Patent Number: 054835712
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS To produce a radiographic Moire pattern that is capable of demonstrating stress and other deformations in a rectangular matrix of RTV.RTM. rubber the present invention has been implemented in the following manner. The first pattern as set out in the claims was in the form of a series of 0.005" diameter steel wires that were fixed to the matrix of RTV.RTM. rubber. Each wire was placed 0.020" from its neighbor and substantially parallel. An x-ray photograph of this wire plus rubber test piece is shown in FIG. 1 (note that in the test piece four wire positions were unintentionally crossed, causing the two dark bands). The test piece underwent various deformations including inducing a curvature of diameter 8", and applying a tensile load of zero, 5 lb. and 10 lb. An x-ray image was produced on film for each instance. These images were then digitally scanned into a computer. The line resolution of the digital scanning provided the second pattern necessary to produce a Moire pattern. The resulting Moire patterns are shown in FIGS. 2 and 3 respectively. Another preferred embodiment is to use a series of metal dots in place of parallel wires. In measuring material properties it is desirable not to include the properties of the device used for measuring. By the substitution of dots the tensile properties of the wires are eliminated from any measurements. Another preferred embodiment is to make use of existing patterns contained in the workpiece such as the belts of a tire. Another preferred embodiment is to make use of real time radiography to produce images quickly, eliminating the film stage. Further, with proper setting of the resolution the digital display will act as the second pattern and the Moire image will be captured directly. Another preferred embodiment is to make use of a flash x-ray or dynamic radiography system. This operates at a higher rate of speed than real time radiography and could be used to make measurements on a specimen under dynamic loads. Another preferred embodiment is to attach both the first and second patterns to the material being inspected. This allows observation of the motions of two different depths of the material to be made so that differential movements can be quantified.