Radiographic interpretation trainer/test system

An improved system for training and testing radiographic interpreters is providing by cracking or otherwise causing structural defects in vinyl floor tiles which, when radiographic images of the floor tiles are made, produce images that accurately mimic the radiographic images of structural aluminum aircraft components. Other plastic, or aluminum, plates, called radiographic eliminating plates, are variously combined with the simulated aluminum sheets, called radiographic imaging plates, to produce a series of increasingly difficult to read radiographs for training and testing.

BACKGROUND OF THE INVENTION 
The present invention relates generally to radiographic structural crack 
detection methods, and more particularly to standardized radiographs of 
simulated aluminum test specimens for training and testing radiographic 
interpreters. 
Radiographic structural crack detection uses X-ray or gamma irradiation of 
structural components, generally aluminum aircraft components, to produce 
radiographs that can be examined and interpreted to reveal developing 
cracks. Accurate interpretation of radiographs is an acquired skill. 
Successful training of radiographic interpreters depends on the knowledge, 
patience and sight of a trainer, and the number of example cracks 
identified during training. Experience, in number, quality and variety, 
are critical to the successful training of a radiographic interpreter. 
Unfortunately, there are no standardized training aids or visual accuracy 
test programs for radiographic interpreters. Old radiographs of actual 
aircraft components found in the field to have defects are not even 
generally saved to be used as examples because they can be recycled for 
their silver, and for other reasons. Even if some individual trainers or 
training sites have been able to accumulate individual collections of 
example radiographs for training and testing trainees, these individual 
collections suffer from lack of variety and consistency between 
collections, and the limited number of different radiographs in each 
collection makes it impossible to give functionally equivalent tests to 
individual trainees without the dishonesty risks inherent with having to 
test all the students using the same radiographs. 
Complete training will require a greater number and variety of sample 
radiographs than are now available. Attempts to deliberately crack 
aluminum structural components to create the variety and number of 
radiographs needed for training has not proved successful in practice. An 
example of the need for more test sample radiographs is that, with the few 
test samples available, it is often difficult to make clear to a student 
how and why a false positive is not, in fact, a real defect and how to 
avoid such false positives in the future. 
Thus it is seen that there is a need for a greater number and wider variety 
of radiographs suitable for training and testing radiograph interpreters 
than are now available. 
It is, therefore, a principal object of the present invention to provide a 
method for making simulated aluminum plates having simulated structural 
defects that produce radiographic images that accurately mimic the 
radiographic image of an actual aluminum structural component with a 
selected defect. 
It is another object of the present invention to provide a method for 
simulating blurring and non-relevant indications on a radiograph to 
provide better training and testing. 
It is yet another object of the present invention to provide a means for 
certification of radiographic interpreters. 
It is a feature of the present invention that a great variety of different 
structure defects can be simulated. 
It is another feature of the present invention that a system of 
incrementally differing example radiographic images can be made to 
facilitate training. 
It is an advantage of the present invention that it allows rapid weeding 
out of radiographic interpreting trainees who do not have good contrast 
discrimination. 
It is another advantage of the present invention is that it allows use of 
expired X-ray film, thus reducing cost and waste. 
It is a further advantage of the present invention that the simulated 
aluminum sheets are inexpensive and straightforward to make and use. 
These and other objects, features and advantages of the present invention 
will become apparent as the description of certain representative 
embodiments proceeds. 
SUMMARY OF THE INVENTION 
The present invention provides an accurate simulated aluminum aircraft 
component having a desired simulated defect that, when irradiated by 
x-rays or gamma radiation, accurately mimics the radiographic image of an 
actual aluminum structural component with a selected defect. The unique 
discovery of the present invention is that a conventional plastic vinyl 
composition floor tile, called here a radiographic imaging plate, has 
almost the same radiographic density as aluminum and, when hand cracked at 
different temperatures, will produce radiographic images that accurately 
mimic different types of fatigue cracks, and when cut, will accurately 
mimic hardness type cracks. Another discovery is that placing a second 
sheet of plastic or aluminum, called a radiographic eliminating plate, 
over or under the radiographic imaging plate allows the introduction of 
blurring or non-relevant indications for improved training and testing. 
