Radiometric crack detection in fast moving surfaces

摘要

Cracks in the surfaces of metal shafts rotating up to 3200 rpm were detected by passive, radiometric sensing of the 8ndash;12hyphen;mgr;m 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 lsquo;lsquo;onhyphen;linersquo;rsquo; monitoring of the development of cracks, even in the presence of surface blemishes.