Nondestruction coating adhesion evaluation using surface ultrasonic waves and wavelet analysis

A method for remotely detecting quality of adhesion of a bonded metal coating on a substrate, the combined coating and substrate constitutes a test specimen, comprising the steps of:

• a. generating an oscillating signal that is indicative at least in part of a surface motion of the test specimen;
• b. detecting an amplitude and a frequency of the generated oscillating signal;
• and
• c. generating a set of processed data that includes the detected signal and analyzing the set of processed data using a ridge-following technique using wavelet analysis, comparing the results of the ridge-following technique using associated dispersion curves of two extreme states, one state corresponding to a “welded” contact bond state and the other state corresponding to a “smooth” contact bond state that define a range of bond adhesion.

An apparatus for determining adhesion quality of a coating surface on a substrate within a gun bore, the apparatus comprising:

• a) impulse means for generating an impulse beam and for directing said impulse beam to the surface of the gun bore for launching an elastic wave therewithin;
• b) interferometer means for detecting a displacement of the surface of the wafer in response to the launched elastic wave;
• c) ridge-following technique using wavelet analysis means for determining, from said detected displacement, a time-varying characteristic of said elastic wave within the surface of the gun bore;
• and
• d) means for correlating said determined time varying characteristic with a theoretical “welded” bonding state of the surface to the substrate.