is an advanced Transient
Eddy-Current Scanning System using probes containing Hall Sensors. The system
has recognized potential for the detection of deep corrosion and cracks in
aging aircraft structure. Significant benefits can be realized from the use
of Transient Eddy-Currents.
-
Reduced Inspection Time
-
Ease of Acquisition and Analysis of the Scan Data
-
Large Areas of Structure With Multiple
Variations in thickness can be scanned without the need for probe or
set-up changes. Transient eddy-current Non-Destructive Testing is arousing
increasing interest for the detection of cracks and corrosion in aging
metallic aircraft structures. A major attraction is that a single scan
over a large area of structure contains sufficient information for both
detection and characterization of defects, regardless of structural
variations. Due to the simple data acquisition procedures minimal operator
training is required. A further benefit is the ability to use advanced
analysis methods, supported by analytical models, to determine location,
depth, size, and severity of defects. The transient eddy-current method
requires no parameter changes at acquisition time to allow for changes in
thickness or conductivity and the analysis methods enable the removal of
lift-off, edge effects, and other structural changes.
Above is an example of various time-slice images of a DC10 Crown Splice
from a C-scan using the
system.
Transient eddy currents allow us to look deeper into aluminum structures
with a time component. By using these time-slices, we can extract much
more information from inspection results than conventional eddy current.
What is Transient Eddy Current?
The transient eddy-current method generates an electric field pulse
with a coil at the surface of a structure and as it propagates down into
the structure, over the course of a few milliseconds, eddy currents are
generated as a response. The magnetic field measured at the surface will
be modified by any changes in the propagation path of the pulse, changes
caused by defects, conductivity changes, edges or interfaces. The
eddy-current pulse contains a broad frequency spectrum, which is of
great benefit during analysis of the signals because it includes the
equivalent of numerous single-frequency scans using a conventional
eddy-current system. The transient response is a slowly varying function
so it is possible to characterize it adequately with a 'compact
transient' containing just twelve or so 'time-slice' measurements of the
field.
Advantages of
- A broad frequency-range is captured in each transient data set.
-
Large areas of structure with multiple variations in thickness can be
scanned without the need for probe or set-up changes
- The use of a Hall sensor as a field detector improves the spatial
resolution and the detect ability of deep defects.
- Structure variations can be optimized during analysis.
- Advanced
post-processing analysis tools.
Unique Post Analysis Tools
- Lift-off Compensation
- Edge Subtraction
- Total Thickness Measurement
- Plate Separation Effect Elimination
- Time-slice viewing
- Time Domain Signal Processing
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