Diagnostics of Metal Structures Made of Ferro- and Paramagnetic Materials Using the Coercive Force Method

Abstract—Coercitimetry, by the use of Hall effect as a source of primary information, is the main method of magnetic control (when classified according to the primary informative parameter) in the technical inspection of potentially dangerous metal constructions. Coercive force, considered as the intensity of an external magnetic field applied to a ferromagnet been magnetized to saturation for its complete demagnetization, is the most structurally sensitive characteristic of a material, the change of which allows for express diagnostics in production conditions. A linear character of change in coercive force upon application of cyclically varying stresses makes it possible to reliably determine the residual life of the construction. A method for determining the residual life of constructions made of nonferromagnetic materials, which experience cyclically changing over time mechanical loads, based on the change in the coercive force of steel samples-witnesses (samples made of ferromagnetic material operating together with the studied construction made of nonferromagnetic material) is presented. It is shown that the rate of change in coercive force in a ferromagnetic sample witness can be used to determine the stresses in it, which are correlated with the stresses in a nonferromagnetic construction. This allows the residual life of the nonferromagnetic constructions to be directly determined significantly increasing the accuracy of assessing the residual life of potentially hazardous constructions made of nonferromagnetic materials. The obtained results can be used to determine the technical condition (according to the level of accumulated damage), e.g., of constructions made of aluminum alloys (pedestrian bridges, etc.).