Scholarly Publications - Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11693/115626

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Open Access
On-chip flow rate sensing via membrane deformation and bistability probed by microwave resonators
(Springer Link, 8-04-2023) Seçme, Arda; Pisheh, Hadi Sedaghat; Tefek, Uzay; Uslu, H. Dilara; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, Mehmet Selim
Precise monitoring of fluid flow rates constitutes an integral problem in various lab-on-a-chip applications. While off-chip flow sensors are commonly used, new sensing mechanisms are being investigated to address the needs of increasingly complex lab-on-a-chip platforms which require local and non-intrusive flow rate sensing. In this regard, the deformability of microfluidic components has recently attracted attention as an on-chip sensing mechanism. To develop an on-chip flow rate sensor, here we utilized the mechanical deformations of a 220 nm thick Silicon Nitride membrane integrated with the microfluidic channel. Applied pressure and fluid flow induce different modes of deformations on the membrane, which are electronically probed by an integrated microwave resonator. The flow changes the capacitance, and in turn resonance frequency, of the microwave resonator. By tracking the resonance frequency, liquid flow was probed with the device. In addition to responding to applied pressure by deflection, the membrane also exhibits periodic pulsation motion under fluid flow at a constant rate. The two separate mechanisms, deflection and pulsation, constitute sensing mechanisms for pressure and flow rate. Using the same device architecture, we also detected pressure-induced deformations by a gas to draw further insight into the sensing mechanism of the membrane. Flow rate measurements based on the deformation and instability of thin membranes demonstrate the transduction potential of microwave resonators for fluid–structure interactions at micro- and nanoscales.
Open Access
Schema changes in an object-oriented database system
(ASME, 1992) Alhajj, Reda; Arkun, M. Erol
Proper and efficient handling of schema changes is an important aspect of any object-oriented database management system. Clearly, it is desirable for an object-oriented database management system to satisfy as many schema operations as possible. This paper deals with schema changes in ODS; an object-oriented database management system prototype. A brief description of the basic features of ODS along with its storage and indexing models are included to facilitate the treatment. The invariants of the class hierarchy/lattice as well as the rules for resolving ambiguities due to schema changes are discussed. In addition, schema changes handled by ODS are described. Schema modifications are done through the user interface of ODS that provides both a class browser and a programming shell. Versions are supported by ODS in handling both methods and messages. For composite objects name conflicts are handled by considering both superclasses and nesting classes.
Open Access
Hard turning with variable micro-geometry PcBN tools
(Elsevier, 2008) Özel, T.; Karpat, Y.; Srivastava, A.
This paper presents investigations on hard turning with variable edge design PcBN inserts. Turning of hardened AISI 4340 steel with uniform and variable edge design PcBN inserts is conducted, forces and tool wear are measured. 3D finite element modelling is utilized to predict chip formation, forces, temperatures and tool wear on uniform and variable edge micro-geometry tools. Predicted forces and tool wear contours are compared with experiments. The temperature distributions and tool wear contours demonstrate the advantages of variable edge micro-geometry design.
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.
Open Access
Vibration absorption using non-dissipative complex attachments with impacts and parametric stiffness
(Acoustical Society of America, 2009) Roveri, N.; Carcaterra, A.; Akay, A.
Studies on prototypical systems that consist of a set of complex attachments, coupled to a primary structure characterized by a single degree of freedom system, have shown that vibratory energy can be transported away from the primary through use of complex undamped resonators. Properties and use of these subsystems as by energy absorbers have also been proposed, particularly using attachments that consist of a large set of resonators. These ideas have been originally developed for linear systems and they provided insight into energy sharing phenomenon in large structures like ships, airplanes, and cars, where interior substructures interact with a master structure, e.g., the hull, the fuselage, or the car body. This paper examines the effects of nonlinearities that develop in the attachments, making them even more complex. Specifically, two different nonlinearities are considered: (1) Those generated by impacts that develop among the attached resonators, and (2) parametric effects produced by time-varying stiffness of the resonators. Both the impacts and the parametric effects improve the results obtained using linear oscillators in terms of inhibiting transported energy from returning to the primary structure. The results are indeed comparable with those obtained using linear oscillators but with special frequency distributions, as in the findings of some recent papers by the same authors. Numerically obtained results show how energy is confined among the attached oscillators. © 2009 Acoustical Society of America.
