scholarly journals Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Michelangelo-Santo Gulino ◽  
Mara Bruzzi ◽  
James Norbert Caron ◽  
Dario Vangi
Keyword(s):  
Laser Beam ◽  
Acoustic Waves ◽  
Detection System ◽  
Surface Acoustic Waves ◽  
Ultrasonic Inspection ◽  
Two Dimensions ◽  
Probe Laser ◽  
Acoustic Detection ◽  
Probe Laser Beam ◽  
Subsurface Defects

AbstractGas-Coupled Laser Acoustic Detection (GCLAD) is an ultrasonic, non-contact detection technique that has been recently proven to be applicable to the inspection of mechanical components. GCLAD response raises as the intersection length between the probe laser beam and the acoustic wavefront propagating in the air increases; such feature differentiates the GCLAD device from other optical detection instruments, making it a line detection system rather than a point detector. During the inspection of structures mainly extending in two dimensions, the capability to evidence presence of defects in whichever point over a line would enable moving the emitter and the detector along a single direction: this translates in the possibility to decrease the overall required time for interrogation of components compared to point detectors, as well as generating simpler automated monitoring layouts. Based on this assumption, the present study highlights the possibility of employing the GCLAD device as a line inspection tool. To this end, preliminary concepts are provided allowing maximization of the GCLAD response for the non-destructive testing of components which predominantly extend in two dimensions. Afterwards, the GCLAD device is employed in pulse-echo mode for the detection of artificial defects machined on a 12 mm-thick steel plate: the GCLAD probe laser beam is inclined to be perpendicular to the propagation direction of the airborne ultrasound, generated by surface acoustic waves (SAWs) in the solid which are first reflected by the defect flanks and subsequently refracted in the air. Numerical results are provided highlighting the SAW reflection patterns, originated by 3 mm deep surface and subsurface defects, that the GCLAD should interpret. The subsequent experimental campaign highlights that the GCLAD device can identify echoes associated with surface and subsurface defects, located in eight different positions on the plate. B-scan of the component ultimately demonstrates the GCLAD performance in accomplishing the inspection task.

scholarly journals Non-Contact Ultrasonic Inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

2021 ◽  
Author(s):  
Michelangelo-Santo Gulino ◽  
Mara Bruzzi ◽  
James Caron ◽  
Dario Vangi
Keyword(s):  
Laser Beam ◽  
Acoustic Waves ◽  
Detection System ◽  
Surface Acoustic Waves ◽  
Ultrasonic Inspection ◽  
Two Dimensions ◽  
Probe Laser ◽  
Acoustic Detection ◽  
Probe Laser Beam ◽  
Subsurface Defects

Abstract Gas-Coupled Laser Acoustic Detection (GCLAD) is an ultrasonic, non-contact detection technique that has been recently proven to be applicable to the inspection of mechanical components. GCLAD response raises as the intersection length between the probe laser beam and the acoustic wavefront propagating in the air increases; such feature differentiates the GCLAD device from other optical detection instruments, making it a line detection system rather than a point detector. During the inspection of structures mainly extending in two dimensions, the capability to evidence presence of defects in whichever point over a line would enable moving the emitter and the detector along a single direction: this translates in the possibility to decrease the overall required time for interrogation of components compared to point detectors, as well as generating simpler automated monitoring layouts. Based on this assumption, the present study highlights the possibility of employing the GCLAD device as a line inspection tool. To this end, preliminary concepts are provided allowing maximization of the GCLAD response for the non-destructive testing of components which predominantly extend in two dimensions. Afterwards, the GCLAD device is employed in pulse-echo mode for the detection of artificial defects machined on a 12 mm-thick steel plate: the GCLAD probe laser beam is inclined to be perpendicular to the propagation direction of the airborne ultrasound, generated by surface acoustic waves (SAWs) in the solid which are first reflected by the defect flanks and subsequently refracted in the air. Numerical results are provided highlighting the SAW reflection patterns, originated by 3 mm deep surface and subsurface defects, that the GCLAD should interpret. The subsequent experimental campaign highlights that the GCLAD device can identify echoes associated with surface and subsurface defects, located in eight different positions on the plate. B-scan of the component ultimately demonstrates the GCLAD performance in accomplishing the inspection task.