Accordingly, the present invention is directed to a method for making a 
training and testing radiograph that accurately mimics a radiograph of a 
hypothetical aluminum sheet having a preselected structural defect, 
comprising the steps of providing a sheet of stiff plastic, cracking the 
plastic sheet in a preselected manner to create a structural defect in the 
floor tile sheet, and making a radiograph of the cracked plastic sheet, 
whereby the radiographic image of the created structural defect in the 
plastic sheet radiograph mimics a radiographic image of the preselected 
structural defect in the hypothetical aluminum sheet. The method may, 
wherein the preselected structural defect is a fastener hole crack, 
further comprise the steps of drilling at least two spaced holes in the 
plastic sheet, and bending the plastic sheet about a line connecting two 
spaced holes in the plastic sheet until a crack connecting the two holes 
appears. The method may also, wherein the preselected structural defect is 
a fastener hole crack, further comprising the steps of drilling at least 
two spaced holes in the plastic sheet, providing a cracking tool, 
comprising a cylindrical rod and a tang attached to and extending radially 
from the rod, placing a hole in the plastic sheet over the rod and sliding 
the plastic sheet down the rod until the sheet contacts the tang, and 
bending the plastic sheet over the tang until a crack extending from the 
hole results. The stiff plastic sheet may be a sheet of vinyl composition 
floor tile. Before making the radiograph of the cracked plastic sheet, 
there may be placed over the cracked plastic sheet a second sheet of 
material to reduce the visibility of the crack on the resulting 
radiograph. The second sheet may also include marks that produce 
non-relevant indications on the resulting radiograph. 
The present invention is also directed to a plate for radiographically 
simulating an aluminum structural component having a crack, comprising a 
sheet of vinyl composition floor tile, a plurality of drilled holes 
through the floor tile sheet, at least one crack in the floor tile sheet 
extending between two drilled holes.

DETAILED DESCRIPTION 
Referring now to FIG. 1 of the drawings, there is shown a perspective view 
of a stiff plastic sheet 10 being hand cracked over a cracking tool 12 to 
make a radiographic imaging plate 14. Plastic sheet 10 is made of 
conventional vinyl composition floor tile. Various grades of Armstrong 
brand commercial floor tile have worked successfully, particularly Supreme 
Classic Vinyl Corlon, Imperial Texture Excelon and Classic Travertime 
Tiles, as described in the Armstrong 1983 Floors Product Information and 
Technical Data Brochure 9.23. These plastic floor tiles have almost the 
same radiographic density as aluminum. They produce, therefore, a 
radiographic image almost identical to aluminum. 
Radiographic imaging plate 14 was made from a 12 inch square, 0.125 inch 
thick, vinyl composition floor tile. An 7.5 inch square area was marked 
off in the center of plate 14 and ten vertical and ten horizontal lines 
drawn 0.75 inches apart inside the inside square. To simulate fastener 
holes in an actual aluminum plate, 0.1875 inch diameter holes 16 were 
drilled at each line intersection. To simulate a crack 18 between fastener 
holes 16, imaging plate 14 was slid wear side down on shaft 20 of cracking 
tool 12 until hole 16 rested on a tang 22. Using a thumb and forefinger, 
imaging plate 14 was flexed over tang 22 until the plate cracked. 
To simulate fatigue type cracks, radiographic imaging plate 14 should be 
first heated in an oven to about 95.degree. F. to 110.degree. F. To mimic 
the radiographic image of a stress corrosion type crack, or a integranular 
corrosion type crack, sheet 10 material should be heated in an oven to 
about 80.degree. F. to 90.degree. F. Cold type cracks can be simulated by 
cutting with a razor blade. The crack depth and type is generally 
controlled with temperature and pressure. The crack length is generally 
controlled with tang length, temperature and pressure. 
To simulate an aluminum plate without fastener holes, a radiographic 
imaging plate without holes is bent over a tee tool until a crack results. 
After the cracks are made, the radiographic imaging plate is exposed to 
make a radiograph to check the radiographic images. If the cracks are too 
vivid or too long, holes 16 can be drilled to a larger size. 
