Crush Analysis of Structural Foams Inside a Hollow Steel Tube Under Low-Velocity Uni-axial Compressive Loading

摘要

The impact response of structural foams inserted in a hollow circular steel tube has beeninvestigated. Three different density structural foams (designated A, B and C for proprietary reasons)have been studied for their energy absorption characteristics under low-velocity uni-axialcompressive loading. Out of the three, foam-C had the lowest density; the density of foam-B wasapproximately twice the density of foam-C, while the density of foam-A was about three times thedensity of foam-C. The cylindrical foam samples were impacted at different velocities in a DYNATUPModel 8250 instrumented impact test machine. The load-time data obtained from the impact machinewas filtered using LS DYNA-POST and the filtered stress-strain data of the different density foamswas used to define their material properties for input to finite element modeling. Non-linear finiteelement analysis of the foams, hollow steel tubes of different thickness, and foam-filler (i.e. foaminside steel tube) was performed under displacement controlled quasi-static compressive monotonicloading. A hyper-foam constitutive model was used and large deformation gradients were accountedfor in the variable load stepping incremental algorithm using PATRAN as pre-processor andABAQUS Standard commercial software. Finally, each of the three foams was modeled as fillerinside a 0.8 mm thick hollow steel tube, and crush loads of the three foam fillers compared. The areaunder the load-deflection curve was calculated to obtain the energy absorbed. Results indicate thatthe highest density foam-A was most effective as filler inside the hollow steel tube, with theintermediate density foam-B performing equally well under uni-axial compressive loading. Thelowest density foam-C was found to be ineffective as filler in this application due to the largedifferences in stiffness between this foam and steel tube.