Utilizing non-specular reflection of bounded ultrasonic beams for assessing damage in solid plates

This paper investigates the potential of utilizing non-specular reflection of a bounded ultrasonic beam in a liquid -solid-liquid structure as a method for assessing damage in solid plates. The study focuses on understanding the acoustic field formulation resulting from this type of reflection, as well as examining the impact of incident angles and material damage (indicated by reduced Young's modulus) on the non-specular reflection field. To quantify the effects of non-specular reflections, the specular reflection coefficient (SRC) proposed by the authors is employed (Wang and Deng, 2023) [1]. A finite-element (FE) model is developed to analyze the SRC response concerning the incident angle and material damage. Through FE simulations involving obliquely incident bounded ultrasonic beams at different angles, the research reveals a significant, monotonically increasing sensitivity of the SRC change rate at the S0 critical angle to the level of material damage. This finding offers a precise approach for accurately evaluating material damage in plates. Experimental tests are conducted on a water-aluminum sheet-water structure, which validates the theoretical predictions and FE simulation results. The experimental results consistently demonstrate an increased change rate of the SRC at the S0 critical angle in response to the fatigue cycle, confirming the effectiveness of using non-specular reflection of a bounded ultrasonic beam at the S0 critical angle as a method for evaluating material damage in plates.