Open Access
Energy equipartition and frequency distribution in complex attachments
(Acoustical Society of America, 2009) Roveri, N.; Carcaterra, A.; Akay, A.
As reported in several recent publications, an undamped simple oscillator with a complex attachment that consists of a set of undamped parallel resonators can exhibit unusual energy sharing properties. The conservative set of oscillators of the attachment can absorb nearly all the impulsive energy applied to the primary oscillator to which it is connected. The key factor in the ability of the attachment to absorb energy with near irreversibility correlates with the natural frequency distribution of the resonators within it. The reported results also show that a family of optimal frequency distributions can be determined on the basis of a variational approach, minimizing a certain functional related to the system response. The present paper establishes a link between these optimal frequency distributions and the energy equipartition principle: optimal frequency distributions are those that spread the injected energy as uniformly as possible over the degrees of freedom or over the modes of the system. Theoretical as well as numerical results presented support this point of view. © 2009 Acoustical Society of America.
Open Access
Disc brake squeal characterization through simplified test rigs
(Elsevier, 2009-11) Akay, A.; Giannini, O.; Massi, F.; Sestieri, A.
This paper presents a review of recent investigations on brake squeal noise carried out on simplified experimental rigs. The common theme of these works is that of approaching the study of squeal noise on experimental set-ups that are much simpler than commercial disc brakes, providing the possibility of repeatable measurements of squeal occurrence. As a consequence, it is possible to build consistent and robust models of the experimental apparatus to simulate the squeal events and to understand the physics behind squeal instabilities. © 2009.
Open Access
Combined component swapping modularity for a VCT engine controller
(ASME, 2010) Çakmakcı, Melih; Ulsoy, A.G.
The use of bi-directional communication provides additional design freedom which can be used to maximize the swapping modularity of networked smart components. In this paper, application of a design method for combined swapping modularity of two or more system components is discussed. Development of measures for combined swapping modularity is important to be able to analyze more realistic engineering cases. The combined modularity problem is a more difficult problem compared to the individual component swapping modularity problem. First, two approaches (simultaneous and sequential) for combining component swapping modularity of two or more components are presented. Then these combined modularity approaches are used to design controllers which maximize the component-swapping modularity of the Variable Camshaft Timing (VCT) component (i.e. actuator and sensor) and the Exhaust Gas Oxygen (EGO) sensor for an internal combustion engine. Copyright © 2009 by ASME.
Open Access
Swappable distributed MIMO controller for a VCT engine
(2011) Çakmakci M.; Ulsoy, A. G.
In the early days of computer control, only one centralized computer was responsible for executing the algorithms. Increasingly, computer control algorithms reside inside individual system components in a distributed fashion. Variable camshaft timing (VCT) is an appealing feature for automotive engines because it allows optimization of the cam timing over a wide range of operating conditions. In this paper, a method to distribute the discrete multiple-input mutiple-output controller for the VCT engine to improve the component swapping modularity of the VCT actuator and the EGO sensor components using network communications is presented. First, a discrete LQG controller is designed, and then this controller is distributed to the engine control unit, the VCT controller, and the EGO sensor controller in order to maximize the component swapping modularity of the system. A control oriented pre-optimization technique, which simplifies the optimization problem, and a candidate solution was devised to maximize component modularity. © 2006 IEEE.
Open Access
A method of two-scale chemo-thermal-mechanical coupling for concrete
(CIMNE, 2011) Wu, T.; Temizer, İlker; Wriggers, P.
The Alkali Silica Reaction(ASR) is one of the most important reasons to cause damage in cementitious constructions, which can be attributed to the expansion of hydrophilic gel produced in the reaction. In this contribution, the chemical extent is described depending on the temperature and it has influences on damage parameters. Expansions of the gel are assumed to only happen in the micropores of Hardened Cement Paste. Afterwards, the homogenization of damage in the microscale is initialized and the effective damage can be applied in the mesoscale directly. Moreover, parameter identification is implemented to extract the effective inelastic consititutive equation. In all, 3D multiscale chemo-thermo-mechanical coupled model is set up to describe the damage in the concrete due to ASR.
Open Access
Tactile perception by friction induced vibrations
(2011) Fagiani, R.; Massi, F.; Chatelet, E.; Berthier, Y.; Akay, A.
