Vibration analysis and contact mechanics

As part of our research, we develop innovative measurement methods for investigating vibrations as well as contact interactions. We also implement these methods in prototypical form in our laboratories.

Nonlinearities such as friction and impacts play a central role in this context and are exploited for the damping of turbomachinery blades and for novel concepts for vibration mitigation. Our experimental investigations form the basis for validating the modeling and simulation methods we develop and for identifying parameters and data-driven models.

In addition to engine blades, we also investigate academically motivated and project-specific structures as part of our fundamental research. The dynamics of these structures are significantly influenced by friction damping and/or impacts. Only through these designs can we determine and expand the limits of the methods we have developed.

The methods we have developed for the experimental investigation of vibrations are based on feedback control concepts. Only by controlling the excitation can we make the complex behavior of structures and systems measurable.

Dry friction at joints is responsible for most of the damping in aerospace structures. Even if the components oscillate by several millimeters, the relative movements (sliding distances) in the highly preloaded contacts are in the sub-micrometer range. On this length scale, the topography of the surface plays a decisive role; this is the result of manufacturing and wear. We develop multi-scale methods to make friction damping predictable and validate them in our laboratories.

The Black Metal Tribometer we have developed is unique worldwide and enables the measurement of contacts with unprecedented precision. Force-displacement relationships can be recorded for both normal contact and friction (tangential to the surface) with millinewton and nanometer resolution. In addition to state-of-the-art measurement technology, the key to this precision is the play-free and friction-less guidance of movement thanks to flexures.

We use state-of-the-art measuring instruments for our research. Rapid control prototyping systems enable the fast and precise implementation of our control-based methods. Using various electrodynamic shakers, we can apply force and base excitation in the range from milli-Newtons to over 10 kilo-Newtons.

Several laser vibrometry systems enable contactfree and highly precise measurement of vibrations without influencing the dynamics of the structures under investigation. The multipoint vibrometer, which is unique at the University of Stuttgart, enables simultaneous measurement with 24 sensor heads that can be combined in any way to record spatial movement. Simultaneous measurement is crucial, as the processes we investigate are often non-periodic or transient.

In addition, we are equipped with high-quality sensors for force and acceleration, high-speed cameras as well as a commercial module for linear modal analysis.