Non-destructive evaluation method for metal loss type flaws having oblique edge side-planes by far-side magnetic flux leakage method

摘要

Far-side MFLT inspection is used in NDT for integrity of structures and components, especially for detection and characterization of underside metal loss type flaws in oil storage tank floors. This paper describes the experiment on flaw shapes which are similar to real flaws in order to apply the Far-side magnetic flux leakage method to tank bottom floors. The magnetic leakage field can experimentally be measured from the flaws whose sections were wedge and trapezoid, and then the magnetic leakage field was theoretically analyzed by the dipole model. The calculation results by the analytical expressions are in good agreement with the experimental ones. After the flaw signals were processed by the Fourier transform, multiple regression analysis was done to evaluate the flaw angle. The quantitative method was also proposed to evaluate the flaws.