On the Effect of Hysteresis in Shock Isolators for Aeronautical Applications

An overview of the use of shock isolators based on dry friction is briefly presented, and the possibilities for the development of a more efficient shock isolation system are discussed. Cable isolators, also known as wire rope isolators, are studied and their characteristics are discussed. Such isolators present nonlinear stiffness behaviour in different directions, i.e. tension-compression, roll and shear, as well as dry friction damping. These isolators show hysteresis when subjected to cyclic loading and are known for being excellent shock isolators. However, little is known about the actual dynamic behaviour under shock loading. The Bouc-Wen model of hysteresis is widely used for representing the dynamic behaviour of nonlinear systems and structures under cyclic loading, as it can reproduce a variety of softening and hardening hysteresis loops by proper selection of its parameters. Recently, the interest towards the use of this model has increased, particularly for the modelling of dry friction isolators, such as wire rope springs. This chapter presents a theoretical analysis of the shock response of isolators based on the Bouc-Wen model, considering different scenarios for hardening and softening parameters. Different parameters such as absolute and relative response are studied, and the advantages and issues are discussed. It is concluded that the combination of nonlinear stiffness and damping could lead to improved vibration and shock isolation.