The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Irene Fernandez Villegas - One of the best experts on this subject based on the ideXlab platform.
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strength development versus process data in ultrasonic welding of thermoplastic composites with flat energy directors and its application to the definition of optimum processing parameters
Composites Part A-applied Science and Manufacturing, 2014Co-Authors: Irene Fernandez VillegasAbstract:Abstract Ultrasonic welding of thermoplastic composites is a very interesting joining technique as a result of good quality joints, very short welding times and the fact that no foreign material, e.g. a metal mesh, is required at the welding interface in any case. This paper describes one further advantage, the ability to relate weld strength to the welding process data, namely Dissipated Power and displacement of the sonotrode, in ultrasonic welding of thermoplastic composite parts with flat energy directors. This relationship, combined with displacement-controlled welding, allows for fast definition of optimum welding parameters which consistently result in high-strength welded joints.
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modeling of the heating phenomena in ultrasonic welding of thermoplastic composites with flat energy directors
Journal of Materials Processing Technology, 2014Co-Authors: Arthur Levy, Steven Le Corre, Irene Fernandez VillegasAbstract:Abstract A model for the mechanics (oscillating deformation), heat transfer including viscoelastic heat generation and friction dissipation, and degree of adhesion (intimate contact and healing) is proposed for the initial transient heating phase. Numerical resolution was performed using a multi-physical finite element code. The predicted Dissipated Power evolution exhibits a good correlation with previous experimental measurement of delivered Power, and shows that the apparatus has a global efficiency of 13%. The predicted degree of adhesion also confirms the experimental observation that adhesion starts at the edge of the contact area, and progressively extends to the whole contact area. The numerical model was further used to investigate the physical mechanisms occurring during the welding process. As suggested in the literature, the first heating mechanism is confirmed to be due to interfacial friction. Bulk viscoelastic dissipation becomes predominant when the interface reaches higher temperatures. The Dissipated Power is suddenly increased when the whole interface reaches the glass transition temperature.
Wonho Jhe - One of the best experts on this subject based on the ideXlab platform.
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the Dissipated Power in atomic force microscopy due to interactions with a capillary fluid layer
Journal of Applied Physics, 2008Co-Authors: Nastaran Hashemi, Mark Paul, Harry Dankowicz, Myung Woo Lee, Wonho JheAbstract:We study the Power Dissipated by the tip of an oscillating micron-scale cantilever as it interacts with a sample using a nonlinear model of the tip-surface force interactions that includes attractive, adhesive, repulsive, and capillary contributions. The force interactions of the model are entirely conservative and the Dissipated Power is due to the hysteretic nature of the interaction with the capillary fluid layer. Using numerical techniques tailored for nonlinear and discontinuous dynamical systems we compute the exact Dissipated Power over a range of experimentally relevant conditions. This is accomplished by computing precisely the fraction of oscillations that break the fluid meniscus. We find that the Dissipated Power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. Even for regions where the cantilever dynamics are highly irregular the fraction of oscillations breaking the fluid meniscus exhibits a simple trend. Using our results we also explore the accuracy of the often used harmonic approximation in determining Dissipated Power.
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the Dissipated Power in atomic force microscopy due to interactions with a capillary fluid layer
Journal of Applied Physics, 2008Co-Authors: Nastaran Hashemi, Mark Paul, Harry Dankowicz, Myung Woo Lee, Wonho JheAbstract:We study the Power Dissipated by the tip of an oscillating micron-scale cantilever as it interacts with a sample using a nonlinear model of the tip-surface force interactions that includes attractive, adhesive, repulsive, and capillary contributions. The force interactions of the model are entirely conservative and the Dissipated Power is due to the hysteretic nature of the interaction with the capillary fluid layer. Using numerical techniques tailored for nonlinear and discontinuous dynamical systems we compute the exact Dissipated Power over a range of experimentally relevant conditions. This is accomplished by computing precisely the fraction of oscillations that break the fluid meniscus. We find that the Dissipated Power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. Even for regions where the cantilever dynamics are highly irregular the fraction of oscillations breaking the fluid meniscus exhibits a simple ...
