Signal loss of double transmissions of ultrasonic waves through random rough surfaces

This paper establishes a model evaluating the signal loss of double transmitted acoustic beams through random rough liquid–solid surfaces based on Fresnel approximation and the phase-screen approximation. The numerical solution is replaced with a simple analytical solution through using the exponential substitution approach to remove the nonlinear integral terms. Therefore, the real-time inspection by using C-scan imaging systems of flaws in materials can be achieved through the proposed model. The research results show that the signal loss of double transmissions from random rough surfaces mainly depends on two factors: the root-mean-square (RMS) of the roughness and the depth of the flaw in materials. The experimentally measured signal loss is in good agreement with the theoretical predictions. The evaluation of the signal loss can be useful for improving the accuracy and reliability of the non-destructive testing (NDT).