The Synthetic Aperture Focusing Technique (SAFT) is an imaging algorithm used in laser ultrasonics (LU) to visualise the appearance of defects. However, ultrasound excited by a pulsed has characteristics wide bandwidth and multi-mode directivity patterns, leading common problems SAFT process, such as low utilisation information possible artefacts. To solve these problems, Multi-mode Time-domain (MMT-SAFT) proposed this paper. influence ultrasonic discussed according depth range, with...

The Laser Ultrasonic (LU) technique has been widely studied. Detected ultrasonic signals can be further processed using Synthetic Aperture Focusing Techniques (SAFTs), to detect and image internal defects. LU-based SAFT in frequency-domain (F-SAFT) is developed visualize horizontal hole-type defects aluminum. Bulk acoustic waves are non-destructively generated by irradiating a laser line-source, detected Doppler vibrometer at point away from the generation. influence of this non-coincident...

Noninvasive photoacoustic (PA) imaging techniques afford abundant microstructure information for the diagnosis and therapeutic monitoring of diseases. However, their use bone tissue is challenging owing to high scattering attenuation properties tissue. The PA signal waveforms inherently contain optical ultrasonic related health. This study entailed development a robust, compensation-free eigen waveform analysis (PEWA) method characterizing high-scattering cancellous in transmission mode....

Abstract Photoacoustic transducers with a single photoacoustic conversion layer generate waves relatively uniform energy distribution across wide bandwidth. The spectral characteristics of the formed by multilayer optical absorbers are studied. Under excitation, transduce laser pulse into train ultrasound pulses varying time intervals. time-domain and generated acoustic field analyzed in simulation based on boundary conditions, number layers, spacing absorber. results indicate that, constant...

Abstract To address the issue of crack detection based on traditional laser ultrasonic results, conventional neural networks (CNNs) fail to utilize physical information implicitly contained in data. overcome this problem, paper adopts Physics-Informed Neural Networks (PINN), incorporating wave equation as a constraint. By using finite element simulation, we obtain out-of-plane displacement data field containing surface cracks and train PINN model capable predicting location depth cracks. The...

Abstract Based on the photoacoustic nonlinear mixing mechanism, crack contact state is affected by factors such as laser heating, signal intensity, width, interface morphology, and friction coefficient, which change characteristics of generated. To effectively utilize mechanism for micro-crack detection, it necessary to investigate relationship among source parameters, states, acoustic signals characteristics. The morphology real complex various, hence essential consider influence other...

The results of the direct experimental evaluation all elastic constants single crystal hybrid organic–inorganic perovskite (HOIP) methylammonium lead bromide, a material known due to its possible solar‐energy, optoelectronics, X‐ray detector and thermoelectricity applications, are reported. measurements anisotropic elasticity CH 3 NH PbBr by technique laser ultrasonics demonstrate that properties HOIPs can be even more remarkable than theoretical expectations: extracted shear modulus is...

The synthetic aperture focusing technique (SAFT) is used as a laser ultrasonic imaging algorithm for non-destructive internal defect testing, and multi-mode time domain SAFT (MMT-SAFT) developed to enhance the capability of detection. However MMT-SAFT has problem artifacts caused by ultrasound (LU) modes waves. Thus solve this problem, an automatic based on called Reconstructed (Re-SAFT) proposed. This consists two steps: preliminary firstly performed locate position tentatively futher...

All-optical monitoring of the nonlinear motion a surface-breaking crack is reported. Crack closing induced by quasi-continuous laser heating, while Rayleigh surface acoustic pulses and bulk longitudinal skimming are also generated detected lasers. By exploiting strong dependence reflection transmission efficiency on state—open or closed—of contacts between faces, parametric modulation ultrasonic achieved. It observed that waves along can be more sensitive to than waves.

This research focuses on analyzing the frequency characteristics of ultrasonic waves induced by a partially closed surface-breaking crack. When acoustic interact with crack, transmission, reflection, and mode conversions occur signals perform obvious changes. A pulsed laser line source is used to generate in sample one can see how detected change as beam scans across surface. The optical deflection method developed detect experimentally. fast Fourier transform (FFT) analyze time-domain data,...

The monitoring and characterization of laser-heated crack by the laser ultrasonics technique are reported. In comparison with existing studies, where Rayleigh bulk skimming waves were generated laser-induced line source, point source is used here. Crack closure thermoelastic stresses modifies propagation paths acoustic rays from a to receiver. Thus, arrival times contain useful information on state induced particular level heating. An important dependence detected signals initial width/state...

In conventional laser ultrasonic (LU) single-mode frequency domain synthetic aperture focusing technique (F-SAFT) imaging, the precision of imaged defect profile is limited due to influence directionality laser-induced ultrasound and detection. To solve this problem, LU-based F-SAFT imaging with shear wave, longitudinal mode-converted wave proposed in article. experiment, multimode bulk waves are excited by a pulsed laser, Doppler vibrometer employed detect waves. The performed signals,...

Nonlinear acoustic techniques are established tools for the characterization of micro-inhomogeneous materials with higher sensitivity, compared to linear ultrasonic techniques. In particular, evaluation material elastic quadratic nonlinearity via detection second harmonic generation by waves is known provide an assessment state variation heat treated micro-structured materials. We report on first application non-destructive diagnostics thermal aging finite-amplitude longitudinal pulses...

The application of laser ultrasonic technology to defect detection is being widely studied. Synthetic Aperture Focusing Techniques (SAFTs) one the imaging algorithms for detecting and internal defects. SAFT based on Delay Sum (DAS-SAFT) known high-quality results. However, it has disadvantages large calculation amount, which severely restricts its application. This work proposes a Co-Overlay Software Hardware method (SAFT-COSH) Zynq, uses parallelism pipeline FPGA can efficiently accelerate...

This Letter focuses on the selectively non-contact generation of Lamb wave modes in plates by using a continuous-wave (CW) laser moving along sample surface. Compared with generated waves broadband, multiple (the existence at least two any given frequency) excited pulsed laser, desired single narrowband mode can be CW as long scanning speed matches phase velocity mode. Moreover, dispersion curves obtained directly from power spectrum time-domain signal recorded each laser's speed. Single A0...

A hybrid non-destructive surface breaking crack evaluation technique, combining a Scanning Laser Source (SLS) technique and Dual is presented studied by FEM method experimentation. By using this information, such as location, depth orientation can be measured in one measurement cycle. First, the SLS employed to locate crack, detecting characteristic changes amplitude content. Then utilised quantify orientation. Numerical simulating results show good agreement with experimental results....