Archive issue - vol.10, No.3



   No.   Author(s) - Title
Pages

   1.
 

 M.L. Adams Jr. And M.A. Laurich -- Inside-Out Pivoted-Pad Bearing With Controllable Stiffness
 

395-406
 

   2.
 

 M. Arghir And J. Frene -- Problems Of High Reynolds Number Lubrication: The Turbulent Regime And The Inertia Effects
 

407-422
 

   3.
 

 R. Bassani And E. Ciulli, B. Piccigallo -- Investigation On Plain Journal Bearings For Severe Working Conditions
 

423-439
 

   4.
 

 M. Fillon -- On The Thermal Effects In Hydrodynamic Journal Bearings
 

441-450
 

   5.
 

 I. Green -- Poisson Ratio Effects And Critical Values In Spherical And Cylindrical Hertzian Contacts
 

451-462
 

   6.
 

 M.F. Letelier, D.A. Siginer -- On The Steady Flow Of Magnetorheological Fluids In Pipes
 

463-474
 

   7.
 

 K.R. Rajagopal And L. Tao, G.Q. Chen -- On Some Issues Concerning The Modeling Of The Motion Of Fluids
 

475-487
 

   8.
 

 M. Massoudi And T.X. Phuoc -- Heat Transfer In Flowing Granular Materials: The Effects Of Radiation Boundary Condition
 

489-503
 

   9.
 

 Fuping Zhou And S.G. Advani, E.D. Wetzel -- Characterization Of The Viscous Behavior Of Compacted Ceramic Particles Under Shear And Pressure Loads
 

505-514
 

   10.
 

 Jerzy T. SAWICKI -- Cavitation Effects On The Dynamics Of Journal Bearings
 

515-526
 

   11.
 

 A. Walicka And E. Walicki -- Rotational Inertia And Surface Roughness Effects In Curvilinear Thrust Bearings Lubricated By A Couple Stress Fluid
 

527-541
 

 



1.

INSIDE-OUT PIVOTED-PAD BEARING WITH CONTROLLABLE STIFFNESS

M.L. ADAMS JR. and M.A. LAURICH

Mechanical and Aerospace Engineering
The Case School of Engineering, Case Western Reserve University
Cleveland, Ohio, 44106-7222, USA
e-mail: mla5@mae.cwru.edu

     It has recently been demonstrated that high-speed grinding principles can be applied to the finishing of silicon nitride (ceramic) with considerable improvements in throughput, costs, and quality. This will require new high-speed high-power centerless grinding machines (7.000 rpm, 50 hp), with high-stiffness (2.000.000 lb/in) spindles. To meet the life, stiffness and speed requirements of this next generation grinding spindle, a novel inside-out, three-pad, pivoting-pad oil-fed hydrodynamic journal bearing has been devised, built and tested. The journal rotates externally about the bearing pads which are thus loaded against an internal shaft diameter. That is, an inside-out version of the conventional pivoted-pad journal bearing. Two of the three pivoting pads have fixed-support pivot points while the third pad’s pivot point is supported by a hydraulically-actuated radial-motion loading piston. This radial pad actuation provides a real-time controllable preload to the other two bearing pads and thereby controls the overall stiffness of the bearing. With this new bearing design, it is now possible to control spindle support stiffness, in real time, providing less-stiff spindle bearings for initial rough grinding and very high stiffness spindle bearings for precision finish grinding. Extensive bearing test data compare favourably with theoretically predicted bearing performance.

Key words:

bearing, pivoted-pad, spindle, centerless grinder, actuator.

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2.

PROBLEMS OF HIGH REYNOLDS NUMBER LUBRICATION: THE TURBULENT REGIME AND THE INERTIA EFFECTS

M. ARGHIR and J. FRENE

Laboratoire de Mécanique des Solides
Université de Poitiers, FRANCE
e-mail: Jean.frene@lms.univ-poitiers.fr

     The present paper is a synthesis of the work performed by the authors on the problems characterising the high Reynolds number lubrication namely the turbulent flow regime and the presence of inertia effects. The paper introduces the first approach of the turbulent regime based on the mixing length concept and shows how the Reynolds equation was modified. The problem of distributed inertia forces is then addressed by showing the adaptation of an approach borrowed from the boundary layer theory. The inertia dominated thin film model is reliable as long as the main hypotheses of lubrication theory are verified. A different approach should be used if concentrated inertia effects have an important influence as for hydrostatic and hybrid bearings and for labyrinth seals. This approach is based on a combination between the inertia dominated thin film model and the numerical solution of the complete Navier-Stokes equations. The thin film model predicts the characteristics of the seal or of the bearing and the numerical solution of the Navier-Stokes equations enables the estimation of concentrated inertia effects. On the authors experience this is a successful compromise between the accuracy and the computational effort. The paper briefly presents how this combined approach is used for stator-grooved labyrinth seals and for hybrid bearings.

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3.

