Electromagnetic Acoustic Transducers (EMATs) Design Evaluation of their Performances

摘要

The non-destructive testing (NDT) by ultrasounds is increasingly asked by manufacturers in the framework of the products quality insurance and preventive maintenance. It offers, as compared to the radiography many advantages among others: the security, the flexibility and the cost. However, this technique requires some precautions during a testing, namely: 1) the use of a couplant. 2) the necessity to have a good state of surface, 3) The method involve mechanical contact between the power source and the pieces tested. To improve the flexibility and the rapidity of this method, it would be useful to generate and receive acoustical waves with a contactless electromagnetic probe. The contactless electromagnetic-acoustic transducers (EMATs) offer several advantages, which have an essential importance for the non-destructive testing with ultrasound. This work consists of EMATs conception and construction for the contactless excitation and detection of different wave-types. We have conceived and realised receivers and transmitters EMATs. This paper is a report of experiments results with these different types of EMATs. We examine the different parameters that influence them in order to optimise them and to know the degree of the applicability of this technique in the non-destructive testing of materials in Algeria.