smart technologies for safety engineering

Adaptive Impact Absorption 211
Deceleration [g]
10
5
0
Experiment
Simulation
0 40 80 120
Time [ms]
Figure 5.57 Comparison of FE and test results: impacting mass deceleration versus time for the active
mode [43]
deflagration chamber (Figure 5.55). Rapidly growing pressure acting on the pyroconnection’s
piston broke the sheared pin made of soldering alloy, causing unlocking of the absorber’s
members. A battery of capacitors, pre-charged to 311 V, on the triggering signal was rapidly
discharged through the initiator wire. The initiator wire vaporized in a time shorter than 250 μs
after receiving the signal coming from the real-time control system. The initiation process was
controlled by the electrical control circuit, which was optically separated from the controller.
The silicon-controlled rectifiers (SCR) were used for fast response switching of the initiating
current. The acceleration sensor measured the deceleration of the impacting mass.
During the high-energy mode test, all pyroconnections remained locked through the crushing
time (Figure 5.56, left). The test of the low-energy mode (Figure 5.56, right) was conducted
with the same initial conditions as the passive one. A photocell activated by the dropping head of
the hammer sent the signal to the control system. When the impulse was received by the control
system, the initiation circuit was triggered with a pre-set time offset, causing deflagration of
the powder, opening of the connections and disconnection of the additional members. The
average delay time between the initiation and explosion, due to statistical dispersion, was
around 3–4 ms. A comparison of FE and test results is given in Figure 5.57.
The demonstrated example shows another possible direction of the AIA system development,
which may be applied in wide range of applications.
References
1. J. Holnicki-Szulc, P. Paw̷lowski and M. Wik̷lo, High-performance impact absorbing materials – the
concept, design tools and applications, Smart Materials and Structures, 12(3), 2003, 461–467.
2. J. Holnicki-Szulc and C. A. Mota Soares, Advances in Smart Technologies in Structural Engineering,
Vol. 1, Computational Methods in Applied Sciences Series, Springer, New York, 2004.
3. N. Jones and T. Wierzbicki, Structural Crashworthiness. Butterworths, London, 1983.
4. N. Jones and T. Wierzbicki, Structural Failure, John Wiley & Sons, Inc., New York, 1989.
5. N. Jones and T. Wierzbicki, Structural Crashworthiness and Failure, Elsevier Applied Science,
1993.
6. C. M. Harris and A. G. Piersol, Harris’ Shock and Vibration Handbook, McGraw-Hill, 2002.
7. R. Grybos, Teoria uderzenia w dyskretnych uk̷ladach mechanicznych (in Polish), PWN, 1969.