Numerical identification of the dynamic characteristics of a nonlinear foil bearing structure: effect of the excitation force amplitude and the assembly preload

2021 ◽  
pp. 116663
Author(s):  
Grzegorz Zywica ◽  
Pawel Baginski ◽  
Malgorzata Bogulicz ◽  
Adam Martowicz ◽  
Jakub Roemer ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Structure Effect ◽  
Force Amplitude ◽  
Foil Bearing ◽  
Excitation Force ◽  
Bearing Structure

Non-Linear Dynamics of Gear Pair With Combined Internal and External Periodic Excitations

2014 ◽  
Author(s):  
Yinggang Li ◽  
Tianning Chen ◽  
Xiaopeng Wang
Keyword(s):  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Damping Ratio ◽  
Primary Resonance ◽  
Harmonic Balance Method ◽  
Time Varying ◽  
Gear Pair ◽  
Force Amplitude ◽  
Nonlinear Dynamic Characteristics ◽  
Excitation Force

In this paper, we theoretically investigate the nonlinear dynamic characteristics of gear pair system under combined internal and external periodic excitations. The dynamic model of a viscously damped gear pair model with periodic time-varying stiffness, backlash, static transmission error and external periodic excitation is established. The incremental harmonic balance method (IHBM) is applied to analyze the frequency response characteristics as well as the effects of the periodic time-varying stiffness, excitation force amplitude and viscous damping ratio on the dynamic characteristics. Results show that, under combined internal and external periodic excitations, the multi-valued properties and jump phenomena occur not only in primary resonance frequency but also in super harmonic frequency, the excitation force amplitude has less influence on the nonlinear dynamic characteristics and the increase of the excitation force amplitude could no longer control the nonlinear vibration of gear system, which are different from the dynamic characteristics under internal periodic excitations.

Design and structural performance measurements of a novel multi-cantilever foil bearing

2014 ◽  
Vol 229 (10) ◽  
pp. 1830-1838 ◽  
Author(s):  
Kai Feng ◽  
Xueyuan Zhao ◽  
Zhiyang Guo
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Foil Bearing ◽  
Load Tests ◽  
Stiffness And Damping ◽  
Motion Amplitude

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

scholarly journals Study on dynamic characteristics of rolling agricultural tire (Identification of lug excitation force)

2016 ◽  
Vol 82 (837) ◽  
pp. 15-00656-15-00656
Author(s):  
Katsuhide FUJITA ◽  
Takashi SAITO ◽  
Mitsugu KANEKO
Keyword(s):  
Dynamic Characteristics ◽  
Excitation Force

The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 3: Rotation in Foil Bearings of Reduced Length, With Starting and Stopping Unaided by External Pressurization

1972 ◽  
Vol 94 (3) ◽  
pp. 211-220 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Experimental Methods ◽  
Wear Characteristics ◽  
Foil Bearings ◽  
Foil Bearing

Experiments and analysis, reported in detail in references [1] through [5], demonstrated that high-speed rotors, supported by foil bearings, were free from whirl-instability and sensitivity to excitation at frequency equal one half the speed of rotation. It was shown also that the foil bearing could accommodate thermal and geometrical distortions, combining this attribute with excellent wipe-wear characteristics and tolerance of particles. The present investigation was directed toward the solution of two important problems: (a) the reduction of foil bearing length without detriment to rotor performance, and (b) the elimination of the foil-lift system and attainment of multiple start-stops without the aid of external pressurization. A description of experimental methods, which lead to the realization of the foregoing objectives, is given.

EXPERIMENTAL INVESTIGATION OF A FOIL BEARING STRUCTURE WITH A POLYMER COATING UNDER DYNAMIC LOADS

Tribologia ◽  
2018 ◽  
Vol 281 (5) ◽  
pp. 5-12 ◽  
Author(s):  
Paweł BAGIŃSKI ◽  
Grzegorz ŻYWICA
Keyword(s):  
Excitation Frequency ◽  
Dynamic Loads ◽  
Test Rig ◽  
Static Tests ◽  
Structural Part ◽  
Foil Bearing ◽  
Wide Range ◽  
Load Tests ◽  
Excitation Force ◽  
Stiffness And Damping

This paper presents the results of research on the structural elements of a prototypical foil bearing in terms of its dynamic loads. In the framework of dynamic tests, several dozens of measurement series were carried out on a test rig specially prepared for this purpose. Dynamic excitations were applied using an electromagnetic exciter that enables changing the amplitude and frequency of the excitation force. Owing to this, it was possible to determine characteristics of the tested system in a wide range of loads and frequencies. A value of 400 Hz was assumed as the upper limit of the excitation frequency. The test rig enabled considering the direction of dynamic loads, which, as it turned out, had a significant impact on the obtained results. The research findings show that both the amplitude and frequency of an excitation force have a major impact on the stiffness and damping of the structural part of the foil bearing. The results of dynamic load tests complement the results of static tests performed earlier.

