Analysis of Contacts in Friction Damped Turbine Blades Using Dimensionless Numbers

A novel design approach for friction hysteresis measurements is introduced to simplify the characterization of turbine blade contact dynamics. It makes use of dimensionless numbers of a metallic friction contact undergoing small, periodic displacements. Such contacts are used in turbine blades to lower resonance amplitudes by energy dissipation through friction. Nonetheless, this approach is not limited to this field. The dimensionless numbers for characterization of the contact are derived based on a generic contact that is typical for applications in turbine blades. A dimensionless number can be found that characterizes the contact extensively. Several friction hysteresis measurements are conducted on a special test rig in a systematic manner exploring a large parameter space for the derived dimensionless number. Based on the experiments, it is concluded that the normalized measured friction hysteresis loops show similitude despite being measured with parameters spanning a wide range. It results in the possibility to design friction hysteresis tests for friction damped turbine blades in a simple and representative way.