DEFECT CHARACTERIZATION IN 3 DIMENSIONS BY ACOUSTIC-EMISSION

A calibrated six-channel recording system has been used to detect, locate and characterise acoustic emission events associated with the growth of a fatigue crack in a compact tension specimen of 7010 aluminum alloy, The 3D force dipole representation of each event was deduced from the arrival strengths by inversion of the Green tensor. The principal strain components and the orientation relative to the specimen axes were then calculated. It was found that while all events contained dilatational and shear components, approximately 70% were in good agreement with mode I crack opening, while approximately 30% took the form of shear-like (slip) events. The significance of errors in the measurement and inversion procedures is discussed.