In April 2016 Manchester eScholar was replaced by the University of Manchester’s new Research Information Management System, Pure. In the autumn the University’s research outputs will be available to search and browse via a new Research Portal. Until then the University’s full publication record can be accessed via a temporary portal and the old eScholar content is available to search and browse via this archive.

Related resources

Search for item elsewhere

University researcher(s)

Academic department(s)

DEVELOPMENT OF METHODOLOGY TOWARDS A LASER BASED FULL MATRIX CAPTURE INSPECTION TECHNIQUE

Knight-Gregson, Benjamin John

[Thesis]. Manchester, UK: The University of Manchester; 2017.

Access to files

FULL-TEXT.PDF (pdf)

Abstract

This thesis presents the development of a fully non-contact laser based application of the FMC inspection strategy (L-FMC), allowing improved understanding of the benefits and capabilities of laser based arrays for ultrasonic testing. Motivated by the desire to work towards an industrially viable system, an optically rough (Ra 456.468 nm) aluminium sample containing side drilled holes (SDH) was inspected. The results obtained from the L-FMC inspection were compared to the current state of the art of laser array imaging and found to offer improved signal to noise ratios by up to 6 dB. The investigation highlighted areas of improvement to be investigated in order to increase the industrial viability of L-FMC. Investigations were aided by the use of piezoelectric arrays so as to minimise experimental variables and increase repeatability. The investigation of these areas resulted in new findings regarding FMC in general, not just the laser based approach. The areas looked at were the acquisition speed of the system, the ability of the system to make use of diffracted wave fronts, a calibration procedure for the diffracted wave front strategy and the application of coherence weighting for the reduction of noise. A new data acquisition strategy, SA-FMC, was developed as part of this thesis in order to increase inspection speed by reducing the amount of data that is acquired and processed during an inspection. It was shown that SA-FMC can produce cross-sectional images of a similar quality to FMC whilst only collecting 35% of the data. It was also shown, using piezoelectric arrays, that for on-axis reflectors, SA-FMC gives improved results compared to FMC at depths less than 18 mm and similar results at greater depths. An investigation into diffraction based TFM imaging (D-TFM) using piezoelectric transducers showed the ability to correctly position vertical notches in both the horizontal and vertical dimensions without the need for an additional scan, either mechanical or electronic. A calibration procedure was developed which improved the on-axis imaging performance of D-TFM by up to 38.8% and increased the depth sizing capabilities to within 0.05 mm for the inspected sample. Finally, coherence weighting (CW) algorithms were investigated in order to suppress the effect of noise on cross-sectional images. This investigation showed that CW algorithms could be used on L-FMC and D-TFM as well as coarse grained samples. It is shown that for some known scenarios it may be advantageous to directly image the weighting map produced by the CW algorithms.