Abstract Friction damping devices such as tip shrouds are commonly used in Low Pressure Turbine (LPT) blades to reduce large vibration amplitudes. From an engineering perspective, experimental validation of numerically predicted blade dynamics is essential to demonstrate the damping performance of shrouds in LPTs. This study compares experimental and numerical results to investigate the dynamic behavior of shrouded turbine blades in detail. A brief overview of the experimental test rig, previously developed to simultaneously measure nonlinear forced responses and contact forces, is first presented. The experimental results show the effects of different normal preloads and excitation force levels on the measured parameters. To compute the nonlinear forced response and shroud contact forces, the test rig is modeled using commercial finite element software, with system matrices extracted in reduced order form. The Harmonic Balance Method is applied through a dedicated nonlinear solver incorporating a 3D contact model. Comparisons of experimental and numerical results are presented, particularly in cases where low normal preload-to-excitation force ratios result in alternating stick-slip transitions. The results indicate that the experimental dynamic behavior of the shrouded blade is computationally captured in most cases. However, discrepancies arise in some scenarios where non-unique contact forces introduce response variability. For such cases, numerical response boundaries are estimated using an optimization algorithm. Overall, the outcomes of this study present a detailed validation procedure for simulation tools and provide insights into numerical challenges such as convergence.
Ahmed et al. (Mon,) studied this question.