Experimental investigation and numerical simulation of stress-wave dispersion characteristics in solid-wood plates

Current understanding of how propagation path and board thickness affect stress-wave dispersion in solid wood is limited, particularly regarding the distinctions between surface and internal propagation. This study combined experimental testing with finite-element simulation to explore the dispersion behaviour and influencing factors of stress waves in solid wood boards across frequencies from 20 kHz to 180 kHz. Sinusoidal excitations at different frequencies were produced using an arbitrary waveform generator, and stress-wave signals were recorded from boards with thicknesses of 3, 6, 9, and 12 mm. Frequencies of 40, 95, and 170 kHz were chosen based on signal energy distribution and dominant-frequency stability, while apparent longitudinal- and shear-wave velocities were determined using the cross-correlation function and the time difference of arrival method. The findings reveal that longitudinal-wave velocity remains relatively constant across frequencies, whereas shear-wave velocity increases significantly with frequency, indicating pronounced dispersion. Internal propagation demonstrates stronger dispersion than surface propagation, with dispersion increasing as board thickness increases. These results reveal how propagation path and structural scale affect stress-wave dispersion, providing a theoretical basis for optimising excitation frequency selection, propagation path design, and dispersion compensation in acoustic non-destructive testing of wood.