Assessing Strand Steel Wire Prestress Level Using Guided Wave Dispersion Properties

As an effective non-destructive testing method, guided waves have been widely used in assessing the condition of various structures, such as pipelines, rails, plates, etc. In this paper, the characteristic equations of steel strands are obtained by the updated semi-analytic finite element method, on the basis of spatial arrangement law of spiral period structure. From the characteristic equations, the frequency disperses behavior for guided waves propagating in the steel wire waveguide is investigated, and the disperse curves for the group velocity are obtained. Then, from the characteristic equation, the axial stress level of the strand steel wires, can be estimated from the dispersion properties available such as group velocity. Finally, a numerical example for a 7-wire steel strand is adopted to demonstrate the accuracy of the proposed method. From the obtained results, the proposed method can accurately estimate the axial prestress level of the stranded streel wires by using the guided wave group velocity available.