Vibration Tests of a Turbine Blade with Internal Damping Manufactured using Additive Technology

Vibration-induced fatigue cracks in turbine blades can lead to engine failure and the forced withdrawal of an aircraft or other turbine-powered machine from service. One means of preventing such cracks is to reduce blade vibration through increased damping. This paper presents a concept for enhancing the vibration damping of a turbine blade by implementing damping mechanisms within the blade structure itself. A prototype blade was manufactured using additive technology, which enabled the creation of internal pockets containing non-melted metallic powder. Lattice bars and pins of various geometries, and consequently different natural frequencies, were built into the pockets as elements fixed to the solid structure, with the function of absorbing vibration energy and transferring it into the surrounding powder volume, where the energy is dissipated. The blade was subjected to experimental testing on an electrodynamic shaker to determine its natural frequencies, mode shapes, and modal damping ratio. A significant increase in the damping ratio was observed relative to a reference Solid blade manufactured using the same technology. While the results demonstrate the effectiveness of the proposed solution, they also reveal pronounced vibration nonlinearity. Accordingly, subsequent work will focus on optimizing the blade damping structures and developing a correlated computational model.