NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
Noncontact Acousto-Ultrasonics for Material CharacterizationA NdYAG 1064 nm, laser pulse was employed to produce ultrasonic waves in specimens of SiC/SiC and SiC/Ti 6-4 composites which are high temperature materials of interest for aerospace applications. Air coupled transducers were used to detect and collect the signals used for acousto-ultrasonic analysis. Conditions for detecting ultrasonic decay signals were examined. The results were compared to those determined on the same specimens with contact coupling. Some non-contact measurements were made employing conventional air focused detectors. Others were performed with a more novel micromachined capacitance transducer. Concerns of the laser-in technology include potential destructiveness of the laser pulse. Repeated laser pulsing at the same location does lead to deterioration of the ultrasonic signal in some materials, but seems to recover with time. Also, unlike contact AU, the frequency regime employed is a function of laser-material interaction rather than the choice of transducers. Concerns of the air coupled-out technology include the effect of air attenuation. This imposes a practical upper limit to frequency of detection. In the case of the experimental specimens studied ultrasonic decay signals could be imaged satisfactorily.
Document ID
19980210773
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Kautz, Harold E. (NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1998
Subject Category
Quality Assurance And Reliability
Report/Patent Number
E-11245
NASA/TM-1998-208410
NAS 1.15:208410
Funding Number(s)
PROJECT: RTOP 523-22-13
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available