PhD Studentship (Sponsored by Lloyds Register Foundation) – Non-Destructive Evaluation of Stress and Heterogeneity using Acoustic Methods
With increasing demands for automated/quicker manufacture routes there is a greater need for capability in-situ quality monitoring. For example, as a part is undergoing elastic/plastic deformation during machining there is a vital need to be able to measure the level of machine induced residual stresses (RS). Current methods for detecting the level of experienced RS in a material require the use of specialist equipment, handling and timely procedures which all relate to increased cost and less applicability to an automated environment. To have a method that can detect residual stresses in-situ/after machining is considered the ‘Holy Grail’ when machining safety critical parts.
Material properties and the size and shape of defects are both fundamental inputs into structural integrity assessments. Measuring these, however, is difficult for an individual component and often it is necessary to make pessimistic assumptions based on a material class or destructive testing of a small subset of components. Despite the safety margins, these assumptions may still fail to capture the true variability in a complex, manufactured component leading to unexpected failures in service.
In this project we investigate the use of acoustic emission microphones in concert with thermal and optical sensors to provide a diagnosis of high levels of RS. A simple, non-destructive test of this kind may be indicative of a part that is likely to perform poorly during subsequent service. The novel aspects of this project are the use of advanced classifiers to interpret the complex and diverse range of signals, the potential for real-time, non-destructive monitoring of manufacturing processes and the link with laser peening and additive manufacture that will be used to produce controlled and deliberate variations in internal features to validate the predictions.
The proposed research aims to verify appropriate sensor fusion for measuring RS of homogeneous materials.
The project is structured into three themes:
Collection of Acoustic Data: This will use acoustic emission sensors coupled with a range of sources to measure signatures in a range of test specimens. The initial tests will be on simple deformed plates but will evolve into measurements on complex geometries and include part with high RS or internal flaws. It may also be possible to include samples during powder deposition or welding to provide real-time monitoring of a manufacturing process.
Advanced Data Characterisation: This will employ a variety of signal analysis, sensor fusion and cognitive decision making algorithms to provide an assessment of the health of the part. The acoustic signals will be subject to processing using wavelet and short Fourier transforms in order to be able to process the results in near real-time. These will then be fed into a decision making/classifier technologies. The combination of sensory data from disparate sources will provide information that is more accurate, complete or dependable than the individual measurements.
Physical Modelling of Acoustic Propagation: This will implement a finite element model of propagation of high frequency sound waves from a range of point sources to a detector through a polycrystalline metal with anisotropic and heterogeneous properties in order to replicate the effects of RS or microstructure variation. This will provide valuable guidance to the data collection programme for optimisation of detection frequencies, pulse characteristics and sensor placement and also; trial inputs into the data characterisation programme to allow signal processing on simulated perfect or, noisy streams.
About the Industrial Sponsor
The Lloyd’s Register Foundation funds the advancement of engineer-related education and research and supports work that enhances safety of life at sea, on land and in the air, because life matters. Lloyd’s Register Foundation is partly funded by the profits of their trading arm Lloyd’s Register Group Limited, a global engineering, technical and business services organisation.
NSIRC is a state-of-the-art postgraduate engineering facility established and managed by structural integrity specialist TWI, working closely with, top UK and International Universities and a number of leading industrial partners. NSIRC aims to deliver cutting edge research and highly qualified personnel to its key industrial partners.
About the University
Coventry University has a proud tradition as a provider of high quality education and a focus on multidisciplinary research, the University has established a robust academic presence regionally, nationally and across the world.
Coventry is the proud winner of THE Awards’ 2015 University of the Year, becoming the first university to be named Modern University of the Year three times running and awarded the prestigious Queen’s Award for Enterprise in 2015 in recognition of its international growth and success over the past six years.
Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in engineering or materials science. Candidates with suitable work experience and strong capacity in numerical modelling and experimental skills are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable.
This project is funded by Lloyds Register Foundation, TWI and academic partners. The studentship will provide successful Home/EU students with a stipend of £16k/year and will cover the cost of tuition fees. Overseas applicants are welcome to apply, with total funding capped at £20k/year.