İstanbul Gedik Üniversitesi Kurumsal Akademik Arşivi
DSpace@Gedik, İstanbul Gedik Üniversitesi 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
Comparison of the mechanical properties and drilling performance of the AISI 316 parts produced with casting, LPBF and WAAM
(Springer Science and Business Media Deutschland GmbH, 2024) Kocaman, Engin; Köklü, Uğur; Morkavuk, Sezer; Coşkun, Mert; Koçar, Oğuz; Dilibal, Savaş; Gürol, Uğur
AISI 316 stainless steel parts are widely utilized in many industrial fields with a vast scope of applications. These steel parts, which are used in many fields, can be produced using different production methods, but the mechanical properties of the parts produced with different processes may be different, and the machinability characteristics will also be different. In this study, the drilling machinability characteristics of AISI 316 stainless steel parts manufactured via cast, LPBF and WAAM methods were experimentally investigated and compared considering thrust force generation, burr analysis and chip morphology. In order to clarify the differences in machinability behavior among the tested samples, the corresponding microstructure, microhardness and mechanical strength (yield strength, UTS and elongation) were also examined in detail. The experimental results showed the manufacturing method, and particularly cooling rate, significantly affecting the microstructure, mechanical response and further machinability characteristics; besides, due to higher cutting forces generation, the machinability of the parts produced by additive manufacturing methods (LPBF and WAAM) is more difficult compared to the parts produced by conventional manufacturing methods (cast and cast-HT).
Mechanical and ballistic performance of high-hardness armor steels welded with ASS-LHF sandwich joint design
(Elsevier Ltd, 2025) Gürol, Uğur; Çelik, Ceren; Çoban, Ozan; Göçmen, Müesser; Koçak, Mustafa
Armor steels are widely recognized for their exceptional mechanical and ballistic performance, particularly in the fabrication of armored vehicles. Austenitic stainless steel (ASS) wires are commonly used in their welding processes to mitigate hydrogen-induced cracking. However, joints formed using ASS often suffer from reduced ballistic performance due to the strength mismatch (undermatching) compared to the base material. This study explores the application of butt joints, integrating low hydrogen ferritic (LHF) deposits between softer ASS weld layers, which can be expressed as sandwich layer design, in gas metal arc welded (GMAW) armor steel plates. The mechanical properties were evaluated through hardness, tensile, and Charpy V-notch impact tests. Ballistics test performances were measured using depth of penetration (DoP) and width of penetration (WoP) values. The microstructural analysis utilized stereo, optical, and scanning electron microscopes. The results demonstrated that the sandwich joint configuration met the Charpy-V impact toughness requirements of the base metal, achieving 31.4 J and 65 J at −40 °C for the WM and HAZ regions, respectively, compared to 20 J for the base material. Moreover, this innovative joint design effectively combined the high toughness and ductility of austenitic wire, reaching a low DoP value of 7.2 mm, with the superior strength of ferritic filler metal, which contributes to a low WoP value of 12.5 mm and a joint efficiency of 48 %. By combining these properties, the joint design significantly enhances ballistic performance in welded regions, traditionally considered vulnerable to ballistic threats, without compromising overall mechanical integrity.
Effect of post-deposition heat treatments on high-temperature wear and corrosion behavior of Inconel 625
(Elsevier Ltd, 2025) Kocaman, Engin; Gürol, Uğur; Günen, Ali; Çam, Gürel
This study uses the arc-directed energy deposition method to fabricate and heat treatment of a Ni-based Inconel 625 wall structure. Heat treatment involved solution treatment at 980°C with and without aging at 720°C, comparing results to the as-built condition. The effects of these heat treatments were analyzed through microstructural investigations, nanoindentation tests, and high-temperature wear and corrosion tests in 0.5 M NaCl and 0.5 M HCl solutions. In the as-built state, the Inconel 625 alloy exhibited a columnar dendritic structure predominantly composed of a gamma matrix along with Laves phase and MC carbides. Solution treatment dissolved the Nb-rich Laves phases and encouraged the formation of needle-like particles in regions with high Nb segregation, while also reducing voids and minimizing corrosion susceptibility along grain boundaries. This resulted in the formation of a uniform oxide layer on the surface, significantly enhancing wear and corrosion resistance. Both heat-treated samples showed improvements in mechanical ratios such as H/E, H³/E², and H²/2E in the WAAM-produced Inconel 625 alloy, resulting in a 67 % enhancement in wear resistance compared to the as-built sample. Corrosion tests also revealed that solution treated samples showed the highest corrosion resistance, followed by aged treatment and as-built samples, respectively. In conclusion, this study provides a thorough understanding of the substantial impact of heat treatments on the microstructure, mechanical properties, and corrosion resistance of Inconel 625, offering valuable insights for advancements in the field.
Design today save future
(Istanbul Gedik University, 2019) Yahya, Noorhana; Pereira, Carlos Mourão; Canci Matur, Utku; Özbudak, Özgün; Önal, Feride; Tolon, Mart; Karabuga, Arif
Along with the development of technology, industrialization and rapid population growth have increased the energy demand. The awareness of the energy crisis has led researchers to search for new solutions and use new technologies in this area. Renewable energy has an extremely important place in energy requirement of the countries with domestic resources, reducing the external dependency, diversifying the resources and ensuring sustainable energy usage and minimizing the damages to the environment as a result of energy consumption. Today, around 20 percent of the world’s consumed energy is supply from renewable sources. Despite the high level of dependence on fossil fuels in the current situation, the use of renewable energy has been increasing steadily over the years. The conventional energy sources that already supply most of the energy demand. However, it is estimated that fossil fuels, especially petroleum, will be consumed in the next 200-300 years. In order to be able to produce solutions for this situation, it is necessary to carry out many research/development and production/development projects related to both conventional energy sources and alternative energy sources.
Innovative surface improvement of GFRC using hydrothermally produced Ch-TiO2-CuO nanohybrid composite additives
(Elsevier Ltd, 2024) Ramazanoğlu, Doğu; Subaşı, Serkan; Maraşlı, Muhammed
This study examines the impact of the Ch-TiO2-CuO nanohybrid composite on the surface properties and antimicrobial effects of Glass fiber-reinforced concrete (GFRC) panels. GFRC panels are known for their durability and aesthetic compatibility, making them suitable for exterior facades and historic restoration work. However, their porosity and hydrophilic nature make them susceptible to microbial colonization, affecting their durability and visual appeal. To address this, antimicrobial nanohybrid crystals (Ch-TiO2-CuO) were developed using a hydrothermal method and incorporated into GFRC panels. This integration offers significant advantages, including reduced maintenance, long-term structural integrity, and preserved aesthetic properties. Additionally, this approach aligns with sustainability goals by enhancing the environmental friendliness of GFRC over its lifetime. The study concludes that incorporating antimicrobial agents into GFRC production supports smart city initiatives by providing long-term protection against microbial degradation while maintaining aesthetic standards, thus contributing to cleaner, safer urban environments.
