Process and apparatus for the non-destructive examination of ferromagnetic bodies having sections of surface adjoining each other along edges and/or at corners

摘要

This invention relates to a process and an apparatus for the non-distructive examination of ferromagnetic bodies having sections of their surface adjoining along edges. The bodies or body parts are examined for structural faults or disturbances, including the regions along the edges and/or at the corners. A magnetic field is produced in the given body or body section. This field is stationary with respect to magnetic field sensors provided for measuring the stray fields on the surface. In a first measuring phase, measurements obtained for stray flux which are characteristic for the various positions of the magnetic field sensors along the surface of the body or body section are stored as reference values. In a second measuring phase, the reference values allocated to the various positions are subtracted from the stray flux values measured at these positions. The differences are then compared with predetermined threshold values.