*4.2. Measuremet*

The transfer functions of the individual blades were obtained by the measurements using subsequent the mathematical procedure according to Equation (3). The resulting transfer function of the first blade is shown in Figure 9. In this case, no additional masses on other blade tips were used. Therefore, this figure is shown here to illustrate the difference from the resulting transfer function in Figure 10 showing the measurement variant when placing additional masses on other blades.

**Figure 9.** Transfer function and natural frequencies from FE model—without additional masses.

**Figure 10.** Transfer function and natural frequencies from FE model—with additional masses.

This method is very effective in suppressing the influence of the slightly different natural frequencies of the unmeasured blades and makes it possible to obtain the natural frequencies of individual blades of a real turbine wheel and to create a mistuned 3D model for further detailed dynamic analyses.

In Figure 10, red lines are visible to symbolise the natural frequencies of the turbocharger turbine blade from the FE simulation. Compliance with the measurement is very good and it is obvious that the method using FE model is well prepared for further utilization with much simpler demands than using expensive 3D scanning laser. Furthermore, applying this method, the user can concentrate on the natural blade dominant frequencies only, without having to deal with other spectrum peaks that belong entirely or predominantly to the turbine bladed disc.
