A New Technique for Sizing Cracks in Metals, Utilizing an Induced Surface Magnetic Field
The new technique, introduced in this paper, has originated in the course of development of an inducing mechanism for use with the ac field measurement instrument used in detection and sizing of cracks in metals[t]. It had been known for some time that the application of an inducing mechanism capable of producing the required uniform field over the surface of the metal would add to the advantages of the ac field measurement (ACFM) technique[1,2]. This led to some activities in identifying current carrying structures which can fulfil this requirement. One structure proposed consists of two parallel wires forming a U shape which can be readily integrated with the ACFM probe, Fig.l. In practice, in order to maintain the original characteristic of the induced surface field produced by this inducing arrangement, the feeding terminals and the related wiring should be located adequately far from the metal surface.
KeywordsCrack Edge Crack Depth Incident Field Surface Field Induce Mechanism
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