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We would like to congratulate Matthias Hüls

on completing his PhD final presentation on October 15th, 2020

The IDS would like to congratulate Matthias Hüls on successfully passing his PhD oral exam.

Matthias Hüls held his presentation about:

 Der Einfluss geometrischer Auslegungsparameter auf die Dynamik reibungsgedämpfter Turbinenschaufeln

  on thursday, october 15th, 2020 at the Institute of Dynamics and Vibration Research and successfully passed his oral exam.


 The Influence of Geometric Design Parameters onto the Dynamics of Turbine Blades with Friction Joints

The global energy market is pivoting toward decentralized systems and renewable energy sources. At the same time, highly-efficient combined cycle power-plants are gaining increased market share among the remaining fossil power generation. Core of these plants are the gas turbines which are subject to large thermal and mechanical loads during operation. Above all, design is focused on high-cycle fatigue (HCF) which is caused by selfor force-excited vibrations. For the critical case of resonance, the resulting amplitudes can be lowered effectively by introducing friction joints provided by snubber contact faces or damping elements. This work investigates the relations between geometric turbine design parameters and the vibrational behavior under friction damping, as this topic is yet to be addressed thoroughly. For this purpose, an appropriate parametrization is developed and a well-proven mechanical model for non-linear vibration is embedded into a complex simulation toolchain, which is based on geometric input parameters only and allows for efficient calculation of HCF-safety. In addition to that, an analytical strategy based on surrogate modeling and design-of-experiment methods is developed which is used to quantify the main and interaction effects of design parameters onto a variety of outputs. The developed approach is applied to a turbine blade coupled by a snubber contact and a blade with underplatform damper. Consequently, the influence of geometric design parameters onto the static contact force in the friction joint, the resonance amplitude of the first bending mode and the dynamic stresses are systematically outlined. It will be shown that the HCF-safety of a directly coupled turbine blade can be optimized through minimization of the resonance amplitudes. In this case, the system parameters act onto the damped system response mainly based on their influence onto the static normal contact load under untwist. HCF-safety is improved similar to resonance amplitudes. For freestanding blades with underplatform damper coupling, it will be shown that the HCFsafety
can not always be improved through minimizing the resonance amplitudes and in fact could yield a reasonably worse geometry with respect to the vibratory design criteria.