Separation of longitudinal and flexural wave in a cylindrical structure based on sensor arrangement for non-destructive evaluation

Abstract

Low strain integrity testing is commonly used to assess the in situ condition of the poles or piles. For poles, it is important to calculate the embedment length and location of damage which is highly influenced by the accurate determination of the wave velocity. In general, depending on impact location and orientation, both longitudinal and bending waves may generate inside the pole, and these two waves have very distinct characteristics and wave velocity. These differences are even more prominent in the low frequency which is usually induced in the low strain non-destructive testing. Consequently, it will be useful if these two waves can be separated for the condition assessment of the poles. In this paper, a numerical analysis is performed on a pole considering that both waves are generated, and a method is proposed to differentiate these two waves based on an appropriate sensor arrangement that includes the location and the orientation of the sensors. Continuous wavelet transform is applied on the numerical signal to calculate the phase velocity of the waves and compared with analytical phase velocity curves. From the results, it can be seen that appropriate location and orientation of the sensors can separate the longitudinal and flexural waves as they match significantly well with the corresponding analytical phase velocity curves of these two waves.

An Improved Hilbert–Huang Transform for Vibration-Based Damage Detection of Utility Timber Poles

“…From Figure 11, it can be witnessed that circumferential component is dominant at 90° position and contains more energy than that of longitudinal component at the same position. Behaviour of these three displacement components can be found in details in [41,42]. nents at 0° and 180° position are not in same phase, and they are not out of phase as well.…”

“…From Figure 11, it can be witnessed that circumferential component is dominant at 90 • position and contains more energy than that of longitudinal component at the same position. Behaviour of these three displacement components can be found in details in [41,42].…”

“…Since timber is an orthotropic material, its material properties vary in three different directions: longitudinal, radial, and circumferential. Subhani et al [41] proposed an appropriate sensor set up for the non-destructive assessment of cylindrical type structures which has been utilised in this study in order to capture the three dimensional behaviour of timber pole. For field testing, an impact hammer, 12 accelerometers and a data acquisition system were employed.…”