İstanbul Sağlık ve Teknoloji Üniversitesi Kurumsal Akademik Arşivi
DSpace@İSTÜN, Üniversite mensupları tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Localization of a high strength and vibration resistant fastening element for the defense industry
(Liberty Academic Publishers, 2026) Demirel, Yusuf Soner; Şentürk, İsmail Hakkı; Tanrıver, Kürşat; Ay, Mustafa; Şahin, Ethem İlhan
In the modern defense and aerospace industry, maintaining the structural integrity of air platforms and optimizing their operational life cycles are directly dependent on the high-precision domestic production of critical components. The indigenization of strategic parts not only minimizes foreign dependency but also ensures supply chain security against embargo risks and international logistical disruptions. This study comprehensively addresses the localization and technical validation processes of a specialized structural pin, which serves as a primary fastener in aerospace structures, aircraft wings, and missile systems, characterized by high strength and vibration damping capabilities. Within the scope of the research, Al 7075-T6 aluminium alloy, a premium material in aerospace standards known for its superior strength-to-weight ratio, was selected as the raw material. During the manufacturing phase, "Swiss-Type Lathe" (Sliding Headstock) technology was utilized to provide high dimensional stability in tight-tolerance geometries, and samples underwent heat treatment processes in accordance with aerospace norms. The mechanical performances of the manufactured specimens were subjected to static and dynamic tests within the framework of internationally recognized NASM1312 standards. In the design validation phase, non-linear static Finite Element Analysis (FEA) was performed using ANSYS software. In these numerical simulation processes, based on experimental data obtained from physical testing equipment, displacement values of 0.55 mm for tensile analysis and 0.23 mm for double shear analysis were defined as boundary conditions in the system. When the numerical analysis results were compared with the experimental data obtained from production samples, a high-correlation alignment was determined with an acceptable deviation of approximately 5%. The fact that both tensile and double shear strength values exceeded the minimum limits specified by the standards, and that the physical fracture lines perfectly overlapped with the plastic deformation zones in the simulation model, proves the reliable applicability of domestic production in critical defense systems with concrete and scientific data.
Fixture design for high-strength fasteners and the effect of surface clearance on test results
(Liberty Publishing House, 2026) Demirel, Yusuf Soner; Acar, Ayberk Okan; Tanrıver, Kürşat; Ay, Mustafa; Sinha, Thuna
In this study, the effects of fixture designs and surface clearance tolerances on test results were investigated for the shear performance of high-strength fasteners, such as 7075-T6 aluminum, which are of critical importance in aerospace assemblies. With reference to ISO 8749 (maximum clearance of 0.15 mm) and NASM 1312-13 (maximum clearance of 0.0125 mm), the performance of compression-type and tension-type fixtures was comparatively evaluated using the Finite Element Method. The analyses were conducted in ANSYS 2025, employing mesh sizes of 0.6 mm for the pin, 0.8 mm for the hole surfaces, and 0.05 mm for the shear region. For fixture material selection, AISI 4140, Toolox 40, and AISI 4340 steels were assessed; AISI 4140 was found to be sufficient to meet the target yield strength criterion of 1.5 times the tensile strength of 7075-T6 aluminum. According to the simulation results, undesired stress levels on the order of 500 MPa were observed on surfaces outside the shear plane in the tension-type fixture. Consequently, the compression-type fixture, which concentrates stresses more effectively on the shear plane, was preferred. To examine the effect of tolerance between the fixture walls, analyses were performed for clearance scenarios of 0.3 mm and 0.025 mm. For these two clearance values, the maximum von Mises stresses were calculated as 641 MPa and 643 MPa, respectively, while the maximum shear stresses were 370.42 MPa and 370.95 MPa. These results, obtained for an 8 × 28 mm pin geometry, indicate that tolerance tightness does not lead to a statistically significant difference in stress outcomes. Consequently, it was concluded that ISO-compliant designs with relatively looser tolerances can be employed to reduce manufacturing costs without compromising test reliability.
