Characterisation of fatigue crack extension by quantitative acoustic emission

• Published in: International journal of fracture 1985-08, Vol.28 (4), p.201-222
• Main Authors: SCRUBY, C. B, BALDWIN, G. R, STACEY, K. A
• Format: Article
• Language: English
• Subjects: acoustic emissions; aluminum alloys; Applied sciences; elastic waves; Exact sciences and technology; fatigue; Industrial metrology. Testing; Mechanical engineering. Machine design; Non-destructive testing: methods and equipments; transducers
• ISSN: 0376-9429; 1573-2673
• DOI: 10.1007/BF00035216

A calibrated four-channel elastic wave recording system has been used to detect and characterize acoustic emission events associated with the growth of a fatigue crack in a compact tension specimen of 7010 Al alloy. The transducers sampled the elastic wave field in four independent directions in a plane perpendicular to the crack. The 2-D force dipole representation of each event, assumed to be a point source, was deduced by inversion of the Green's tensor. Each emission event was then characterized in terms of source type (e.g. microfracture, slip), orientation relative to fatigue crack and size (e.g. crack volume). All of the events (other than clearly distinguishable signals due to fretting at the loading pins) were located within 0.5 mm of the crack tip. 80% of the recorded events had the character of fracture, and were mostly oriented approx. parallel to the fatigue crack. The typical event size was approx 2000 mu m exp 3 . It is believed that the principal source of emission was brittle inclusion fracture at, or close to, the crack tip. 17 ref.--AA(UK/US).