Elastic Guided Waves in Plates With Surface Roughness

Professor Dale E. Chimenti
Dept. of Aerospace Engineering and Engineering Mechanics
Iowa State University
Ames, Iowa

Sponsored by the Center for Materials Research and Analysis

Date:  Friday, April 21, 2000
Time:  1:30 p.m.
Place:  241 WSEC


This talk will discuss the problem of ultrasonic guided waves in plates and the effect of surface roughness on these waves.  The talk will include a discussion of the phenomenology, modeling, and experiments related to this work.  The roughness is assumed to be small and its effect on the guided wave is treated in a minimal model by decomposing the wave modes into their constituent partial waves and considering individually the effect of the roughness on the partial wave components as they reflect from the plate surfaces.  Calculations of the plate reflection coefficients in the presence of roughness illustrate the phenomena for the case coupling to guided waves.  Measurements on aluminum samples prepared by sandblasting are presented for cases of fluid immersion.  The influence of the roughness in immersion experiments varies with frequency and wave mode and with transducer location.  Rather good agreement between the simple model and the experiments is demonstrated, except in narrow regions of incident angle where the model ought not to work.  It is shown how these results could be used as a sensitive measure of hidden corrosion.