the surface of the groove is placed on the surface of the test
object. According to most standards in the world, when perform-
ing MT, magnetization of the test object generally requires a flux
density of 1 T (RMS value) [3]. The study [6] also investigated the
magnetization intensity of 1 T of the test object using an adjacent
conductor technique.
To the best of the authors’ knowledge, there are very few
studies on standard test shims to determine magnetization
intensity of a test object. Katoh [7,8] investigated the leakage
field from the artificial groove as a function of several factors,
including lift-off value of the magnetizing yoke and the air gap
between the type A standard test shim and the test object using
two-dimensional finite element analysis. However, the extent to
which the magnetization intensity of a test object can be
measured with the type A standard test shim is not yet fully
understood.
In the present study, analytical and experimental approaches
were used to clarify the mechanism to determine the magnetiza-
tion intensity using the type A standard test shim. Materials with
different B–H properties, including a cold-reduced carbon steel
sheet and a carbon tool steel were selected for the test object. The
excitation current of the magnetizing yoke to obtain magnetic
particle indication was experimentally measured. An exact ana-
lytical model to simulate the experimental conditions was then
constructed and the amplitudes of the magnetic flux inside the
test object and the test shim were obtained. Using the obtained