Fretting damage assessment in Ti-6Al-4V by magnetic sensing

As a result of recent technological advances in high-sensitivity magnetic sensors, state of the art magnetometers, make it possible to obtain new assessment measurements of the near-surface layers (5–60 μm) in fretting damage zone. In particular, the experimental method used in this investigation is based on magnetic sensing of local thermoelectric currents produced by material imperfections such as texture, inclusions, residual stress, cold work, heat treatment etc., when a temperature gradient is established in the material. These thermoelectric currents generate flux magnetic densities that are detected by a highly sensitive magnetometer. According to our preliminary results, the magnetic flux density measurements was found to be rather sensitive to changes in near-surface layers produced by the fretting damage in Ti-6Al-4V alloy specimens with the exception of the intrinsic material background magnetic signal that affected deeply the detectability of subtle material variations in noncontacting thermoelectric measurements. This study shows a non-destructive test method that can detect the level of fretting damage in metals, that is difficult to characterize by other well known NDE methods.