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great effect on the crushing behavior of tube. Lower values of taper angle were shown<br />

to improve SEA and mean load/maximum load values.<br />

5.5. Optimization of 1050H14 Al Crush Box – Alulight Al Foam Filler<br />

Binary System<br />

The optimization process was to maximize SEA of partially filled 1050H14 Al<br />

crush box (70.2X67.6X125.2 mm). The fixing parts of the box were also included in the<br />

optimization study in order to represent the real <strong>crash</strong> behavior of the box. SEA and<br />

mean load values were defined by two independent variables: box wall thickness and<br />

foam filler relative density. A quadratic (4 th order) polynomial objective function was<br />

used to create the response surface of filled <strong>crash</strong> box. Full factorial design, r s , was used<br />

to generate sampling points of the response surface. The created mesh of sampling<br />

points had r points spaced intervals in each variable direction. To create an<br />

approximation of order of r, at least (r+1) s factorial designs were required. In the<br />

optimization study r and s were taken as 4 and 2, respectively. The optimization<br />

problem is defined as,<br />

Maximize : SEA (t, * )<br />

The constraints were:<br />

Mean Load (t, * ) < 55 kN<br />

1 < t < 3.0 mm<br />

0 < * < 0.2<br />

98

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