Analysis for propagation characteristics of longitudinal mode and torsional mode guided waves in rod
Regarding the application of guided waves in one-dimensional structure, the propagation characteristics of the longitudinal guided wave and torsional guided wave are investigated. The dispersion equations of guided wave in the longitudinal and torsional modes in one-dimensional component are derived. Through programming numerical calculation in MATLAB, the frequency dispersion curves of the two modes are obtained, which imply that the engineering application of guided waves in detection of rod needs to choose an appropriate frequency and the corresponding propagation characteristics of the waves should be combined to get reliable results. The dispersion characteristics analysis results in different radius of rods show that it is feasible for detecting the defects in rod using L(0,1) mode of ultrasonic guided waves.
Wire breaking localization of parallel steel wire bundle using acoustic emission tests and finite element analysis
The precise localization of cable damage is a major issue in bridge engineering. The acoustic emission (AE) method has been applied to detect defects for cable structures in bridges. In this paper, an AE localization method is proposed to localize both lateral and longitudinal positions of defects in a parallel steel wire bundle composed of seven steel wires. The proposed method is verified numerically and experimentally. Tension failure test of the parallel steel wire bundle composed of seven wires was carried out, and the precise localization of defects was realized by through modal AE techniques and the analysis of the characteristics of AE signal. A Multiphysics model based on COMSOL was established to facilitate the visualization of stimulated AE propagated in the parallel wire bundle. The propagation mechanism of AE signal was studied, and the feasibility of localization method was verified.
Torsional guided wave attenuation in buried pipe
The torsional mode T(0, 1) of guided waves is generated to detect discontinuities in pipelines. However, a large number of pipelines are buried in soil or concrete environments at most refineries, chemical and petrochemical plants. The attenuation of the incident torsional guided wave is investigated experimentally. The amplitude of the reflected signals from weld and flange features on the pipe are measured before and after embedding the soil or concrete for attenuation calculation. The results show that the concrete embedded on the pipe has a 25 dB/m (0.6 dB/in.) attenuation factor. The distance amplitude correction curve of the soil is 0.6 dB/m (0.015 dB/in.) both before and after embedding. In addition, the traveling distance of guided waves in the pipe is also evaluated for the concrete and soil embedded cases. It can travel about 1.28 m (50.4 in.) for the concrete embedded case, and for the soil embedded case the propagating range is only dependent on distance due to the natural decay of the material properties of the pipe.