Crack imaging and quantification in aluminum plates with guided wave wavenumber analysis methods

Abstract Noncontact and remote NDE systems and methods are highly desired in a broad range of engineering applications such as material property characterization. This paper aims to develop such a noncontact/remote NDE system based on laser ultrasonic guided waves and establish its fundamental capability for material thickness evaluation. The noncontact system employs pulsed laser (PL) for guided wave actuation and scanning laser Doppler vibrometer (SLDV) for guided wave wavefield sensing. A cylindrical planoconvex lens is adopted to focus the pulsed laser beam to a line source in order to excite broad band signals in the target plate. Aluminum plates with different thicknesses are evaluated through SLDV line scans and 2D time-space wavefields are acquired. Frequency-wavenumber (f-k) spectra are obtained through 2D Fourier transform, and the A0 dispersion curve for each plate is extracted. Through Comparing the extracted A0 curve with the theoretical A0 dispersion curves, the thicknesses of the tested plates are identified. Reflective tape effect on the plates are also studied: the reflective tape attached for SLDV enhancement affects the guided waves in the target plate significantly when the plate is relatively thin.

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Nonlinear Guided Wave Tomography for Detection and Evaluation of Early-Life Material Degradation in Plates

Sensors ◽

10.3390/s21165498 ◽

2021 ◽

Vol 21 (16) ◽

pp. 5498

Author(s):

Chengwei Zhao ◽

Sunia Tanweer ◽

Jian Li ◽

Min Lin ◽

Xiang Zhang ◽

...

Keyword(s):

Early Life ◽

Guided Waves ◽

Lamb Waves ◽

Tone Burst ◽

Guided Wave ◽

Material Degradation ◽

Third Order Elastic Constants ◽

Metal Plates ◽

Wave Tomography ◽

Aluminum Plates

In this paper, the possibility of using nonlinear ultrasonic guided waves for early-life material degradation in metal plates is investigated through both computational modeling and study. The analysis of the second harmonics of Lamb waves in a free boundary aluminum plate, and the internal resonance conditions between the Lamb wave primary modes and the second harmonics are investigated. Subsequently, Murnaghan’s hyperelastic model is implemented in a finite element (FE) analysis to study the response of aluminum plates subjected to a 60 kHz Hanning-windowed tone burst. Different stages of material degradation are reflected as the changes in the third order elastic constants (TOECs) of the Murnaghan’s model. The reconstructed degradations match the actual ones well across various degrees of degradation. The effects of several relevant factors on the accuracy of reconstructions are also discussed.

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Characterization of Roll-Cladded Aluminum Plates With Laser-Based Surface-Acoustic-Wave Measurements

10.1115/qnde2021-74927 ◽

2021 ◽

Author(s):

Clemens Grünsteidl ◽

Georg Watzl ◽

Christian Kerschbaummayr ◽

Edgar Scherleitner ◽

Günther Mayr ◽

...

Keyword(s):

Optimization Procedure ◽

Guided Wave ◽

Laser Ultrasound ◽

Ultrasound Technique ◽

Wave Measurements ◽

Dispersion Data ◽

Free Parameters ◽

Aluminum Plates ◽

Non Destructive

Abstract We investigated roll-cladded aluminum structures consisting of a layer of Al4045 on Al3003 with a non-destructive laser-ultrasound technique. We determined the thickness of the cladding layer based on the dispersion of the fundamental guided wave propagating along the surface. We analyzed eight surfaces, with cladding thicknesses ranging from 0 to approximately 400μm The inversion of the dispersion data to obtain the thickness yielded in consistent results, which we compare to reference values obtained from micrographs. For the optimization procedure we allowed the material properties to be free parameters, but constrained them to be equal for all samples.

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