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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Design methodology microelectromechanical systems. Case study: torsional scanner mirror(Asme-Amer Soc Mechanical Eng, 2007) N/A; N/A; Department of Mechanical Engineering; Meral, Faik Can; Başdoğan, İpek; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940Future optical microsystems, such as microelectromechanical system (MEMS) scanners and micromirrors, will extend the resolution and sensitivity offered by their predecessors. These systems face the challenge of achieving nanometer precision subjected to various disturbances. Predicting the performance of such systems early in the design process can significantly impact the design cost and also improve the quality, of the design. Our approach aims to predict the performance of such systems under various disturbance sources and develop a generalized design approach for MEMS structures. In this study, we used ANSYS for modeling and dynamic analysis of a torsional MEMS scanner mirror. ANSYS modal analysis results, which are eigenvalues (natural frequencies) and eigenvectors (mode shapes), are used to obtain the state-space representation of the mirror. The state-space model of the scanner mirror was reduced using various reduction techniques to eliminate the states that are insignificant for the transfer functions of interest. The results of these techniques were compared to obtain the best approach to obtain a lower order model that still contains all the relevant dynamics of the original model. After the model size is reduced significantly, a disturbance analysis is performed using Lyapunov approach to obtain root-mean-square values of the mirror rotation angle under the effect of a disturbance torque. The magnitude levels of the disturbance torque are obtained using an experimental procedure. The disturbance analysis framework is combined with the sensitivity analysis to determine the critical design parameters for optimizing the system performance.Publication Metadata only Future mars mission demonstrationwith gamification and socioeconomictraits: nextgenerationworkforce development and self-knowledge management(American Institute of Aeronautics and Astronautics Inc, AIAA, 2015) N/A; N/A; Kara, Ozan; PhD Student; Graduate School of Sciences and Engineering; N/AThis research enhance proper gamification scenerios for future Mars missions. Scenarios include mars atmosphere and surface design, cubesat Mars orbiter, micro flying robot demonstration, in-situ research support, human health risk reduction, digital 3D printing and hands-on rover experiments. The scheduled Mars mission concepts consisting of gamification allow the first uncrewed orbital return with Orion around 2024. The forecasted crewed mission can be realized in early 2030. The next generation workforce development for Mars exploration is presented from 2014 IPMC Young Professional workshop “entering and growing into the space sector” group findings, 2014 OECD Space report and NASA APPEL studies. The workshop findings compare young professional development in academia, industry and government. In addition, findings are classified under student, K12 education, boss relations, sociological conditions and global workforce demand data. OECD report show total space economy is $256B US dollars in 2013. NASA APPEL and CKO has new knowledge map for NASA to unite people and systems in sustainable and effective way. The groundwork of the young professional development and impacts of gamification are comprehended by self-knowledge management and decision making. Finally, reflections of space missions such as Orion, Rosetta and New Horizons inspire public society and have different impacts in countries.Publication Metadata only Feedrate scheduling strategies for free-form surfaces(Elsevier Sci Ltd, 2006) N/A; Department of Mechanical Engineering; N/A; Erdim, Hüseyin; Lazoğlu, İsmail; Öztürk, Burak; PhD Student; Faculty Member; N/A; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391; N/AFree-form machining is one of the commonly used manufacturing processes for several industries such as automobile, aerospace, die and mold industries. In 3D complicated free-form surfaces, it is critical, but often difficult, to select applicable cutting conditions to achieve high productivity while maintaining high quality of parts. It is essential to optimize the feedrate in order to improve the machining efficiency of the ball-end milling. Conservative constant feedrate values have been mostly used up to now since there was a lock of physical models and optimization tools for the machining processes. The common approach used in feedrate scheduling is material removal rate (MRR) model. In the MRR based approach, feedrate is inversely proportional to either average or instantaneous volumetric removal rate. Commonly used CAM programs and NC code generators based on only the geometric and volumetric analysis, but they do not concern the physics of the free-form machining process yet. The new approach that is also introduced in this paper is based on the mechanics of the process. In other words, the force-based models in which feedrate is set to values which keep either average or instantaneous machining forces to prescribed values. In this study, both feedrate scheduling strategies are compared theoretically and experimentally for 3D ball-end milling of free-form surfaces. It is shown that MRR based feedrate strategy outputs higher feedrate values compared to force based feedrate strategy. High feedrate values of the MRR strategy increase