Laser ultrasonic testing

In this paper, the performanees of laser-ultrasound are estimated in order to identify lacks of weld penetration. The laser-ultrasonic technique is applied to cylindrical metallic strucmres (few mm thick) in a single-sided control. The results obtained for different materials (gold-nickel alloy and tantalum) are presented by B-sean views for which the control configuration is discussed with regard to the thermal effects at the laser impact. This testing is performed for different lacks of weld penetration (up to 0.5 mm for a thickness of 2 mm) even in the presence of the weld bead, which corresponds to an actual industrial problem. 

Scotch-tape test [13,16-20] Abrasion test [18,21] Bend and stretch test [15,22] Shearing stress test [22-24] Direct pull-off method [15,25-39] Moment or topple test [40-43] Electromagnetic tensile test [44] Laser spalation test [45] Ultracentrifuge test [13,22,46-50] Ultrasonic test [13,76] Peeling test (13, 51-54] Tangential-shear test [55,56] Scratch test [50,52, 57-73]... 

Monchalin J-P (1993) Progress towards the application of laser ultrasonics in industry. In Thompson DO, Chimenti DE (eds) Review of progress in QNDE 12. Plenum Press, New York, pp 495-506 Monchalin J-P (2007) Laser-ultrasonics principles and industrial applications. Chap 4. In Chen CH (ed) Ultrasonic and advanced methods for nondestructive testing and material characterization. World Scientific, Singapore, pp 79-115 Pilarski A, Rose JL, Balasubramian K (1990) The angular and frequency characteristics of reflectivity from a solid layer embedded between two solids with imperfect boundary conditions. J Acoust Soc Am 87 532-542... 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

For composite samples the method discriminated separate Ti02 and CaC03 components and accurately determined their proportions. In addition, in combination with ultrasonic attenuation measurements, the size fractions of iron ore slurries below 10 and 30 pm were determined to within 1.3% and 1.0% respectively when compared with laser diffraction measurements [272]. According to Coghill et. al. velocity measurements are complementary to attenuation methods but better suited to the finer size fractions. A description of the analyzer and the results of plant feasibility tests and on-line installation has been presented [273]. 

Chemical analysis of polymers typically deals with monomers or functional groups rather than constituent atoms. Thermal infrared and laser optical Raman spectrometry are the typical tools (36) (see Test Methods Vibrational Spectroscopy), but frequently, specific specimen size or form is required. For physical properties, mechanical and sonic/ultrasonic NDT methods are available (see above). Molecular mass distribution and related properties of polymers, or fiber or particle volume fraction and distribution for PMC, are usually determined destructively (see Test Methods). 

Billson, D.R., Hutchins, D.A., Laser-EMAT ultrasonic measurements of bonded metals. Nondestr. Test. Evai., 10(1), 43-53 (1991). 

It is shown that a variety of techniques are available for disbond detection, ultrasonics, and different types of bond tester being the most commonly used. These techniques are very time consuming, especially if large bond areas are to be tested. Monitoring interfacial properties is much more difficult and there is currently no reliable test after the joint is made although there are some indications of a possible way forward using high-powered lasers. 

The wheelchair used as an experimental validation of the proposed system has improved navigation for quadriplegic users. The research group has implemented the system in a way that it can navigate in a semiautonomous mode, in both indoor and outdoor environments. With a set of ultrasonic sensors, a laser beam sensor, a solid-state compass, and accelerometer sensors, among others, the wheelchair provides an ideal platform to test and validate the secure navigation system proposed in this work. 

---