Browsing by Author "Akar, Samet"
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Item AN INVESTIGATIONS INTO THE MICRO WIRE ELECTRICAL DISCHARGE MACHINING OF SHAPE MEMORY ALLOY(2022-01-26) Meshri, Hassan Ali; Akar, Samet; Kılıç, Sadık EnginRecently, the use of nitinol as a shape memory alloy (SMA) has become significant in vital industries, such as the medical and aerospace industries, due to its distinctive characteristics of pseudoelasticity and shape memory effect. Due to its high hardness, high fracture toughness, strain hardening and issued such as rapid tool wear the use of conventional machining processes has become difficult when producing complex shapes from nitinol. Therefore, non traditional machining processes, especially wire electro-discharge machining (WEDM) has become the dominant method of machining nitinol alloy. However, WEWD faces some challenges, especially in terms of surface integrity of the workpiece which requires an in-depth investigation. In this study, the effect of µ-WEDM process on nitinol alloy was studied. 100 µm diameter brass wire was used for the cutting in addition to a set of µ-WEDM adjustable input cutting parameters, such as peak current (Ip), servo voltage (Sv), pulse on time (Ton), and pulse off time (Toff) are selected. The experiments were designed based on L27 Taguchi orthogonal array to reduce the number of experiments. Multi-regression analysis was applied based on the surface response methodology (RSM) to determine the effect of µ-WEDM process parameters on the surface integrity of the nitinol alloy. The aim of surface integrity studies was to minimizing Kerf width variation, minimizing white layer thickness (WLT), maximizing metal removal rate (MRR), minimizing surface roughness (Ra), and minimizing µ-hardness. Optimization studies were performed using two algorithms, the gradient algorithm (GA) and the particle swarm optimization algorithm (PSO) to determine the best µ-WEDM cutting parameters set for each output parameter individually according to the target that was specified. Moreover, a combined multi-response optimization analysis was performed to find the best set of µ-WEDM process parameters to achieve the best surface integrity of the nitinol alloy sample that satisfies the goal of all output responses’ simultaneously.Article Combined use of ultrasonic-assisted drilling and minimum quantity lubrication for drilling of NiTi shape memory alloy(Machining Science and Technology, 2023-06-24) Namlu, Ramazan Hakkı; Lotfi, Bahram; Kılıç, S. Engin; Yılmaz, Okan Deniz; Akar, SametThe drilling of shape-memory alloys based on nickel-titanium (Nitinol) is challenging due to their unique properties, such as high strength, high hardness and strong work hardening, which results in excessive tool wear and damage to the material. In this study, an attempt has been made to characterize the drillability of Nitinol by investigating the process/cooling interaction. Four different combinations of process/cooling have been studied as conventional drilling with flood cooling (CD-Wet) and with minimum quantity lubrication (CD-MQL), ultrasonic-assisted drilling with flood cooling (UAD-Wet) and with MQL (UAD-MQL). The drill bit wear, drilling forces, chip morphology and drilled hole quality are used as the performance measures. The results show that UAD conditions result in lower feed forces than CD conditions, with a 31.2% reduction in wet and a 15.3% reduction in MQL on average. The lowest feed forces are observed in UAD-Wet conditions due to better coolant penetration in the cutting zone. The UAD-Wet yielded the lowest tool wear, while CD-MQL exhibited the most severe. UAD demonstrated a ∼50% lower tool wear in the wet condition than CD and a 38.7% in the MQL condition. UAD is shown to outperform the CD process in terms of drilled-hole accuracy.Item DESIGNING AND DEVELOPING A DIGITAL LIGHT PROCESSING BASED STEREOLITHOGRAPHY 3D PRINTER(2022-01-20) Sahib, Mohammed; Tirkeş, Güzin; Akar, SametThe Digital Light Processing (DLP) 3D printer is a device using Computer-Aided Design (CAD) to produce a 3D model directly from the CAD model, by using the Additive Manufacturing (AM) technology. There are different ways of 3D printing technologies that vary in most aspects such as the material, the methods of forming the sample, the speed and accuracy and many other parameters. Choosing the right way of production depends on the required task so that the material and quality fits the level required. The DLP technology is recognized by its simple structure yet it provides a remarkable range of quality and flexibility. This research suggests a custom build that promises to provide a good production quality. Three types of experiments have been made with different CAD designs to ensure the ability of the designed 3D printer. These experiments have been successfully implemented in terms of surface quality, tiny details and accurate measurements. Furthermore two different tests were made to verify the desirable output results.