Steady-State Dynamic Response of Preisach Hysteretic Systems

2005 ◽  
Author(s):  
P. D. Spanos ◽  
A. Kontsos ◽  
P. Cacciola
Keyword(s):  
Steady State ◽  
Dynamic Response ◽  
Numerical Data ◽  
Equation Of Motion ◽  
Equivalent Linearization ◽  
State Dynamic ◽  
Hysteretic Systems ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Steady State Amplitude

The goal of this paper is to study the steady-state dynamic response of an oscillator with a hysteretic component to harmonic excitations. This is accomplished by using the Preisach formalism in the description of the contribution of the hysteretic part. Two cases are considered. In the first the hysteretic component is modeled using a series of Jenkin’s elements, while in the second the same component is modeled by a zero-memory plus a purely hysteretic term. The steady-state amplitude of the response is determined analytically by using the equivalent linearization technique which involves input-output relationships for the equivalent linear system the stiffness and damping coefficients of which are response-amplitude dependent. The derived results are compared with pertinent numerical data obtained by integrating the nonlinear equation of motion of the oscillator. The analytical and numerical results are found in excellent agreement, and supplement the analytical findings of certain previous studies.

Steady-State Dynamic Response of Preisach Hysteretic Systems

2005 ◽  
Vol 128 (2) ◽  
pp. 244-250 ◽  
Author(s):  
P. D. Spanos ◽  
A. Kontsos ◽  
P. Cacciola
Keyword(s):  
Steady State ◽  
Dynamic Response ◽  
Numerical Data ◽  
Harmonic Excitation ◽  
Equivalent Linearization ◽  
State Dynamic ◽  
Hysteretic Systems ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Steady State Amplitude

The goal of this paper is to study the steady-state dynamic response of an oscillator involving a hysteretic component and exposed to harmonic excitation. This is accomplished by using the Preisach formalism in the description of the contribution of the hysteretic component. Two cases are considered. In the first one, the hysteretic component is modeled using a series of “Jenkin’s elements,” while in the second one the same component is modeled by a zero-memory plus a purely hysteretic term. The steady-state amplitude of the response is determined analytically by using the equivalent linearization technique which involves input-output relationships for the equivalent linear system, the stiffness and damping coefficients of which are response-amplitude dependent. The derived results are compared with pertinent numerical data obtained by integrating the nonlinear equation of motion of the oscillator. The analytical and the numerical results are found in excellent agreement and supplement the findings of certain previous studies.

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part II: Dynamic Response

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Dynamic Response ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Static Response ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

Part II presents a novel approach for predicting dynamic coefficients for a tilting pad journal bearing (TPJB) using computational fluid dynamics (CFD) and finite element method (FEM), including fully coupled elastic deflection, heat transfer, and fluid dynamics. Part I presented a similarly novel, high fidelity approach for TPJB static response prediction which is a prerequisite for the dynamic characteristic determination. The static response establishes the equilibrium operating point values for eccentricity, attitude angle, deflections, temperatures, pressures, etc. The stiffness and damping coefficients are obtained by perturbing the pad and journal motions about this operating point to determine changes in forces and moments. The stiffness and damping coefficients are presented in “synchronously reduced form” as required by American Petroleum Institute (API) vibration standards. Similar to Part I, an advanced three-dimensional thermal—Reynolds equation code validates the CFD code for the special case when flow Between Pad (BP) regions is ignored, and the CFD and Reynolds pad boundary conditions are made identical. The results show excellent agreement for this validation case. Similar to the static response case, the dynamic characteristics from the Reynolds model show large discrepancies compared with the CFD results, depending on the Reynolds mixing coefficient (MC). The discrepancies are a concern given the key role that stiffness and damping coefficients serve instability and response predictions in rotordynamics software. The uncertainty of the MC and its significant influence on static and dynamic response predictions emphasizes a need to utilize the CFD approach for TPJB simulation in critical machines.

Steady-State and Dynamic Behaviour of Multi-Recess Hybrid Oil Journal Bearings

1979 ◽  
Vol 21 (5) ◽  
pp. 345-351 ◽  
Author(s):  
M. K. Ghosh ◽  
B. C. Majumdar ◽  
J. S. Rao
Keyword(s):  
Perturbation Theory ◽  
Steady State ◽  
Theoretical Analysis ◽  
Dynamic Behaviour ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Time Dependent ◽  
Damping Coefficients ◽  
Stiffness And Damping

A theoretical analysis of the steady-state and dynamic characteristics of multi-recess hybrid oil journal bearings is presented. A perturbation theory for small vibrations is used to solve an incompressible, finite journal bearing with a time-dependent term. Load capacity, attitude angle, friction parameter, stiffness and damping coefficients are evaluated for a capillary-compensated bearing.

