Improvement of Displacement, Stress and Position Tracking

The generation of electrical charges in response to mechanical deformations is a distinctive feature of piezoelectric materials. This property can be exploited to avoid mechanical stresses, to prevent undesired deformations and also to develop position sensitive devices. This project focuses on the development of innovative control methods by means of smart or intelligent materials. The piezoelectric effect is similar to the well-known thermoelastic effect, which everybody faces in the daily routine. Most materials, like e.g. metals, expand when they are exposed to heat or temperature increase, but some also contract, e.g. water between 0C and 4C. Examples of this physical phenomenon are the expansion joints in road bridges to avoid damage from thermal expansion or the shattering of glass when pouring hot water into it. Inadmissibly high stress is prevented by the expansion gaps in the first example, whereas the sudden amount of heat causes excessive high strains in brittle objects such as glass in the latter example. Replacing the thermoelastic effect by the piezoelectric effect as well as the temperature and the heat flow by the corresponding electrical properties, i.e. the voltage and the charge flow, similar phenomena exist for piezoelectric materials. High levels of mechanical stress and deflection reduce the lifespan of construction components, which is true for nearly all types of materials. Smart or intelligent materials, that can actively counteract such effects, have been available for special applications for some years now. The so-called piezoelectric effect is the ability to convert energy between the mechanical and the electric domain. This means that a piezoelectric material reacts if is electrically actuated. If the motion of a construction is to be controlled, then it is also possible to manipulate the motion in a desired manner by influencing the electrical variables. This enables the development of intelligent control algorithms. Alternatively, it is possible to influence the stress distribution of these materials, if they are subject to arbitrary external forces. The aim of the project is to increase the durability and the life-cycle of materials and to derive new displacement tracking possibilities. The key for these smart solutions is based on accurate mathematical models, which yield explicit relations between external load cases and electrical actuation. In this project special focus is laid on rectangular strips or beam-type structures, since these are the main components of many engineering constructions (e.g. vehicle bodies, bridges, truss structures). Possible applications are the atomic force microscopy (AFM) and the development of nano- and micro positioning devices.