Improvement of the dipole model of a surface crack

Journal Article · Mon May 01 04:00:00 EDT 2000 · Materials Evaluation

OSTI ID:20030392

Minkov, D; Lee, J; Shoji, Tetsuo

In the frame of the dipole model of a crack, a new analytical expression is derived for the z component of the intensity of the leakage magnetic field in the vicinity of a right angular parallelepiped surface crack, assuming parabolic distribution along the crack depth of the surface density of magnetic charge at the crack walls (m). This allows calculation of the Hall voltage to be measured by a Hall element outside the specimen in the proximity of a crack that is proportional to the intensity of a leakage magnetic field. Measurements of the Hall voltage distribution are done on specimens in different magnetization conditions containing artificial cracks. Regression is performed for the Hall voltage distribution, which allows determination of the parameters of the parabolic depth distribution of m. It is shown that the depth distribution of m should not be considered constant, although this has always been done. Instead, a linear depth distribution of m can be used for accurate description of the Hall voltage distributions measured, while m is always larger at the crack tip with respect to the crack mouth. The performance of DMC for nondestructive testing based on magnetic methods can be improved by taking into account the precise depth distribution of m.

• Research Organization: Tohoku Univ., Sendai, Miyagi (JP)
• OSTI ID: 20030392
• Journal Information: Materials Evaluation, Journal Name: Materials Evaluation Journal Issue: 5 Vol. 58; ISSN MAEVAD; ISSN 0025-5327
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
CRACKS
MAGNETIC FIELDS
MAGNETIC TESTING
MATHEMATICAL MODELS
PIPELINES
STEELS