Parameters Optimization and Energy Absorption Evaluation of the Steel Ball Friction Energy Absorber

Table 4

Filling ratio and porosity of the ball column with different ball diameters.

Ball diameter, d0 (mm)	Filled ball number, n	Compressed column height, H’ (mm)	Filling ratio, ϕ	Porosity, λ	Energy reflectivity, γ
8	269	92.42	0.621	0.379	0.289
7	350	88.33	0.566	0.434	0.267
6	580	90.85	0.575	0.425	0.281
5	1249	94.29	0.690	0.310	0.290
4	2482	94.43	0.701	0.299	0.302