the cutting forces extensively which can be damaging to the part quality and to the CNC Machine. When the new force based feedrate-scheduling strategy introduced in this paper is used, it is shown that the machining time can be decreased significantly along the tool path. The force-based feedrate scheduling strategy is tested under various cutting conditions and some of the results are presented in the paper. (C) 2005 Elsevier Ltd. All rights reserved.Publication Metadata only An investigation on the impact fatigue characteristics of valve leaves for small hermetic reciprocating compressors in a new automated test system(Wiley, 2012) Oguz, E.; Kara, S.; N/A; Department of Mechanical Engineering; Altunlu, Abdullah Can; Lazoğlu, İsmail; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391This paper presents an investigation on the impact fatigue characteristics of valve leaves that are prevalently used in hermetic reciprocating compressors especially for the household type refrigerators. A unique automated impact fatigue test system has been designed and produced, which enables to carry out impact fatigue tests of the compressor valve leaves under the desired impact velocities. The test system incorporates a noncontact actuation, a data acquisition system and an acoustic-based damage detection technique, which continuously monitors the health of the structure. The damage detection system allows parametrical investigation on the impact fatigue life by detecting any possible damage and automatically terminating the test. The investigation relates the impact fatigue lifetime of the valve leaves with the impact velocity, asymmetrical impact, operation temperature, material type (carbon strip steel, stainless strip steel and new stainless strip steel grade) and tumbling operation duration. The observations show that the cracks have initiated from the edges of the valve leaf where is in contact with the valve plate. Subsequently, the cracks initially have propagated in the radial direction inwards the center of the impact area. Various failure cases have been resulted in by either a single crack or inter-related multiple cracks. Microscopic and metallographic observations have been performed on the specimens to enhance the understanding of the damage mechanisms. The investigation and introduced test system guide the design optimization of the valve leaves in terms of compressor performance due to the energy consumption and lifetime of the valve leaf.Publication Metadata only Finite element modeling of a vibrating touch screen actuated by piezo patches for haptic feedback(Springer, 2012) N/A; N/A; Department of Mechanical Engineering; Baylan, Buket; Arıdoğan, Mustafa Uğur; Başdoğan, Çağatay; Master Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489The aim of our work is to design a touch screen for displaying vibrotactile haptic feedback to the user via piezo patches attached to its surface. One of the challenges in the design is the selection of appropriate boundary conditions and the piezo configurations (location and orientation) on the screen for achieving optimum performance within the limits of human haptic perception. To investigate the trade-offs in our design, we developed a finite element model of the screen and four piezo actuators attached to its surface in ABAQUS. The model utilizes the well-known Hooke's law between stress and strain extended by piezoelectric coupling. After selecting the appropriate boundary condition for the screen based on the range of vibration frequencies detectable by a human finger, the optimum configuration for the piezo patches is determined by maximizing the vibration amplitude of the screen for a unit micro Coulomb charge applied to each piezo patch. The results of our study suggest that the piezo patches should be placed close to the clamped sides of the screen where the boundary conditions are applied. © 2012 Springer-Verlag.Publication Metadata only Machining of free-form surfaces. Part II: calibration and forces(Elsevier Sci Ltd, 2006) N/A; N/A; Department of Mechanical Engineering; N/A; Lazoğlu, İsmail; Öztürk, Burak; Erdim, Hüseyin; Master Student; Faculty Member; PhD Student; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 179391; N/Ain the machining simulations of 3D free-form surfaces by ball-end milling, calibration coefficients play very critical role in force predictions. in other words, obtaining the calibration coefficients from calibration tests is a very influential process in the prediction of cutting forces. accurately obtained calibration coefficients lead to better force predictions. in the literature, the calibration coefficients are assumed to be independent of start and exit angles of the engagement region, thus they are assumed to be identical for any engagement region. Calibration coefficients are obtained from the horizontal slot cutting tests and these tests are repeated for different depth of cuts. in this paper, in order to achieve, more accurate force predictions in free-form machining simulations, A new modification algorithm for calibration coefficients is presented. in this research, with theoretical analysis and experimental force signals, it is shown that the inclination angle has a great importance in calibration and in force simulation of 3D free-form machining.Publication Metadata only A front tracking method for computational modeling of temperature and species gradient based phase change(International Conference on Computational Fluid Dynamics 2016, 2016) N/A; N/A; Department of Mechanical Engineering; Irfan, Muhammad; Muradoğlu, Metin; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 