Refining automated ultrasonic
inspections with simulation models
by Michael Garton
Summary
A software package, UTSIM, has been created that can
simulate ultrasonic measurements. A particular capability of this
package, namely simulating and refining inspection scan plans, has been
described in detail. Three examples were shown. The first example
leveraged the axial symmetry of the set-up to solve for the optimum
step size semi-analytically with a beam width calculation on one plane.
The second example had less symmetry, requiring the beam width to be
calculated on two planes. Again the optimum scan step size was
determined using semi-analytical methods. The third example
demonstrated a general method to keep track of scan coverage that can
be used in cases that are too complex for the semi-analytical methods.
The capability to quantitatively determine and
refine the coverage of a scan is believed to be unique to this
software. Many examples exist in the literature of simulating a flaw
response at a single point, but none claim to simulate scan coverage by
calculating a response for each point in the volume and for each probe
location in the scan.
Applicability to Real
World Problems
The software is applicable to most ultrasonic
inspections. It is particularly useful for unusual probes and/or
complex geometries were the field propagates in the least intuitive
ways. Visualizing the fields is a great aid to understanding the
consequences of particular choices of parameters. The ability to look
at a map of the coverage inside UTSIM, a slice at a time in any
direction, is very useful. The software was written with complex
geometries in mind, so it can immediately be applied to an entire class
of inspection problems. It is expected that the technology will draw
greatest interest in safety critical applications as found for example
in the nuclear industry.
Future Work
Future work to improve the software includes
removing restrictions and broadening the class of problems that can be
solved with UTSIM. The major restrictions on the system currently come
from the approximations in the beam models and flaw models. The system
can use better and less-restricted models as they become available.
Also, more automation will be added in the software to solve the most
general case with minimum user input.
Disclaimer and Acknowledgment
This paper was originally presented as a Thesis for a Master of Science
degree at Iowa State University. Mike Garton is a staff researcher and
software developer at the Center for Non-destructive Evaluation (CNDE)
in Ames, Iowa, USA. Mike would not call himself an "expert"
in ultrasonics. There are other researchers at CNDE that are certainly
more knowledgeable in ultrasonics than Mike. Mike would especially like
to acknowledge the assistance of two such experts, Les Schmerr and Tim
Gray. This work was supported by NIST.
Questions can be directed to Mike by any of these means:
Michael Garton
Email: mike@iastate.edu
phone in USA: (515) 294-1429
fax in USA: (515) 294-6368
mail: Mike Garton
1915 Scholl Road
Ames, IA 50011
USA
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© Copyright 1. Oct 1997 Rolf Diederichs,
rd@ndt.net