A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in "Advanced Electromagnetic Probes for Characterizing Materials"; (GSC-13878), NASA Tech Briefs, Vol. 21, No. 11 (November 1997), page 4a. To recapitulate:
A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.
This work was done by David G. Kinchen of Lockheed Martin Corp. for Marshall Space Flight Center. For further information contact Gary Willett at (504) 257-4786. Title to this invention has been waived under the provisions of the National Aeronautics and Space Act [42 USC 2457 (f)] to Lockheed Martin Space Systems Company -Michoud Operations. Inquiries concerning licenses for its commercial development should be addressed to
Lockheed Martin Michoud Space Systems
P.O. Box 29304
New Orleans, LA 70189.
Refer to MFS-31979.