Linear Stability Analysis and Dynamic Response of Shimmy Dampers for Main Landing Gears

2016 ◽  
Vol 83 (8) ◽  
Author(s):  
Carlos Arreaza ◽  
Kamran Behdinan ◽  
Jean W. Zu
Keyword(s):  
Dynamic Response ◽  
Theory Model ◽  
Multibody Model ◽  
Damping Coefficients ◽  
Aerospace Systems ◽  
Numerical Tools ◽  
Simulation Results ◽  
Landing Gears ◽  
Stiffness And Damping ◽  
Dynamics Stability

This paper presents the analysis and study of common shimmy dampers used today for main landing gears with the use of analytical and numerical tools. The shimmy phenomenon is studied by using the tire stretched string theory model and by developing linear approximations of the dynamics of a single tire landing gear. The dynamics of commonly used shimmy dampers are then incorporated into the model. The objectives of this paper are to study already developed shimmy damper designs and to develop tools to design a new innovative and better shimmy damper for main landing gears, those which have nonsteerable wheels. Two shimmy damper designs are studied in this paper, one developed by Boeing and another by UTC Aerospace Systems (UTAS). A linear approximation of the dynamics of these dampers is obtained, omitting the freeplay, saturation, and nonlinear dynamics. Stability plots are then created by changing the system's parameters, such as the velocity, caster length, and the shimmy damper stiffness and damping coefficients. These plots show the comparison of using a UTC two-arm design against the Boeing damper, for which the former spans larger zones of stability but requires higher damping coefficients due to the UTC damper's geometry which is very impractical. In addition, a multibody model is developed in MSC adams (from MSC Software Corporation) to study the dynamic response of these systems and to create a modeling tool that can be used to design a new and improved shimmy damper for main landing gears. The simulation results from the model show the disadvantages of using the UTC two-arm damper, which include an asymmetrical vibration response. Further recommendations are given to design an improved shimmy damper.

Helical-Grooved Journal Bearing Operated in Turbulent Regime

1970 ◽  
Vol 92 (2) ◽  
pp. 346-357 ◽  
Author(s):  
C. Y. Chow ◽  
J. H. Vohr
Keyword(s):  
Steady State ◽  
Journal Bearing ◽  
Critical Mass ◽  
Reynolds Numbers ◽  
Turbulent Regime ◽  
Damping Coefficients ◽  
Radial Stiffness ◽  
Performance Curves ◽  
Stiffness And Damping ◽  
Laminar And Turbulent Regimes

An analysis for helical bearings operated in turbulent regime, with negligible inertia in an incompressible fluid film, was performed [10, 11]. The analysis is based on the linearised lubrication theory developed by Ng and Pan [4]. The outlines for this analysis and, in particular, the bearing performance data for various helical groovings are given in this paper. The data presented include the bearing performance at the steady state, the stiffness and damping coefficients, and the critical mass of journal in both laminar and turbulent regimes. To facilitate designs, these data are computed for optimal geometries of helical grooved bearings to provide maximum radial stiffness at various Reynolds numbers. In addition, the effect of external pressurized supply of lubricant are shown in the performance curves.

scholarly journals Stability of a Rigid Rotor Supported on Flexible Oil Journal Bearings

1988 ◽  
Vol 110 (1) ◽  
pp. 181-187 ◽  
Author(s):  
B. C. Majumdar ◽  
D. E. Brewe ◽  
M. M. Khonsari
Keyword(s):  
Steady State ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Elasticity Parameter ◽  
Damping Coefficients ◽  
Pressure Dependent Viscosity ◽  
The Stability ◽  
Dependent Viscosity ◽  
Stiffness And Damping

This investigation deals with the stability characteristics of oil journal bearings, including the effect of elastic distortions in the bearing liner. Graphical results are presented for (1) steady-state load, (2) stiffness and damping coefficients, and (3) the stability. These results are given for various slenderness ratios, eccentricity ratios, and elasticity parameters. The lubricant is first assumed to be isoviscous. The analysis is then extended to the case of a pressure-dependent viscosity. It has been found that stability decreases with increase of the elasticity parameter of the bearing liner for heavily loaded bearings.

Axial, Relative Motion of a Circular Step Bearing

1959 ◽  
Vol 81 (2) ◽  
pp. 109-115 ◽  
Author(s):  
L. Licht
Keyword(s):  
Thrust Bearing ◽  
Equation Of Motion ◽  
Analog Computer ◽  
Small Displacement ◽  
Axial Motion ◽  
Computer Solution ◽  
Damping Coefficients ◽  
Displacement Equation ◽  
Stiffness And Damping ◽  
Local Stiffness

Equations relating the flow of the lubricant and the axial motion of an externally pressurized thrust bearing are developed. The bearing is shown to be stable when the fluid is incompressible. Expressions for local stiffness and damping coefficients, useful in the evaluation of the dynamic response of the bearing, are given. An analog computer solution of the equation of motion is compared with the results of the corresponding, small displacement equation.

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