber raises the neat matrix's glass transition temperature. The developed materials are intended to be employed in the automotive industry to produce inner fender liners, with an optimal composition determined by an optimization research. Highlights Carbon fiber (CF) derived from aerospace fresh scraps significantly improved the mechanical properties of the polymer matrix. Anhydride-grafted polyethylene incorporation remarkably enhanced the impact resistance of the polymer. CF demonstrated a bridge effect and improved the fracture toughness of the composites. The use of recycled CF presents encouraging prospects in the automotive industry for the production of inner fender liners.
  • Öge
    Inspection of microwave self-healing efficiency in carbon nanotube reinforced polymer composites for aerospace applications
    (Wiley, 2024) Irez, Alaeddin Burak ; orcid.org/0000-0001-7316-7694 ; Makina Mühendisliği
    The aerospace industry is evolving very rapidly every day, and due to the low operational and maintenance costs, unmanned aerial vehicles (UAVs) are utilized for many duties, including imaging, patrol, surveillance, and delivery. Flying platforms prioritize effective load-carrying capacity and light weight. To achieve this, lightweight materials with sufficient strength are utilized, and design optimizations are implemented. This study investigates material development for a UAV propeller, taking into account the possible consequences of a bird strike or hard landing such as micro damage occurrence. In this study, a twin-screw extruder was used to produce hybrid composites by blending a thermoplastic, polyamide-6 (PA6) with olefin block copolymers (OBC) and carbon nanotubes (CNT). After manufacturing test specimens by injection molding, tensile and Charpy impact tests were performed. OBC increased the elongation capacity and impact resistance of the PA6 through maleic anhydride (MAH) grafting while reducing the tensile strength. CNT incorporation compensated for this drop, but it rendered the composites more brittle. More importantly, due to the CNT's microwave (MW) absorption capacity, the hybrid composites have gained self-healing properties. Extended MW exposure time and high MW powers may cause localized burning of the material, resulting in a decrease in its self-healing efficiency. Following the failure of the examined composites, SEM microscopy revealed various toughening mechanisms in the composites. The use of a modified Halpin-Tsai model to estimate the elastic characteristics of CNT-reinforced composites revealed promising results, with minimal discrepancies when compared to experimental data. Highlights CNTs were found efficient for the self-healing behavior which is critical for improving the lifetime and planning maintenance for UAV propellers. CNT content, MW power & exposure time all impact the self-healing efficiency. Extended MW exposure time and high MW powers can cause localized burning of the material, resulting in a decrease in its self-healing efficiency. CNTs created bridge effects, ultimately leading to an enhancement in the strength of the composites. The use of a modified Halpin-Tsai model yielded good accuracy with experimental data.
  • Öge
    Precise orientation control of gimbals with parametric variations using model reference adaptive controller
    (Wiley, 2024) Çakmak, Ömer ; Altuğ, Erdinç ; orcid.org/0000-0002-5581-7806 ; Makina Mühendisliği
    This study focuses on a model reference adaptive control method that ensures identical orientation outputs for different prototypes of a two-axis gimbal produced in mass production. In this method, unlike traditional MRAC structures, an MRAC structure is used in conjunction with state feedback control. First, the reasons for the need for an adaptation mechanism in gimbals and why Model Reference Adaptive Control (MRAC) alone won't be sufficient have been discussed. In the first section, various applications of MRAC have also been mentioned. Then, the mathematical foundation of the model reference adaptive controller used in this study is elaborately explained, followed by stability analyses. In the next step, an ideal reference model exhibiting desired behavior and a real system model with different dynamics are created in a simulation environment. This allows a comparison of the adaptation capabilities of only MRAC and MRAC+State Feedback controllers. Based on the information gathered in this section, the recommended approach in the article is tested on a real gimbal system, and the results are shared. The obtained results demonstrate that the MRAC+State Feedback control structure significantly reduces the error in the gimbal's orientation response compared to the reference model.
