Influence of Realistic Lubricant Density-Pressure Dependence on the Stiffness of Elastohydrodynamic Lubricated Contacts

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
J. S. Issa ◽  
W. Habchi
Keyword(s):  
Steady State ◽  
Pressure Dependence ◽  
Accurate Estimation ◽  
Correction Procedure ◽  
Oil Film ◽  
The Real ◽  
Lubricated Contacts ◽  
Analytical Correction ◽  
Universal Law ◽  
Film Stiffness

Abstract The analysis of the dynamic response of elastohydrodynamic lubricated contacts has often invoked a universal law for lubricant density–pressure dependence, even though the densities of many lubricants exhibit a substantial deviation from this widely adopted law. The current work investigates the influence of real lubricant density–pressure behavior on the stiffness of elastohydrodynamic lubricated contacts. It is shown that accounting for the real lubricant density–pressure dependence is crucial for an accurate estimation of the oil film stiffness, under steady-state considerations. The influence on the overall stiffness of the contact is found to be negligible though. Finally, an analytical correction procedure is provided, allowing a correction of oil film stiffness predictions that are based on the universal law for lubricant density–pressure dependence (or any other unrealistic law), to account for the real lubricant density–pressure response.

Alternative calculation on transient elasto-hydrodynamic lubrication

2018 ◽  
Vol 70 (2) ◽  
pp. 423-431 ◽  
Author(s):  
Shaocheng Zhu ◽  
Weihua Zhang ◽  
Daniel Nelias
Keyword(s):  
Steady State ◽  
Elastic Deformation ◽  
Hydrodynamic Lubrication ◽  
Rolling Bearings ◽  
Content Type ◽  
Oil Film ◽  
Transient Regimes ◽  
Time Marching ◽  
Stiffness And Damping ◽  
Film Stiffness

Purpose The purpose of this study is to propose a new method to solve transient elasto-hydrodynamic lubrication (EHL) problem. Design/methodology/approach First, the steady-state EHL solution is modified so that the elastic deformation theory is combined with oil film stiffness distribution instead of steady-state Reynolds equation. Second, subsequent dynamic EHL procedure develops, recursively using transient distributed oil film stiffness and damping, where each time-marching solution is iteratively searched by ensuring both oil film force growth and elastic deformation update for each load increment. Findings This method increases calculation speed and provides both distributed EHL stiffness and damping for transient regimes. Originality/value This method is of interest for fast applications such as rolling bearings or gears.

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 Study and Application of Intelligent Sliding Mode Control for Voltage Source Inverters

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2544 ◽  
Author(s):  
En-Chih Chang
Keyword(s):  
Steady State ◽  
Sliding Mode Control ◽  
Digital Signal Processor ◽  
Sliding Mode ◽  
Transient Behavior ◽  
Voltage Source ◽  
Accurate Estimation ◽  
Inference System ◽  
Mode Control ◽  
State Error

In this paper, an intelligent sliding mode controlled voltage source inverter (VSI) is developed to achieve not only quick transient behavior, but satisfactory steady-state response. The presented approach combines the respective merits of a nonsingular fast terminal attractor (NFTA) as well as an adaptive neuro-fuzzy inference system (ANFIS). The NFTA allows no singularity and error states to be converged to the equilibrium within a finite time, while conventional sliding mode control (SMC) leads to long-term (infinite) convergent behavior. However, there is the likelihood of chattering or steady-state error occurring in NFTA due to the overestimation or underestimation of system uncertainty bound. The ANFIS with accurate estimation and the ease of implementation is employed in NFTA for suppressing the chatter or steady-state error so as to improve the system’s robustness against uncertain disturbances. Simulation results display that this described approach yields low distorted output wave shapes and quick transience in the presence of capacitor input rectifier loading as well as abrupt connection of linear loads. Experimental results conducted on a 1 kW VSI prototype with control algorithm implementation in Texas Instruments DSP (digital signal processor) support the theoretic analysis and reaffirm the robust performance of the developed VSI. Because the proposed VSI yields remarkable benefits over conventional terminal attractor VSIs on the basis of computational quickness and unsophisticated realization, the presented approach is a noteworthy referral to the designers of correlated VSI applications in future, such as DC (direct current) microgrids and AC (alternating current) microgrids, or even hybrid AC/DC microgrids.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

scholarly journals Influence of oil film stiffness on natural characteristics of single-rotor three-input helicopter main gearbox

