WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 1Citation - Scopus: 1Evaluating the Effects of Design and Manufacturing Parameters on Friction at the Surrogate Skin-3D Textile Interface(Sage Publications Ltd, 2025-10-30) Temel-Cicek, Mevra; Cicek, Umur I.; Lloyd, Alex B.; Johnson, Andrew A.Additive manufacturing (AM) is increasingly employed in the development of 3D-printed wearables, including medical wrist supports, textiles, and protective garments. While the general tribological behavior of 3D-printed components has been widely studied, limited research has focused on the friction behavior of 3D-printed wearables when in contact with human skin, which is a crucial factor for improving wearer comfort by minimizing local skin friction. This study, therefore, investigates the influence of material type, manufacturing technology, and print parameters of 3D-printed textiles on frictional behavior against skin. Specimens were fabricated using three AM technologies: material extrusion (MEX), vat photopolymerization (VATP), and powder bed fusion (PBF). Each technology employed various materials and print parameters, specifically layer thickness (ranging from 0.05 to 0.3 mm) and print orientations (horizontal and vertical). Friction was measured using a custom-built handheld device at the interface between 3D-printed specimens and two surrogate skin models: lorica (representing the dorsal forearm) and silicone (representing the chest). The results revealed that friction was significantly influenced by both layer thickness and print orientation. For MEX specimens, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, and polycarbonate showed the highest friction, while for VATP, durable resin resulted in the highest friction coefficient. In contrast, PBF specimens exhibited very similar frictional behavior. Regarding layer thickness, higher values consistently resulted in the highest friction coefficients, regardless of manufacturing method or material type. These findings provide valuable insights for designers and engineers seeking to optimize the comfort of 3D-printed wearables, guiding the selection of suitable AM processes and parameters for products intended for direct skin contact.Article Failure Analysis of Fused Deposition Modeling 3D Printed Poly Lactic Acid Polymer(Sage Publications Ltd, 2025-10-04) Yilmaz, Cagatay; Eltahir, Sara Saeed AbdulrahmanAdditive manufacturing, commonly known as 3D printing (AM), has emerged as one of the most transformative technological advances in the last few decades in global manufacturing, as it allows for the production of intricate components without the use of costly molds. Fused Deposition Modeling (FDM) is widely adopted among various AM techniques due to its accessibility and effectiveness. FDM 3D-printed PLA (Poly Lactic Acid) shows a transversely isotopic symmetry similar to laminated composite structures. Therefore, classical lamination theory can be applied to FDM 3D-printed PLA. This study attempts to expand the knowledge by relying on classical lamination theory and several imposed failure theories like maximum stress, Tsai-Hill, Tsai-Wu, and Hashin to determine how FDM 3D printing of PLA fails. We investigate eight different raster orientations (0 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees) and compare the theoretical prediction of strength with experimental findings. With this comprehensive analysis, we are seeking to better understand the failure analysis of FDM 3D printed PLA. The maximum stress, Tsai-Wu, Tsai-Hill, and Hashin failure theories show good agreement with experimental findings for 0 degrees and 90 degrees raster orientations. As the raster orientation shifts from 0 degrees, the discrepancy between experimental results and theoretical predictions increases, peaks at mid-angles, and then decreases, becoming negligible at 90 degrees.Article Citation - WoS: 5Citation - Scopus: 10Three Dimensional Patient-Specific Guides for Guide Pin Positioning in Reverse Shoulder Arthroplasty: An Experimental Study on Different Glenoid Types(Sage Publications Ltd, 2022-01) Sadeghi, Majid Mohammad; Kececi, Emin Faruk; Kapicioglu, Mehmet; Aralasmak, Ayse; Tezgel, Okan; Basaran, Murat Alper; Bilsel, Kerem; Mohammad Sadeghi, MajidIntroduction Incorrect positioning is one of the main factors for glenoid component loosening in reverse shoulder arthroplasty and component placement can be challenging. This study aimed to assess whether Patient-Specific Instrumentation (PSI) provides better guide pin positioning accuracy and is superior to standard guided and freehand instrumentation methods in cases of glenoid bone deformity. Materials and Methods Based on the Walch classification, five different scapula types were acquired by computed tomography (CT). For each type, two different surgeons placed a guide pin into the scapula using three different methods: freehand method, conventional non-patient-specific guide, and PSI guide. Each method was repeated five times by both surgeons. In these experiments, a total of 150 samples of scapula models were used (5 x 2 x 3 x 5 = 150). Post-operative CT scans of the samples with the guide pin were digitally assessed and the accuracy of the pin placement was determined by comparison to the preoperative planning on a three-dimensional (3D) model. Results The PSI method showed accuracies to the preoperative plan of 2.68 (SD 2.10) degrees for version angle (p < .05), 2.59 (SD 2.68) degrees for inclination angle (p < .05), and 1.55 (SD 1.26) mm for entry point offset (p < .05). The mean and standard deviation errors compared to planned values of version angle, inclination angle, and entry point offset were statistically significant for the PSI method for the type C defected glenoid and non-arthritic