The effect of underplatform dampers on the forced response of bladed disks by a coupled static/dynamic harmonic balance method

Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

“…The impact of the inclusion of this term for the dynamic analysis of blade-damper models is shown in section 5.3. A previous study [18] addressed the importance of the "zero" harmonic term for the dynamic analysis, but the main difference with the present study is that a coupled static/dynamic analysis was used there.…”

“…Difficulties encountered during the validation of the latter models suggested that the required hypotheses were not always realistic [6]. In more advanced models [16][17][18][19][20], these hypotheses were removed and the damper motion is calculated purely as the result of its interaction with the blades by means of the nonlinear contact forces. To reproduce damper motions, advanced 3D friction contact elements were employed; these account for normal load variation with separation effects and 2D tangential in plane motion [21].…”

“…For this reason, a combination of the harmonic balance method (HBM) [18,[23][24][25] which is based on a fundamental harmonic or multi-harmonic approximation of the nonlinear forces, together with model reduction techniques [26][27][28] has emerged as a widely used approach to solve vibration problems.…”

“…Higher fidelity models [16][17][18][19]22] comprise several parameters describing the contact interface but their impact in capturing the physics of the phenomena needs to be fully understood before those models can be used with confidence. The aim of the present work is to improve the fidelity of the current explicit damper modelling approach [22], to better capture the strong nonlinear dynamics often observed in real environments [29].…”

Nonlinear Forced Response of a Stator Vane With Multiple Friction Contacts Using a Coupled Static/Dynamic Approach

“…the amplitudes of oscillation are reduced increasing the fatigue life of the blade arrays. The major sources of friction damping in the bladed disk turbine are attributable to the blade-disc interfaces (blade root joint) [3,4], the contact between adjacent blades connected by interference at the tip (shrouds) or mid-span airfoil (snubber, [5]) and the presence of underplatform dampers [6,7]. Typical joints for vane segments are the so-called interlocking joints [8] located at the inner radius of the sector connecting adjacent sectors.…”