Department of Modeling and Design Engineering Systems
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Browsing Department of Modeling and Design Engineering Systems by Subject "metallurgical and materials engineering"
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Item A STUDY ON THE WIRE ARC ADDITIVE MANUFACTURING OF DUPLEX STAINLESS STEEL PLATES: OPTIMIZATION OF PROCESS PARAMETERS AND INVESTIGATION OF MECHANICAL PROPERTIES(2022-03-01) SAADAWI, HASSAN; Konca, Erkan; Tur, KâzımIn recent years, additive manufacturing (AM) for metals, which is used to create products using layer-by-layer deposition of materials, has been a subject of interest as a means of enhancing the efficiency of manufacturing processes in various industries. In this thesis, super duplex stainless steel parts have been wire arc additively manufactured (WAAM) using the cold metal transfer welding technique. To obtain the optimum combination of additive manufacturing parameters (voltage, current and speed) that yields the desired bead quality, response surface method has been used to build statistical models based on numerical simulation of additive welding process. COMSOL Multiphysics 5.5 software has been used to perform the experimental instead of real process and Expert-Design software was used to obtain the statistical models. The optimal values of the controlled variables were found as 200 amperes and 15 volts for current and voltage, and 10 mm/s for welding speed. Then, the fracture toughness tests using the single edge notched tension (SENT) specimens were implemented at a sub-zero temperature. Fracture toughness data has been used to establish crack-growth resistance curves for both, as-received rolled plate and additively manufactured parts and compare the results based on J-integral (energy release rate). The J-integral value at the initiation of stable crack growth (Ji) of SDSS Grade 2507 as-received plate specimens is approximately 17% higher than the (Ji) value of WAAM’d DSS Grade 2209 and 31% higher than the (Ji) value of WAAM’d SDSS Grade 2509.Item PROCESS DESIGN OPTIMIZATION FOR THE POST-WELD CONTROLLED ACCELERATED COOLING OF R350HT HEAD HARDENED RAIL JOINTS(2022-02-21) Ramadan, Nizar; TUR, Kazım; KONCA, ErkanIn order to benefit fully from the use of head hardened rails, the weld and the heat affected zones of these rails must have microstructures with mechanical properties similar to those produced by the fine pearlitic microstructures of the rails themselves. For the flash butt welding of head hardened rails, this is only possible through the accelerated controlled cooling of the related zones just after the welding operation. In this study, the required method and the conditions for the controlled accelerated cooling of flash butt welded head hardened R350HT rails have been investigated. Dilatometer experiments were performed on R350HT rail steel samples in order to determine the heat treatment conditions to produce microstructures that would give the hardness values required by the related rail and rail welding standards. A computer simulation study was undertaken to improve the design of the apparatus to be used for the accelerated cooling of the rail welds. A custom accelerated cooling system that employs this specially designed apparatus was used on flash butt welded R350HT rail joints of the 60E1 profile and results satisfying the related EN 14587-2 standard were obtained. For the aluminothermite welding of the head hardened rails, it was shown that the related EN 14730 standard could be met through the use of the proper weld portion.