Eddy Current Imaging of Machined Grooves on a Nickel Wave Strip Page: 4 of 12
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Eddy current measurements offer a means of rapidly detecting, imaging, and characterizing a
variety of features on the surfaces of metallic objects. In this case, the target of interest was a
set of machined grooves in a small strip of nickel sheet. A series of brief tests were
performed using an automated X-Y scanner and an available test probe to scan the test strip.
Although the coil in the probe was too large to resolve individual grooves, the system
successfully imaged the grooves, accurately determined the groove spacings along the length
of the strip, and provided data from which the depths of the grooves could be calculated.
Supplemental measurements made with an optical profilometer provided data needed to
convert the eddy current voltages to groove depths.
These tests indicate that an operational eddy current system would be an effective means of
inspecting nickel surfaces. Scans to detect surface topography such as the grooves on the test
strip require only measurements of the lift-off response of the sensor and are not adversely
affected by the ferromagnetic property of nickel. An operational system designed to detect
and characterize features as small, or as closely spaced, as the grooves on the test strip should
include smaller sensors than those used in our tests. Much smaller coils than our .060-in.-
diameter coil are available or can be fabricated. Solid-state magnetoresistive sensors are an
alternative to coils and are available in very small sizes. Numerical modeling offers an
efficient means of evaluating alternate sensor configurations and the performance of sensors
in specific applications. Modeling, hardware tests, and the development of calibration
standards would be important facets of an effort to develop an eddy current inspection system
for the type of application discussed in this report.
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Andersen, Eric S.; Mathews, Royce & Sandness, Gerald A. Eddy Current Imaging of Machined Grooves on a Nickel Wave Strip, report, January 1, 2006; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc837120/m1/4/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.