As modern blade designs are breaking historical technical barriers to blade loading levels, adding extra damping is needed to improve blade resistance against excitation. For this purpose, various ways of blade coupling are used. One of most commonly used method is to design a special shroud geometry that makes it touch the adjacent shroud through an interface. These contacting surfaces are assembled with a preload providing a normal acting force. Performing FEM analyses is required to study the influence of manufacturing tolerances and assembly procedure on contact conditions.
In recent years, a new coupling design has been developed in Skoda Power. This work describes the analytical approach selected for simulation of bladed disk assembly procedures regarding blade-to-blade and blade-to-disk contact conditions and consequent stress distribution. First, the common method of assembly that is used for similar blades with free-standing design was studied with an unsatisfactory coupling condition results. Consequently, a new assembly method was developed to improve the disadvantages of the common method. Experimental measurements were performed to verify the credibility of computational analyses for both methods and confirmed their results.
The contact conditions were studied both in state after assembly and during operation, and based on the findings, dynamic properties were predicted. A full scale bladed disk was manufactured for experimental tests to investigate dynamic behaviour. Based on the results of the test, it was possible to choose the most convenient FEM model that can be used for blade tuning during blade design procedure. Additionally, vibration damping was evaluated for several mode shapes and as a whole the measurement confirmed benefits of the coupling design.