Abstract

The Acoustic Emission (AE) characteristics and source mechanism during fatigue crack growth in steel structures and weld connections are investigated experimentally by three point bending testing of specimens under low cycle constant amplitude fatigue loading using the Hilbert Huang Transform (HHT). The characteristic frequencies corresponding to crack growth sequence, that is, initiation, crack propagation and fracture is studied using Hilbert’s Spectral analysis. AE sources at the three stages during fatigue cracking were investigated using the AE counts and the constitutive ratios of the Intrinsic Mode functions of HHT. The effect of peak load on AE during fatigue crack propagation was discussed. A comparison of results with Linear Elastic Fracture Mechanics (LEFM) analysis indicated that HHT is an effective technique superior to the traditional envelope spectrum method for signal feature extraction during fatigue crack growth in steel structures.

Key words: Acoustic emission technology, Linear Elastic Fracture mechanics, Hilbert Huang Transform, Intrinsic Mode Function.