glenoid. Conclusion Using the PSI guide created by an image processing software tool for guide pin positioning showed advantages in glenoid component positioning over other methods, for defected and intact glenoid types, but correlation with clinical outcomes should be examined.Article Citation - WoS: 7Citation - Scopus: 11Robust Estimator-Based Optimal Control Designs for U-Tube Steam Generators(Sage Publications Ltd, 2014-05-19) Ablay, Gunyaz; Hamamci, SerdarU-tube steam generator level control systems are used to maintain the water level within prescribed narrow limits and to provide constant supply of high-quality steam during power demand variations. Traditional level control systems are often found to be unsatisfactory during low power operations and start-up conditions. Robust non-linear estimator-based optimal control systems are proposed for steam generator level control systems to solve the water level tracking problem during power (or steam) demand variations. It is shown that the proposed control strategies provide optimal and robust water level tracking with a single controller over the complete range of power operation with model and parameter uncertainties and noisy measurements.Article Citation - WoS: 5Citation - Scopus: 5Large Transformations With Moderate Strains of Tensile Membrane Structures(Sage Publications Ltd, 2016-04-28) Beatini, Valentina; Carfagni, Gianni Royer; Royer Carfagni, GianniUsing a classical non-linear theory, we analytically investigate possible ways for transforming the shape of a curved elastic membrane while keeping it tensioned and moderately strained. This is a critical issue because, as a rule, membranes must be considerably stretched in order to avoid wrinkling and slackening. If the final configuration is fixed, the membrane can be cut and formed according to the final shape, but this cannot be done if more configurations, considerably distant from one another, have to be achieved. Nevertheless, we propose large transformation movements that can be obtained starting from flat membranes while maintaining their strain as limited. We discuss in detail the paradigmatic example of the hyperbolic-paraboloid-shaped membrane. These opportunities are suitable for applications of transformable architecture because they do not require excessive tensioning, compatible with the strength of materials used for this kind of structures.Article Citation - WoS: 3Citation - Scopus: 3Investigations of Strain Rate, Size, and Crack Length Effects on the Mechanical Response of Polycaprolactone Electrospun Membranes(Sage Publications Ltd, 2021-06-18) Bayram, Ferdi C.; Kapci, Mehmet F.; Yuruk, Adile; Isoglu, Ismail A.; Bal, BurakThe effects of strain rate, size (height x width), and pre-existing crack length on the mechanical response of polycaprolactone electrospun membranes were investigated by tension tests conducted at room temperature. In particular, tensile tests were performed with three different strain rates for strain rate effect tests, seven different geometries for elucidating the size effect, and three different initial notch lengths for crack growth experiments. The electrospun membranes were produced by the electrospinning technique using a polycaprolactone solution prepared in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol as the solvent. Scanning electron microscopy was utilized to show the continuous fiber structure without bead formation. The average fiber diameter was calculated as 1.113 +/- 0.270 mu m by using scanning electron microscopy images of the membranes. The chemical structure of polycaprolactone was analyzed by Fourier transform infrared spectroscopy, and the toxicity and cell viability of the electrospun membranes were shown by CellTiter 96(R) Aqueous One Solution Cell Proliferation Assay (MTS test). It was observed that the ultimate tensile strength and Young's modulus decreased, and the elongation at failure value increased as the strain rate decreased from 10(-1) to 10(-3) s(-1). Besides, positive strain rate sensitivity was observed on the mechanical response of electrospun polycaprolactone membranes. Moreover, the dependency of mechanical response on the size geometry has been well studied, and the optimum height and width combinations were specified. Also, crack growth was studied in terms of both macroscopic and microstructural deformation mechanisms and it is observed that individual fiber deformations and interactions are highly effective on the mechanical behavior and also propagation of the crack. Consequently, in this study, the size and strain rate effects and crack growth on the mechanical response of electrospun polycaprolactone membranes have been investigated extensively, and the results presented herein constitute an essential guideline for the usage of polycaprolactone electrospun membranes at different loading scenarios.Article Citation - WoS: 3Citation - Scopus: 5Feedback Controller Designs for an Electromagnetic Micromanipulator(Sage Publications Ltd, 2019-09-09) Boyuk, Mustafa; Eroglu, Yakup; Ablay, Gunyaz; Icoz, KutayMagnetic micromanipulators are capable of generating wide range of magnetic forces to manipulate magnetic microparticles for biomedical applications. In this study, a multipole magnetic micromanipulator system including electromagnets, driver circuitry and control unit is designed, modeled and implemented. The micromanipulator can produce a broad range of magnetic forces up to 25 pN on a single magnetic microparticle (1-10 mu m diameter) that is 5 mm away from the electromagnet core tip. Both linear and nonlinear controllers are designed and implemented, and the proposed nonlinear controller produces smooth control currents to assure closed-loop stability of the system with 1 s non-overshoot transient