  • Öge
    The investigation of the effect of operating conditions in gearboxes on efficiency
    (Sage Publications, 2024) Kaya, İsmail ; Baykara, Cemal ; https://orcid.org/0000-0002-1933-5316 ; Makina Mühendisliği
    Efficiency is a concept that evaluates the optimal utilization of resources, including time, energy, finances, or materials, in order to accomplish a particular goal or objective. As widely acknowledged, energy losses occur in systems involving relative motion between interacting machine elements due to friction. In the case of a gearbox, these losses can arise from tooth friction in the gear mechanism, friction in sealing elements, friction in roller bearings, and the influence of the lubricant used in the system, all of which are subject to environmental conditions. This study aims to experimentally determine the efficiency of the gearbox under various operating conditions by considering the gearbox as a comprehensive system encompassing all its components. A measurement system was designed in order to obtain the efficiency of a gearbox. Experiments and measurements were carried out via software support. The measurement system contains two torque transducers, electrical resistive load device, an electrical motor with temperature measurement thermocouple, and two stage helical gearbox. In experiments conducted through computer commands, input revolutions were incrementally increased with 400 rpm intervals within the range of 700–2700 rpm. Moreover, experiments were carried out at different lubricant levels in the gearbox. At the same time lubricant temperature was measured and effects to the gearbox efficiency were investigated. Subsequently, different lubricant with distinct viscosity indices were employed. As a result of this experimental design, regime efficiency values were obtained for each case. Thus, power loss of the gearbox system has been determined. These results were examined using a general full factorial design. Analysis of variance (ANOVA) tables were created and the effects of the parameters on the system and the efficiency results were determined by checking whether the parameters were interacting or not. Finally, regression analysis was performed and the regression function was obtained in order to develop a predictive model to estimate the efficiency of a gearbox.
  • Öge
    Experimental test of fault tolerant real time operational modal analysis method by voting algorithm for aircrafts
    (ACM, 2024) Köken, Metin ; Altuğ, Erdinç ; https://orcid.org/0009-0007-9703-0722 ; https://orcid.org/0000-0002-5581-7806 ; Makina Mühendisliği
    Operational modal analysis (OMA) is a key technique to obtain real-time modal parameters (natural frequency, damping ratio, mode shapes) for aircraft. Due to the nature of an aircraft, an extended flight envelope leads to the flexible structures being highly nonlinear and time-variant. For structural health monitoring and real-time flutter test purposes, automated and robust operational modal analysis methods are required. However, each automated OMA method has its own advantages and disadvantages in specific conditions. In this paper, stochastic subspace identification (SSI), autoregressive poly reference (AR PR), Ibrahim time domain (ITD), eigensystem realization algorithm (ERA) and frequency-spatial domain decomposition method (FSDD) operational modal analysis algorithms were investigated on real-time aircraft flight data. Automated versions of these algorithms are used to obtain real-time modal parameters (natural frequency, damping ratio, and mode shapes). Furthermore, the present work focuses on the development of an enhanced method by utilizing each algorithm simultaneously. The enhanced method aims to calculate the real-time modal parameters without the requirement of users to pick physical modes by voting algorithm between the calculated parameters from each method. Each method and enhanced method were tested for flight data and results were verified by ground vibration test (GVT). It is observed that the voting algorithm improves the robustness of the real-time results in different flight conditions when disadvantageous methods in that specific condition are influenced, by compensating with advantageous methods.
  • Öge
    Aerodynamic performance evaluation of a coaxial octocopter based on taguchi method
    (ASME, 2024) Geydirici, Evren ; Derman, Kuzey C. ; Çadırcı, Sertaç ; Makina Mühendisliği
    The design and optimization of propellers for unmanned aerial vehicles (UAVs) are essential for optimal performance and high efficiency. This study presents a numerical investigation of the aerodynamic performance of coaxial octocopters using openfoam as flow solver. While the aerodynamic performance is affected by many parameters, the current study focuses on four main parameters: the propeller type, the horizontal and vertical separation distances between the propellers, and the ratio between the rotational speeds of the upper propeller and the lower one. To find the minimum number of simulations to be performed within defined limits, and reduce the number of computational fluid dynamics (CFD) simulations that cause high computational cost, Taguchi method was employed. In this study, average thrusts were calculated for the preliminary design of the octocopter by examining an isolated single propeller and dual- and quad propellers taking their rotation directions into account. The Taguchi design matrix revealed that for all cases investigated, the propeller type is the most dominant design parameter followed by the velocity ratio of the upper propeller to the lower one (⁠ ⁠) and vertical (z/D) and horizontal (⁠ ⁠) orientation of coaxial propellers. However, it was shown that and z/D may play a significant role in vortex formation and pressure fluctuations which should be considered as design criteria for coaxial octocopters associated with flow attributes. The results showed that the aerodynamic performance parameters are not dependent on all the selected parameters, and demonstrated that the selected propeller designs improved aerodynamic performance.