smart technologies for safety engineering

5
Adaptive Impact Absorption
Piotr K. Pawl̷owski, Grzegorz Mikul̷owski, Cezary Graczykowski,
Marian Ostrowski, L̷ ukasz Jankowski and Jan Holnicki-Szulc
5.1 Introduction
The objective of this chapter is to present the concept of adaptive impact absorption (AIA) and
some examples of its engineering applications. Assuming that the impact load can be identified
(cf. real-time dynamic load identification discussed in Chapter 4, Section 4.1), the safety
engineering based approach to structural design requires equipment of the structure with special
devices allowing active control (in real time) of mechanical properties (e.g. local stiffness) in
order to improve the dynamic response scenario (e.g. reduction of force or acceleration peaks).
As a consequence, the desired AIA process is dissipative, with an optimal amount of impact
energy absorption, while the applied control devices (actuators with small external energy
consumption) modify only the local structural properties, without feeding the system with
additional mechanical energy.
In general, the AIA system should be designed for random impact multiloads, which creates
new research challenges due to optimal forming of structural geometry and the location of
controllable devices. These problems will be discussed in Chapter 6. In this chapter it is
assumed that the structural geometry has already been determined.
Another challenge is to invent innovative technologies applicable to the controllable devices
mentioned above. One option discussed in this chapter deals with the concept of structural fuses
with an elastoplastic type of overall performance and a controllable yield stress level, where
the active device (controllable joints) itself can be based on various types of actuators, e.g.
electromagnetic, piezoelectric, magnetostrictive or magneto-SMA. Another important option
discussed below is based on the idea of so-called adaptive inflatable structures (AIS) with a
controllable (in real-time) release of pressure. Shock absorbers based on MRFs or piezo-valves
can be successfully used for AIA in repetitive exploitive impacts, which will be discussed in
the case of adaptive landing gears. Finally, micro pyro-technique systems (MPS) can be used
for detaching (in real time) selected structural joints in order to improve the structural response
in emergency situations (e.g. in a crash of vehicles).
Smart Technologies for Safety Engineering Edited by J. Holnicki-Szulc
© 2008 John Wiley & Sons, Ltd. ISBN: 978-0-470-05846-6