smart technologies for safety engineering

194 Smart Technologies for Safety Engineering
Figure 5.37 Two-dimensional model of collision: initial state and resulting deformation
in the cavities will be fixed and equal to 100 % in the front cavity, 50 % in adjacent cavities
and 10 % in others. In all considered examples, the initial inflation of the chambers will be
executed during 200 ms and the ship will impact the structure directly afterwards.
5.5.2.1 Minimization of Ship Acceleration
The first objective of the pressure adjustment is to decrease ship accelerations. In the case
of an inflatable torus, the equivalence of acceleration and pressure minimization problems
is disrupted due to the influence of an initial change in the chamber volume, forces arising
during rubber deformation and a change in the contact area between the ship and the inflatable
structure during collision. In the simplest semi-active case, only the initial pressure is
adjusted so after the inflation phase, the mass of the gas in the chambers remains constant. A
minimal ship acceleration of 58.84 m/s2 (cf. Figure 5.38, dark line) is obtained for the highest
admissible initial pressure (3 atm), which is the consequence of the significant expansion of
the front chamber after inflation.
A more sophisticated type of semi-active system includes the exhaust valves, the opening of
which can be adjusted for a particular impact scheme, but it remains constant during the impact
Pressure in the front cavity [MPa]
0.80 60.00
0.60
0.40
0.20
Ship acceleration [m/s2]
50.00
40.00
30.00
20.00
10.00
0.00
0.00
0.00 0.20 0.40 0.60 0.80
0.00 0.20 0.40 0.60 0.80
Time [s] Time [s]
(a) (b)
Figure 5.38 Semi-active adaptation without pressure release (dark line) and with pressure release
(bright line): (a) pressure in the front chamber, (b) corresponding ship acceleration