A technique to measure two-dimensional deformation fields of a layer inside materials during dynamic events such as impact experiments is presented. Even optically opaque materials like cement can be evaluated when flash x rays are used. Blocks of polyester and cement were prepared with a layer of x-ray-absorbing lead particles. The specimens were then hit by a 9-mm-diameter steel sphere (ball bearing) fired from a 9-mm-bore gas gun at a velocity of 373.5 ∓ 3.0 ms<sup>−1</sup>. A 30-ns-long x-ray pulse exposed one radiograph before impact; another radiograph was exposed a short time after the impact on the specimen. The two-dimensional displacement field was obtained when the x-ray radiographs were digitized by a conventional flatbed scanner, and a digital speckle photography algorithm was used to calculate the displacements. The flash x-ray technique allowed examination of the deformation at the layer inside the material during failure, thus giving interesting data about the material flow field around the impactor.
© 1999 Optical Society of America
Per Synnergren, H. Timothy Goldrein, and William G. Proud, "Application of Digital Speckle Photography to Flash X-ray Studies of Internal Deformation Fields in Impact Experiments," Appl. Opt. 38, 4030-4036 (1999)