Santiago D Solares - One of the best experts on this subject based on the ideXlab platform.
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selection of higher eigenmode amplitude based on Dissipated Power and virial contrast in bimodal atomic force microscopy
Journal of Applied Physics, 2014Co-Authors: Alfredo J Diaz, Babak Eslami, Enrique A Lopezguerra, Santiago D SolaresAbstract:This paper explores the effect of the amplitude ratio of the higher to the fundamental eigenmode in bimodal atomic force microscopy (AFM) on the phase contrast and the Dissipated Power contrast of the higher eigenmode. We explore the optimization of the amplitude ratio in order to maximize the type of contrast that is most relevant to the particular study. Specifically, we show that the trends in the contrast range behave differently for different quantities, especially the Dissipated Power and the phase, with the former being more meaningful than the latter (a similar analysis can be carried out using the virial, for which we also provide a brief example). Our work is based on numerical simulations using two different conservative-dissipative tip-sample models, including the standard linear solid and the combination of a dissipation coefficient with a conservative model, as well as experimental images of thin film Nafion® proton exchange polymers. We focus on the original bimodal AFM method, where the hi...
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mapping of conservative and dissipative interactions in bimodal atomic force microscopy using open loop and phase locked loop control of the higher eigenmode
Applied Physics Letters, 2011Co-Authors: Gaurav Chawla, Santiago D SolaresAbstract:We compare the ability of higher cantilever eigenmodes to map conservative and dissipative tip-sample interactions in bimodal atomic force microscopy under three different control schemes, namely, open-loop (OL), constant-excitation phase-locked-loop (CE-PLL), and constant-amplitude phase-locked-loop (CA-PLL). We perform a direct comparison of these schemes by applying analytical expressions of the virial and Dissipated Power to imaging and spectroscopy experiments conducted on a two-component polymer sample in air. We find that OL and CE-PLL provide similar information, while CA-PLL explores a broader range of interactions, especially for softer samples, due to its constant sensitivity to tip-sample forces.
Nastaran Hashemi - One of the best experts on this subject based on the ideXlab platform.
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the Dissipated Power in atomic force microscopy due to interactions with a capillary fluid layer
Journal of Applied Physics, 2008Co-Authors: Nastaran Hashemi, Mark Paul, Harry Dankowicz, Myung Woo Lee, Wonho JheAbstract:We study the Power Dissipated by the tip of an oscillating micron-scale cantilever as it interacts with a sample using a nonlinear model of the tip-surface force interactions that includes attractive, adhesive, repulsive, and capillary contributions. The force interactions of the model are entirely conservative and the Dissipated Power is due to the hysteretic nature of the interaction with the capillary fluid layer. Using numerical techniques tailored for nonlinear and discontinuous dynamical systems we compute the exact Dissipated Power over a range of experimentally relevant conditions. This is accomplished by computing precisely the fraction of oscillations that break the fluid meniscus. We find that the Dissipated Power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. Even for regions where the cantilever dynamics are highly irregular the fraction of oscillations breaking the fluid meniscus exhibits a simple trend. Using our results we also explore the accuracy of the often used harmonic approximation in determining Dissipated Power.
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the Dissipated Power in atomic force microscopy due to interactions with a capillary fluid layer
Journal of Applied Physics, 2008Co-Authors: Nastaran Hashemi, Mark Paul, Harry Dankowicz, Myung Woo Lee, Wonho JheAbstract:We study the Power Dissipated by the tip of an oscillating micron-scale cantilever as it interacts with a sample using a nonlinear model of the tip-surface force interactions that includes attractive, adhesive, repulsive, and capillary contributions. The force interactions of the model are entirely conservative and the Dissipated Power is due to the hysteretic nature of the interaction with the capillary fluid layer. Using numerical techniques tailored for nonlinear and discontinuous dynamical systems we compute the exact Dissipated Power over a range of experimentally relevant conditions. This is accomplished by computing precisely the fraction of oscillations that break the fluid meniscus. We find that the Dissipated Power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. Even for regions where the cantilever dynamics are highly irregular the fraction of oscillations breaking the fluid meniscus exhibits a simple ...