scholarly journals The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 2: Operation With Heating and Thermal Gradients

1970 ◽  
Vol 92 (4) ◽  
pp. 650-659 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Elevated Temperatures ◽  
Load Capacity ◽  
Temperature Gradients ◽  
Thermal Gradients ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Geometrical Imperfections ◽  
The Stability

A high-speed rotor, supported by gas-lubricated foil bearings, is free from self-excited whirl and displays no loss of load capacity when vibrated at frequency equal half the rotational speed [1]. It is demonstrated here that in addition to tolerance of geometrical imperfections, misalignment, and foreign particles [3, 4], the foil bearing performs well at elevated temperatures and accommodates appreciable temperature gradients. The foil bearing is endowed with superior wipe-wear characteristics, and the flexibility of the foil accounts not only for the stability of the foil bearing but also for its forgiveness with respect to distortion, contamination, and contact.

Experimental Analyses of a First Generation Foil Bearing: Start-Up Torque and Dynamic Coefficients

2010 ◽  
Author(s):  
Laurent Rudloff ◽  
Mihai Arghir ◽  
Olivier Bonneau ◽  
Pierre Matta
Keyword(s):  
Dynamic Characteristics ◽  
Static Load ◽  
Excitation Frequency ◽  
Base Plate ◽  
Test Rig ◽  
Dynamic Coefficients ◽  
Foil Bearing ◽  
Start Up ◽  
Lift Off ◽  
Stiffness And Damping

The paper presents the results of the experimental analysis of static and dynamic characteristics of a generation 1 foil bearing of 38.1 mm diameter and L/D = 1. The test rig is of floating bearing type, the rigid shaft being mounted on ceramic ball bearings and driven up to 40 krpm. Two different casings are used for start-up and for measurement of dynamic coefficients. In its first configuration, the test rig is designed to measure the start-up torque. The foil bearing casing is made of two rings separated by a needle bearing for enabling an almost torque free rotation between the foil bearing and the static load. The basic results are the start up torque and the lift off speed. In its second configuration a different casing is used for measuring the impedances of the foil bearing. Misalignment is a problem that is minimized by using three flexible stingers connecting the foil bearing casing to the base plate of the test rig. The test rig enables the application of a static load and of the dynamic excitation on the journal bearing casing, and can measure displacements, forces and accelerations. Working conditions consisted of static loads comprised between 10 N and 50 N and rotation frequencies ranging from 260 Hz to 590 HZ. Excitation frequencies comprised between 100 Hz are 600 Hz are applied by two orthogonally mounted shakers for each working condition. Stiffness and damping coefficients are identified from the complex impedances and enable the calculation of natural frequencies. The experimental results show that the dynamic characteristics of the tested bearing have a weak dependence on the rotation speed but vary with the excitation frequency.

Experimental Analyses of a First Generation Foil Bearing: Startup Torque and Dynamic Coefficients

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Laurent Rudloff ◽  
Mihai Arghir ◽  
Olivier Bonneau ◽  
Pierre Matta
Keyword(s):  
Dynamic Characteristics ◽  
First Generation ◽  
Static Load ◽  
Excitation Frequency ◽  
Base Plate ◽  
Test Rig ◽  
Dynamic Coefficients ◽  
Foil Bearing ◽  
Lift Off ◽  
Stiffness And Damping

This paper presents the results of the experimental analysis of static and dynamic characteristics of a generation 1 foil bearing of 38.1 mm diameter and L/D=1. The test rig is of floating bearing type, the rigid shaft being mounted on ceramic ball bearings and driven up to 40 krpm. Two different casings are used for startup and for measurement of dynamic coefficients. In its first configuration, the test rig is designed to measure the startup torque. The foil bearing casing is made of two rings separated by a needle bearing to enable an almost torque free rotation between the foil bearing and the static load. The basic results are the startup torque and the lift-off speed. In its second configuration, a different casing is used to measure the impedances of the foil bearing. Misalignment is a problem that is minimized by using three flexible stingers connecting the foil bearing casing to the base plate of the test rig. The test rig enables the application of a static load and of the dynamic excitation on the journal bearing casing and can measure displacements, forces, and accelerations. Working conditions consisted of static loads comprised between 10 N and 50 N and rotation frequencies ranging from 260 Hz to 590 Hz. Excitation frequencies comprised between 100 Hz and 600 Hz are applied by two orthogonally mounted shakers for each working condition. Stiffness and damping coefficients are identified from the complex impedances and enable the calculation of natural frequencies. The experimental results show that the dynamic characteristics of the tested bearing have a weak dependence on the rotation speed but vary with the excitation frequency.

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