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Modeling and analysis of a phase change material thermohydraulic membrane microactuator
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.ORCID iD: 0000-0003-3336-1462
Micro systems technology programme, Uppsala University.
(Micro systems technology programme, Uppsala University)
2013 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 22, no 1, 186-194 p.Article in journal (Refereed) Published
Abstract [en]

Presented in this work, is a Finite Element Method (FEM)-based model for phase change material actuators, modeling the active material as a fluid as opposed to a solid. This enables the model to better conform to localized loads, as well as offering the opportunity to follow material movement in enclosed volumes. Modeling, simulation and analysis of an electrothermally activated paraffin microactuator has been conducted. The paraffin microactuator used for the analysis in the current study exploits the large volumetric expansion of paraffin upon melting, which combined with its low compressibility in the liquid state allows for high hydraulic pressures to be generated. The purpose of the study is to supply a geometry independent model of such a microactuator through the implementation of a fluid model rather than a solid model, which has been utilized in previous studies. Numerical simulations are conducted at different frequencies of the heating source and for different geometries of the microactuator. The results are compared with the empirical data obtained on a close to identical paraffin microactuator, which clearly show the advantages of a fluid model instead of a solid state approximation.

Place, publisher, year, edition, pages
2013. Vol. 22, no 1, 186-194 p.
Keyword [en]
Finite element methods, fluid dynamics, microactuators, microelectromechanical devices, steel
National Category
Other Mechanical Engineering
URN: urn:nbn:se:kth:diva-118450DOI: 10.1109/JMEMS.2012.2222866ISI: 000314726900026ScopusID: 2-s2.0-84873288511OAI: diva2:606220
Swedish Research Council

QC 20130219

Available from: 2013-02-18 Created: 2013-02-18 Last updated: 2013-03-08Bibliographically approved
In thesis
1. Phase change with stress effects and flow
Open this publication in new window or tab >>Phase change with stress effects and flow
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis two kinds of phase change i.e., solid state phase transformation in steels and solid-to-liquid phase transformation in paraffin, have been modeled and numerically simulated. The solid state phase transformation is modeled using the phase field theory while the solid-to-liquid phase transformation is modeled using the Stokes equation and exploiting the viscous nature of the paraffin, by treating it as a liquid in both states.The theoretical base of the solid state, diffusionless phase transformation or the martensitic transformation comes from the Khachaturyan's phase field microelasticity theory. The time evolution of the variable describing the phase transformation is computed using the time dependent Ginzburg-Landau equation. Plasticity is also incorporated into the model by solving another time dependent equation. Simulations are performed both in 2D and 3D, for a single crystal and a polycrystal. Although the model is valid for most iron-carbon alloys, in this research an Fe-0.3\%C alloy is chosen.In order to simulate martensitic transformation in a polycrystal, it is necessary to include the effect of the grain boundary to correctly capture the morphology of the microstructure. One of the important achievements of this research is the incorporation of the grain boundary effect in the Khachaturyan's phase field model. The developed model is also employed to analyze the effect of external stresses on the martensitic transformation, both in 2D and 3D. Results obtained from the numerical simulations show good qualitative agreement with the empirical observations found in the literature.The microactuators are generally used as a micropump or microvalve in various miniaturized industrial and engineering applications. The phase transformation in a paraffin based thermohydraulic membrane microactuator is modeled by treating paraffin as a highly viscous liquid, instead of a solid, below its melting point.  The fluid-solid interaction between paraffin and the enclosing membrane is governed by the ALE technique. The thing which sets apart the presented model from the previous models, is the use of geometry independent and realistic thermal and mechanical properties. Numerical results obtained by treating paraffin as a liquid in both states show better conformity with the experiments, performed on a similar microactuator. The developed model is further employed to analyze the time response of the system, for different input powers and geometries of the microactuator.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 58 p.
Trita-MEK, ISSN 0348-467X ; 2013:04
Martensitic transformation, phase-field method, polycrystal, stress-effects, microactuator, finite-element simulations.
National Category
Materials Engineering Mechanical Engineering
urn:nbn:se:kth:diva-118451 (URN)978-91-7501-655-9 (ISBN)
Public defence
2013-03-13, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)

QC 20130219

Available from: 2013-02-19 Created: 2013-02-18 Last updated: 2013-02-19Bibliographically approved

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