Importance

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Abstract

A plurality of magnetic field members are provided, each for selectively generating a time-varying magnetic field for combination into a o time-varying composite longitudinal magnetic field with magnetic flux lines which are substantially aligned with the central longitudinal axis of the cylindrical ferromagnetic member. Additionally, a traverse magnetic field member is provided which selectively generates a time-varying traverse magnetic field with magnetic flux lines which are substantially traversed to the central longitudinal axis of the cylindrical ferromagnetic member. The plurality of magnetic field members and the traverse magnetic field member are maintained out of contact with the cylindrical ferromagnetic member. Magnetic particles are placed on selected portions of the cylindrical ferromagnetic member. A time-varying composite longitudinal magnetic field and a time-varying traverse magnetic field are applied to the cylindrical magnetic member, while it is being rotated. An operator inspects the outer and/or inner peripheral surfaces of the cylindrical member to detect defects therein from accumulations in magnetic particles at leakage fields corresponding to magnetic discontinuities of defects in the cylindrical ferromagnetic member.

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First Claim