The Numerical and Experimental Characteristics of Multimode Dry-Friction Whip and Whirl

Abstract

The nature of dry-friction whip and whirl is investigated through experimental and numerical methods. A test rig was designed and constructed to demonstrate and record the character of multimode dry-friction whip and whirl. These tests examined steady-state whip and whirl characteristics for a variety of rub materials and clearances. A simulation model was constructed using tapered Timoshenko beam finite elements to form multiple-degree-of-freedom rotor and stator models. These models were reduced by component mode synthesis to discard high-frequency modes while retaining physical coordinates at the rub location to model rotor-stator interaction using a nonlinear contact model with Coulomb friction. Simulations were performed for specific test cases, and compared against experimental data; these comparisons are favorable. Experimental data analysis showed multiple whirl and whip regions, despite claims of previous investigators that these regions are predicted analytically but not produced in simulations or experiments. Spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions.

Development and Experimental Validation of Auxiliary Rolling Bearing Models for Active Magnetic Bearings (AMBs) Applications

“…Wilkes et al [7] investigated, through experimental and numerical methods, the nature of multimode dry friction whip and whirl for a variety of rub materials and clearances; their experimental results showed multiple whirl and whip regions.…”

Unilateral contact induced blade/casing vibratory interactions in impellers: Analysis for rigid casings

“…Structural unilateral and frictional contact interactions correspond to one type of possible nonlinear dynamical couplingusually referred to as rotor/stator interactions [8]-within turbomachines. They are in a vast majority generated due to minimal operating clearances between rotating and stationary components and shall be split into two main categories: (1) contact occurs at the journal/bearing interface [9,10] in supporting devices, or (2) between blade tips and surrounding casings [11,12]. The present works aims at modeling impeller/casing interactions that may be observed in aeronautical engines and intends to provide a comprehensive analysis of the possible nonlinear mechanisms induced by blade-tip/casing contact interactions for elaborate geometries such as the one depicted in Figure 1.…”

Two-Dimensional Modeling of Shaft Precessional Motions Induced by Blade/Casing Unilateral Contact in Aircraft Engines

“…Good agreement was obtained between the prediction of precession frequencies and experimental values, and potentially destructive dryfriction whip was witnessed in the test rig. Similarly, a multiple-DoF rotor and stator model using Timoshenko beams was built [10], combined with a component mode synthesis method to discard high frequency modes and implementing a nonlinear contact model with Coulomb friction. Good concordance between experimental data and simulation results was achieved, showing multiple whirl and whip regions.…”