Browsing by Author "Bakar AHA"

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    Estimation of the Rod Velocity in Wood using Multi-frequency Guided Wave Measurements
    (Elsevier Ltd, 2023-01) Bakar AHA; Legg M; Konings D; Alam F
    This study presents a new approach for measuring the acoustic “rod velocity” in wood using guided wave measurements. The approach fits the acoustic guided wave longitudinal L(0,1) wave mode dispersion curve, through experimental guided wave phase velocity measurements taken over a range of frequencies. The rod velocity is obtained by measuring the phase velocity of the fitted L(0,1) wave mode dispersion curve at zero frequency. This technique is used to obtain rod velocity measurements for cylindrical wood and aluminium samples. The same approach was also performed on resonance measurements at a wide range of harmonics. These rod velocities are then compared to acoustic velocities obtained using the traditional time of flight and resonance methods.
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    The effects of dispersion on time-of-flight acoustic velocity measurements in a wooden rod
    (Elsevier BV, 2023-03) Bakar AHA; Legg M; Konings D; Alam F
    The stiffness of wood can be estimated from the acoustic velocity in the longitudinal direction. Studies have reported that stiffness measurements obtained using time-of-flight acoustic velocity measurements are overestimated compared to those obtained using the acoustic resonance and bending test methods. More research is needed to understand what is causing this phenomenon. In this work, amplitude threshold time-of-flight, resonance, and guided wave measurements are performed on wooden and aluminium rods. Using guided wave theory, it is shown through simulations and experimental results that dispersion causes an overestimation of time-of-flight measurements. This overestimation was able to be mitigated using dispersion compensation. However, other guided wave techniques could potentially be used to obtain improved measurements.