Non-destructive testing and evaluation of materials using magnetic sensors: Defect detection

The sensitivity of a non-destructive testing (NDT) technique can be characterised by the smallest detectable defect. The sensitivity of magnetic flux leakage technique or eddy current technique depends on the sensitivity of the used magnetic sensor and of the testing situation, especially on the presence of disturbing influences which also affect the magnetic measurment, i. e. for example, variations of the sensor lift-off during the measurement or inhomogenity of the magnetic or electric properties of the specimen. The choice of the sensor type and the optimal design of the sensor strongly depend on the application. The following paper describes sensor arrangements for selected applications from experience of the IZFP Saarbrücken.