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Some of the most popular flexural damping apparatuses use the well-known cantilevered beam method. However, these apparatuses suffer from a major disadvantage: some energy is always lost in the grips leading to a systematic error in the measured value of damping. Another popular damping apparatus uses a free-free beam suspended at its nodes by two strings. Since it is virtually impossible to find the exact location of the nodes, some energy is inevitably lost in the vibration of the strings, leading once again to a systematic error in the measured value of damping. Historically, specific damping capacity (Ψ) values have been reported with an accuracy εΨ = O(10-3). Here Ψ ≡ ΔW/W, where ΔW is the energy dissipated per cycle, and W is the maximum elastic stored energy.
In this paper, we report some simple experimental procedures for improving the measurement accuracy by one order of magnitude. We will show that either the cantilevered beam or the free-free beam can be used to measure the specific damping capacity to an accuracy of εϵ = O(10-4).
specific damping capacity, flexural damping, cantilevered beam, free-free beam, end-mass, material damping, internal stress, internal friction, mechanical properties
Graduate research assistant, Texas A&M University, College Station, TX
Professor of Aerospace Engineering and associate director, Center for Mechanics of Composites, Texas A&M University, College Station, TX