Interférométrie holographique par double exposition, appliquée â l'étude du début de la déformation d'un-matériau dur soumis à l'impact d'un projectile

摘要

An arrangement based on the use of holographic interferometry by double exposure was designed and built. This arrangement was used together with a ruby laser serving as a coherent light source in order to visualize and measure the dynamic deformations of a ceramic plate subjected to the impact of projectiles. Thus the deformations occurring on the rear side of the plate can be recorded at several instants prior to the beginning of the fracture. Two projectile velocities are considered, that is, a low velocity range (100 to 300 m/s) and high velocities (800 m/s). For high-velocity investigations, a system including two ruby lasers was developed which generates two pulses within a very short and adjustable period of time (0.1 to several microsec). The pulse duration of the ruby laser was then reduced from 20 to 5 ns. An investigation of certain parameters governing the phenomenon makes it possible to explain the deformation and to obtain information on the influence of ceramics used as a first layer in certain composite armors.