Low velocity impact of empty and foam filled circumferentially grooved thick-walled circular tubes

In this work, the energy absorption and collapse mode of circumferentially grooved thick-walled tubes are scrutinized analytically and experimentally under dynamic loading condition. Circumferential grooves are machined around thick-walled tubes and thin-walled portions are acquired within the groove spaces. Low velocity impact tests of the specimens are conducted using the drop hammer rig. An analytical formulation based on the energy dissipation through the plastic hinges is presented and the effect of strain rate is incorporated into the equations by implementing the Cowper-Symonds constitutive equation. In the case of foam filled tubes, the interaction at the interface of foam and tube is taken into account. Comparison of the analytical results with experimental ones shows reasonable accuracy for the analytical model. According to the experiments, circumferentially grooved tubes show favorable energy absorption behaviour and concertina mode of deformation is dominant under dynamic loading condition. Foam filled tubes show an approximately 26% increase in the energy absorption compared to empty tubes which is much lower than in the case of quasi-static loading condition. This shows that foam filling in dynamic loading, though effective from the energy absorption perspective, is not as effective as in the case of quasi-static loading.