Cracks in the surfaces of metal shafts rotating up to 3200 rpm were detected by passive, radiometric sensing of the 8–12‐μm thermal radiation emitted. This detection is possible because the effective crack emissivity approaches that of a black body, while the metal itself has a much lower emissivity. By the use of signal storage and signal subtraction, the technique is expected to permit ‘‘on‐line’’ monitoring of the development of cracks, even in the presence of surface blemishes.
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© 1985 American Institute of Physics.
1985
American Institute of Physics
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