Detecting the flaws in prestressing strands using guided waves based on the magnetostrictive effect

The use of guided waves based on the magnetostrictive effect to detect the small defect and broken wires in the prestressing strand is described. Signals acquired from the seven-wire steel prestressing strand before and after cutting an indented flaw in one wire and breaking several wires are given. Results show that the technique is able to detect small defects and broken wires. In addition, the increasing number of the broken wires has an almost linear relationship with the ratio of the increase in the peak-to-peak amplitude of the defect signals. This result indicates that the method can be applied to not only detect the defects but also quantify the broken wires of the prestressing strand.