A New Solenoid-Type Sensor for Nondestructive Stress Estimation in Prestressed Steel Strands

In this study, we introduce a novel solenoid-type sensor for nondestructively estimating stress in prestressed steel strands through magnetic Barkhausen noise (MBN) measurements. The sensor features a unique dual-coil system: one coil induces a magnetic field, and the other coil detects changes in magnetic flux. This is particularly advantageous in civil engineering, where steel strands are often covered with protective materials, rendering traditional contact-based MBN sensors, commonly used in railway and mechanical engineering, ineffective. Limitations due to the skin effect control the frequency of current in the magnetic-field inducing coil, while the characteristics of MBN determine the sampling rate of the detection coil. An infinite impulse response filter is proposed for extracting MBN from the signals, and the root mean square (RMS) value is employed to assess the intensity of the MBN. Laboratory tests on a 15.2 mm diameter seven-wire steel strand demonstrate a clear correlation between the stress in the steel strand and the RMS of MBN. This correlation mirrors findings from earlier studies using contact-type sensors and suggests that the newly developed solenoid-type MBN sensor can effectively estimate the prestressing stress in steel strands within ducts.