Tensile failure analysis of structural materials using acoustic emission.

摘要

Materials testing is an extremely important process in the modern world with new colossal structures being built in every corner of the earth, with the ever increasing size of structures making safety of vital importance. This project examines the mechanical behaviour of three commonly used structural metals when subjected to a tensile loading; Steel, Aluminium and Brass. The tensile load was applied to the metallic specimens at different loading rates. Acoustic Emission (AE) was the main monitoring tool implemented into the procedure to record in real time the elastic waves produced from the three individual materials, as they were applied with the load until failure. Fractography was also implemented into the analysis to compare the AE signals with microscopic deformation characteristics of the materials. The discussion of AE activity was divided up into individual regions on the loading graphs. Although displaying unique graph shapes, the same regions were still available for all materials. The results showed that for the three materials, steel produced the most amount of AE activity for all loading rates tested. It was also concluded that the elastic region of loading graph produced highest accumulation of AE activity for all the materials. The AE signals were also seen to be amplified when increasing the loading rate of tensile load applied to specimens. Each material displayed unique characteristics in relation to the AE activity with defining features when monitoring until failure. Fractography was an effective method for determining the type of fracture of the material, however interpretation of AE source from photographs was highly dependent on investigator- further research into the field would be required. The AE technique proved effective at distinguishing between the three materials, when applied with a tensile load until failure. Through further investigation into specific field, the AE technique could be implemented into any structure to ensure integrity monitoring.