The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearing: Part 4 — Fitted Type of Bearings

Tribology ◽  
2006 ◽  
Author(s):  
A. W. Yacout ◽  
A. S. Ismaeel ◽  
S. Z. Kassab
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Major Effect ◽  
Design Parameters ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Spherical Bearing ◽  
Stiffness And Damping ◽  
Fluid Compressibility

Analytical solutions are not available for spherical bearing problems except for very specialized cases. However, this study offers a theoretical analysis, using the first order perturbations, to evaluate the frequency dependent stiffness and damping characteristics of compensated hydrostatic thrust spherical bearing including the surface roughness, the shaft rotation and the recess volume fluid compressibility effects. The dynamic stiffness and damping coefficients are presented for capillary tube and/or office compensated bearing. Results are obtained for various vibration frequencies or squeeze parameters (frequency parameters) and recess volume fluid compressibility parameters in addition to the other usual bearing design parameters. The study shows that both of the surface roughness and the centripetal inertia have slight effect on the stiffness and the damping coefficients while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

On the Dynamics of Elastohydrodynamic Mixed Lubricated Ball Bearings. Part I: Formulation of Stiffness and Damping Coefficients

2005 ◽  
Vol 219 (6) ◽  
pp. 411-421 ◽  
Author(s):  
M Sarangi ◽  
B. C. Majumdar ◽  
A. S. Sekhar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Design Parameters ◽  
Asperity Contact ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Stiffness And Damping

The problems of stiffness and damping characteristics of isothermal elastohydrodynamic mixed lubricated point contact are evaluated numerically considering surface roughness effect including asperity contact load. A set of equations under steady-state and dynamic conditions is derived from the classical Reynolds equation, using linear perturbation method. The elasticity equation and steady-state Reynolds equation are solved simultaneously for finding the steady-state pressure distribution, using finite difference method. Then, the set of perturbed equations is solved for the dynamic pressure distribution in the contact. A Gaussian surface roughness is adopted to model both surface roughness and mixed lubrication. Total load capacity of the contact is calculated from the lubricant film pressure and contact pressure distribution. Results are compared with those of smooth isothermal cases. The stiffness and damping coefficients of the contact are determined using the dynamic pressures. The asperity contact stiffness is calculated separately. Effect of various design parameters on stiffness and damping characteristics of a ball bearing is investigated.

Dynamic Stiffness and Damping Characteristics of Compensated Hydrostatic Thrust Bearings

1982 ◽  
Vol 104 (4) ◽  
pp. 491-496 ◽  
Author(s):  
M. K. Ghosh ◽  
B. C. Majumdar
Keyword(s):  
Load Capacity ◽  
Dynamic Stiffness ◽  
Fluid Inertia ◽  
Thrust Bearings ◽  
Continuity Equations ◽  
Damping Characteristics ◽  
Oil Flow ◽  
Stiffness And Damping ◽  
Compressibility Effects ◽  
Fluid Compressibility

This paper deals with an analysis of the dynamic behavior of compensated hydrostatic circular step thrust bearings taking into account fluid inertia and recess volume fluid compressibility effects. The Reynolds equation for fluid film and the recess flow continuity equations are linearized using perturbation methods. Results in terms of dimensionless load capacity, oil flow rate, stiffness, and damping are presented for capillary and orifice compensated bearings. Results show a marked influence of fluid inertia and recess volume fluid compressibility on the performance of the bearing.

Technical Note: Rolling dynamic stiffness and damping characteristics of small-sized pneumatic tyres

2000 ◽  
Vol 214 (3) ◽  
pp. 243-248 ◽  
Author(s):  
V. H. Saran ◽  
V. K. Goel
Keyword(s):  
Normal Load ◽  
Dynamic Stiffness ◽  
Technical Note ◽  
Inflation Pressure ◽  
Laboratory Technique ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Stiffness And Damping

In this paper, a laboratory technique for determination of rolling dynamic stiffness and damping coefficients of small-sized, bias-ply tyres has been discussed. The effect of normal load, inflation pressure and speed on four different tyres has been reported. The results show similar trends to those reported by other investigators.

