Contrôles non destructifs par ultrasons aux AMD-BA. Résultats d’une politique de métrologie^*

Experience of quantitative NDE by UT at AMD-BA : success of a continuous calibration policy

Chef de Service Contrôle Qualité, Avions Marcel Dassault-Bréguet Aviation, Biarritz

Abstract

Non Destructive Testing and design evolution towards composite main structures for aircrafts have to match: this is the reason why Avions Marcel Dassault-Breguet Aviation (AMD-BA) has developped a continuous calibration policy in UT technique which is the only way leading to industrial quantitative evaluation. The authors illustrate the previous statement by an actual recognized example: inspection of graphite-epoxy skins by Double- Through transmission technique. The complete policy is detailed, from calibration of the measuring method (material behaviour) to final adjustments of the multichannel facilities. Impressive results, such as repeatability within a ± 1 dB range, are the consequences of this approach. Then calibration of ultrasonic transducers is described, with the various methods in use at AMD-BA including a dedicated “Reference Transducer”. Because application of a comparable policy is of great interest for portable units or in service inspection, specific calibration stands have been integrated in its laboratories and perform tests on AMD-BA and French Air Force equipments. Many NDT specialists may say that this policy needs a lot of money to be applied, and that is true with conventional laboratory test equipments which are expensive and call for experienced technicians. Thus a cooperation team, General Research Corporation in USA and AMD-BA in France, has designed a low cost/easy to use/portable calibration system which is under development. A first version of this system is commercially available for transducers evaluation (Transducer Evaluation System).