Papers by Author: M.G. Baxter

Abstract: Acoustic emission (AE) monitoring was performed on an aluminium landing gear component that was undergoing testing to investigate its fracture resilience. The type of component was identified from FE analysis and previous fatigue testing. The component was loaded in fatigue for 500 flight cycles before re-greasing of the bearings. After 2,000 cycles the component was removed for NDT inspection. The AE investigations were implemented after 83,000 flight cycles had been completed. NDT at this point had shown that the component contained no damage. This paper presents the findings of the final 2,000 cycles monitored. The AE investigation detected and located, using both linear and planar location approaches, one region of activity around the grease pin. Fretting damage at this location was confirmed using dye pentrant testing. It was also shown that the increase in rate of detected activity is a significant tool in the identification of damage in landing gear components.

Abstract: Current analysis of Acoustic Emission (AE) signals is dominated by waveform parameter assessment, such as amplitude, rise-time, absolute energy, initiation frequency etc. whilst the actual waveform collected is often ignored. This paper explores the dispersive behaviour of Lamb Wave propagation as a means of estimating source to sensor distance and source orientation from collected waveforms.

Abstract: This investigation considers the identification of fatigue crack growth in aerospace grade steel using Acoustic Emission (AE) techniques. Four specimens with small radius crack initiation sites were investigated under four-point bending (SENB4). A linear array of 4 resonant AE sensors was utilised to locate the crack growth. Detection and location of fatigue crack growth in aerospace grade steel SENB4 specimens using appropriate AE techniques was successful. Time of arrival (TOA) linear location has provided an invaluable tool for separating AE signals arising from fatigue crack growth from the notch from those emanating from the loading points. Analysis of the AE feature data from the notch has allowed initial categorisation of AE from fatigue crack growth. AE data from this research was found to correspond with that reported in previous studies [1] examining Compact Tension (CT) specimens.