Technique for the continuous measurement of projectile velocities in plate impact experiments

Abstract

This paper describes a simple yet accurate technique for the continuous measurement of projectile velocities in plate impact experiments (the impact velocity is a critical parameter in the interpretation of such experiments). The technique, known as the laser line velocity sensor (LLVS), uses a laser line generator to generate a laser sheet of uniform intensity that is incident on a photodiode at the focus of a collecting lens. The amount of light reaching the photodiode diminishes as the projectile intersects the laser sheet, and so a simple calibration procedure in conjunction with a high-bandwidth optoelectronic system provides a measure of the projectile velocity. Since the measurement is continuous, both the projectile velocity and acceleration can be obtained. The LLVS is very stable, does not need reconstruction after impact, does not need frequent recalibration, and is insensitive to rigid body motions. An example of the application of the technique is provided.