Enhancement of the thermal lens signal induced by sample matrix absorption of the probe laser beam

2002 ◽  
Vol 41 (27) ◽  
pp. 5814 ◽  
Author(s):  
Victor I. Grishko ◽  
Chieu D. Tran ◽  
Walter W. Duley
Keyword(s):  
Laser Beam ◽  
Thermal Lens ◽  
Probe Laser ◽  
Sample Matrix ◽  
Probe Laser Beam ◽  
Thermal Lens Signal

scholarly journals Acoustic tweezers via sub–time-of-flight regime surface acoustic waves

2016 ◽  
Vol 2 (7) ◽  
pp. e1600089 ◽  
Author(s):  
David J. Collins ◽  
Citsabehsan Devendran ◽  
Zhichao Ma ◽  
Jia Wei Ng ◽  
Adrian Neild ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Acoustic Waves ◽  
Optical Waveguides ◽  
Surface Acoustic Waves ◽  
Time Of Flight ◽  
Microfluidic Channel ◽  
Two Dimensions ◽  
Acoustic Standing Wave ◽  
Spatial Dimensions ◽  
Acoustic Tweezers

Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides.

Prozessüberwachung beim Laser-Strahlschmelzen mit akustischen Signalen*/Monitoring a laser beam melting process with acoustic signals

2017 ◽  
Vol 107 (11-12) ◽  
pp. 818-823
Author(s):  
N. Eschner ◽  
J. Lingenhöhl ◽  
S. Öppling ◽  
G. Prof. Lanza
Keyword(s):  
Laser Beam ◽  
Acoustic Waves ◽  
Ultrasonic Inspection ◽  
Melting Process ◽  
Acoustic Signals ◽  
Inspection System ◽  
Near Surface ◽  
Surface Areas ◽  
Melt Pool ◽  
Laser Beam Melting

Gegenwärtig ist bei der additiven Fertigung eine prozessbegleitende Überwachung des Bauteils auf das Schmelzbad und oberflächennahe Bereiche limitiert. Mithilfe akustischer Signale lassen sich typische Defekte, die im Rahmen des LBM (laser beam melting – Laserstrahlschmelzen)-Verfahrens auftreten, detektieren. Dies umfasst neben Porosität und Rissen auch Eigenspannungen. In diesem Fachbeitrag werden die Möglichkeit eines in den LBM-Prozess integrierten akustischen Prüfsystems sowie alternative Sensorkonzepte diskutiert und evaluiert.   Current process monitoring techniques for additive manufacturing are limited to the melt pool and near-surface areas. Typical defects that occur within the LBM-process, such as porosity and cracks, as well as residual stress, can be detected by using acoustic waves. In this article, the possibility of an integrated ultrasonic inspection system, as well as various sensor concepts are discussed and evaluated.

Spatial Mapping of Transient Atomic Concentrations Using Acousto-Optic Deflection

1986 ◽  
Vol 40 (6) ◽  
pp. 863-868 ◽  
Author(s):  
Carmen W. Huie ◽  
Edward S. Yeung
Keyword(s):  
Laser Beam ◽  
Sodium Tungstate ◽  
Imaging System ◽  
Region Of Interest ◽  
One Dimension ◽  
Probe Laser ◽  
Spatial Mapping ◽  
Spatial Region ◽  
Probe Laser Beam ◽  
Transient Events

We report a new imaging system for obtaining spatially and temporally resolved atomic absorption profiles for transient events. This is based on an aconsto-optic beam deflector that scans the probe laser beam in one dimension repeatedly across the spatial region of interest. Scan rates of 10 µs durations essentially freeze the absorbing species in time to allow a spatial resolution of 0.06 cm over a 1.2 cm length. With the use of 2K of buffer memory and a digitization interval of 200 ns (12 bits), the time evolution can be followed up to a total of 400 µs. The capabilities are demonstrated in the study of atom formation in a laser-generated plume from a sodium tungstate surface.

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