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    Effect of boric acid addition to seawater on wear and corrosion properties of ultrashort physical vapor deposited Ti layer on a 304 stainless steel
    (Walter De Gruyter Gmbh, 2023) Karabeyoglu, Sencer Sureyya; Eker, Bulent; Yaman, Pasa; Eksi, Olcay
    AISI 304 stainless steel specimens are deposited with Ti using physical vapor deposition method for 3, 5, and 8 min. Then, specimens are subjected to wear test with 10 and 20 N applied loads in seawater and boric acid reinforced seawater. Optical microscope and scanning electron investigations showed that ultrashort PVD process formed non-uniform Ti deposit zones on the substrate. Abrasive wear mechanism is observed for 10 N applied load and increasing the applied load to 20 N transformed the wear into adhesive which is attributed to counteract dynamic reaction of the surface. Besides, boric acid addition to seawater lowered the wear rate and coefficient of friction for all tests and stick-slip phenomenon is removed in boric acid addition. In corrosion properties, boric acid addition improved the corrosion resistance of the specimens.
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    Experimental and numerical study on the thermoforming process of amorphous thermoplastic polymers
    (Carl Hanser Verlag, 2019) Eksi, Olcay; Karabeyoğlu, Sencer Süreyya; Çınar, Kenan
    Thickness distribution has an important impact on the quality of thermoformed products. It has significant effects not only on durability but also on the oxygen and gas transmission rate of thermoformed packaging products. In this study, acrylonitrile butadiene styrene and polystyrene sheets were thermoformed using a lab scale thermoforming machine. Three different mold shapes were considered: conical, spherical and cylindrical. The thickness distribution of thermoformed acrylonitrile butadiene styrene and polystyrene samples for each mold was investigated based on geometric element analysis (GEA) and finite element analysis (FEA). Finite element analysis yielded more accurate results than geometric element analysis. Process parameters such as temperature distribution on the sheets before mol ding, have a crucial effect on thickness distribution for all configurations.
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    Prediction of Wall Thickness Distribution in Simple Thermoforming Moulds
    (Assoc Mechanical Engineers Technicians Slovenia, 2014) Erdoğan, Ertuğrul Selçuk; Eksi, Olcay
    Thermoforming is widely used in manufacturing industries to produce large and labour-intensive products. Compared to other manufacturing techniques, thermoforming is an extremely efficient process that is suitable for high-efficiency mass production. In this paper, experimental thermoforming operations were carried out using a lab-scale, sheet-fed thermo former. Carbon fibre-reinforced PP and unreinforced PS thermoplastic sheets were used in experimental thermoforming operations. The processing parameters were determined for each thermoformed material. Furthermore, a simulation of the thermoforming process was performed using LS-Dyna (TM) software. The thickness distributions obtained from the experiments were compared with the simulation results. The results show that the parameter that most affects the wall thickness distribution is the geometry of the clamping ring. To produce thermoformed products that have a more uniform thickness distribution, the clamping tool geometry must be selected according to the geometry of the product being thermoformed.
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    Thermoforming behavior of 3D-printed PLA sheets
    (Carl Hanser Verlag, 2020) Eksi, Olcay; Karabeyoğlu, Sencer Süreyya; Çınar, Kenan; Muhurcu, Aydin
    Fused deposition modeling is one of the most well-known additive manufacturing methods. It might be considered the easiest way to produce particle reinforced composites or unreinforced sheets which are biodegradable and used in the packaging industry as well as for custom products. In this study, polylactic acid (PLA) sheets were produced by 3D printing and thermoformed using a lab-scale thermoforming machine. This article aims to determine the deformation behavior of 3d printed PLA sheets during thermoforming. In addition to experimental work, finite element analysis was performed to investigate the prediction capabilities of Mooney-Rivlin and Ogden models for PLA sheets. In addition, the initial thickness of the sheet was optimized using PEA and a python script to obtain final uniform thickness distribution. Thanks to 3D printing's capability for printing sheets of variable thickness, sheets of variable thickness were printed to verify the material models. As a result, based on the thickness distribution obtained from the experimental study, Mooney-Rivlin and Odgen material models were found to be inadequate for representing the actual deformation behavior of PLA sheets.