Experimental Analysis of Elastic-Plastic Free Vibrations of Beam Models Caused by Impact

Abstract

An experimental analysis was performed to model transverse impact of free-free and free supported square duralumin beams loaded at different locations along their length. The applied impact load was obtained from tests carried out on a single Hopkinson pressure bar equipped with a high speed camera. The experimental set-up consisted of an Hopkinson measuring bar that is brought in contact with the beam. In this one-point impact experiment, a cylindrical striker, fired by the air gun, impacts the Hopkinson bar and generates stress waves that travel along the bar and impinge upon the aluminum beam. The stress waves are recorded by strain gages mounted on the Hopkinson measuring bar. These are used to calculate the applied load on the beam. Dynamical displacements of the impact zone of tested beam were recorded by the high speed camera. The dynamic experiments show that the plastic deformation, adjacent to the impact location, is due to combined dominant bending and stretching modes. Most of the plastic deformation is confined to the impact zone of tested beams. The plastic strain magnitude and distribution near the impact zone is similar for all tested impact locations, but higher for the more symmetrical impacts. The conversion of impact energy into kinetic, elastic strain energy and plastic dissipation work is characterized for various impact locations along the specimen of beam.