When a finger moves to scan the surface of an object (haptic sensing), the sliding contact generates vibrations that propagate in the finger skin activating the receptors (mechanoreceptors) located in the skin, allowing the brain to identify objects and perceive information about their properties. The information about the surface of the object is transmitted through vibrations induced by friction between the skin and the object scanned by the fingertip. The mechanoreceptors transduce the stress state into electrical impulses that are conveyed to the brain. A clear understanding of the mechanisms of the tactile sensing is fundamental to numerous applications, like the development of artificial tactile sensors for intelligent prostheses or robotic assistants, and in ergonomics. While the correlation between surface roughness and tactile sensation has already been reported in literature, the vibration spectra induced by the finger-surface scanning and the consequent activation of the mechanoreceptors on the skin have received less attention. In this paper, frequency analysis of signals characterizing surface scanning is carried out to investigate the vibration spectrum measured on the finger and to highlight the changes shown in the vibration spectra as a function of characteristic contact parameters such as scanning speed, roughness and surface texture. An experimental set-up is developed to recover the vibration dynamics by detecting the contact force and the induced vibrations; the bench test has been designed to guarantee reproducibility of measurements at the low amplitude of the vibrations of interest, and to perform measurements without introducing external noise. Two different perception mechanisms, as a function of the roughness wavelength, have been pointed out. The spectrum of vibration obtained by scanning textiles has been investigated. © 2011 Elsevier Ltd. All rights reserved.
Open Access
Dielectrophoresis in microfluidics technology
(2011) Çetin B.; Li, D.
Dielectrophoresis (DEP) is the movement of a particle in a non-uniform electric field due to the interaction of the particle's dipole and spatial gradient of the electric field. DEP is a subtle solution to manipulate particles and cells at microscale due to its favorable scaling for the reduced size of the system. DEP has been utilized for many applications in microfluidic systems. In this review, a detailed analysis of the modeling of DEP-based manipulation of the particles is provided, and the recent applications regarding the particle manipulation in microfluidic systems (mainly the published works between 2007 and 2010) are presented. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Open Access
Model-in-the-loop development for fuel cell vehicle
(IEEE, 2011) Çakmakçı, Melih; Li, Y.; Liu, S.
In this paper, the work on developing and validating a model-in-the-loop (MIL) simulation environment for a group of prototype fuel cell vehicles is presented. The MIL model consists of a vehicle plant model and an integrated vehicle system controller model. First, the vehicle simulation plant model is functionally validated with a simple vehicle system controller (VSC) model and then improved to satisfy the input output interface and fidelity requirements. The developed MIL system is then verified for basic functionality against the simple VSC controller model and shows uniform correlation results. It is further validated against vehicle dynamometer test data and demonstrates satisfactory consistency. A rapid model building approach which is suitable for model-based controller design process was also discussed. This approach enabled the developers to use model-to-code algorithms unlike many comparable simulation models. © 2011 AACC American Automatic Control Council.
Open Access
A large deformation frictional contact formulation using NURBS‐based isogeometric analysis
(John Wiley & Sons, 2011-02-23) De, L.; Temizer, I.; Wriggers, P.; Zavarise, G.
This paper focuses on the application of NURBS-based isogeometric analysis to Coulomb frictional contact problems between deformable bodies, in the context of large deformations. A mortar-based approach is presented to treat the contact constraints, whereby the discretization of the continuum is performed with arbitrary order NURBS, as well as C0-continuous Lagrange polynomial elements for comparison purposes. The numerical examples show that the proposed contact formulation in conjunction with the NURBS discretization delivers accurate and robust predictions. Results of lower quality are obtained from the Lagrange discretization, as well as from a different contact formulation based on the enforcement of the contact constraints at every integration point on the contact surface. Copyright © 2011 John Wiley & Sons, Ltd.
Open Access
Dissipation in a finite-size bath
(American Physical Society, 2011-07-18) Carcaterra, A.; Akay, A.
We investigate the interaction of a particle with a finite-size bath represented by a set of independent linear oscillators with frequencies that fall within a finite bandwidth. We discover that when the oscillators have particular frequency distributions, the finite-size bath behaves much as an infinite-size bath exhibiting dissipation properties and thus allowing irreversible energy absorption from a particle immersed in it. We also present a reinterpretation of the Langevin equation using a perturbation approach in which the small parameter represents the inverse of the number of oscillators in the bath, elucidating the relationship between finite-size and infinite-size bath responses.
