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Öğe Fabrication and experimental study of micro-gripper with electrothermal actuation by stereolithography method(Springer, 2022) Ülkir, Osman; Ertuğrul, İshak; Akkuş, Nihat; Özer, SalihThe aim of the study is to get high displacement values with low actuation voltage from the micro-gripper fabricated by stereolithography (SLA) method. Micro-grippers are devices based on a micro-electro-mechanical system (MEMS) preferred for manipulation and assembly in micro-fabrication. This article presents the modeling, fabrication, and experimental studies of a U-type electrothermal MEMS micro-gripper. The fabrication of the gripper was made by SLA, which is one of the additive manufacturing methods. The arm tip displacement of the gripper has been characterized in real-time by optical microscopy. In electrical characterization studies, the electrical voltage was applied to the pads of the micro-gripper. This voltage value was increased starting from 0V with 1V increments until deterioration was observed in the gripper. The micro-gripper is shown to actuate to a maximum opening displacement of 28.35 mu m at an applied voltage of 5V. The models are employed to examine key factors of the micro-gripper's performance including temperature distribution, displacement, and stresses based on an elastic analysis of structures. Experimental results for the displacement of the micro-gripper's arm tips were found to be in good agreement with the simulation results.Öğe Investigation of residual stress variation in sequential butt welding and pocket material removal machining processes utilizing pre-stress method: a 3D simulation approach(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Çetintav, Işık; Can, Yılmaz; Akkuş, NihatThis study investigates the residual stresses arising from welding and machining processes, recognizing their adverse implications in manufacturing. Employing experimental analysis and simulation techniques, the research scrutinizes residual stress alterations resulting from sequential butt welding and subsequent machining. Utilizing MSC Marc Mentat software(version 2016), three-dimensional models are developed to simulate these processes. The finite element model from welding simulation seamlessly integrates into cutting simulations via the pre-state option. The experimental procedures involve 100 × 100 × 10 mm AISI 304 steel plates subjected to sequential welding and machining, with residual stresses measured at each stage. A comparative analysis between experimental and simulation results elucidates variations in residual stresses induced by sequential processes. The study focuses on examining the initial stress state post-welding and numerically assessing stress modifications due to milling. The results suggest minimal material removal insignificantly affects stress distribution and magnitude at the weld centerline. However, increased material removal leads to noticeable changes in through-thickness transverse stress within the weld zone, contrasting with marginal alterations in through-thickness longitudinal stress. Regions distanced from the weld seam show substantial increases in through-thickness longitudinal stress compared to marginal changes in through-thickness transverse stress.Öğe Production of piezoelectric cantilever using MEMS-based layered manufacturing technology(Elsevier Gmbh, 2023) Ülkir, Osman; Ertuğrul, İshak; Akkuş, Nihat; Özer, SalihPiezoelectric cantilever is widely preferred in many fields due to its small size, simple and perfect design, easy control process, easy integration with integrated circuits. The tip displacement is the most important character of piezoelectric cantilever and many models have been used for char-acterization. These models are only suitable for piezoelectric cantilever structures of the same length and layer thickness. In this study, a new model is proposed to estimate the tip displacement of a micro-electro-mechanical system (MEMS) based piezoelectric cantilever with layers of different lengths and thicknesses. Modeling was carried out in COMSOL Multiphysics software in 3D format with reference to the bimorph structure. The fabrication of the piezoelectric cantilever was made by Stereolithography (SLA), which is one of the additive manufacturing methods. Theoretical, simulated and real-time experiments were carried out to measure the tip displace-ment of the piezoelectric cantilever. An electrical characterization experiment was set up to measure tip displacement under constant voltage of the cantilever in real-time experiments. This setup includes an optical microscope and digital camera to observe displacements in the probe station. As a result of the characterization, it was found that the cantilever produced a maximum 14.98 mu m tip displacement of 900 mu m length, 225 mu m width and 40 mu m thickness under 10 V voltage. In addition, it has been determined that the tip displacement of the piezoelectric cantilever is directly proportional to the length and inversely proportional to the layer thickness. The results show that the model is in good agreement with the finite element method (FEM) simulation, theoretical and experimental measurements.Öğe Virtual reality remote access laboratory for teaching programmable logic controller topics(Tempus Publications, 2020) Yerden, Aytaç Uğur; Akkuş, NihatThis study is concerned with improving the effectiveness and quality of technical education through the use of virtual reality technology. To do so, we have examined the effects of an application of a Virtual Reality-Supported Remote Access Laboratory (VRRALAB) system we developed using remote access and virtual reality technologies on students' learning experience. The advantage of such a remote access laboratory is that use of equipment that requires experience, such as working under high voltage, can be hazardous to novice users, whereas interactively using a real device from a virtual reality-supported remote access laboratory environment comes with no such risk. We have used an experimental design with 74 associate degree mechatronics program second class students who were divided into the control and experiment groups. They were enrolled on the same Programmable Logic Controller (PLC) course using the applications prepared for VRRALAB design. The experimental group was given a 4-hour training session using the basic subjects of a PLC lesson with the VRRALAB application with a traditional method, whilst the control group was taught only in conventional fashion. Both the control and experiment groups were assessed using the same exam questions. It was found that students who studied with VRRALAB were more successful than those who did not. Satisfaction levels among students using VRRALAB were also found to be high when measured by a questionnaire survey. The results indicate that remote access laboratories using virtual reality are likely to increase the quality of learning and satisfaction levels.
