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http://hdl.handle.net/1947/10169
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| Title: | Transient Eddy-Current Nondestructive Evaluation Benchmark Data for Backface Slots in a Plate. |
| Report number: | DSTO-TN-1047 |
| AR number: | AR-015-159 |
| Classification: | Unclassified |
| Report type: | Technical Note |
| Authors: | Burke, S.K.
Ibrahim, M.E. |
| Issue Date: | 2011-12 |
| Division: | Maritime Platforms Division |
| Abbreviation: | MPD |
| Release authority: | Chief, Maritime Platforms Division |
| Task sponsor: | CMPD |
| Task number: | ERP 07/368 |
| File number: | 2011/1081004/1 |
| Pages or format: | 16 |
| References: | 14 |
| DSTORL/DEFTEST terms: | Non-destructed tests
Electromagnetic induction
Magnetic fields
Magnetic measurement |
| Abstract: | The results of a benchmark experiment for transient eddy-current non-destructive evaluation are
reported. The benchmark configuration corresponds to the canonical geometry of an air-cored
probe coil positioned above a conductive plate containing a long back-face slot. The coil is excited
by an exponentially-damped step function current and measurements are made of the change in
the transient magnetic field due to the slot. The aim of the work is to provide experimental data
for validation of theoretical models under development within the wider NDE community and to
provide a common geometry against which the performance of a range of such models can be
compared. A further aim of the work is to stimulate the ongoing development of quantitative
methods in transient eddy-current research. |
| Executive summary: | Eddy-current testing (ET) is a well-established and reliable non-destructive evaluation
(NDE) technique that is used extensively to ensure the structural integrity of military
platforms. It relies on a time-varying magnetic field, produced by a probe coil, to induce
eddy currents in a metallic component under test. The presence of defects such as fatigue
cracks or corrosion perturb the local eddy-current distribution, leading to a change in the
induced coil voltage, signalling the presence of a flaw.
The two principal variants of ET are distinguished by the time variation of the applied
field. Conventional ET utilises an alternating current to excite a probe coil, and
measurements are performed in the frequency domain. The emerging technique of
transient eddy-current testing consists of time-domain measurements where the probe coil
is excited by a pulsed current. Significant interest has been generated in the transient
technique because of its potential advantages over conventional ET in circumstances such
as the detection of buried defects in multi-layer metallic structures.
A range of mature numerical modelling packages can be used to predict the probe
response and optimise inspection parameters for conventional ET. However, there is a
distinct lack of such tools for transient eddy-current testing. Further development of the
transient technique requires similar validated quantitative models to underpin probe
design and inspection philosophy.
With this in mind, the aim of the present work is to provide high-quality experimental
transient eddy-current data for a well-characterised benchmark configuration. These data
will then be employed to validate numerical models, currently under development within
the wider NDE community. The benchmark experiment also provides a common
geometry against which the performance of a range of numerical models can be compared,
and is expected to stimulate ongoing development of quantitative transient eddy-current
methods.
The benchmark configuration is typical of the case where transient eddy-current NDE
could be considered in preference to conventional eddy-current NDE. The experimental
configuration and parameters for the benchmark problem are presented within the body
of the report and, for ease of access, the transient magnetic field data are provided in
electronic form in a series of files accompanying this report.
This work was initiated by the TTCP Technical Panel MAT-TP-5 Nondestructive Evaluation
for Asset Life Extension and Integrity through the operating assignment TTCP MAT-TP-5
O33 ‘Transient Eddy-current Systems.’ |
| Appears in Collections: | DSTO Formal Reports
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