The Crack Of The Alternating Current Field Measurement And Inversion Study

This paper discusses the origion and theory of the alternating current field measurement and constructs numerical model through the numerical simulation method with the three-dimensional finite element analysing software ANSYS, which has stong ability in finite element analysis. At first,in order to get magnetic distribution in the vicinity of the any crack the general numerical model of ACFM is built using a low-frequency formulation software developed by ANSYS, which can obtain the with irregular shape. Then, in order to offer some suggestions on production design and use, the study on the effects due to lift-off, material properties , intensity and frequency of current on the measurements are discussed based on this model, which shows that, compared with the others testing methods, ACFM is not sensitive to the above factors. Through a large number of testing result semi-elliptical cracks,the rules of magnetic signals and crack size are concluded. Furthermore, an inversion algorism to evaluate the surface-breaking crack size is put forward based on above rules using the interpolating method. At last, the inversive algorism of 2-D surface crack shape reconstruction is put forward according to the similarity between spatial distributing of magnetic field and surface-breaking crack shape, which is simple and avoids the ill-posedness of general inversion problems.