Abstract
This article studies energy dissipation of a friction damper (due to stick–slip vibration) in the context of harmonic excitation. There are numerous applications of such friction dampers in engineering. One particular example is a new kind of under-platform dry friction dampers for aero engines. The model consists of a clamped cross-like beam structure and two masses (friction dampers) in contact with the short beam of the cross. The two masses are allowed to slide along two extra short vertical clamped beams. They can exhibit three distinct dynamic regimes: pure slip, pure stick and a mixture of stick–slip relative to the short horizontal beam. The finite element method is used to obtain the numerical modes of the structure. The friction at the contact interface between the short horizontal beam and the friction dampers is assumed to follow the classical discontinuous Coulomb friction law in which the static coefficient of friction is greater than the kinetic coefficient. Modal superposition method is applied to solve the dynamic response of the structure with numerical modes. One major finding of this investigation is that there is an intermediate range of the normal contact forces (in stick–slip regime) that provides the best energy dissipation performance.
Highlights
Friction causes energy dissipation and as such acts as a stabilisation mechanism
The ‘blade’ tip could manifest periodic motion when the normal contact force is small, but when the normal contact force is high enough, the motion of the ‘blade’ tip could change to quasi-periodic vibration
Because blade tip vibration is the most concerned quantity in aero engine vibration, it is often used as an indicator of vibration level in industry
Summary
Friction causes energy dissipation and as such acts as a stabilisation mechanism. Various friction dampers have been used in buildings against vibration caused by earthquakes and underplatform dampers have been used to reduce vibration magnitudes and high dynamic stresses of turbine blades in aero engines. The latter is the motivation of this article. Friction can excite vibration at certain conditions, for example, earthquake motion, sound generated by a bowed string,[1] door hinges, squeaky chalk on a blackboard, brake squeal[2,3] that happens in the brake system of an automobile and dry friction dampers in aero engines These problems are outside the scope of this article.
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