Next, a sheet of clear, stiff plastic 24, indicated in FIG. 2, is attached 
to the adhesive side of floor tile, or radiographic imaging plate, 14 as 
support. The thickness of radiographic imaging plate 14 is then reduced to 
0.0625 inch or thinner by removing the wear side surface. This also 
removes any dings that may have resulting from the cracking step. A disk 
sander has worked well to perform this step. A second sheet of clear, 
stiff plastic 26 is then attached to the now ground down wear side of 
radiographic imaging plate 24. The two sheets of plastic help prevent 
radiographic imaging plate 14 from breaking. 
FIG. 2 is a schematic perspective view of a radiograph 30 being made of 
cracked radiographic imaging plate 14. An X-ray head 32 provides X-rays 
for the exposure. In addition to the previously described protective 
plastic sheets 24 and 26, FIG. 2 also shows a radiographic eliminating 
plate 28. Radiographic eliminating plate 28 is a plate of aluminum, other 
metal, or plastic, and is the same size as radiographic imaging plate 14. 
Radiographic eliminating plate 28 serves to provide blurring to a 
resulting radiograph 30 so that a more realistic image for training and 
testing is provided. This is particularly important for testing contrast 
discrimination. Radiographic eliminating plate 28 may also be scratched or 
otherwise marked to provide non-relevant indications to resulting 
radiograph 30 to further refine training and testing. Eliminating plate 28 
may be placed either over or under, or both, radiographic imaging plate 
14. It will provide greater blurring when placed under radiographic 
imaging plate 14. 
For training and testing, a variety of series of radiographs 30 should be 
prepared. First, a baseline radiograph with maximum crack visibility and 
minimum non-relevant indications should be made by making a clean 
radiograph of radiograph imaging plate 14 without any interfering 
radiographic eliminating plates 28, followed by other exposures of the 
same radiographic imaging plate with different combinations of 
radiographic imaging plate and radiographic eliminating plates to 
increasing blur the images and to add non-relevant indications. The 
radiographs should further be exposed in different densities, preferably 
divided into four radiographic density groups. The density groups 
preferably should be 0.5 to 1.4; 1.5-2.19; 2.20-2.90; and, 2.90-3.50. 
Then, other series of radiographs based on different baseline radiographic 
eliminating plates, with varying sizes and kinds of simulated cracks, 
should be made. 
In use, radiographic interpreter trainees would start with more difficult 
to interpret radiographs and progress to baseline radiographs. The use of 
a baseline radiograph gives immediate positive feedback, especially where 
the trainee has available the baseline radiograph of any series to 
immediately detect mistakes and be better trained not only to detect 
defects, but also to avoid false positives. 
The advantage of making radiographs in four different density groups, or 
families, the lower number families being less exposed and presenting 
lighter images, is that trainees quickly learn which family, from light to 
dark, they find easier to read. Then, in the future, they will know what 
exposure levels to use to improve their accuracy and efficiency. 
Unfortunately, the modern practice is to standardize at a density of 2.5, 
which sacrifices the increased accuracy available in the past by allowing 
individual interpreters more leeway over exposure densities. 
The disclosed radiographic imaging plate and radiographic eliminating plate 
successfully demonstrates the use of a commonly available and easily 
workable material to simulate structural aluminum aircraft components 
having example structural defects for making otherwise unavailable sets of 
training and testing radiographs. Although the disclosed apparatus is 
specialized, its teachings will find application in other areas where 
training and testing sets are now unavailable due to high cost and other 
factors. 
Radiographic images of cracks in structural aluminum components generally 
show up as dark lines. In medical X-rays, the search is generally for 
light lines, particular when searching for cancers in soft tissue. An 
example of extending the teachings of the present invention to medical 
X-rays would be to mill aluminum plates down to 0.001 inches, welding 
round welds onto the aluminum plate, and then machining or drilling small 
depth differences into the welds to create the light marks for training. 
It is understood that various modifications to the invention as described 
may be made, as might occur to one with skill in the field of the 
invention, within the scope of the claims. Therefore, all embodiments 
contemplated have not been shown in complete detail. Other embodiments may 
be developed without departing from the spirit of the invention or from 
the scope of the claims.