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Publication Metadata only A novel hybrid frost detection and defrosting system for domestic refrigerators(Elsevier, 2020) N/A; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Malik, Anjum Naeem; Khan, Shaheryar Atta; Lazoğlu, İsmail; PhD Student; PhD Student; Faculty Member; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391The frosting is a phenomenon most detrimental to the efficiency of refrigeration systems. The accumulation of frost blocks the airflow, deteriorating the cooling capacity and the coefficient of performance. The commercially available refrigeration systems use a blind and periodic defrosting cycle without any quantification of frost, which leads to lower efficiencies. Considering the new and tougher energy regulations in the refrigerators, nowadays increasing the efficiencies of the refrigerators becomes more critical. In this article, a new hybrid frost detection - defrosting system (HFDDS) is proposed that comprises of a novel photo-capacitive sensing technique and a dual-purpose additively manufacturable sensor and defrosting heater. The HFDDS can detect the formation of frost, measures the thickness of frost from 1.3 to 8 mm with a 5% margin of error, and triggers a defrosting response once a critical frost thickness is attained. The HFDDS is targeted to provide a defrosting on-demand instead of the inefficient blind and periodic defrosting cycles.Publication Open Access A novel mosaic quality measurement method for UAV surveillance and remote sensing(Copernicus Publications, 2013) Bayraktar, S.; Department of Mechanical Engineering; Department of Mechanical Engineering; Büyükyazı, Tolga; Lazoğlu, İsmail; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391A novel hardware independent real-time aerial image stabilization and mosaicing system is developed for mini UAV surveillance and remote sensing operations. In order to measure the quality of the constructed mosaics, several in-door and flight tests were performed. A novel mosaic quality measurement method utilizing 5 axis CNC for 3D positioning of the camera and printed high resolution aerial images for ground truth information is described. Results of the path following tests employing several state of art registration algorithms are provided. Mosaics constructed in real-time during flight tests are presented.Publication Open Access A solid modeler based engagement model for 5-axis ball end milling(Elsevier, 2015) Department of Mechanical Engineering; Department of Mechanical Engineering; Yiğit, İsmail Enes; Khavidaki, Sayed Ehsan Layegh; Lazoğlu, İsmail; Faculty Member; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 1793915-axis sculptured surface milling is a difficult machining process to model due to the complex geometrical engagement between the workpiece and the cutter. Due to the complexity of the process, the engagement cannot be found analytically with conventional methods. Therefore, solid modeler based simulations are utilized to compute the engagement map. This paper presents a comprehensive and efficient strategy for engagement modeling of ball end milling using a solid modeler kernel, namely Parasolid. Accuracy of the model is validated by simulating the cutting forces based on the calculated engagements and compare it with experimentally measured cutting forces. (C) 2015 The Authors. Published by Elsevier B. V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Publication Open Access Adaptive Q control for tapping-mode nanoscanning using a piezoactuated bimorph probe(American Institute of Physics (AIP) Publishing, 2007) Department of Mechanical Engineering; Department of Mechanical Engineering; Günev, İhsan; Varol, Aydın; Karaman, Sertaç; Başdoğan, Çağatay; Master Student; Faculty Member; College of Engineering; N/A; N/A; N/A; 125489A new approach, called adaptive Q control, for tapping-mode atomic force microscopy (AFM) is introduced and implemented on a homemade AFM setup utilizing a laser Doppler vibrometer and a piezoactuated bimorph probe. In standard Q control, the effective Q factor of the scanning probe is adjusted prior to the scanning depending on the application. However, there is a trade-off in setting the effective Q factor of an AFM probe. The Q factor is either increased to reduce the tapping forces or decreased to increase the maximum achievable scan speed. Realizing these two benefits simultaneously using standard Q control is not possible. In adaptive Q control, the Q factor of the probe is set to an initial value as in standard Q control, but then modified on the fly during scanning when necessary to achieve this goal. In this article, we present the basic theory behind adaptive Q control, the electronics enabling the online modification of the probe's effective Q factor, and the results of the experiments comparing three different methods: scanning (a) without Q control, (b) with standard Q control, and (c) with adaptive Q control. The results show that the performance of adaptive Q control is superior to the other two methods.Publication Metadata only An analytical model for engagement regions in machining of 3-d free-form surfaces(Japan Society of Mechanical Engineers (JSME), 2005) N/A; Department of Mechanical Engineering; N/A; Department of Mechanical Engineering; Lazoğlu, İsmail; Öztürk, Burak; Faculty Member; Master Student; Manufacturing and Automation Research Center (MARC); College of Engineering; Graduate School of Sciences and Engineering; 179391; N/AIn the machining simulations of 3D free-form surfaces with ball-end-mill process, determinations of instantaneously changing tool-workpiece contact regions and chip load play very critical roles in forces and surface quality predictions. Cutting force models for ball-end milling are based on the undeformed chip thickness. Undeformed chip thicknesses can be constructed from the boundaries of instantaneous contact region between the ball-end mill