Application of digital speckle photography to flash x-ray studies of internal deformation fields in impact experiments

Abstract

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(-1). 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.

Review of experimental techniques for high rate deformation and shock studies

“…(vi) What sort of 2D experiments should be performed to measure the dynamic properties of failed ceramics (or confined sand) which might be more relevant to their ballistic behaviour? Recent developments in X-ray speckle techniques are proving particularly exciting here [258][259][260][261][262][263][264][265][266].…”

“…If X-ray flashes are used, the motion of dynamic systems can be studied effectively, since a typical X-ray flash will have a duration of as little as 30 ns. Thus, the internal deformations of various dynamic events can be studied [259][260][261][262][263][264][265][266]318]. Illustrated below in Fig.…”

Simulation of precise setforward and setback experiments

“…These experiments are carried out using DSR, which is a technique based on digital speckle photography (DSP) combined with flash X-rays and has been tested on polyester, cement [1], sand [2] and glass [3].…”

The use of digital speckle radiography to study the ballistic deformation of a polymer bonded sugar (an explosive simulant)

“…Digital speckle radiography (DSR) is an X-ray technique [1][2][3][4] that makes use of digital speckle algorithms originally developed for digital speckle photography (DSP) [5][6][7] to measure displacement fields within optically opaque deforming specimens [8] . Measurements are made on a plane within a specimen which is seeded with high-density, X-ray opaque particles.…”

“…DSR can also be used to study events where debris clouds obscure the specimen (as often occurs in ballistic impact) or if impact results in light emission. DSR has already been successfully applied in our laboratory to the study the dynamic deformation of polymers and cements [6] , sand [9,10] , failure fronts in glass [11] , ballistics [2,12] and explosives [3,13] .…”