Calculation and Measurement of the Stiffness and Damping Coefficients for a Low Impedance Hydrodynamic Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 57-63 ◽  
Author(s):  
M. J. Goodwin ◽  
P. J. Ogrodnik ◽  
M. P. Roach ◽  
Y. Fang
Keyword(s):  
Experimental Data ◽  
Dynamic Stiffness ◽  
Perturbation Technique ◽  
The Novel ◽  
Oil Film ◽  
Hydrodynamic Bearing ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Novel Design

This paper describes a combined theoretical and experimental investigation of the eight oil film stiffness and damping coefficients for a novel low impedance hydrodynamic bearing. The novel design incorporates a recess in the bearing surface which is connected to a standard commercial gas bag accumulator; this arrangement reduces the oil film dynamic stiffness and leads to improved machine response and stability. A finite difference method was used to solve Reynolds equation and yield the pressure distribution in the bearing oil film. Integration of the pressure profile then enabled the fluid film forces to be evaluated. A perturbation technique was used to determine the dynamic pressure components, and hence to determine the eight oil film stiffness and damping coefficients. Experimental data was obtained from a laboratory test rig in which a test bearing, floating on a rotating shaft, was excited by a multi-frequency force signal. Measurements of the resulting relative movement between bearing and journal enabled the oil film coefficients to be measured. The results of the work show good agreement between theoretical and experimental data, and indicate that the oil film impedance of the novel design is considerably lower than that of a conventional bearing.

scholarly journals Dynamic Stiffness and Damping Characteristics of a Shaft Damping Ring: A Combined Hyperelastic and Viscoelastic Constitutive Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Miaomiao Li ◽  
Jian Chen ◽  
Rupeng Zhu ◽  
Cheng Duan ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Constitutive Models ◽  
Operating Conditions ◽  
Uniaxial Tensile ◽  
Bending Vibrations ◽  
Damping Characteristics ◽  
Shaft System ◽  
Stiffness And Damping

At higher velocities, the helicopter tail transmission system encounters notable difficulties due to excessive bending vibrations. The shaft damping ring installed on the shaft system was shown to effectively suppress the shaft system vibrations. In this paper, the dynamic stiffness and damping characteristics of polyurethane shaft damping rings were studied using hyperelastic and viscoelastic constitutive models. The constitutive model and the damping ring material parameters were determined using uniaxial tensile and double-shear frequency scanning tests. Based on the test results, the dynamic damping ring characteristics were simulated and verified by dynamic stiffness tests; the influence of structural parameters and operating conditions on the dynamic stiffness and damping characteristics of the damping ring were obtained. The results provide a theoretical basis for the design of shaft systems with reduced sensitivity to vibrations.

scholarly journals Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing

2001 ◽  
Vol 44 (4) ◽  
pp. 657-663 ◽  
Author(s):  
Samuela Howard ◽  
Christopher Dellacorte ◽  
Mark J. Valco ◽  
Joseph M. Prahl ◽  
Hooshang Heshmat
Keyword(s):  
High Temperature ◽  
Journal Bearing ◽  
Dynamic Stiffness ◽  
Damping Characteristics ◽  
Stiffness And Damping

Plain and Full Floating Bearing Simulations With Rigid Shaft Dynamics

2007 ◽  
Author(s):  
Ian McLuckie ◽  
Scott Barrett
Keyword(s):  
System Development ◽  
Equations Of Motion ◽  
Time Integration ◽  
Forced Response ◽  
Design Parameters ◽  
Integration Scheme ◽  
Damping Coefficients ◽  
Time Integration Scheme ◽  
Combined Solution ◽  
Stiffness And Damping

This paper shows a promising predictive bearing model that can be used to reduce turbocharger bearing system development times. Turbocharger development is normally done by varying design parameters such as bearing geometry in a very time consuming experimentation process. Full Floating Bearings (FFB) are used in most automotive turbochargers and, due to emissions regulations, there has been a push towards downsizing engines and applying turbo charging to generate optimized engine solutions for both gasoline and diesel applications. In this paper the turbocharger rotor is regarded as being rigid, and the equations of motion are solved using the Bulirsch Stoer time integration scheme. These equations are solved simultaneously with the bearing model which is used also to determine nonlinear stiffness and damping coefficients. The bearings are solved using a Rigid Hydro Dynamic (RHD) Finite Difference Successive Over Relaxation (SOR) scheme of Reynolds equation that includes both rotational and squeeze velocity terms. However the solver can also consider bearing and rotor elasticity in a Multi-Body Dynamic (MBD) and Elasto-Hydro Dynamic (EHD) combined solution. Two bearing types have been studied, a plain grooved (PGB) and a full floating bearing (FFB) for comparative purposes. The mathematical models used are generic and suitable for whole engine bearing studies. The results in this paper show they are suitable for determining the onset of turbocharger bearing instability, and also the means by which bearing instability may be suppressed. The current study has investigated forced response with the combined effects of gravity and unbalance. It is worth noting that the effects of both housing excitation and aerodynamic excitation from the compressor and turbine can be easily accommodated, and will be the subject of a future paper. Other topics introduced here that will be explored further in the future include the effect of bearing and rotor flexibility in the MBD and EHD solution and the use of automatically generated stiffness and damping coefficients for any bearing geometry.

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