cross section crash boxes
cross section crash boxes
cross section crash boxes
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CHAPTER 10<br />
CONCLUSIONS<br />
The present thesis focused on the optimization of the crushing behavior of<br />
partially foam filled commercial 1050H14 Al <strong>crash</strong> <strong>boxes</strong> in 2, 2.5 and 3 mm wall<br />
thickness. The <strong>boxes</strong> were partially filled, 50% of the total length of the box, with<br />
commercially available closed-cell Al foam (Alulight AlSi10) with two relative<br />
densities, 0.11 and 0.15. In the first part the thesis, empty and foam filled <strong>boxes</strong> with<br />
various configurations, with and without trigger and with and without corrugations were<br />
crushed at a quasi-static strain rate in order to determine the box crushing behavior and<br />
to provide experimental data for the subsequent modeling and optimization studies. Few<br />
filled and empty <strong>boxes</strong> were also compression tested at a relatively high velocity (5.5<br />
mm/s) using a drop-weight impact tester. In the second part of the thesis, the quasi-<br />
static crushing of empty and filled <strong>boxes</strong> was simulated using LS-DYNA explicit finite<br />
element program. In the simulations, the box material was modeled with plastic-<br />
kinematic material card (Mat 3) and the foam filler with the Honeycomb model<br />
(Mat26). To simulate quasi-static crushing, the material mass density was scaled down<br />
by a factor of 1000 and the deformation speed was increased to 2 m/s. The final part of<br />
the thesis focused on the optimization of partially foam filled 1050H14 Al <strong>crash</strong> box<br />
crushing using the response surface methodology to maximize the specific energy<br />
absorption. A full factorial design was used to create the sample mesh. Dynamic test<br />
simulations were also run in accord with the design points of the sampling mesh. In the<br />
optimization, the wall thickness and foam filler relative density were selected as<br />
independent variables, while a mean crushing load of less than 55 kN, a box wall<br />
thickness between 1 and 3 mm and a foam filler density ranging between 0 and 0.2 were<br />
considered as constraints. The used optimization methodology was also applied to the<br />
<strong>boxes</strong> made of a stronger Al alloy, 6061T4 Al, and filled with a higher strength Al<br />
foam, Hydro Al closed cell foam, in order to clarify the effect of box material and foam<br />
filler strength on the crush behavior of the filled <strong>boxes</strong>. Finally, the benefits of partially<br />
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