Open Access
A computational homogenization framework for soft elastohydrodynamic lubrication
(Springer, 2012) Budt, M.; Temizer, İlker; Wriggers, P.
The interaction between microscopically rough surfaces and hydrodynamic thin film lubrication is investigated under the assumption of finite deformations. Within a coupled micro-macro analysis setting, the influence of roughness onto the macroscopic scale is determined using FE 2-type homogenization techniques to reduce the overall computational cost. Exact to within a separation of scales assumption, a computationally efficient two-phase micromechanical test is proposed to identify the macroscopic interface fluid flux from a lubrication analysis performed on the deformed configuration of a representative surface element. Parameter studies show a strong influence of both roughness and surface deformation on the macroscopic response for isotropic and anisotropic surfacial microstructures.
Open Access
Probing three-dimensional surface force fields with atomic resolution: measurement strategies, limitations, and artifact reduction
(Beilstein - Institut zur Foerderung der Chemischen Wissenschaften, 2012) Baykara, M. Z.; Dagdeviren, O. E.; Schwendemann, T. C.; Mönig, H.; Altman, E. I.; Schwarz, U. D.
Noncontact atomic force microscopy (NC-AFM) is being increasingly used to measure the interaction force between an atomically sharp probe tip and surfaces of interest, as a function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image interpretation. In this paper, we analyze their impact on the acquired data, compare different methods to record atomic-resolution surface force fields, and determine the approaches that suffer the least from the associated artifacts. The related discussion underscores the idea that since force fields recorded by using NC-AFM always reflect the properties of both the sample and the probe tip, efforts to reduce unwanted effects of the tip on recorded data are indispensable for the extraction of detailed information about the atomicscale properties of the surface. © 2012 Baykara et al.
Open Access
A mixed formulation of mortar-based frictionless contact
(2012) Temizer, I.
A class of mortar-based frictionless contact formulations is derived based on a classical three-field mixed variational framework. Within a penalty regularization complemented by Uzawa augmentations, discrete mortar constraints are naturally induced by the variational setting. Major aspects of earlier mortar approaches are obtained through constrained, lumped or unconstrained recovery procedures for the mixed kinematic and kinetic mortar quantities from their projected counterparts. Two- and three-dimensional examples at the infinitesimal and finite deformation regimes highlight the local and global quality of the contact interactions. © 2012 Elsevier B.V.
Open Access
Three-dimensional mortar-based frictional contact treatment in isogeometric analysis with NURBS
(2012) Temizer, I.; Wriggers, P.; Hughes, T. J. R.
A three-dimensional mortar-based frictional contact treatment in isogeometric analysis with NURBS is presented in the finite deformation regime. Within a setting where the NURBS discretization of the contact surface is inherited directly from the NURBS discretization of the volume, the contact integrals are evaluated through a mortar approach where the geometrical and frictional contact constraints are treated through a projection to control point quantities. The formulation delivers a non-negative pressure distribution and minimally oscillatory local contact interactions with respect to alternative Lagrange discretizations independent of the discretization order. These enable the achievement of improved smoothness in global contact forces and moments through higher-order geometrical descriptions. It is concluded that the presented mortar-based approach serves as a common basis for treating isogeometric contact problems with varying orders of discretization throughout the contact surface and the volume. © 2011 Elsevier B.V.
Open Access
Exploring atomic-scale lateral forces in the attractive regime: a case study on graphite (0001)
(Institute of Physics Publishing, 2012) Baykara, M. Z.; Schwendemann, T. C.; Albers, B. J.; Pilet, N.; Mönig, H.; Altman, E. I.; Schwarz, U. D.
A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of lateral forces with piconewton and picometer resolution as a function of both the in-plane tip position and the vertical tip-sample distance, without limitations due to a finite contact area or to stick-slip-related sudden jumps of tip apex atoms. After reviewing the measurement principle, the data obtained in this case study are utilized to illustrate the unique insight that the method offers. In particular, the local lateral forces that are expected to determine frictional resistance in the attractive regime are found to depend linearly on the normal force for small tip-sample distances. © 2012 IOP Publishing Ltd.