Symmetric friction dampers in beam-to-column joints for low-damage steel MRFs

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

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Friction Damper Optimisation: Simulation of Rainbow Tests

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award; General ◽

10.1115/99-gt-336 ◽

1999 ◽

Cited By ~ 1

Author(s):

Kenan Y. Sanliturk ◽

David J. Ewins ◽

Robert Elliott ◽

Jeff S. Green

Keyword(s):

Harmonic Balance Method ◽

Lumped Parameter Model ◽

Friction Damper ◽

Blade Vibration ◽

Friction Dampers ◽

Lumped Parameter ◽

Engine Order ◽

Resonance Response ◽

Theoretical Predictions ◽

Different Characteristics

Friction dampers have been used to reduce turbine blade vibration levels for a considerable period of time. However, optimal design of these dampers has been quite difficult due both to a lack of adequate theoretical predictions and to difficulties in conducting reliable experiments. One of the difficulties of damper weight optimisation via the experimental route has been the inevitable effects of mistuning. Also, conducting separate experiments for different damper weights involves excessive cost. Therefore, current practice in the turbomachinery industry has been to conduct so-called ‘rainbow tests’ where friction dampers with different weights are placed between blades with a predefined configuration. However, it has been observed that some rainbow test results have been difficult to interpret and have been inconclusive for determining the optimum damper weight for a given bladed-disc assembly. A new method of analysis — a combination of Harmonic Balance Method and structural modification approaches — is presented in this paper for the analysis of structures with friction interfaces and the method is applied to search for qualitative answers about the so-called ‘rainbow tests’ in turbomachinery applications. A simple lumped-parameter model of a bladed-disc model was used and different damper weights were modelled using friction elements with different characteristics. Resonance response levels were obtained for bladed discs with various numbers of blades under various engine-order excitations. It was found that rainbow tests, where friction dampers with different weights are used on the same bladed-disc assembly, can be used to find the optimum damper weight if the mode of vibration concerned has weak blade-to-blade coupling (the case where the disc is almost rigid and blades vibrate almost independently from each other). Otherwise, it is very difficult to draw any reliable conclusion from such expensive experiments.

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Optimization of location and forces of friction dampers

REM - International Engineering Journal ◽

10.1590/0370-44672015700065 ◽

2017 ◽

Vol 70 (3) ◽

pp. 273-279 ◽

Cited By ~ 4

Author(s):

Sergio Pastor Ontiveros-Pérez ◽

Letícia Fleck Fadel Miguel ◽

Leandro Fleck Fadel Miguel

Keyword(s):

Friction Dampers

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The Effect of slit-friction hybrid damper on the Performance of Dual System

The Open Civil Engineering Journal ◽

10.2174/1874149501913010271 ◽

2019 ◽

Vol 13 (1) ◽

pp. 271-280

Author(s):

Azadeh Khoshkroodi ◽

Hossein Parvini Sani

Keyword(s):

Time History ◽

Steel Structures ◽

Repair Cost ◽

Friction Dampers ◽

History Analysis ◽

Different Types ◽

Moment Resisting ◽

Hybrid Damper ◽

Large Earthquakes ◽

Different Levels

Aims: The aim of the present paper is to evaluate the behavior of slit friction hybrid dampers (SFHD) on steel structures. Therefore, the behavior moment resisting steel frames of structures in original stats and structures equipped with hybrid damper with two different types of behavior was analyzed and evaluated. Background: The recent study evaluated the combined effect of shear-friction dampers and slit dampers with measurements of non-uniform strips in seismic protection for different levels of energy. The recent study was carried out a about hybrid dampers, consisting of friction and split dampers in response to small and large earthquakes. Previous results have shown the ability of inactive hybrid systems in improving the reaction of structures to traditional lateral-systems. Kim and Shin showed that structures consisted of hybrid dampers needed less repair cost and time. Methods: Pushover and time history were carried out on original structures and structures equipped with dampers, in 5 and 10 stories structures. Results: Analysis about the probability of collapse showed about 30% and 84%. Conclusion: According to the result, by adding the SFHD, increased stiffness by 17% in retrofitted structures such as drift and displacement of roof decreases by 27% and 20% in push over analysis, respectively. Also, displacement in time history analysis up to 55% reduces in average. Also, the results of the IDA show that adding the SFHD to structures significantly increases by 55% the spectral acceleration capacity in structures.

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