Weapon pylon structure topology optimization and stress comparison
(Liberty Publishing House, 2026) Akın, Furkan; Ay, Mustafa; Tanrıver, Kürşat; Sinha, Tuhina
This study focuses on the structural optimization of an aircraft weapon pylon by topology optimization techniques under realistic operational loading conditions. Weapon pylons are critical load bearing components that enable aircraft to carry external stores such as missiles, fuel tanks, and sensor pods. Due to their function, these structures are exposed to complex combinations of aerodynamic forces, inertial loads, and operational stresses, which can significantly influence both flight safety and overall aircraft performance. Therefore, achieving an optimal balance between structural strength and weight reduction is a key design objective in aerospace applications. In this research, multiple load cases representing different flight conditions were defined in accordance with commonly accepted military and aerospace design standards to ensure realistic boundary conditions. The baseline weapon pylon geometry was modeled and analyzed using finite element methods to identify stress distributions and critical regions. Aluminum alloy was selected as the structural material due to its high strength-to-weight ratio, good fatigue performance, and widespread use in aerospace structures. Topology optimization was performed with different mass fraction constraints, specifically 0.4, 0.5, and 0.6, resulting in three optimized design configurations with varying material distributions. The optimized density layouts were subsequently interpreted and transformed into manufacturable solid geometries while preserving the main load paths identified during the optimization process. These redesigned models were then subjected to detailed stress analyses to evaluate their structural performance and to compare them with the original, non-optimized configuration. The results highlights the trade-off between lightweight design and structural durability in weapon pylon structures. Overall, this work presents a practical and systematic methodology for integrating topology optimization with numerical validation, contributing to the development of more efficient and reliable aerospace structural components.
An integrated machine learning and optimization approach for enhanced strength prediction in riveted joints
(Obuda University, 2026) Tanrıver, Kürşat; Ay, Mustafa
In this study, experimental tests, finite element analysis, and machine learning techniques were integrated to predict the maximum shear stress of riveted joints. First, ten tensile tests were conducted, yielding an average stress of 76.0383 MPa on the plates, and the regression analysis of the stress–strain data demonstrated a 95-99% level of agreement. A finite element analysis performed in Ansys under conditions similar to the experiments, produced a result of 78.875 MPa, which falls within an error margin consistent with the literature. Subsequently, a dataset of 20 samples containing various rivet diameters, plate thicknesses, hole coordinates and tensile loads was generated and used, to train a Regression Decision Tree model in MATLAB. For a new design case, the model predicted 7.480 MPa instead of 7.291 MPa, corresponding to an error of approximately 2.50%. When the dataset was expanded to 50 samples, this deviation decreased to 0.82%, indicating a significant improvement in accuracy. Overall, the results demonstrate that the machine learning model rapidly improves, as additional data become available and can provide reliable, fast predictions, including the effects of bending moments, offering a promising approach that may reduce the need for extensive experimental and numerical analyses.
Ketamine induces apoptosis and inhibits proliferation in HT-29 colorectal cancer cells
(MDPI Publishing, 2026) Korkmaz, Irmak Fatoş; Elgün, Tuğba; Aktaş, Çiğdem; Gündeğer, Ersin; Gök Yurttaş, Asiye
Background: Colorectal cancer (CRC) is one of the most prevalent malignancies worldwide and remains a major health concern due to its high recurrence and mortality rates. Recent studies suggest that anesthetic agents, including ketamine, may have direct effects on cancer cell viability and apoptosis. Objective: This study aimed to investigate the in vitro effects of ketamine on the HT-29 human colorectal adenocarcinoma cell line, focusing on its cytotoxic and pro-apoptotic potential. Material and Methods: HT-29 cells were treated with ketamine for 24 h. Cell viability was evaluated using the MTT assay. Apoptosis rates were determined by flow cytometry with Annexin V-FITC/7-AAD staining. Furthermore, quantitative PCR (qPCR) was performed to assess the expression levels of key genes associated with proliferation and apoptosis. GeneQuery™ Human Basal Cell Carcinoma qPCR Array Kit (GQH-BCC-GK015-C) was used for qPCR analysıs. Molecular docking simulations were performed to investigate the potential molecular interactions between ketamine and three target proteins: the N-methyl-D-aspartate (NMDA) receptor, epidermal growth factor receptor (EGFR), and casein kinase 1 delta (CSNK1D). To ensure robustness of predictions, two independent docking methods were employed. Results: Ketamine significantly reduced cell viability in a dose-dependent manner, with an IC50 value of approximately 1.05 µM. Flow cytometry analysis demonstrated a marked increase in early apoptosis (23.9%) in treated cells. These findings suggest that ketamine exhibits potential anti-proliferative and pro-apoptotic effects on HT-29 colorectal cancer cells. Conclusions: These findings suggest that ketamine exhibits potential anti-proliferative and pro-apoptotic effects on HT-29 colorectal cancer cells in vitro. Further studies are warranted to elucidate the underlying molecular mechanisms and potential clinical implications.
