Dynamic measurements of internal three-dimensional displacement fields with digital speckle photography and flash x rays

A metrology system is presented that measures internal three-dimensional (3 -D) displacement fields. The system uses a stereo pair of flash x-ray heads and correlation analysis to measure the true deformation of a layer of x-r ay-absorbent particles inside the specimen. The 3-D deformation field insid e blocks of polyester was determined. The polyester blocks were impacted by a 9-mm steel ball bearing fired from a g-mm-bore gas gun at a speed of 373 .5 +/- 3.0 m s(-1). At a given time after impact, a short-duration (30 ns) flash x-ray pulse exposes the x-ray radiographs and freezes the events duri ng impact. Thereafter, the x-ray radiographs are scanned into a personal co mputer and analyzed as in digital speckle photography. (C) 1999 Optical Soc iety of America.