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Static displacement component and its significance in nonlinear ultrasonic measurements
Date Issued
24-03-2008
Author(s)
Narasimha, Karthik Thimmavajjula
Kannan, Elankumaran
Indian Institute of Technology, Madras
Abstract
In the recent times nonlinear ultrasonics is being extensively studied to explore its viability to discern early material damage. The propagation of an ultrasonic wave through a damaged material leads to the generation of the harmonics of the original wave. The second harmonic generated quantifies the amount of nonlinearity present in the material and is related to the third order elastic constants of the material. However if the frequency spectrum of the transmitted wave is examined we find that there is an induced static displacement component due to the nonlinearities present in the material. This static displacement component is also related to the third order elastic constants of the material. The present paper presents a numerical simulation of propagation of an ultrasonic wave through a damaged material with focus on the generation of a static displacement component and suggests a simplified technique for measuring it. Demonstrating the fact that an asymmetry in the stress strain relationship of the material is required for the generation of a static displacement component, this paper explores its dependence on various parameters like the input amplitude, input frequency, propagation distance and the nonlinearity parameters of the material. The numerical simulations are validated against existing theories for generation of static displacement. © 2008 American Institute of Physics.
Volume
975