Horia Andrei - One of the best experts on this subject based on the ideXlab platform.
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Matrix formulations of minimum Dissipated Power principles and nodal method of circuits analysis
2013 8TH INTERNATIONAL SYMPOSIUM ON ADVANCED TOPICS IN ELECTRICAL ENGINEERING (ATEE), 2013Co-Authors: Horia Andrei, Paul Cristian AndreiAbstract:This paper introduces new basic concepts for electrical circuits' theory. The minimum Dissipated Power is defined and demonstrated as a general principle for electrical circuits in stationary and quasi-stationary regime. Based on the matrix formulation of these principles the nodal method analysis is obtained. A number of examples presented here prove the originality of the main novel concepts.
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minimum Dissipated Power and energy two general principles of the linear electric and magnetic circuits in quasi stationary regime
2011Co-Authors: Horia Andrei, Gianfranco Chicco, Fanica SpineiAbstract:The use of the variational formulation of Power and energy functionals in the analysis of electric and magnetic circuits makes it possible to appreciate the equilibrium state attained in the circuit at a certain moment. In the present work, a Power and energy functional is built for electric and magnetic circuits in static, stationary and quasi-stationary conditions, and its limit is determined. It is shown that the minimum of this functional corresponds to the minimum Dissipated (absorbed) Power and energy in the circuit. Some applications to electric circuits and magnetic are shown
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evaluation of hilbert space techniques and lagrange s method for the analysis of Dissipated Power in dc circuits
European Conference on Circuit Theory and Design, 2009Co-Authors: Horia Andrei, Fanica Spinei, Paul Cristian Andrei, Ulrich L Rohde, Marius A Silaghi, Helga SilaghiAbstract:The basic circuit laws of DC circuits are interpreted in this paper by defining suitable functionals in terms of Dissipated Power. It is then shown that the minimum of Dissipated Power determined by taking the derivative of these functionals verifies the first Kirchhoff's law. This allows interpreting the circuit equations by using the second Kirchhoff's law and the minimum Power principles. In order to estimate the extreme values of Dissipated Power for DC circuits with modifiable parameters, and the relation between the variation in one or all the resistances of the networks and the variation of Dissipated Power we use the Lagrange's method. Numerical examples obtained with Mathematica are provided to show the practical applications and comparison between of two proposed principles of DC circuits.
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the principle of minimum Dissipated Power and the minimum energetic principle two general theorems of the linear electric and magnetic circuits in stationary regime
ISTASC'08 Proceedings of the 8th conference on Systems theory and scientific computation, 2008Co-Authors: Horia Andrei, Fanica Spinei, Nicolae JulaAbstract:The use of the Power functional in the analysis of the electric and magnetic circuits makes it possible to appreciate the equilibrium state attained in the circuit at a certain moment. In the present work, a Power functional is built for a circuit in steady-state conditions and its limit is determined. It is shown that the minimum of this functional corresponds to the minimum Dissipated Power in the circuit. Some applications to electric circuits and magnetic are shown.
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on existence of the principles of minimum Dissipated Power for linear and nonlinear electric circuits
International Conference on Mathematical Methods and Computational Techniques in Electrical Engineering, 2006Co-Authors: Horia Andrei, Fanica Spinei, Costin Cepisca, Gianfranco Chicco, Sorin Dan Grigorescu, Nicolae JulaAbstract:The principles of the minimum Dissipated Power are extremely important in the analysis of electrical circuits, and represent the equilibrium state of all the circuit. For demonstrate these principles, in the present work, a Power functional is built for a circuit in steady-state conditions and its limit is determined. It is shown that the minimum of this functional corresponds to the minimum Dissipated Power in the circuit. Some applications to electric linear and nonlinear circuits are shown.