Brittle fracture of a conductor in a strong pulsed magnetic field

Abstract

The main factors resulting in conductor failure under the action of a strong pulsed magnetic field are analyzed. The theoretical model describes the geometry of a cylindrical thick-walled solenoid and considers magnetic field diffusion, ohmic heating of the material and mechanical stresses arising in it. The magnetic field amplitude at which induced stresses in the material reach the von Mises yield criterion is used as the Bth threshold field separating the areas of safe (non-destructive) and dangerous fields. In the case of an initially uniform material, the maximum heating temperature corresponding to this limit, which predetermines the thermomechanical stress, has been derived analytically. In the general case, based on the analysis of the calculated threshold field, the influence of various parameters (magnetic pulse characteristics, elastic moduli of the material, etc.) on the conductor resistance in the pulsed magnetic field is studied and ways of increasing the threshold field are proposed, in particular, by using different spatial profiles of the initial resistivity. It is shown that in comparison with a uniform material, a modified layer with increased resistivity formed on the surface allows to significantly increase the amplitude of the magnetic pulse withstood by the material without fracture. Keywords: Magnetic field diffusion, plastic deformation, thermomechanical stress, yield strength, von Mises yield criterion.