Abstract:
A method for obtaining real-time estimates of flexural wave energy flow (or intensity) in beams at high frequencies is presented, targeted at structural health monitoring applications. Beam response and energy flow are expressed within the framework of Timoshenko beam theory, and the significance of the presence of a second propagating wave type at high frequencies is discussed. Digital filtering of the outputs of a sensor array, based on wave decomposition theory, to obtain estimates of the velocity, rotational velocity, bending moment and shear force is proposed. These parameters are then combined to yield an estimate of structural intensity The design of the necessary digital filters is discussed, and the results of simulations and experimental measurements are presented. It is shown that the approach is applicable to frequencies both below and above the ,cut-on, of the second propagating wave type. In particular, it is shown that the approach makes it possible to discriminate between the two wave types, based on differing contributions of the shear force and the bending moment to the vibrational energy flow. This has potentially significant implications for structural health monitoring applications, as it allows the differing characteristics of these wave types to be exploited for improved defect location.