The influence of surface roughness on measurement of ultrasonic waves - theoretical analysis and experimental verification

The influence of surface roughness on the reflection and transmission of ultrasonic waves was investigated through an integrated theoretical–experimental approach. In the theoretical model, both the transducer surface and the rough interface are reconstructed using pseudo-random samples from a Quasi-Monte Carlo (QMC) method, and the ultrasonic wave fields are then calculated using mathematical expectations. Consequently, the roughness-induced attenuation of reflection and transmission coefficients is quantitatively assessed by comparing results obtained from rough versus smooth surfaces. The proposed approach optimally balances accuracy and computational efficiency, enabling high-fidelity simulation of the entire ultrasonic propagation process to systematically analyze how system parameters and inspection conditions influence measurement accuracy. Simulations show that increased surface roughness increases errors in reflection-based attenuation estimates; however, these errors can be reduced by using transmission-based attenuation or larger transducers. Moreover, in the case of a curved interface, the apparent attenuation of the reflection coefficient is reduced owing to enhanced diffraction effects, and the roughness-induced attenuation is accurately quantified by the proposed method. All major theoretical predictions are corroborated by experimental data, demonstrating the robustness and practical relevance of the approach for quantitative ultrasonic nondestructive evaluation of solid structures with rough surfaces.