Automation of an Ultrasonic Technique for Nondestructively Monitoring Changes in Properties for Films and Coatings
Donald L. Hunston
Nondesctructively monitoring the mechanical properties of films, coatings, or layered materials (paints, adhesives, laminates, etc.) is a difficult challenge, and yet there are many instances where this would be useful. Examples include following the changes that occur during fabrication, environmental attack, and aging. One method that has been successful uses shear waves to measure the ultrasonic properties (dynamic shear modulus) of a film or coating applied to a substrate. Although the technique is well established, the measurement is very tedious. The present study uses modern digital electronics to acquire the data, and develops computer programs to control data acquisition and analysis. This not only simplifies the measurement but also completely automate the process so time dependent process like curing or degradation can be monitored easily. A number of calculations and experiments were conducted to test and to verify the analysis procedure.