Experimental Research on the Reflection Characteristics of Guided Waves from Defects in Steel Wires

The aim of this work is to develop a technique for inspecting parallel wire cables by a quantitative study of the interaction of guided waves with artificial defects in steel wires. The reflection of the L(0,1) mode from notches of varying axial extents and cross-sections in 7-mm diameter wires has been studied by laboratory experiments. Results show that the reflection coefficient of this mode around 50 kHz is a strong function of the defect axial extent, two maximum reflection coefficients occurring respectively at a defect length of about 25 percent of the wavelength and 75 percent, while a local minimum occurring at 50 percent. And the reflection coefficient is approximately linear with defect cross-section when the defect axial length is given. Results imply that the maximum and minimum reflection coefficients at many different frequencies can be utilized for sizing of the axial extent of the defect. If the defect axial extent is found, the reflection coefficient at any frequency can be used to estimate the cross-sectional area of the defect. These findings will provide a certain foundation for the detection of parallel wire cables if the reflection characteristics of guided waves in the wire bundles are similar to those in an individual wire.