Experimental analysis and prediction of antisymmetric wave motion in a tapered anisotropic waveguide

Abstract

This paper presents experimental results for wave propagation in an anisotropic multilayered structure with linearly varying cross section. Knowing the dispersion and wave propagation properties in such a structure is of great importance for non-destructive material testing and structural health monitoring applications for accurate damage detection and localization. In the proposed study, the wavefield is generated by a circular piezoelectric wafer active sensor and measured by a scanning laser-Doppler-vibrometer. The measurements are compared with a theoretical group delay estimation and a signal prediction for the antisymmetric wave motion along the non-uniform propagation path. The required dispersion curves are derived from the well-known global matrix method for segments of constant thickness. A multidimensional frequency-wavenumber analysis of linescan data and the full wavefield provides further insight of the adiabatic wave motion because the wavenumber changes along the tapered geometry of the waveguide. In addition, it is demonstrated that a terahertz time-domain system can be used in glass-fiber reinforced plastic structures as a tool to estimate the thickness profile of thin structures by means of time-of-flight measurements. This information is particularly important for guided wave-based diagnostics of structures with unknown thickness.

Damage localization in composite structures with smoothly varying thickness based on the fundamental antisymmetric adiabatic wave mode

“…Recently, it was found experimentally that the wave velocity of the antisymmetric wave mode changes in a glass-fiber reinforced structure with smoothly varying cross section [1]. Similar results for the second shear horizontal wave mode SH 2 can be found in [5].…”

“…The point-like damage in this example is located at (0.25 m, 0.36 m). It has been assumed that dispersion does not have a significant influence on the sensor signals as demonstrated in [1].…”

“…Each segment has an equidistant length of approximately 83 mm. The phase and group velocity are based on those values that have been used in a previous experimental study to predict the antisymmetric wave motion in a similar structure [1]. Fig.…”

Guided Waves for Damage Detection in Complex Composite Structures: The Influence of Omega Stringer and Different Reference Damage Size

“…In principle, prediction of frequency-selective reflection and attenuation is challenging, because it depends on the exact boundary conditions of a discontinuity, such as the bonding of a stringer. However, from the study of tapered waveguides, it is known that the change of thickness, e.g., due to the foot of a stringer, can lead to a frequency-selective velocity alteration in the S 0 -mode [35] and A 0 -mode [36].…”

Variable Thickness in Plates—A Solution for SHM Based on the Topological Derivative

“…The planform of the plate is curved and complex [21], which produces very complex reflected waves that may even lead to caustics [22].…”