2018 ◽  
Vol 17 ◽  
pp. 7-12 ◽  
Author(s):  
Ru Peng Zhu ◽  
Yuan Chen ◽  
Zai Chun Feng ◽  
Guang Hu Jin ◽  
Wei Zhang
Keyword(s):  
Oil Film ◽  
Film Stiffness ◽  
Natural Characteristics

scholarly journals VICES OF CONSENT CONCERNING THE CIVIL LEGAL ACT

2018 ◽  
Vol 11 (2) ◽  
pp. 106-111
Author(s):  
Roxana Denisa Vidican ◽  
Ionel DIDEA ◽  
Diana Maria ILIE
Keyword(s):  
The Real ◽  
Legal Relationship ◽  
The Will ◽  
Legal Equality ◽  
The Right ◽  
Universal Law

"The right is the totality of the conditions under which the will of each can coexist with the will of all, according to a universal law of freedom".Immanuel Kant.The requirement that the expression of will to be uncorrupted is a legal necessity, but also a guarantee of compliance with the principle of freedom of civil legal acts, the real principle of will and the principle of law which enshrines the legal equality of the parties to civil legal relationship since the legal civil act must be the consequence of a volitional attitude, free and conscious expressed

scholarly journals Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

1996 ◽  
Vol 23 ◽  
pp. 382-387 ◽  
Author(s):  
I. Hansen ◽  
R. Greve
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Ice Sheet ◽  
Physical Parameters ◽  
Water Mixture ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Real ◽  
Thermomechanical Behaviour ◽  
The Antarctic

An approach to simulate the present Antarctic ice sheet with reaped to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important because an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice water mixture. Measurements indicate that the geothermal heat flux below the Antarctic ice sheet appears to be remarkably higher than the standard value of 42 m W m−2 that is usually applied for Precambrian shields in ice-sheet modelling. Since the extent of temperate ice at the base is highly dependent on this heat input from the lithosphere, an adequate choice is crucial for realistic simulations. We shall present a series of steady-state results with varied geothermal heat flux and demonstrate that the real ice-sheet topography can be reproduced fairly well with a value in the range 50–60 m W m−2. Thus, the physical parameters of ice (especially the enhancement factor in Glen’s flow law) as used by Greve (1995) for polythermal Greenland ice-sheet simulations can be adopted without any change. The remaining disagreements may he explained by the neglected influence of the ice shelves, the rather coarse horizontal resolution (100 km), the steady-state assumption and possible shortcomings in the parameterization of the surface mass balance.

Investigation of the tyre characteristics under non-steady-state conditions on the basis of road tests

2016 ◽  
Vol 231 (1) ◽  
pp. 3-15 ◽  
Author(s):  
Hubert Sar ◽  
Andrzej Reński ◽  
Janusz Pokorski
Keyword(s):  
Steady State ◽  
Computer Simulations ◽  
Dynamic Characteristics ◽  
Slip Angle ◽  
Real Motion ◽  
Side Force ◽  
The Real ◽  
Different Types ◽  
Non Linear ◽  
The Difference

This paper presents a method of identifying the dynamic characteristics of tyres for non-steady-state conditions on the basis of road measurements on a vehicle. The side force acting on the tyre is presented as a function of not only the slip angle but also the slip angle derivative (i.e. the velocity of the change in the slip angle). Hence, the influence of the manoeuvre dynamics on the tyre characteristics and the difference between the characteristics obtained for steady-state conditions and the characteristics for non-steady-state conditions are shown. Also the results of computer simulations prepared for different types of tyre characteristics are presented in this paper. It is evident from the presented graphs that applying dynamic non-linear tyre characteristics for computer simulations instead of steady-state characteristics enables us to describe the real motion of a vehicle better.

Wear Prediction in Connecting Rod Bearings During Running-In and Transient Speed Conditions

2010 ◽  
Author(s):  
Aurelian Fatu ◽  
Dominique Bonneau
Keyword(s):  
Steady State ◽  
Connecting Rod ◽  
Wear Coefficient ◽  
Wear Prediction ◽  
The Real ◽  
Time Required ◽  
Wear Condition

During running-in conditions, contact occurs between surface asperities, which induce wear and bearing shell profile adaptation. Firstly, the bearing wear evolution is investigated for different but constant engine rotational speeds. Secondly, the wear is investigated for transient speed conditions. By comparison with a realistic wear coefficient, the real engine time required to reach a steady-state wear condition is predicted.

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