Search results for "Laser Ultrasonic"
showing 7 items of 17 documents
Observability of the Risken–Nummedal–Graham–Haken instability in Nd:YAG lasers
2003
Multilongitudinal mode instability in ring Nd:YAG lasers is theoretically analyzed. After we review the way in which the standard two-level laser theory applies to this laser we extend the theoretical treatment to include transverse effects. We do this by taking into account the finite transverse section of the active medium and by assuming a Gaussian transverse distribution for the intracavity field. Finally we demonstrate that multimode emission develops whenever the intracavity field waist diameter is almost equal to the active rod diameter. We conclude that continuous-wave diode-pumped Nd:YAG lasers with low cavity losses are good candidates for the observation of the Risken–Nummedal–Gr…
Laser-ultrasonics: a non-contact method to link the acoustic attenuation to metal damping properties up to the melting point
2004
The objective of this work is to describe the viscoelastic behavior of metals up to their melting temperature by measuring the velocity and the attenuation of ultrasonics waves. For that purpose, a technique called laser-ultrasonics has been optimized for the high temperature domain and the solid to liquid transition. This paper is especially applied to the viscoelastic characterization of tin, from room temperature up to the melting point.
Laser ultrasonics for defect evaluation on coated railway axles
2020
Abstract This scientific paper focuses on the application of an advanced non-destructive technique for an effective inspection of railway axles. The method pertains to ultrasonic techniques, which are widely used in the railway field. The experimental investigation was carried out on simulated defects tooled near the cross section reduction of the axle, in order to simulate fatigue cracks which, due to notch effect, can trigger crack propagation and axle failure. The aim of this research activity is to evaluate how efficiently the proposed technique detects defects and to verify its applicability to axles with a black coating for protection. In view of the experimental setup, comprising a p…
Defect detection in laser powder deposition components by laser thermography and laser ultrasonic inspections
2013
Laser Powder Deposition (LDP) techniques are being adopted within aerospace and automotive manufacturing to produce innovative precision components. Non-destructive techniques (NDT) for detecting and quantifying flaws within these components enables performance and acceptance criteria to be verified, improving product safety and reducing ongoing maintenance and product repair costs. In this work, software enabled techniques are presented for in-process analysis of NDT laser ultrasonic signals and pulsed laser thermography images of sequential metallic LPD layers. LPD tracks can be as thin as 200μm while deposited at a rate of 500 mm/min, requiring ultrafast inspection and processing times. …
The Development and Commissioning of a Laser-Based Ultrasonic Rail Inspection System
2009
Inspection of laser powder deposited layers
2013
Rail and Joint Bar (Fish Plate) NDE Advances in North America
2010
Improvement and development of rail track nondestructive inspection (NDI) technologies to reduce in-service failures of rail and joint bars (fish plates) in a continuous effort to make rail transport safer is a primary focus for the railroad industry. Researchers at The Transportation Technology Center, Inc., working under the direction of the Association of American Railroads and its Strategic Research Initiative Program, have worked with companies worldwide to develop novel NDI approaches for dynamic inspection of rail and joint bars. In the area of rail inspection an ultrasonic rail (U-Rail) system for noncontact rail flaw inspection has been developed. This system combines high energy l…