Size adapted GMR arrays for the automated inspection of surface breaking cracks in roller bearings

摘要

Their small size together with a remarkable field sensitivity arc the most prominent features of present-day GMR sensors paving the way for various applications in automated non-destructive testing (NDT). This work presents a prototype for fast and automated magnetic testing of roller bearings. A local magnetization unit excites the magnetic field inside the bearing. As a result of a design study and the following wafer fabrication the probe was equipped with NDT-adaptcd GMR sensor arrays in which 48 elements measures the field response. The detection of artificial and 40 μm deep defects could be resolved with a SNR better than 20 dB. In addition, we report of a POD (Probability of Detection) analysis using GMR sensors to investigate bearings with EDM (electronic discharge machining) notches having depths down to 10 μm.