9812820 Harris Thin films or coatings are used as thermal barriers to increase hardness in the manufacture of engine parts. It is important to develop ways to nondestructively inspect such coatings to assess their quality before a part is placed in service. Analytical expressions that describe the time delay, and transmission loss or attenuation of ultrasonic waves caused by thinning, flaking, or cracking of the coatings are developed. Surface waves are especially useful as they sample a larger volume of the coating than do waves reflected from coated surface and provide stronger received signal. The work is done in collaboration with Caterpillar Corporation. ***
