Assessing the effect of defect induced stresses on magnetic flux leakage (MFL) signals is a complicated task due to nonlinear magnetomechanical coupling. To facilitate the analysis, a multiphysics finite elemental simulation model is proposed based on magnetomechanical theory. The model works by quasi-statically computing the stress distribution in the specimen, which is then inherited to solve the nonlinear magnetic problem dynamically. The converged solution allows identification and extraction of the MFL signal induced by the defect along the sensor scanning line. Experiments are conducted on an AISI 1045 steel specimen, i.e. a dog-bone shaped rod with a cylindrical square-notch defect. The experiments confirm the validity of the proposed model that predicted a linear dependency of the peak-to-peak amplitude of the normalized MFL signal on applied stress. Besides identifying the effect of stress on the induced MFL signal, the proposed model is also suitable for solving the inverse problem of sizing the defects when stress is involved.

Previous studies on Lamb wave touchscreen (LWT) were carried out based on the assumption that the unknown touch had the consistent parameters with acoustic fingerprints in the reference database. The adaptability of LWT to the variations in touch force and touch area was investigated in this study for the first time. The automatic collection of the databases of acoustic fingerprints was realized with an experimental prototype of LWT employing three pairs of transmitter–receivers. The self-adaptive updated weight coefficient of the used transmitter–receiver pairs was employed to successfully improve the accuracy of the localization model established based on a learning method. The performance of the improved method in locating single- and two-touch actions with the reference database of different parameters was carefully evaluated. The robustness of the LWT to the variation of the touch force varied with the touch area. Moreover, it was feasible to locate touch actions of large area with reference databases of small touch areas as long as the unknown touch and the reference databases met the condition of equivalent averaged stress.