A laboratory simulation of low velocity projectile impact on thin plates
Master Thesis
1999
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University of Cape Town
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Abstract
This project concerns the development of a test apparatus that will both accurately simulate a projectile impact event and provide an accurate means of analysing a material response to projectile impact events. A low velocity apparatus, based on the conventional instrumented drop tower apparatus, was designed and constructed. The apparatus is instrumented in order that the penetration resistance force history and impact velocity can be measured by a data acquisition system for further analysis. A software package, developed specifically for the apparatus, manipulates the acquired load-time trace and generates the necessary force and energy-deflection curves. A series of tests were performed to verify the validity and reproducibility of the results. The plastic deformation that occurs during a rebound impact event is compared to the plastic deformation as measured by the impact testing apparatus. These tests show that the apparatus can accurately measure the plastic deformation that occurs during a rebound impact event. A series of reproducibility tests proved that the apparatus is capable of generating almost identical force-deflection curves for tests conducted with given impact parameters. A series of tests were performed to analyse the impact response of the ductile material, aluminium alloy grade 1200. The aim of these tests is to illustrate the performance capabilities of the test apparatus and to analyse the influence of individual system variables, such as impact velocity, kinetic energy and projectile shape, on the impact response of a ductile material. The impact apparatus generates force-deflection curves that are in agreement with the observed impact response. The essential features that define a material response to impact loading such as stiffness, yield point and point of maximum load were identified on the force-deflection curves. A secondary aspect of this study was to investigate the impact behaviour of aluminium and glass laminate plates. The impact response of the laminate plates was compared to that of singular glass and aluminium plates. The apparatus is capable of generating force-deflection curves for the short duration, impact response of a singular 6mm thick glass plate and well as the highly sensitive laminate plate tests.
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Includes bibliographical references.
Reference:
Cartmel, P. 1999. A laboratory simulation of low velocity projectile impact on thin plates. University of Cape Town.