A New Method for Obtaining Stress-Depth Calibration Profiles for Non-Destructive Evaluation Using a Frequency-Dependent Model of Barkhausen Emissions

Abstract

This study presents the development of a non-destructive method of detecting stress as a function of depth, useful for inspecting steel structures and components without the need to calibrate against x-ray diffraction data. A new frequency-dependent model for Barkhausen emissions based on the attenuation of emission with frequency and distance is used to extract depth-dependent stress information. Controlled, uniform stresses are induced in an ASTM A36 steel specimen, which are then used as a reference to obtain stress-voltage calibration profiles. An inversion process can then be employed to assess specimens of unknown stress states, by using the previously calculated profiles. The slope of the calibration profiles is found to vary with depth, and a simple computer algorithm may be used to extract stresses at different depths by using an averaging method.