抄録
The alternating magnetic flux leakage testing has been applied in the inspection process for detecting cracks on the surface of steel. In order to develop a precise inspection method, the flux and eddy current distribution should be investigated taking account of nonlinearity of steel. This paper describes 3-D numerical analysis and experiment for this testing. The property of leakage flux from the crack of steel under ac excitation is investigated using 3-D edge-based hexahedral finite element method. It is shown that the 3-D analysis is obligatory in the precise analysis of magnetic phenomena of this testing. The effect of crack width and depth on leakage flux is clarified and the relationship between the lift off and the amplitude of leakage flux is also illustrated. The characteristic of leakage flux is confirmed by verification experiment.