46561A front-tracking method is developed for the direct numerical simulation of evaporation process in a liquid–gas multiphase system. One-field formulation is used to solve the flow, energy and species equations in the framework of the front tracking method, with suitable jump conditions at the interface. Both phases are assumed to be incompressible; however, the divergence-free velocity field condition is modified to account for the phase-change/mass-transfer at the interface. Both temperature and species gradient driven evaporation/phase-change processes are simulated. For the species gradient driven phase change process, the Clausius–Clapeyron equilibrium relation is used to find the vapor mass fraction and subsequently the evaporation mass flux at the interface. A number of benchmark cases are first studied to validate the implementation. The numerical results are found to be in excellent agreement with the analytical solutions for all the studied cases. The methods are then applied to study the evaporation of a static as well as a single and two droplets systems falling in the gravitational field. The methods are demonstrated to be grid convergent and the mass is globally conserved during the phase change process for both the static and moving droplet cases.Publication Metadata only Modeling cutting forces for five axis milling of sculptured surfaces(Trans Tech Publications Ltd, 2011) Erdim, H.; N/A; Department of Mechanical Engineering; Boz, Yaman; Lazoğlu, İsmail; Master Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; College of Engineering; N/A; 1793915-axis ball-end milling processes are used in various industries such as aerospace, automotive, die-mold and biomedical industries. 5-axis machining provides reduced cycle times and more accurate machining via reduction in machining setups, use of shorter tools due to improved tool accessibility. However, desired machining productivity and precision can be obtained by physical modeling of machining processes via appropriate selection of process parameters. In response to this gap in the industry this paper presents a cutting force model for 5-axis ball-end milling cutting force prediction. Cutter-workpiece engagement is extracted via developed solid modeler based engagement model. Simultaneous 5-axis milling tests are conducted on A17075 workpiece material with a carbide cutting tool. Validation of the proposed model is performed for impeller hub roughing toolpaths. Validation test proves that presented model is computationally efficient and cutting forces can be predicted reasonably well. The result of validation test and detailed comparison with the simulation are also presented in the paper.Publication Metadata only Experimental transfer path analysis for a heavy duty truck(Web Portal ASME (American Society of Mechanical Engineers), 2014) Sendur, Polat; N/A; N/A; Department of Mechanical Engineering; Stan, Andrei Cristian; Yenerer, Hakan; Başdoğan, İpek; Master Student; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179940Most of the mechanical systems are composed of different subsystems coupled by several links. Any excitation acting on the system is divided into several internal forces which propagate through these links or so called transfer paths. This paper presents the use of experimental transfer path analysis in identifying the transmission paths for a heavy duty truck in order to estimate the vibration and noise transmitted from the cabin and engine mounts. The most challenging part of the TPA analysis is estimation of the internal operational forces so that the total response can be predicted accurately. At the circumstances where direct measurement of the operational forces is impossible, especially for complex structures, a common approach to address the problem is based on a measured frequency response function (FRF) matrix and a set of operational responses. The main problem of this approach is the inversion of the FRF matrices which can be ill-conditioned. Once the internal operational forces are estimated, the vibration or noise response for the selected location in the truck can be calculated. To validate the predicted results, coherence of the collected data and the condition numbers of FRF matrices are investigated so that the accuracy of the predicted results can be quantified for the frequency band of interest. The predictions of the total response are compared with the experimentally measured data such that the coherence and condition number related observations are validated.Publication Metadata only Tool path selection strategies for complex sculptured surface machining(Taylor & Francis Inc, 2008) N/A; N/A; Department of Mechanical Engineering; Kaymakçı, Mustafa; Lazoğlu, İsmail; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391High performance machining of complex free form surfaces is very critical in many different industries. In this research, an advanced mathematical model of cutting forces that is based on the kinematics and mechanics of the 3D sculptured surface machining is integrated with CAM packages in order to predict the complex tool-workpiece engagements and machining forces for any tool path. Machined 3D free form topographies and distributions of errors between the desired CAD and machined surfaces are also predicted in advance. Now, an evaluation of different tool path strategies for 3D complex sculptured surfaces can be made. Theoretical simulations of forces and surface topographies for different tool paths are presented and compared with experimental measurements.