An attempt was made to develop an ultrasonic nondestructive evaluation technique for detection of poor interfacial bonding between the rubber liner of a cylindrical rocket motor and the solid fuel propellant. The challenge originates from the very poor ultrasonic transmission properties of the rubber liner, and also from the acoustic impedance mismatch between the rubber and outer steel casing of the structure. Experiments were conducted to investigate the feasibility of using various ultrasonic techniques to characterize the bond condition. The frequency dependant shear and longitudinal wave velocities and attenuation coefficients of the rubber liner material used in a solid propellant rocket motor were measured. These, in conjunction with the properties of the other components of the motor were used to characterize the ultrasonic response of the layered motor structure. The vast impedance difference between the rocket casing and rubber liner and the high attenuation coefficient of the rubber makes it extremely difficult to get ultrasonic energy into the liner and then back again into the casing. In particular, the enormous shear wave attenuation coefficient prevents the application of Lamb wave-based techniques. Normal beam compression wave testing is the only realistic method of interrogating the rubber/propellant interface, although such wave modes are not well-known for sensitivity to kissing bonds. Total debonds are detectable by this technique, although the relevant signatures are not very strong and require great care in test setup for obtaining reproducible results. Such indications of debonds were observed in the frequency domain on flat plate samples. The damaged areas of an analog rocket motor with artificial defects were also detectable by ultrasound. Any further work in this area should make a thorough assessment of the effects of casing thickness and the protective paint layer on the detection sensitivity. The authors wish to acknowledge the financial support provided by Defence Research and Development Canada, and project oversight of Dr. Franklin Wong at DRDC Valcartier.


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    Title :

    Ultrasonic evaluation of weak liner/propellant bonding in a rocket motor


    Additional title:

    Überprüfung schwacher Klebungen zwischen Auskleidung und Treibstoff in einem Raketenmotor mit Ultraschall


    Contributors:


    Publication date :

    2004


    Size :

    9 Seiten, 7 Bilder, 16 Quellen


    Remarks:

    (Nicht paginiert)


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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