Study of Direct-Measuring Skin-Friction Gauge with Rubber Sheet for Damping
2002; American Institute of Aeronautics and Astronautics; Volume: 40; Issue: 1 Linguagem: Inglês
10.2514/2.1640
ISSN1533-385X
AutoresSamantha Magill, Matthew MacLean, Joseph A. Schetz, Rakesh K. Kapania, A. K. Sang, Wade J. Pulliam,
Tópico(s)Structural Health Monitoring Techniques
ResumoThis study concerns the direct measuring technique for skin-friction determination. Such a device measures the force on a small, movable surface element as a shear e ow passes over the surface. The typical direct-measuring skin-friction gauge uses a viscous liquid in the gap between the movable surface piece and the casing to dampen vibrations,tocreateanevensurface,tominimizetheeffectsofpressuregradients,andfortemperaturestabilization. In testing, the liquid slowly leaks out. Therefore, we have considered gauges with rubber to e ll all or some of the gap. This led to the development of a gauge with a thin rubber sheet to cover the face of the gauge instead of a previousdesign withrubbere lling theentireinternalvolume.First, ae niteelementmethodmodelwasemployed to fully understand the strain e eld involved and to e nalize the design. The resulting design consisted of a plastic skin frictiongaugewitha12.7-mm-diam e oatingelementonacantileverbeame exure,anapproximately0.51-mm-thick rubber sheet, a 1.6-mm-wide gap around the e oating element on a cantilever beam e exure, and semiconductor strain gauges at the beam base. Vibration tests were performed to determine if this design produced the required damping. These tests were successful. Supersonic wind-tunnel tests at Mach 2.4 with a total pressure of 3 atm and ambient total temperature demonstrated that the rubber sheet survived repeated tests and provided adequate damping. The skin-friction data obtained compared well with theory and other measurements.
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