NONDESTRUCTIVE EVALUATION OF DEFECTS IN NOT-PRESSED CERAMIC NOZZLES BY COMBINED ELECTROACOUSTIC TECHNIQUE
Yanis I. Bulbik*, Nicolaj V. Vasilenko*, Lev N. Loginov**
* Siberian Acrospace Academy, Krasnoyarsk-660014, Russia
** Russian Engineering Academy Siberian Branch, Krasnoyarsk- 660073, Russia
Keywords: NDE, Electro Acoustic, Defect, ceramic, thermal shock
ABSTRACT The main service time limiting component of electric outer space propulsor as so-called closed-drift thruster (CDT) is its discharge ceramic chamber, or more simply the nozzle. The hot- pressed ceramic nozzles, produced on the base of nonoxide powders as BN, AIN, Si3N4 with some additives, can be recognized as responsible parts of the CDT designed for the working under hard conditions. They must possess a low spraying rate at the plasma flow exhausting for long time, very low electrical conductivity at high temperatures, besides, they must endure repeating thermal shocks. A presence of some defective latent zones in the nozzle wall can be brought to its nonuniform erosion wear and to cut the CDT service time. A nondestructive evaluation (NDE) technique of ceramic nozzle properties based on the combined electroacoustic sensing is considered. Combined test action is produced by pulse wise electric field excitation accompanying with an acoustic wave propagation from some selected external zone surface of the nozzle while its opposite surface is being subjected to an additional test heating at varying temperature gradient with respect to the sidewall surface. The setup features and NDE results are also discussed.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.full paper not received
Publisher: Ashgate Publishing Company
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