Abstract
A new, non-destructive methodology is proposed in this work in order to determine the mechanical properties of membrane using vibro-acoustic tests. This procedure is based on the dynamic analysis of the behavior of the membrane. When the membrane is subjected to a sound excitation it responds by vibrating based on its modal characteristics and this modal parameter is directly related to its mechanical properties. The paper is structured in two parts. First, the theoretical bases of the test are presented. The interaction between the sound waves and the membrane (mechano-acoustic coupling) is complex and requires meticulous study. It was broadly studied by means of numerical simulations. A summary of this study is shown. Aspects, such as the position of the sound source, the measuring points, the dimensions of the membrane, the frequency range, and the magnitudes to be measured, among others, were evaluated. The validity of modal analysis curve-fitting techniques to extract the modal parameter from the data measures was also explored. In the second part, an experimental test was performed to evaluate the validity of the method. A membrane of the same material with three different diameters was measured with the aim of estimating the value of the Young’s modulus. The procedure was applied and satisfactory results were obtained. Additionally, the experiment shed light on aspects that must be taken account in future experiments.
Highlights
Thin film materials are elements present in multitude of engineering problems, such as the study of microdevices or biomechanics, and their characterization is essential to predicting and simulating their behavior
Many aspects come into play, especially when the manipulation of small samples is necessary, the magnitude to measure is small and the setup presents many parameters to consider
As described in previous section, the circular fit method is based on the Nyquist diagram, where the presence of a natural mode of vibration can be identified as a circumference on the frequency response function (FRF)
Summary
Thin film materials are elements present in multitude of engineering problems, such as the study of microdevices or biomechanics, and their characterization is essential to predicting and simulating their behavior. The determination of the mechanical properties of a material is a difficult problem to solve when it is in its membrane form. These materials present a small thickness and low stiffness. One of the best-known tests to determine mechanical properties is the tensile test. With this test, the Young’s modulus is determined, among other mechanical characteristics, and it is a destructive test. In [1], both the tensile test and resonance techniques were used to mechanically characterize boron-doped silicon films with thicknesses of 1 to 4 μm. In [3], thin micromembranes were subjected to compressive stresses, with or without initial deflections, to determine the Young’s modulus and the residual stress of the micromembranes for use in microdevices
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