Abstract
When the longitudinal mode guided waves based on magnetostrictive effect were employed to inspect the bridge cables, we found that there was a large difference in the signal’s amplitude of the same specification cable under different tensile force. This difference would affect the test results and the identification of defects. It is necessary to study the effect of tensile force on the signal for the reliability of detection. Firstly, the effective field theory is employed to take the force as an additional bias magnetic field. Then, the effect of the tensile force on generating and receiving longitudinal mode guided waves based on magnetostrictive effect is obtained by the relationship between the bias magnetic field and the magnetostrictive coupling coefficient. Finally, the experiment of the magnetostrictive sensor is carried out on a Φ5 mm steel wire under different force. The experimental results are in good agreement with the theoretical results. The results show that the existence of the tensile force would change the operation point for generating and receiving the longitudinal mode guided waves based on magnetostrictive effect, which associated with the coupling coefficient. In order to obtain the optimal conversion efficiency for the force state wire and cable, the applied bias magnetic field should be set smaller than the bias magnetic field for the force-free state.
Highlights
Cables are widely used in the bridge construction, such as cable-stayed bridges, concrete-filled steel tube arch bridges, and suspension bridges [1]
The longitudinal mode guided wave technology based on the magnetostrictive effect was employed to inspect the bridge cables which could achieve long-range detection from one point [2,3,4,5,6,7,8]
The effective field theory is employed to take the force account into the bias magnetic field
Summary
Cables are widely used in the bridge construction, such as cable-stayed bridges, concrete-filled steel tube arch bridges, and suspension bridges [1]. The longitudinal mode guided wave technology based on the magnetostrictive effect was employed to inspect the bridge cables which could achieve long-range detection from one point [2,3,4,5,6,7,8]. Guided wave testing using the magnetostrictive sensors includes the wave excitation and reception, based on magnetostrictive effect and its invert effect. The energy coupling coefficient of the sensors is concerned with the magnetization state of the ferromagnetic components which is determined by the superimposed magnetization of the static bias magnetic field and the alternating magnetic field. The bias magnetic field provides an operating point in the magnetostrictive curve [9]. The engineers tend to set the bias magnetic field to the optimal operating point which corresponds to the maximum coupling efficiency to improve sensitivity
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