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    Assessment of Combinability of S235JR-S460MC Structural Steels on Fatigue Performance
    (Springer India, 2024) Yilmaz, Ahmet Fatih
    In this study, using flux cored wire, S235JR and S460MC structural steels with a thickness of 16 mm were joined by MAG welding method. Welding processes were carried out to join the same (S235JR-S235JR, S460MC-S460MC) and different types of materials (S235JR-S460MC). In the microstructure examinations, grain coarsening occurred in all conditions, from the base material to the weld metal. From the tensile test results, in all combinations, fracture occurred on the S235JR side. Since fractures are not from the weld zone (weld nugget and HAZ), the weld zone strengths are clearly understood to be higher than the main material tensile strengths. On microhardness tests, the highest microhardness was obtained from the welded metal in all combinations, followed by HAZ and base material. Also, the highest microhardness measured on dissimilar joints of S235JR-S460MC on weld metal was 269 HV (Vickers). The welded specimens were also subjected to fatigue tests; the failure occurred on the base material in all three joints. S460MC-S460MC joint had the highest fatigue strength at the most elevated stress, 625 MPa; however, S235JR-S235JR joint had the lowest fatigue strength at the lowest priority, 300 MPa. Although the fatigue strength results of the same and different combinations and the tensile test results have parallelism, the highest microhardness is seen in S460MC-S235JR dissimilar joints, and its fatigue strength is lower than S460MC-S460MC joints.
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    Finite Element Simulation of a Mercantile Vessel Shipboard Under Working Conditions
    (Elsevier Science Bv, 2014) Ertas, Ahmet H.; Alkan, Veysel; Yilmaz, Ahmet Fatih
    Despite the availability of other transport methods such as land and air, marine transportation is the most preferred and widely used transportation method in the world because of its economical advantages. Due to the economical advantages, ship based studies have gained importance especially in recent years. In order to design safe, ergonomic and at the same time economic ships or vessels, both numerical and experimental methods have to be taken into account. Large-scale structural modeling like the cases in ships, on the other hand, typically relies on Finite Element Analysis (FEA) techniques. With the widespread use of Finite Element Methods (FEM) in the field of Computer Aided Design (CAD) engineering, it is possible to increase the strength of a mercantile vessel shipboard. As a consequence, in this study, the strength of a mercantile vessel shipboard has been investigated under working conditions by using ANSYS package program. The results of this study can provide the designer with some guidelines in designing shipboard of mercantile vessels. (C) 2014 The Authors. Published by Elsevier Ltd.
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    Investigation of Mechanical Strength and Distortion in Submerged Arc Welding of AH36 Ship Steel Plate
    (Soc Naval Architects Marine Engineers, 2017) Yilmaz, Ahmet Fatih; Gunay, Mustafa
    A lot of research has been conducted on welding techniques and appropriate materials to reduce manufacturing time and costs without compromising on desired mechanical properties in shipbuilding. One of them is about reducing dimensional shrinkage after welding process. Shipbuilders achieve this phenomenon by applying overall redundancy of the mismatch between the design and dimension of plates which is formed due to the welding shrinkage during joining of two parts. This situation adds significantly to the material cost when the entire ship is considered. Therefore, it is important to study the stability of welding parameters to achieve a high-quality welding. In this study, welding strength and distortion have been investigated for AH36 ship steel plate joined by submerged arc welding method. In this context, 18 experiments have been conducted using two different gap sizes, with ceramic back plate and double-sided welded without ceramic under the same welding groove, and also different welding methods, currents, welding speeds, and voltages. All welding grooves of samples were prepared as 45 degrees V type after computer numerical control (CNC) cutting. Specimens for mechanical tests were cut with abrasive waterjet cutting technique in order not to affect the weld metal and heat-affected zone. According to tensile test results, fractures in all specimens occurred outside the welding zone of the base metal. It was concluded that double-sided welding method increases the welding strength.