response and zero steady-state tracking error. The maximum output current of the driver circuitry is set to 1 A. The single particle at the center is moved at a speed of 5 mm/s. The fully automatic system can be utilized in applications related to single cell or microparticle manipulations.Article Citation - WoS: 15Citation - Scopus: 14Effects of Silver Nanowires and Their Surface Modification on Electromagnetic Interference, Transport and Mechanical Properties of an Aerospace Grade Epoxy(Sage Publications Ltd, 2024-03-03) Ozkutlu Demirel, Merve; Ozturkmen, Mahide B.; Savas, Muzeyyen; Mutlugun, Evren; Erdem, Talha; Oz, YahyaThe aerospace industry has progressively grown its use of composites. Electrically conductive nanocomposites are among important modern materials for this sector. We report on a bulk composite containing silver nanowires (AgNW) and an aerospace grade epoxy for use in carbon fiber reinforced polymers (CFRPs). AgNWs' surfaces were also modified to enhance their ability to be dispersed in epoxy. Composites were obtained by use of three-roll milling which is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for aerospace grade resins with high curing temperatures. Our main objective is to improve the electromagnetic interference (EMI) shielding performance of CFRPs via improving the properties of the resin material. The addition of AgNWs did not considerably alter the flexural strength of the epoxy, however the composite with surface-modified AgNWs has a 46 % higher flexural strength. Adding AgNWs over a low threshold concentration of 0.05 wt% significantly enhanced the electrical conductivity. Conductivities above the percolation threshold lie around 102 S/m. At a concentration of 5 wt% AgNW, the EMI shielding efficiency (SE) of epoxy increased from 3.49 to 12.31 dB. Moreover, the thermal stability of the epoxy was unaffected by AgNWs. As a result, it was discovered that (surface modified) AgNWs improved the (multifunctional) capabilities of the aerospace grade epoxy resin which might be used in CFRPs to further enhance properties of composites parts, demonstrating suitability of AgNWs' as a reinforcement material in aerospace applications.Article Citation - WoS: 4Citation - Scopus: 5Effect of Pre-Rolling Temperature on the Interfacial Properties and Formability of Steel-Steel Bilayer Sheet in Single Point Incremental Forming(Sage Publications Ltd, 2020-10-14) Hassan, Malik; Hussain, Ghulam; Ali, Aaqib; Ilyas, Muhammad; Malik, Sohail; Khan, Wasim A.; Bal, BurakThe aim of this research was to investigate the effect of pre-rolling temperature on the interfacial properties in delamination modes 1 and 2; and formability in Single Point Incremental Forming (SPIF) of Steel-Steel (St-St) bilayer sheet prepared by roll bonding process. The roll bonding process was performed at three pre-rolling temperatures, 700 degrees C, 800 degrees C, and 950 degrees C, with a constant thickness reduction ratio of 58%. The bond strength and critical strain energy release rate (CSERR) were measured to characterize the interface of St-St bilayer sheet. T-peel test for mode 1 and tensile shear test for mode 2 were conducted to determine the interfacial properties. The formability of St-St bilayer sheet in SPIF was measured in terms of maximum wall angle. The results showed that the increase in pre-rolling temperature from 700 degrees C to 950 degrees C enhanced the bond strength and CSERR, in both mode 1 and 2. The enhancement in bond strength with an increase in pre-rolling temperature was 149.5% and 203% in mode 1 and 2, respectively. However, the increase in CSERR in mode 1 and 2 was 115% and 367%, respectively. The formability of St-St bilayer sheet also showed an increasing trend with an increase in pre-rolling temperature. Moreover, a consistent relation between formability and interfacial parameters was observed. It was also found that to successively deform the bilayer sheet into the desired shape, it is necessary for the sheet to be heated above the critical temperature during fabrication to facilitate good bonding between two sheets.Article Citation - WoS: 1Citation - Scopus: 2Effect of Multi-Cell Approach on Crashworthiness Performance of 3D-Printed Thin-Walled Structures Under Lateral Compression Loading for Unmanned Aerial Vehicle Applications(Sage Publications Ltd, 2025-06-02) Atahan, M. Gokhan; Zeybek, Halil; Gokhan Atahan, M.Recent technological advancements in unmanned aerial vehicles have led to their use in various military and civilian applications. However, weather conditions, operator faults, and electronic or mechanical problems can result in unmanned aerial vehicle accidents. In the event of an accident, energy-absorbing structures can be placed in specific regions of vehicles to protect sensitive and costly cameras, sensors, and cargo from damage, while also preserving the vehicle's structural integrity. In this study, thin-walled energy absorbers with circular, square, hexagonal, and reentrant geometries were proposed, and the experimental investigation focused on the effect of increasing the number of cells on their crashworthiness performance and deformation mechanisms. Lateral compressive load was applied to thin-walled structures produced by fused deposition modeling technology using advanced polylactic acid filament. Experimental results showed that the triple-cell reentrant thin-walled structure demonstrated promising results for unmanned aerial vehicle applications, as it exhibited the highest mean crushing force, energy absorption, and specific energy absorption values. Thanks to the unique geometry of the reentrant structure, a gradual collapse mode was observed, and as a result, the triple-cell reentrant structure exhibited high energy absorption performance.