smart technologies for safety engineering

Adaptive Impact Absorption 159
acceleration [m/s2]
acceleration [m/s2]
1400
1200
1000
800
600
400
200
0
–200
active control
semi-active control
passive response
–400
0 0.01 0.02 0.03 0.04 0.05
time [s]
(a)
0.06 0.07 0.08 0.09 0.1
700
600
500
400
300
200
100
0
–100
active control
semi-active control
passive response
–200
0 0.01 0.02 0.03 0.04 0.05
time [s]
(b)
0.06 0.07 0.08 0.09 0.1
5.2.4 Experimental Results
Figure 5.6 Effects of adaptation to impact
The concept of multifolding was verified experimentally on a macroscale model. The layout of
the experimental set-up representing the most basic, six-element structure is depicted in Figure
5.7. The control of the system is possible due to implementation of six magnetorheological
fluid (MRF) dampers (RD-1005-3) manufactured by Lord Corporation.
Magnetorheological fluids belong to a class of smart fluids, which are sensitive to the applied
magnetic field. They are a noncolloidal suspension of magnetically soft iron particles in a base
fluid (e.g. mineral oil, water, etc.). Changes in the strength of magnetic field along a specially
designed gap in the damper result in a fast change of the damping force. The rheology of MRF
dampers is highly nonlinear, resulting in complicated mathematical models, but under special
circumstances (e.g. velocity of the piston’s movement close to constant) the response of the
damper resembles the process of plastic yielding.