Observations on acoustic emissions from a line contact compressed into the plastic region

Some observations from acoustic emissions recorded during a yield test of a bearing raceway compressed into plasticity using a rolling element are presented. The general objective of the study is to establish whether there is enough evidence of the onset of sub-surface plasticity in the acoustic emissions signature. It is discussed here how acoustic emissions monitoring during compression could indicate the onset of subsurface plasticity as a precursor to damage propagation to the surface. Some comparisons are drawn between the acoustic emissions activity levels and time-frequency response during elastic deformation and at yield loads

Effect of Temperature and Heat Treatment on Crack Growth Acoustic Emission in 7075 Aluminum

The acoustic emission activity due to crack advance in 7075 aluminum alloys has been found to vary with both temperature and heat treatment. An Increase in temperature or overaging of material in the -T6 condition each reduces the acoustic emission activity by changing the probability of occurrence of acoustic emission events and lowering their amplitudes. These observations suggest that the acoustic emission source mechanism is not inclusion fracture but rather is a property of the ductile matrix

A recursive adaptive lattice filters for impulsive signals

The existence of impulsive noise with alpha-stable distributions has been addressed in many applications. Some adaptive lattice algorithms that factional lower order moments of residual errors are used to updated the filter coefficients are presented. In this paper, a new recursive adaptive lattice algorithm is proposed for adaptive filtering of alpha-stable AR processes. The performance of this algorithm is compared to that of those stochastic gradient-based algorithms. It is shown that the proposed algorithm achieves a superior convergence speed with respect to the other algorithms. © 2005 IEEE.link_to_subscribed_fulltex

Clinical significance of ciliary abnormalities in bronchiectasis

Two separate experiments, using different sample materials and sample geometries have been carried out using a number of different AE techniques and measurement systems. In both experiments the AE generated during tensile loading was measured and characterized. The types of AE measurements used simultaneously on each test included: (1) analog rms voltage measurements of the voltage induced at the piezoelectric transducer attached to the sample, (2) computer controlled standard resonant sensor (140 kHz) parameter measurements such as count, events, rise time, duration, etc., and (3) modal AE measurements providing actual wave forms of the AE events. Modal AE should provide distinct wave modes created by different AE sources. The outputs of both resonant piezoelectric and flat, high fidelity wide band transducers were captured with the waveform system. Each of the two experiments will be discussed separately below