SURFACE ROUGHNESS AFFECTS BOTH THE SHAPE OF AN ULTRASONIC IMPULSE TRANSMITTED THROUGH AN INTERFACE AND ITS POWER SPECTRUM.

SURFACE ROUGHNESS AFFECTS BOTH THE SHAPE OF AN ULTRASONIC IMPULSE TRANSMITTED THROUGH AN INTERFACE AND ITS POWER SPECTRUM. TO FULLY APPLY ADVANCED SIGNAL ANALYSIS TECHNIQUES TO DETERMINING QUANTITATIVE INFORMATION ABOUT DEFECTS AND IMPERFECTIONS IT IS NECESSARY TO COMPENSATE FOR THE FREQUENCY DEPENDENT EFFECTS INTRODUCED BY SURFACE ROUGHNESS. THIS PROJECT PROPOSES TO MODEL SURFACE ROUGHNESS TO OBTAIN A MEANS OF NUMERICALLY EVALUATING ITS EFFECT ON BOTH THE POWER SPECTRUM OF A TRANSMITTED IMPULSE AND THE TEMPORAL TRANSMITTED SIGNAL. THE ROUGHNESS IS SCALED RELATIVE TO AN ACOUSTIC WAVELENGTH AND IS DIVIDED INTO FINE GRAINED AND LARGE SCALE IRREGULARITIES. THE FINE GRAINED ROUGHNESS IS MODELED BY AN INTERVENING LAYER WITH EFFECTIVE PHYSICAL PROPERTIES. THE SOLUTION TO THE MODEL ROUGHNESS CONFIGURATION PROVIDES A TRANSFER FUNCTION WHICH YIELDS THE FOURIER SPECTRUM OF THE TRANSMITTED IMPULSE FROM WHICH THE POWER SPECTRUM IS DETERMINED. BY COMPENSATING FOR THE EFFECT OF SURFACE ROUGHNESS, A MORE DETAILED QUANTITATIVE ANALYSIS OF DEFECT STRUCTURE IS POSSIBLE.