Simulation for nondestructive evaluations by magnetic sensors

Simulations of the nondestructive evaluation using magnetic sensor were performed for iron based material with local strains caused by tensile stresses up to 540 MPa. The sample had been observed experimentally by magnetic noises and a magnetic leakage flux distributions. Using the observed values of the residual stress distributions, the local magnetization was determined by the minimum magnetic energy configuration of the anisotropy energy and the elastic energy under assumption which took in edge dislocations along two kinds of directions intersected at almost right angles each other. From these spatial matrix calculated by the summation of magnetic Coulomb potentials, the magnetic leakage flux was simulated and compared to the experimental results with different lift-off distances of the sensors. The result showed the mapping of the magnetic leakage flux reflected the residual stress distribution and was very sensitive to lift-off distance. On the other hand, Monte Carlo simulations for magnetic ensemble including a edge dislocation were also tried to grasp the reduction of the local magnetization around residual stress concentration areas as another aspect