Use of acoustic emission to identify oxide fracture modes

Abstract Acoustic emission (AE) has been investigated as a technique for identifying the onset and type of scale fracture events which occur under applied stress in bend tests at room temperature. Oxide scales have been thermally grown in air at 823 K on mild steel specimens approximately 100×10×1·5 mm in size. Scale was removed from one face of the specimens by carefully abrading with SiC papers. The oxide scale on the opposite face was then subjected to tension or compression stresses by mounting in a three point bend jig with the oxide on either the underside or topside, respectively. Applied load and AE events were monitored during the tests and strain for failure calculated in each mode. The AE waveforms characteristic of scale fracture in tension (through scale) and compression (decohesion) have been identified enabling the mode of failure to be determined non-destructively without the requirement to section material for metallographic examination.MST /1161