Acoustic Emission (AE) testing is capable of detecting a wide range of defects using a relatively sparse sensor array and
as a result is a candidate structural health monitoring technology. The widespread application of the technology is
restricted by a lack of predictive modelling capability and quantitative source characteristic information. Most AE tests
are conducted on small coupons where source characteristics are estimated using the early arriving part of the AE signal.
The early arriving part of an AE signal, and therefore the source characteristics, are dependent on the source location,
source orientation and specimen geometry making them unsuitable for use in predictive models. The work in this paper
is concerned with making source characterisation measurements based on the diffuse field of an AE signal. A practical
approach for calibrating the diffuse field amplitude is proposed and is demonstrated on AE signals from electrochemically
accelerated corrosion of a 316L stainless steel plate. The diffuse field amplitude of several AE events is
calculated and reported as an equivalent absolute force. The low signal to noise ratio and high attenuation of elastic wave
energy are found to reduce the accuracy of the results.
Acoustic emission (AE) testing is a sensitive technique capable of detecting many types of defect with a sparse sensor
array making it an attractive structural health monitoring technology. The widespread application of the technology is
limited by a lack of predictive modelling and in part, the lack of quantitative source characteristics. The vast majority of
current laboratory AE testing is conducted on small coupons which cannot be used to generate quantitative source
characteristics since reflected wave energy from the specimen edges influences the received waveforms. An alternative
approach is to test on large specimens where the modal properties of propagating waves can be examined with no
influence from reflected wave energy. However, the design and testing of large specimens is not trivial.
The work in this paper discusses the design of large fibre reinforced composite (FRC) specimens which are suitable for
making quantitative source measurements. The design considerations include the minimum plate dimensions and
placement of sensors. A novel technique, referred to as the location-time plot technique, is described which links
propagation characteristics, specimen dimensions and sensor locations to map the dispersion of elastic waves in plates.
The technique is demonstrated in the design of a simple AE experiment on a highly anisotropic plate. The technique is
then used in the design of a practical AE testing arrangement for monitoring delamination from artificial defects in a
large FRC plate. Experimental waveforms, recorded using this AE testing arrangement, are presented and are shown to
be in agreement with the location-time plot technique.
Acoustic emission (AE) testing is potentially a highly suitable technique for structural health monitoring (SHM) applications due to its ability to achieve high sensitivity from a sparse array of sensors. For AE to be deployed as part of an SHM system it is essential that its capability is understood. This is the motivation for developing a forward model, referred to as <i>QAE-Forward</i>, of the complete AE process in real structures which is described in the first part of this paper. <i>QAE-Forward</i> is based around a modular and expandable architecture of frequency domain transfer functions to describe various aspects of the AE process, such as AE signal generation, wave propagation and signal detection. The intention is to build additional functionality into <i>QAE-Forward</i> as further data becomes available, whether this is through new analytic tools, numerical models or experimental measurements. <i>QAE-Forward</i> currently contains functions that implement (1) the excitation of multimodal guided waves by arbitrarily orientated point sources, (2) multi-modal wave propagation through generally anisotropic multi-layered media, and (3) the detection of waves by circular transducers of finite size. Results from the current implementation of <i>QAE-Forward</i> are compared to experimental data obtained from Hsu-Neilson tests on aluminum plate and good agreement is obtained. The paper then describes an experimental technique and a finite element modeling technique to obtain quantitative AE data from fatigue crack growth that will feed into <i>QAE-Forward</i>.