The Library
High-sensitivity eddy-current testing technology for defect detection in aerospace superalloys
Tools
Hughes, Robert Rhys (2015) High-sensitivity eddy-current testing technology for defect detection in aerospace superalloys. EngD thesis, University of Warwick.
|
PDF
WRAP_THESIS_Hughes_2015.pdf - Submitted Version - Requires a PDF viewer. Download (17Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2870328~S1
Abstract
Industrial eddy-current testing (ECT) inspections of aerospace superalloys, such as Titanium 6Al-4V, must reliably detect sub-millimetre surface breaking defects. The sensitivity of such measurements is hindered by the materials' low conductivity and high coherent background material noise, making the high sensitivity standards required by industry harder to achieve.
It is demonstrated herein that using eddy-current array (ECA) technology also introduces inspection "blind-spots", whereby small defects could be missed. This supports the motivation to develop techniques for enhancing the sensitivity of typical ECT and ECA measurements. The early stage research and development of a novel ECT measurement method is presented, and shown to improve the standard measurement sensitivity of industrial ECT inspections.
A defect signal enhancement phenomenon within a band of frequencies close to the electrical resonance of an ECT probe, termed near electrical resonance signal enhancement (NERSE), was observed and characterised. This phenomenon was demonstrated to be a direct result of the shifting resonant frequency of the probe in the presence of material discontinuities.
Frequency sweeping chirp signals were used to generate electrical resonance traversing frequency spectra measurements of the inspection probe in the presence of material discontinuities. Critical feature analysis of the results demonstrated a correlation between defect dimensions and peak NERSE amplitude, but failed to draw any conclusive trends between discontinuity dimensions and the resonant frequency shift. This was attributed to the relatively small defect sample set used and the size of many of the machined defects being smaller than the diameter of the inspection coil.
An ECT probe was excited at a single frequency carefully selected to correspond to the NERSE peak frequency. A study was performed to statistically analysis the sensitivity of this NERSE measurement compared to a standard excitation frequency measurement used in industry. The results demonstrated that a NERSE frequency inspection was able to reliably detect a defect size of 0.82mm, compared to 1.09mm achieved by a standard operating frequency.
Item Type: | Thesis (EngD) | ||||
---|---|---|---|---|---|
Subjects: | T Technology > TA Engineering (General). Civil engineering (General) | ||||
Library of Congress Subject Headings (LCSH): | Eddy current testing, Heat resistant alloys -- Testing | ||||
Official Date: | October 2015 | ||||
Dates: |
|
||||
Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | EngD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Dixon, S. ; Edwards, R. S. (Rachel S.) ; Billson, D. R. | ||||
Extent: | xix, 191 leaves : illustrations, charts | ||||
Language: | eng |
Request changes or add full text files to a record
Repository staff actions (login required)
View Item |
Downloads
Downloads per month over past year