Magnetic field disturbance signal processing

A nondestructive evaluation technique for detecting flaws in reinforcing and prestressed steels, the magnetic field disturbance method (MFD), is described. It requires the processing and analyzing of data from a multiplicity of Hall-effect transducers. An evaluation of an MFD system developed for the Federal Highway Department has produced a number of methods for the analysis and characterization of the data produced by the MFD system. These signal processing methods, as related to laboratory and field experiments pertaining to the detection of flaws and fractures in bars and cables, are discussed. It is shown that the correlation and profile analysis methods can both identify flaws in many cases. The profile algorithm yields a quicker method of finding flaws. It compares quite favorably with correlation analysis and in a number of cases surpasses it. Neither data analysis method yields entirely reliable results in all cases