COMPUTING THE EDDY CURRENT COMPONENT OF A DEFECT FIELD DURING MOBILE ELECTROMAGNETIC FLAW DETECTION OF RAILS

K RASCHETU VIKHRETOKOVOI SOSTAVLIAIUSSHCHEI POLIA DEFEKTA SKOROSTNOI ELEKTROMAGNITNOI DEFEKTOSKOPII REL'SOV

Railroad rails, during mobile electromagnetic flaw detection, are exposed to the action of the moving permanent magnetic field created by the horseshoe shaped electromagnet. At this time eddy currents are led into the rails, and the dynamic field of the defect is formed because of the change of magnetization of the rail in the zone of the defect (magnetostatic component of the field of the defect), as well as due to the redistribution of the eddy currents by the defect (the eddy current component of the defect field). The magnetostatic defect field, which is in a given instance the component of the dynamic field, has been studied in detail in a series of theoretical and experimental works. In distinction to this, the eddy current component is generally defined by the resiliency and redistribution of the eddy currents, which are unipolar according to the means of reception, in addition to which the direction and distribution in the unflawed rail depends upon their position in relation to the source of the external magnetic field. The differences in the dimensions and polarities of the calculated components of the eddy current field of the rail defects agree with the data of the study on signals in the inductional data unit of the flaw detector railcar. A comparison of the dimensions of the components of the eddy current field over the defects and over the sound sections of rail lead to the conclusion that a data unit reacting to the vertical component of the defect field would be most effective for the revelation of internal defects. Least effective will be a data unit which reacts to the longitudinal component of the defect field and has a very small dimension over the internal defects and a significant one over the sound sections of the rail. In order to reach practical conclusions, it is necessary to observe not only the eddy current component of the defect field but the magnetic as well. This is necessary because the source of the eddy currents in the rails is a moving permanent field of large size, which leads to the presence on the rail surface of an auxiliary background field and the formation over the defects of field changes of a magnetic character.

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  • Supplemental Notes:
    • Full translation available for reference purposes at the Office of R&D, FRA. Contact Technology Planning Officer.
  • Corporate Authors:

    Plenum Publishing Company

    227 West 17th Street
    New York, NY  United States  10011
  • Authors:
    • Shcherbinina, V A
    • Vlasov, V V
    • Dovnar, B P
  • Publication Date: 0

Language

  • Russian

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00130271
  • Record Type: Publication
  • Source Agency: Federal Railroad Administration
  • Files: TRIS, USDOT
  • Created Date: Dec 1 1977 12:00AM