Numerical study of the Time-of-Flight Pulsed Ultrasonic Polar Scan for the determination of the full elasticity tensor of orthotropic plates

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

et al. 2019

Numerical finite elements simulations and postprocessing analysis methods are presented for Ultrasonic Polar Scan (UPS) measurements involving a Circular Phased Array (C-PA) to determine the plane wave reflection coefficient of plates. Apodization weights for the C-PA elements are determined in order to assure the generation of a quasi-plane wave upon excitation at the plate surface and to mitigate bounded beam effects on the assessed reflection coefficient. In addition, postprocessing of the reflection signals is performed via the synthetic plane wave technique to further filter out any bounded beam effects. Reflection coefficients for three test cases are presented, namely for an aluminum, a unidirectional Carbon Epoxy and a cross-ply Carbon Epoxy plate. For all three cases, the comparison with analytical plane wave theory shows an excellent agreement with the reflection coefficients obtained by the C-PA and the additional post-processing steps for both pulsed and harmonic signals. It is also shown that the agreement becomes considerably worse if the non-specular reflection field is disregarded in the post-processing treatment, thus enforcing the need to capture the full reflected field via the Phased Array whenever plane wave reflection coefficients are needed.

Section: A Simulation Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Study of a Phased Array-Based Ultrasonic Polar Scan to Determine Plane-Wave Reflection Coefficients of Plates

Daemen

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

et al. 2019

“…The contours of these diagrams are related to the viscoelastic properties of the insonified medium. Therefore these diagrams can be used in an inverse characterization routine to identify the viscoelastic properties [6,7]. The technique is well suited for the study of anisotropic samples as it does not require a-priori knowledge on the mechanical symmetry.…”

Section: Introductionmentioning

confidence: 99%

Matching Spectroscopy with the Ultrasonic Polar Scan for Advanced NDT of Composites

Verboven

The 18th International Conference on Experimental Mechanics

et al. 2018

The Pulsed Ultrasonic Polar Scan (P-UPS) is a powerful technique for characterizing anisotropic materials like fiber reinforced plastics. A time-domain analysis of the ultrasonic signals yields amplitude and time-of-flight polar diagrams that provide a fingerprint of the local stiffness properties. Though, this simple analysis ignores a lot of information contained in the ultrasonic signals. In this study, we propose to use the P-UPS technique in combination with the spectroscopic analysis of broadband pulses, to obtain plane wave transmission spectra for all in-plane polar angles. This allows us to combine on one hand the strengths of the P-UPS technique, that does not require a priori knowledge about the sample anisotropy, and on the other hand the frequency-domain analysis that utilizes information contained in the broadband pulses.

“…This signal interacts with the plate after which its reflection or transmission signal is measured by a second transducer. Polar plots of the amplitude or the Time-of-Flight (TOF) of these signals then show characteristic contours which offer a local fingerprint of the stiffness parameters of the material, which can be extracted by means of an inversion algorithm [5][6][7]. For harmonic excitation signals, the extrema in the polar plots correspond to the conditions for efficient Lamb wave stimulation, which offer a similar relation to the stiffness parameters.…”

Section: Introductionmentioning

confidence: 99%

Towards a Phased Array Based Ultrasonic Polar Scan: Simulation Study and Comparison with Plane Wave Results

Daemen

The 18th International Conference on Experimental Mechanics

et al. 2018

Abstract:The ever-increasing use of composite materials in the industry has resulted in the need for new, intricate approaches to not only properly characterize their anisotropic mechanical properties (i.e., the visco-elastic tensor), but also to detect various types of internal flaws. Both goals can be achieved by the Ultrasonic Polar Scan (UPS). During an UPS experiment, a material spot is insonified at many oblique incidence angles Ψ(θ,φ), with θ the vertical incident angle and φ the inplane polar angle, after which the reflected or transmitted ultrasound signal is recorded. The resulting dataset provides an integral view of the angle-dependent reflection (R) and transmission (T) scatter coefficients, and can be employed to infer the material properties. Although the current UPS scanner provides highly accurate experimental data, it is impractical for in-situ measurements. In order to create a more compact and practical measuring device, we propose the use of a hemispherical phased array, consisting of small piezoelectric elements, to generate a broadband, quasi plane wave signal. It will be shown, based on simulations, that a circular phased array concept allows for the determination of the reflection coefficients in θ − f space, from which the dispersion curves can be immediately inferred. Comparison of these results with the plane wave theoretical results show an excellent agreement.