Original Date: 04/01/1993
Revision Date: 01/19/2007
Best Practice : Nondestructive Test Analyses/Equipment
McDonnell Douglas Aerospace (MDA) employs nondestructive evaluation methods to examine manufactured assemblies for defects in material or workmanship. Hand-held probes are used to detect eddy currents that may indicate material anomalies. Hand-held acoustic probes are also used, such as the QFT-2 portable acoustic scanner from DupontTM. MDA also has special X-ray equipment to perform computed tomography and real-time radiography.
New composite structures must be evaluated to determine suitability for potential new designs. Surface flaws can be detected by die penetrant, but sub-surface flaws are typically scanned acoustically. A C- scan of the material translates to X-Y plots of attenuation data, or A- scans can be displayed via oscilloscope. However, this may not accurately determine the depth or the location of the flaw. This was a critical problem for design of a helicopter mast mounted sight.
The Nondestructive Test group at MDA has implemented a technique to address these issues. Developed with IRAD funding, the technique involves totally immersing the system under test in water. Signal sources are placed opposite each other on each side of the structure using a six-axis positioning system.
An Automated Acoustic Analysis System Dupont (ADIS) test system is used to initiate acoustic pulses to establish a performance baseline of the immersed structure. The ADIS equipment has several notable features including an 85 decibel acoustic dynamic range, special programming features to allow fine tuning of test settings to help evaluation, and automated documentation. This automated test system combines several acoustic scanning techniques to present a three-dimensional image that can be analyzed for accurate defect location and defect type.
Since its first use in the mid-1980s, the ADIS Automated Acoustic Analysis System has been used on numerous composite structures to evaluate material performance. The information provided has significantly contributed to safer designs for piloted systems and has resulted in cost savings more than double those originally estimated.
ABSTRACT: Automated Load Programming System
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