Investigation of Barkhausen noise emission in steel wires subjected to different surface treatments

Abstract

Steel rope wires represent the main bearing components of bridges whose long-term operation depends on loading conditions, corrosion attack, and/or pre-stressing. Corrosion attack especially can remarkably reduce the effective cross-sectional area, which in turn over-stresses the wires and redistributes stress to the neighboring wires. The premature collapse of many bridges is very often caused by wire rupture as a result of their poor corrosion protection. For these reasons, various processes-such as galvanizing, phosphating, etc.-have been applied to steel wires to increase their resistance against corrosion. However, these processes can alter the microstructure, especially in the near-surface regions. The Barkhausen noise technique has been already reported as a suitable technique for investigating corrosion extent and true pre-stress in the steel rope wires. This study reports that non-homogeneity of the surface state of wires undergoing different surface treatment makes it more difficult to assess the true stress state and increase the uncertainty of Barkhausen noise measurement. Barkhausen noise signals are correlated with metallographic and SEM observations as well as microhardness measurements. The non-homogeneity of the surface state of wires is also investigated by the use of chemical mapping and linear chemical analyses.