Browsing by Subject "FEM"
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Item Open Access ANN-based estimation of MEMS diaphragm response: An application for three leaf clover diaphragm based Fabry-Perot interferometer(Elsevier BV, 2022-06-23) Yigit, E.; Hayber, Ş. E.; Aydemir, UmutIn this study, an artificial neural network (ANN) based model is developed for MEMS diaphragm analysis, which does not require difficult and time-consuming FEM processes. ANN-based estimator is generated for static pressure response (d) and dynamic pressure response (f) analysis of TLC (three leaf clover) diaphragms for Fabry-Perot interferometers as an example. TLC is one of the unsealed MEMS design diaphragms formed by three leaves of equal angles. The diaphragms used to train ANNs are designed with SOLIDWORKS and analyzed with ANSYS. A total of 1680 TLC diaphragms are simulated with eight diaphragm parameters (3 for SiO2 material, 4 for geometry, and 1 for pressure) to create a data pool for ANN’s training, validation, and testing processes. 80% of the data is used for training, 15% for validation, and the remaining for testing. Only four geometric parameters are used as input in the ANN estimator, and the material parameters are added to the model with an analytical multiplier. Thus, network models that estimate d and f values for all kinds of diaphragm materials are proposed, with a material-independently trained ANN structure. The performance of the ANN model is compared with the empirical equation suggested in the literature, and its superiority is demonstrated. In addition, the d and f parameters of TLC diaphragms designed with five different materials (Si, In2Se3, Ag, EPDM, Graphene) are estimated to be very close to the real ones. By using the proposed method, analyses of TLC diaphragms are quickly performed without the need for time-consuming and costly design and analysis programs.Item Open Access BaTiO3 and TeO2 based gyroscopes for guidance systems: FEM analysis(Taylor and Francis Inc., 2016) Ozer, Z.; Mamedov, A. M.; Özbay, EkmelThis paper presents the design, modeling and finite element model simulation of a micro-electromechanical system based on the ternary ferroelectric compounds and paratellurite. The dynamic behavior of the sensor structure is described by the super position of its dominant vibration mode shapes. The resulting model still considers all the physical domains and is even able to capture nonlinear phenomena, such as the stress stiffening of constraint structures or frequency and stiffening caused by squeezed gas in the sensor cell. Process induced and thermally induced residual stresses and the resulting deformation of the transducer elements are considered. © 2016, © Taylor & Francis Group, LLC.Item Open Access Convection-reaction equation based magnetic resonance electrical properties tomography (cr-MREPT)(Bilkent University, 2013) Hafalır, Fatih SüleymanTomographic imaging of electrical conductivity and permittivity of tissues may be used for diagnostic purposes as well as for estimating local specific absorption rate (SAR) distributions. Magnetic Resonance Electrical Properties Tomography (MREPT) aims at noninvasively obtaining conductivity and permittivity images at RF frequencies of MRI systems. MREPT algorithms are based on measuring the B1 field which is perturbed by the electrical properties of the imaged object. In this study, the relation between the electrical properties and the measured B + 1 field is formulated, for the first time as, the well-known convection-reaction equation. The suggested novel algorithm, called “cr-MREPT”, is based on the solution of this equation, and in contrast to previously proposed algorithms, it is applicable in practice not only for regions where electrical properties are relatively constant but also for regions where they vary. The convection-reaction equation is solved using a triangular mesh based finite difference method and also finite element method (FEM). The convective field of the convection-reaction equation depends on the spatial derivatives of the B + 1 field. In the regions where the magnitude of convective field is low, a spot-like artifact is observed in the reconstructed conductivity and dielectric permittivity images. For eliminating this artifact, two different methods are developed, namely “constrained cr-MREPT” and “double-excitation cr-MREPT”. In the constrained cr-MREPT method, in the region where the magnitude of convective field is low, the electrical properties are reconstructed by neglecting the convective term in the equation. The obtained solution is used as a constraint for solving electrical properties in the whole domain. In the double-excitation cr-MREPT method, two B1 excitations, which create two convective field distributions having low magnitude of convective field in different locations, are applied separately. The electrical properties are then reconstructed simultaneously using data from these two applied B + 1 field. These methods are tested with both simulation and experimental data from phantoms. As seen from