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A facility for characterizing the dynamic mechanical behavior of thin membranes for microelectromechanical systems (2002)

Hall, J. D. ; Apperson, N. E. ; Crozier, B. T. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 73 (2002), S. 2067-2072

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: A bulge testing system capable of applying static and dynamic loads to thin film membranes is described. The bulge tester consists of a sealed cavity, filled with a fluid, bounded on the bottom by a circular stainless steel diaphragm and on the top by the thin film membrane of interest. An actuator is used to apply either a static or a periodic force to the stainless steel diaphragm. The force is transmitted through the water to the thin film membrane. This facility provides for both accelerated lifetime testing and simulated service environment testing. The thin film membranes tested are composite stacks consisting of thin films of silicon, glass, metallic electrodes, and lead-zirconate-titanate. Pressure and deflection of a membrane are acquired simultaneously during loading. An image capture system coupled with an interferometer provides the means to capture interferograms of deflected membranes during both static and dynamic testing conditions. Images are then postprocessed to construct deflection versus pressure relationships, which can be used to extract materials' properties. Accelerated lifetime testing is performed by subjecting the thin film membranes to cyclic loading at strain levels 45%–90% of the static failure strains. In simulated service environment testing thin film membranes are subjected to cyclic loading over a range of frequencies. For a given applied force, as the resonant frequency is approached the dynamic behavior of the thin film structures vary significantly from that observed for static loading. At resonance the deflection of a thin film membrane is almost three times that of a statically deflected membrane subjected to the same applied force. © 2002 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1470227

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Transient temperature measurements in a convectively cooled droplet (1998)

Richards, C. D. ; Richards, R. F.

Springer

Experiments in fluids 25 (1998), S. 392-400

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ISSN: 1432-1114

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The transient cooling of an evaporating water droplet, suspended in a jet of dry air, was experimentally investigated in this study using thermochromic liquid crystal thermography. Microencapsulated beads of thermochromic liquid crystals, suspended in the water droplets, enabled the visualization of the transient temperature fields within the droplets. Digital movies of the convectively cooled droplets reveal spatial and temporal temperature gradients resolved down to length scales of ∼100 μm and time scales of ∼0.03 s. The transient temperature measurements were analyzed to yield total droplet convective heat transfer rates. Droplet heat transfer rates determined from a heat balance on the droplets compare favorably to previously published measurements.