MULTI-LAYER THIN FILM STRESS SENSOR FOR NON-DESTRUCTIVE TESTING OF FERROMAGNETIC MATERIALS

摘要

A non-destructive testing technique and sensor are described for measuring surface magnetic permeability and surface stress distribution in ferromagnetic materials. The sensor uses a thin film magnetoresistive sensing element that is either sandwiched between two thin film current conductors and insulators or placed above or below one conductor. Changes in the magnetic permeability of the ferromagnetic material upon which the sensor is placed create an output voltage which is monotonically depending on the magnetic permeability and also on the stress tensor of the ferromagnetic material. Appropriate calibration of the sensor may provide accurate stress distribution measurements, which may be wirelessly transmitted. Surface scanning is also supported by an integrated position sensor.