-Finite Element modelling is a promising tool for further progressing the 1 development of ultrasonic NDE of polycrystalline materials. Yet its widespread adoption has 2 been held back due to a high computational cost, which has restricted current works to
Abstract-Improving the ultrasound inspection capability for coarse grain metals remains of longstanding interest and is expected to become increasingly important for next generation electricity power plants. Conventional ultrasonic A, B, and C-scans have been found to suffer from strong background noise due to grain scattering which can severely limit the detection of defects. However, in recent years, array probes and Full Matrix Capture (FMC) imaging algorithms have unlocked exciting possibilities for improvements. In order to progress and compare these algorithms we must rely on robust methodologies to quantify their performance. This article proposes such a methodology to evaluate the detection performance of imaging algorithms. For illustration, the methodology is applied to some example data using three FMC imaging algorithms; Total Focusing Method (TFM), Phase Coherent Imaging (PCI), and Decomposition of the Time Reversal Operator with Multiple Scattering Filter (DORT MSF). However it is important to note that this is solely to illustrate the methodology; this article does not attempt the broader investigation of different cases that would be needed to compare the performance of these algorithms in general. The methodology considers the statistics of detection, presenting the detection performance as Probability of Detection (POD) and probability of False Alarm (PFA). A test sample of coarse grained INCONEL 625, manufactured to represent materials used for future power plant components and containing some simple artificial defects, is used to illustrate the method on the candidate algorithms. The data is captured in pulse-echo mode using 64 element array probes at centrefrequencies of 1MHz and 5MHz. In this particular case, it turns out that all three algorithms are shown to perform very similarly when comparing their flaw detection capabilities.
Poor penetration and excessive absorption of high frequencies limit spectroscopic approaches using fast rise pulses for inspecting many engineered structures. So, this study focused on the alternative application of low frequency acoustic and ultrasound waves for the characterisation of challenging structures in airborne and waterborne environments. A simple, transfer matrix model approach was developed for the simulation of 1D sound propagation through layered media that comprise many engineered structures. This model was used to test the feasibility of using sound waves for non-destructive characterisation of an articulated lorry transported trailer and offshore foundation infrastructure. The targets were not in contact with the sound sensors and incorporated highly attenuating layers with acoustic contrasts to the surrounding medium that result in over 90% reflection of incident wave pressure. In both cases, resonances controlled by the thicknesses and interval velocities of component layers modulated sound reflection from, and transmission through the whole structure. These effects were observed as local maxima and minima in the spectra of the transmission and reflection coefficients. These spectral coefficients also determined the modulation to the temporal envelope of a linear frequency modulated pulse used to insonify the targets. In the acoustic study, which comprised only theoretical modelling, discrimination of differing cargo widths and between solid versus empty cargo trailers
6A Finite Element modelling framework is outlined that enables the investigation of ultrasonic 7 array imaging within highly scattering, polycrystalline materials. Its utility is demonstrated by 8 investigating the performance of arrays, within both single and multiple scattering media. By 9 comparison to well-established single scattering models, it is demonstrated that FE modelling 10 can provide new insights to study the stronger scattering regimes. In contrast to established 11 single scattering results, Signal-to-Noise Ratio (SNR) no longer increases monotonically with 12 respect to increasing aperture, which suggests that maximum apertures are not necessarily 13 optimal. Furthermore, by measuring the SNR of the individual transmit receive combinations 14 of the array, it is found that through separating the emitter and receiving source, it is possible 15 to reduce the received backscatter. 16
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