Effective stress monitoring in structures using sideband peak count-index of nonlinear guided waves

Ultrasonic guided waves are widely used for structural health monitoring, while traditional stress detection methods based on weak nonlinear elasticity theory suffer from limited sensitivity. This study presents a numerical investigation using the highly sensitive Sideband Peak Count-index (SPC-I) technique for improved stress assessment in plates. A finite element (FE) model is developed to analyze the transient evolution of higher-order harmonics under various uniaxial stress states. This study explores the influence of both stress magnitude and its orientation relative to the wave propagation direction, establishing a quantitative link to the acoustic nonlinear parameter, β. The results demonstrate that SPC-I is a robust indicator, sensitive not only to the stress magnitude but also to its orientation. Notably, the proposed method significantly enhances measurement sensitivity. Experimental validation confirms that SPC-I values exhibit a pronounced change with stress variations, representing a marked improvement over conventional ultrasonic techniques. The findings establish a theoretical framework for ultrasonic stress detection and provide essential technical guidance for structural health monitoring (SHM) applications.