Feasibility of NDT of ferromagnetic steel structures based on measurementsof residual magnetization as a function of elastic stress

Algorithms for estimating elastic stress in ferromagnetic steel structures are based on measurements of the residual magnetization M-r as a function o f tensile and compressive stress sigma (0) after quenching and tempering at different temperatures T-tcm. The suggested testing technique is highly se nsitive because the range of M-r(sigma (0)) is fairly wide (for the interva l 0.6 sigma (y) greater than or equal to sigma (0) greater than or equal to -0.6 sigma (y), where sigma (y) is the yield limit, the range is 600-800 k A/m). The necessary condition for using this testing technique is the avail ability of calibration curves for the selected testing algorithm measured o n samples of steels to be tested (i.e., of the same sort of steel tempered at the same temperature). All the testing algorithms suggested in the paper enable one to determine both the magnitude and sign of the stress in the m aterial.