A novel acoustic black hole waveguide rod design for acoustic emission signal enhancement: design principles, numerical simulation, and experiments

Acoustic emission (AE) signals experience significant energy attenuation during long-distance transmission through waveguide rods, resulting in low amplitude and increased susceptibility to noise interference, which reduces the reliability of damage identification. To address this issue, a spoon-shaped waveguide rod based on the Acoustic Black Hole (ABH) effect is proposed. The structure concentrates elastic wave energy through geometric tapering to enhance AE signals, while its optimized configuration facilitates sensor installation. Based on elastic wave propagation theory, the key factors governing signal enhancement are derived. A parametric geometric model of the spoon-shaped ABH structure is established and analyzed using COMSOL, demonstrating superior signal amplification compared to conventional waveguide rods. The effects of critical geometric parameters, including rod length, power-law index, ABH platform diameter, and truncation thickness, are systematically investigated. Pencil lead break tests are conducted to validate the numerical model and enhancement performance. Results show that the proposed structure significantly increases signal amplitude without altering the dominant frequency characteristics. In addition, AE wave propagation within the ABH region exhibits pronounced velocity reduction, and the maximum energy storage density follows a power-law relationship with truncation thickness. The proposed design demonstrates strong signal enhancement capability and potential for long-distance AE monitoring.