I am interested in Laser based ultrasonic Testing in Taiwan. Experimental facilities are under construction. But I still felt lack of informations about the present applications in industry, e.g. aerospace/aircraft industry. So, I need more useful informations or comments about where/how to get that.
The Nondestructive Testing Information Analysis Center (NTIAC) has published a state of the art review of laser ultrasonic NDT. You can find more information by visting the NTIAC page at http://www.ntiac.com/pubs/tech.html or sending e-mail to firstname.lastname@example.org.
Hope this helps, Chris
: I am interested in Laser based ultrasonic Testing in Taiwan. Experimental facilities are under construction. But I still felt lack of informations about the present applications in industry, e.g. aerospace/aircraft industry. So, I need more useful informations or comments about where/how to get that.
Re: Laser-Ultrasonic NDT I HAVE RECENTLY BEEN LOOKING AT A WAY OF TESTING LASER WELDS, I WORK FOR GENERAL MOTORS AND I AM CURRENTLY DEVELOPING A SYSTEM WITH KRAUTKRAMER IN COLONGE. I MAY HAVE SOME INFORMATION THAT IS OF USE TO YOU. AND VICE VERSA, IF YOU HAVE ANY INFORMATION THAT MAY HELP ME. PLEASE CONTACT ME AT THE ABOVE E ADDRESS.
05:19 Apr-18-2000 Rainer Meier R & D retired from intelligeNDT Systems & Services, Germany, Joined Nov 1998 15
Re: Laser-Ultrasonic NDT : I HAVE RECENTLY BEEN LOOKING AT A WAY OF TESTING LASER WELDS, I WORK FOR GENERAL MOTORS AND I AM CURRENTLY DEVELOPING A SYSTEM WITH KRAUTKRAMER IN COLONGE. I MAY HAVE SOME INFORMATION THAT IS OF USE TO YOU. AND VICE VERSA, IF YOU HAVE ANY INFORMATION THAT MAY HELP ME. PLEASE CONTACT ME AT THE ABOVE E ADDRESS.
Dear Mr. Goodfrey,
we develloped a UT-technique for the inspection of laserwelded tube sleeves. The tubes and sleeves were made from inconel, which shows a very coarse and directed grain structure in the weld zone. (I suppose, you want to inspect aluminum welds, where the coarse grain structure is possibly a not so big problem).
Two things were very important: The use of focused UT-beam (beam width 0.3 mm) to have a sufficient resolution at a weld with of appr. 1 mm in the keyhole area and a broad band transducer with a center frequency of 15 MHz. The UT inspection is done in 0° immersion technique.
As the result of our devellopment, we are able to determine the weld width and to inspect the weld for flaws. The condition of the weld crone is a sensitive parameter: it must be smooth enough.
I don't know your inspection problem in detail, but I suppose it's not so critical than ours (which was for a German Nuclear Power Plant). So I think there are solutions without grounding the weld crown. It would be interesting, to know your inspection requirements.
Re: Laser-Ultrasonic NDT I guess you need real information. Not just academic ones. This is mostly the problem if you discuss about LaserUS. Lots of people don't really know what they talk about. It was the same for me when we started - we where lots too enthusiastic concerning this theme. But we start now our own business in this subject. So be carefull: The technique is still too slow for industrial applications (pulse rep. rate still max 100Hz), still not scalable (multichannel is far from being availoable), sensitivity is poor.
There are some ways out, I think the most innovative approach is done by GE and Lockheed (look at the QNDE-Proceedings from the 1999 Montreal conference, e.g. Peter Lorraines Presentations) But for several reasons their swystem will not be commercialized in near future.
The only industrial setup I know is that from Dassault Aviation & Aerospatiale Matra in the Biaritz plant (UltraOptec LUIS 72) which is working quiet sufficient, but rep-rate and electronics might be improved to fulfil real tough industrial specifications - the system is already some years old. We have also visited the McClellan AFB, but this installation seems totally overpowered for commercial aeronautical applications, much too expensive and the cost/efficiency ratio is much too bad. We brought some test specimens with us and got some results with the LUIS 747 but simple aircoupled US showed better results (We visited after the AFB the company QMI and they tested the same specimen for us, this was one reason for us to invest in aircoupled US first) The LUIS 747 has the same slow speed and the lack of sensitivity as the Biaritz LUIS 72.
In general you should think of what you need and calculate what would be the best solution. Still there are different fields of application: FRP's and Metalls. It is not easy to combine a system for both as the optical and thermal behaviour is different. For CFRP a CO2 laser is still the usual approach for excitation but they are too slow and have not an optimized wavelength (and you can not send the light through a fibre). There are several options to improve this, which might also increase the Rep-Rate; but this is something to invest improvement work (e.g. Holmium-, Erbium-Laser, known from medical use, or OPO's pumped by XxYAG solid state lasers ore else to get into the range of 3...3.5µm.). On the metallic side NdYAG seems to be a sufficient solution. But who knows.... maybe somethinge better is somewhere around the corner. Even on the receiver side improvement is necessary. CFPI's are the current optimum solution, but have less potential for improvements necessary for instance for multichannel operation. Here might be the photorefractive crystal a future solution, as it is possible to use this with CCD arrays as a multichannnel sensor. But again - this needs some research work. Another way might be the PhotoEMF-solution from Lasson Ind. Finally the electronics must be fitted for advanced signalprocessing to extract the necessary informations out of some LaserUS-typical noise signals. The commercial available system here still have some obstacles left.
So you see it is not easy to decide. The most important thing to do is to improve the LaserUS-Concept is to make it fit for the competition with standard US. People researching in LaserUS often tell LaserUS is faster and more cost efficient. That's really not true. None of the few LaserUS-Systems in the industry have ever reached nearly the speed of Multichannel Squirtersystems. The only advantage might be the easier teach-in on 2-dim curved parts, if you have to test only a few different small parts per day. And there is no couplant contaminating your surface. But with current phased array techniques and multichannel approaches to conventional US as well as for air coupled US LaserUS has to make a long distance in the race to become competitor to the traditional improved US. PLease see this from the viewpoint of an engeneer who had to decide for the QC of a production line and for the QC of future structural designs beeing produced in a cost optimized factory, where each step can decide about your commercial success. In millitary applications (Lockheed, McClellan AFB etc.) things look different - cost is not that factor and production rate is not one aircraft per day etc. So their viewpoint is different. But in terms of economic aspects LaserUS is still not a competitor. If you look at the selling of a company like UltraOptec compared for instance to Krautkrämer you will realize this. On the other hand there is a future and this should be taken into account - invest some money, do some research and improvemente on the right things - and several of the disadvantages might be vanishing and hopefully LaserUS becomes the best alternative, a potential is given. Without a massive interest of the industry LaserUS will stay as it is, a playground of some scientists but with no chance for real industrialization. I think even the universities and institutes should think of what is necessary to give this technique a chance instead of developing academic ideas with no current value for a quick industrialization. Wolfgang Bisle, DaimlerChrysler Aerospace Airbus GmbH