D.C. or A.C. in MPI?
The authors maintain that the purpose of NDT is not necessarily to identify defective parts, but to be sure with the highest degree of confidence that the supposed flawless piece is indeed without deleterious defect. Thus NDT is a positive acceptance procedure rather than a rejection procedure. The detection of a defect is not necessarily a verification of a particular technique. Magnetic particle inspection (MPI) is a reasonably ``forgiving`` technique of crack detection, in that the latitude permissible in test parameters, is quite liberal without greatly affecting the test sensitivity. However, not withstanding the above, MPI is a ``fail to danger`` method in that, if after submitting a component to an MPI examination, there are no indications of a discontinuity, two conclusions may be drawn: (1) there are no defects int eh piece, or (2) the correct technique has not been carried out. On the assumption that the majority of work is without defect, then it is essential that the techniques are very carefully drafted and carried out. The range of variables in MPI is limited compared to other NDT techniques. They are: (1) direction of magnetic flux; (2) method of inducing flux into the piece under test; (3) magnitude of flux and thus the amplitude of the imposed field; (4) duration of application of the imposed field; (5) defect indicating materials, and mode of application; and (6) waveform of current which energizes the magnetizing mode. In the paper the authors discuss current waveform in more detail.
- OSTI ID:
- 207970
- Report Number(s):
- CONF-9510265-; ISBN 1-57117-013-8; TRN: IM9616%%298
- Resource Relation:
- Conference: 1995 American Society for Nondestructive Testing (ASNT) fall conference and quality testing show, Dallas, TX (United States), 16-20 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of ASNT 1995 fall conference and quality testing show: NDT -- The lone star of quality; PB: 204 p.
- Country of Publication:
- United States
- Language:
- English
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