and workpiece. In order to predict the cutting forces accurately, determination of the varying contact region is important. In the literature, there are two main contact region constructing methods; one is the Z-mapping and the other one is using solid modeler based Boolean operation method. Both methods construct the contact region within accuracy limits but the computational time for these methods are long such that it is not possible to calculate the forces at the same time of (CL) points construction. This paper presents development of a new analytical method for the determination of the instantaneous contact regions and chip load in the 3-D machining of monotonic free-form surfaces.Publication Open Access Crack growth behavior of low-alloy bainitic 51CrV4 steel(Elsevier, 2010) Lambers, H. G.; Gorny, B.; Tschumak, S.; Maier, H. J.; Department of Mechanical Engineering; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; College of Engineering; 23433The crack growth behavior of low-alloy bainitic 51CrV4 steel was investigated. The current results indicate that the stress state present during the isothermal bainitic transformation has a strong influence on the crack propagation behavior in the near threshold regime, when the crack growth direction is perpendicular to the loading axis of the original sample undergoing phase transformation. However, the influence of stresses superimposed during the bainitic transformation on the crack growth behavior vanishes when the stress ratio is reduced from R=0.5 to R=0.1. Microstructural investigations revealed a locally pinned crack, indicating that the crack growth behavior in the near threshold regime is also strongly dependent on the local microstructure. Overall, the current results constitute the first step towards establishing a database for understanding and modeling the crack growth behavior in final work pieces exhibiting functionally-graded microstructures.Publication Metadata only Dimensional stability of 51CrV4 steel during bainitic phase transformation under tensile and compressive stresses(Elsevier, 2010) Lambers H.-G.; Maier H.J.; Department of Mechanical Engineering; Department of Mechanical Engineering; Canadinç, Demircan; Faculty Member; College of Engineering; 23433The effect of the prior austenitization treatment on the stress-strain response of a low alloy 51CrV4 steel in its supercooled austenitic state and its effect on the evolution of transformation plasticity strain during a subsequent isothermal bainitic transformation was investigated. One of the key findings is that the prior austenitization treatment strongly affects the evolution of transformation plasticity strains during the subsequent isothermal bainitic transformation under stress, such that higher transformation plasticity strains are present when the austenite grain size is increased. In addition, higher 0.2% offset yield strengths of the supercooled austenite are present following an incomplete austenitization treatment due to the existence of residual carbides. Overall, the current results clearly lay out the effect of the prior austenitization treatment on the stress-strain response of the supercooled austenite and the evolution of transformation plasticity during bainitic transformation.Publication Metadata only Discrete and continuous mathematical models for torsional vibration of micromechanical scanners(Springer, 2007) Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; N/A; College of Engineering; N/A; 8579; N/AMicromechanical scanners are used in various industrial scanning applications like. display and imaging technologies. The desired vibration mode is often the torsional mode, so derivation of an accurate mathematical model for calculation of torsional mode frequency has great importance. In this work, discrete and continuous mathematical models are given for free torsional vibration of a box shaped scanner suspended with two beams. Numerical calculation of torsional rigidity using energy methods is shown. The derivations are extendible to scanners that have non-rectangular beam cross-sections, orthotropic material anisotropy, and different mirror geometries. Analytical formulas are compared with three-dimensional FEM simulations using ANSYS commercial software. The FEM simulations and analytical formulas are verified with experimental results. FEM simulations and experimental results showed that simple discrete models can be used for a wide range of beam dimensions except for the cases where beam inertia is comparable to mirror inertia.Publication Open Access Dynamic characterization and damping control of a MEMS structure - art. no. 671509(Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Mechanical Engineering; Department of Mechanical Engineering; Alaca, Ilgım Veryeri; Başdoğan, İpek; Faculty Member; College of Engineering; 50569; 179940Publication Open Access Fractional order admittance control for physical human-robot interaction(Institute of Electrical and Electronics Engineers (IEEE), 2017) Tokatli, O.; Patoglu, V.; Department of Mechanical Engineering; Department of Mechanical Engineering; Aydın, Yusuf; Başdoğan, Çağatay; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489In physical human-robot interaction (pHRI), the cognitive skill of a human is combined with the accuracy, repeatability and strength of a robot. While the promises and potential outcomes of pHRI are glamorous, the control of such coupled systems is challenging in many aspects. In this paper, we propose a new controller, fractional order admittance controller, for pHRI systems. The stability analysis of the new control system with human in-the-loop is performed and the interaction performance is investigated experimentally with 10 subjects during a task imitating a contact with a stiff environment. The results show that the fractional order controller is more robust than the standard admittance controller and helps to reduce the human effort in task execution.