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cross section crash boxes

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where, K is a dimensionless constant and its value can be found by simply fitting<br />

Equation 9.3 with the experiment and simulation mean load values. In the calculation of<br />

the analytic mean load values for partially filled <strong>crash</strong> <strong>boxes</strong>, Cavg in Equation 9.2 is<br />

taken as 5.5. The fitting gives the value of K as 11.3 for the <strong>crash</strong> box without montage<br />

plates (Figures 9.1(a) and (b)). The same value of K was found previously for the empty<br />

square <strong>section</strong> Al <strong>boxes</strong> by Hanssen et al.(Hanssen, et al. 1999). However, in the study<br />

of Hanssen et al.(Hanssen, et al. 1999) the square <strong>section</strong> <strong>boxes</strong> were fully filled with<br />

Hydro Al foam without trigger mechanism.<br />

The tested G1 and G2 box geometries without montage plates accommodate<br />

triggers at both ends of foam filled <strong>section</strong>. The mean load values of empty <strong>crash</strong> <strong>boxes</strong><br />

with montage plates are further fitted with Equation 9.3 and the value of K is found<br />

13.06 (Figures 9.1(c) and (d)), the same with the value reported by Abromowicz and<br />

Jones (Abramowicz and Jones 1986). The variation of mean load values of G1, G2,<br />

G1WP and G2WP <strong>crash</strong> <strong>boxes</strong> with filler relative density are shown in Figures 9.2(a),<br />

(b), (c) and (d), respectively. It is also noted in the same graphs, the fitted K values of<br />

11.3 and 13.06 give good correlations with the experimental and simulation results. As<br />

with simulations, the analytic model overestimates the mean load values of 2.5 mm<br />

thick empty and partially filled <strong>crash</strong> <strong>boxes</strong>, depicted in Figures 9.2(a), (b), (c) and (d).<br />

(a) (b)<br />

Figure 9.1. Pm,e vs. thickness graph for a) G1, b) G2, c) G1WP and d) G2WP empty<br />

<strong>crash</strong> <strong>boxes</strong><br />

(cont. on next page)<br />

172

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