results, successful electrical property reconstructions are obtained in all regions including electrical property transition region. The performance of cr-MREPT method against noise is also investigated.Item Open Access Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology(2013) Hosseini Kalajahi, M.; Rash Ahmadi, S.; Nadimi Bavil Oliaei, S.In this study, thermal modeling and finite element simulation of electrical discharge machining (EDM) has been done, taking into account several important aspects such as temperature-dependent material properties, shape and size of the heated zone (Gaussian heat distribution), energy distribution factor, plasma flushing efficiency, and phase change to predict thermal behavior and material removal mechanism in EDM process. Temperature distribution on the cathode has been calculated using ANSYS finite element code, and the effect of EDM parameters on heat distribution along the radius and depth of the workpiece has been obtained. Temperature profiles have been used to calculate theoretical material removal rate (MRR) from the cathode. Theoretically calculated MRRs are compared with the experimental results, making it possible to precisely determine the portion of energy that enters the cathode for AISI H13 tool steel. Also in this paper, the effect of EDM parameters on MRR has been investigated by using the technique of design of experiments and response surface methodology. Finally, a quadratic polynomial regression model has been proposed for MRR, and the accuracy of this model has been checked by means of analysis of residuals. © 2013 Springer-Verlag London.Item Open Access Ferroelectric based microgyroscope for inertial measurement unit: Modeling and simulation(IEEE, 2012) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper present the design and modeling of the micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT and Ba xSr 1-xTiO 3) based by using finite element model (FEM) simulation. © 2012 IEEE.Item Open Access Modeling and simulation of the ferroelectric based micro gyroscope: FEM analysis(Taylor and Francis, 2013-09-23) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper presents the design and modeling of micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT) based by using finite element model (FEM) simulation. The conceptual framework establishes five steps to perform the critical analysis: design a novel structure, define the failure mechanisms under the given conditions, analyze different vibrations, analyze the operation principle, and detect resonance modes. In addition, MEMS failure modes were analyzed under different scenarios and the obtained results discussed. Copyright © Taylor & Francis Group, LLC.Item Open Access A modified material model for the finite element simulation of machining titanium alloy Ti-6Al-4V(Taylor & Francis, 2010) Karpat, Y.Because of their desirable properties, such as high strength to weight ratio and corrosion resistance, titanium alloys are commonly employed in the aerospace and medical device industries. Titanium alloys are known to be difficult to machine, so the selection of cutting conditions with minimal experimental effort is important for manufacturers. Finite element modeling, which is an indispensable tool to understand the mechanics of machining, can also be utilized as an alternative method of process design as long as the finite element simulation input parameters are well defined. Developing a modified material model for titanium alloy Ti-6Al-4V by considering the relationships between strain, strain rate and temperature is the subject of this study. The flow softening behavior of the material at high strains is also examined. The influences of the material model parameters on the finite element simulation outputs are investigated. The finite element simulation results are found to be in agreement with the data available in the literature.Item Open Access Process simulations for 3D turning using uniform and variable microgeometry PCBN tools(Inderscience Publishers, 2008) Karpat, Y.; Özel, T.In this paper, uniform and variable edge microgeometry design inserts are utilised and tested for 3D turning process. In 3D tool engagement with workpiece, thickness of the chip varies from a maximum equal to the feed rate (at primary cutting edge) to a minimum on the tool's corner radius (at trailing cutting edge). The ideal tool edge preparation should posses a variable configuration which has larger edge radius at the primary cutting edge than at the trailing cutting edge. Here the key parameter is the ratio of uncut chip thickness to edge radius. If a proper ratio is chosen for given cutting conditions, a variable cutting edge along the corner radius can be designed or 'engineered'. In this study, Finite Element Modelling (FEM)-based 3D process simulations are utilised to predict forces and temperatures on various uniform and variable edge microgeometry tools. Predicted forces are compared with experiments. The temperature distributions on the tool demonstrate the advantages of variable edge microgeometry design.