01:58 Feb-28-1998 Rolf Diederichs Director, Editor, Publisher, Internet, PHP MySQL NDT.net, Germany, Joined Nov 1998 600
This Month's UTonline Forum Introduction
This Month's UTonline Forum Introduction
This month's articles focus on Ultrasonic Transducers and Arrays, generated by piezoelectric or electromagnetic (EMAT). As usual, this will be the theme of our discussion. If you are interested in other ultrasonic testing topics, don't hesitate to discuss them on this forum as well.
We are pleased to introduce this month Rainer Meier and Gerard Fleury as our experts for this month. They will serve as coordinators for comments on their areas of expertise for the March 1998 Forum of NDTnet. Both are current Virtual Session Chairman and will serve on the 'Ask the Experts' panel.
~~~~ Rainer Meier has worked at Siemens in the NDT-field since 1978. He is responsible for the development and implementation of innovative NDE-products and services. He is especially knowledgeable about the use of stochastic methods for signal improvement, Neural Networks for defect recognition, EMAT probes and EMAT applications, and the examination of small laserwelds using extremely focused piezoelectric probes.
Mr. Meier's opening message: The electromagnetic generation of ultrasound requires good conductivity in the material that has to be inspected. The sound generation is very efficient in ferromagnetic materials and in highly conductive materials like aluminum. In materials such as stainless steel or nickel-based alloys the sound generation is usually sufficient. The most significant advantage of EMAT is its ability to generate horizontal polarized shear waves (SH-waves). Other advantages are sound generation without couplant and the possibility of using the EMAT-principle at higher temperatures. The use of SH-waves shows important advantages compared with conventional wave modes:
- propagation of a pure wave mode without energy loss due to wave conversion or dispersion and without unambiguous echoes caused by unexpected wave modes
- corner effect delivers a good echo from the probe's far surface over the whole range of incidence angles less interference with the weld geometry in coarse-grained materials with directed grain structures (stainless steel and dissimilar welds)
- sensitivity for special material properties like texture, etc.
Therefore, EMAT with its advantages enables new and interesting solutions for some important examination tasks.
Related article: http://www.ndt.net/article/0398/meier/meier.htm New EMAT Probes useful for various Applications D. Lingenberg, R. Meier
~~~~~~ Gerard Fleury is managing director of IMASONIC SA. He currently works on new applications of piezocomposite transducers. His experience in transducers includes numerous NDT/NDE applications where piezocomposite technology is used to improve inspections and reach new targets on technical or functionality aspects.
Mr. Fleury's opening message: Current Inspection performance needs vary greatly. Although standard transducers achieve satisfactory results for some applications, there is an increasing demand for new approaches and new features. Transducer design and production according to the specific functionality of each inspection is one way to accomplish this; the use of phased array transducers with variable characteristics, notably beam focusing and beam steering, is another. Articles from TECNATOM (SPAIN) and UPPSALA UNIVERSITY (SWEDEN) illustrate recent developments using innovative transducers.
Related articles: http://www.ndt.net/article/0398/meier/meier.htm Ultrasonic Inspection of Copper Canisters using Phase Arrays T. Stepinski, P. Wu, E. Martinez, Uppsala University
http://www.ndt.net/article/0398/tanarro2/tanarro2.htm Turbine Blade Attachment In Service Inspection through the Central Bore using Ultrasonic Array Technology A. Tanarro; F. Godinez; P. Serrano (TECNATOM,S.A.- MADRID-Spain)
http://www.ndt.net/article/0398/tanarro1/tanarro1.htm Ultrasonic Inspection of Complex Nozzles - Application of new Technologies A. Tanarro and A. Garcia (TECNATOM,S.A.-MADRID-Spain)
~~~~~ Now it's your turn, let's start our discussion. Your personnel question could be answered.
- Enjoy - Rolf Diederichs
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