| 摘要 |
A non-destructive inspection includes: magnetizing a target by a first magnetostatic field (S 2 ); shutting off the magnetostatic field (S 3 ); measuring, at measurement points, the transient change of a differential magnetic flux density of a first residual magnetic field of the target (S 4 ); obtaining a first time constant by the main time constant of the transient change at each measurement point (S 5 ); magnetizing the target by a second magnetostatic field (S 2 ); shutting off the second field (S 3 ); measuring, at the measurement points, the transient change of a differential magnetic flux density of a second residual magnetic field of the target (S 4 ); obtaining a second time constant by the main time constant of the transient change for each measurement point (S 5 ); and obtaining information about the internal structure of the target by the distribution differences between the first and the second time constants at the measurement points (S 7 ).
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