In many fields of engineering the demand of creating structures with advanced static and dynamic behaviour plays more and more a major role in the design process. On one hand the structures should decrease in weight, whereas on the other hand the stiffness and the insensibility against dynamic stimulation should increase. A classical lightweight design satisfies the requirements of reducing the weight and the material usage, but simultaneously the structural stability is reduced as well. To counteract this disadvantage a further step is to make the structure active and smart. This means that distributed actuators and sensors are placed onto a structure in such a way that upcoming stability problems, like buckling, or vibrations can be controlled and reduced. Elements generating actuation strain can be produced with piezoelectric materials, electrostrictive materials, magnetostrictive materials, shape memory alloys as well as thermally controllable materials. Piezoelectric materials are preferentially used as actuators in shape and vibration control, because the piezoelectric effect was well explored during the last decades. For the implementation in plate- or shell-like structures piezoceramics and piezoelectric foils, respectively, are more suitable than piezoelectric crystals due to the individual formability. A disadvantage of piezoceramics is that they have a number of nonidealities like hysteresis, creep, depoling and a nonlinear strain-field relation for high electric fields. Piezoelectric foils are often used for sensors because of their low mechanical stiffness which affects the mechanical behaviour of the structure less than piezoceramics do. To handle all the sensor signals and calculate the optimal output for the actuators in the sense of control theory, a real-time system is needed. All these components are necessary to build a so-called smart structure.
Our laboratory is equipped with high-power amplifiers, different types of distance sensors, data acquisition systems and a real-time controller to perform several experiments in the field of smart structures. A Michelson interferometer for the characterisation of different types of actuators is also available in the institute.
Further information about the experimental work in the field of active structures at the IAM you can find here: