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Proceedings Paper

Metrology and detonics: analysis of necking
Author(s): G. Besnard; B. Etchessahar; J.-M. Lagrange; C. Voltz; F. Hild; S. Roux
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Paper Abstract

The purpose of the experiment discussed in the present paper is to study the deformation of a structure (here a copper cylinder) induced by explosives. During its expansion, the (initially 3-mm thick) cylinder keeps on thinning until fracture appears. Some tens of microseconds before failure, strain localization occurs, which induces mechanical necking. In order to characterize the time for the onset of localization and the necking development, two diagnostic techniques are designed to provide images: one based on X ray observations (for total thickness variations) and a second consisting in 25 stereoscopic acquisitions at about 400,000 frames per second. The latter enables us to estimate the three dimensional shape changes of the cylinder with time. The 3D reconstructions from the single X radiograph and stereoscopic films are described. Both techniques require calibration as a first stage. For the X view, a self calibration is performed in order to convert X measurements (a radiographic stack with 12 detection levels) to total dose in rad using a flashlight on a steel mock-up with calibrated defects. For stereovision, a controlled calibration object is used. The second stage is the reconstruction. For X radiographs, the results of a 2D hydrodynamic computation of the expansion at radiographic time coupled with an X photon transport code provide us an estimate of the scatter field and allow us to perform attenuation evaluations of copper alone, and to estimate its thickness. In stereovision, the reconstruction is achieved by an image correlation software which exploits the random patterns marking on the object outer surface.

Paper Details

Date Published: 10 February 2009
PDF: 12 pages
Proc. SPIE 7126, 28th International Congress on High-Speed Imaging and Photonics, 71261N (10 February 2009); doi: 10.1117/12.821892
Show Author Affiliations
G. Besnard, CEA, DAM, DIF (France)
Ecole Normale Supérieure de Cachan (France)
B. Etchessahar, CEA, DAM, DIF (France)
J.-M. Lagrange, CEA, DAM, DIF (France)
C. Voltz, CEA, DAM, DIF (France)
F. Hild, Ecole Normale Supérieure de Cachan (France)
S. Roux, Ecole Normale Supérieure de Cachan (France)

Published in SPIE Proceedings Vol. 7126:
28th International Congress on High-Speed Imaging and Photonics
Harald Kleine; Martha Patricia Butron Guillen, Editor(s)

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