INVESTIGATION ON PLAIN JOURNAL BEARINGS FOR SEVERE WORKING CONDITIONS

R. BASSANI and E. CIULLI

Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione
University of Pisa, Via Diotisalvi, 2, 56126 Pisa, ITALY
e-mail: bassani@ing.unipi.it
e-mail: ciulli@ing.unipi.it

B. PICCIGALLO
Gruppo Costruzioni e Tecnologia
Accademia Navale Livorno, ITALY
e-mail: b.piccigallo@ing.unipi.it

     In this paper a theoretical and experimental work for design of plain journal bearing able to work up to severe conditions is reported. The mathematical model and the numerical methods on which a purposely developed computer program is based are firstly described. The program is aimed to the evaluation of the behaviour of hydrodynamic plain journal bearings under heavy static loads, considering the elastic deformation of the bearing members, geometrical errors such as the axis misalign¬ment and thermal effects. The experimental apparatus designed and set up for testing plain bearings in several working conditions, by varying speed, load and oil supply up to extremely critical situations, is then briefly described. Theoretical and experimental results obtained at different load, speed and oil flow rate conditions are finally compared showing a good agreement.

Key words:

plain hydrodynamic bearings, journal bearings, elastohydrodynamic lubrication, finite-element method, experimental tests.

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4.

ON THE THERMAL EFFECTS IN HYDRODYNAMIC JOURNAL BEARINGS

M. FILLON

Universite de Poitiers, Laboratoire de Mecanique des Solides
UMR CNRS 6610, SP2MI, BP 30179, 86962 FUTUROSCOPE CHASSENEUIL CEDEX, FRANCE
e-mail: fillon@lms.univ-poitiers.fr

     This paper presents recent works on temperature effects in hydrodynamic journal bearings. This is an over-view of several specific thermal problems encountered particularly in fixed geometry and tilting-pad journal bearings. The temperature-viscosity variation, the heat transfer, the change in bearing clearance, the thermal and mechanical deformations, the flow regime, the transient regime, the risk of seizure, the dynamic loading as well as the misalignment are successively discussed.

Key words:

hydrodynamic bearing, deformations, thermal effects, seizure, misalignment.

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5.

POISSON RATIO EFFECTS AND CRITICAL VALUES IN SPHERICAL AND CYLINDRICAL HERTZIAN CONTACTS

I. GREEN

Georgia Institute of Technology
G.W. Woodruff School of Mechanical Engineering
Atlanta, GA 30332-0405, USA
e-mail: igreen@mail.me.gatech.edu

     This work determines the location of the greatest elastic distress in spherical and cylindrical Hertzian contacts based upon the distortion energy and the maximum shear stress theories. The ratios between the maximum pressure, the von Mises stress, and the maximum shear stress are determined and fitted by empirical formulations for a wide range of the Poisson ratio, which represents material compressibility. Some similarities exist between cylindrical and spherical contacts, where for many metallic materials the maximum von Mises or shear stresses emerge beneath the surface. However, in cylindrical contact if any of the materials is excessively compressible then the maximum von Mises stress appears at the surface. The corresponding Poisson ratios are found. The critical forces that cause yielding onset, and the corresponding interferences and radius or half-width contact are derived along with the maximum stored strain energy. It is shown that the distressing stresses decrease as Poisson’s ratio increases (i.e., as the material approaches incompressibility). The results obtained herein are then used to calibrate FEA meshes intended for cases that do not have closed-form solutions.

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6.

ON THE STEADY FLOW OF MAGNETORHEOLOGICAL FLUIDS IN PIPES

M.F. LETELIER

Departamento de Ingeniería Mecánica
Universidad de Santiago de Chile
Casilla 10233, Santiago, CHILE
e-mail: mletelie@lauca.usach.cl

D.A. SIGINER
Department of Mechanical Engineering, Wichita State University
1845 Fairmount, Wichita, Kansas 67260-0133, USA
e-mail: dennis.siginer@wichita.edu

     A non-affine visco-elasto-plastic constitutive equation with yield stress is proposed to simulate the response of magnetorheological fluids to driving forces. The equation yields realistic flow patterns in the pressure gradient driven fully developed tube flow which combine the effects of viscoelasticity and yield stress. The interplay of yield stress and viscoelasticity results in longitudinal velocity profiles, which can be controlled by adjusting the strength of the applied magnetic field. However, for physically realistic velocity profiles to exist the material parameters of the fluid and the steady pressure gradient must satisfy certain restrictions.

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7.

ON SOME ISSUES CONCERNING THE MODELING OF THE MOTION OF FLUIDS

K.R. RAJAGOPAL and L. TAO

Department of Mechanical Engineering
Texas A&M University College Station, Texas 77843-3123, USA
e-mail: luoyitao@yahoo.com

G.Q. CHEN
Department of Mechanics and Engineering Science
Peking University, Beijing 100871, CHINA

     We address some issues regarding the use of the Lagrangian description and convected frames in describing fluid motions. We also discuss the implications of Brownian motion on modeling the macroscopic motion of fluids and the schemes of filtered simulations. The relevance of these issues to the modeling of turbulence is discussed in detail.

Key words:

constitutive theory, convected frame, discrete modeling, large eddy simulation, Navier-Stokes equations, turbulence modeling.

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8.

HEAT TRANSFER IN FLOWING GRANULAR MATERIALS: THE EFFECTS OF RADIATION BOUNDARY CONDITION

M. MASSOUDI AND T.X. PHUOC

U.S. Department of Energy
National Energy Technology Laboratory
P.O. Box 10940, Pittsburgh, PA 15236, USA
e-mail: mehrdad.massoudi@netl.doe.gov

     In this paper we consider the free surface flow of granular materials down an inclined plane. The surface of the inclined is heated and the effects of radation heat transfer at the free surface are studied. It is assumed that the material behaves like a continuum, similar to a compressible non-Newtonian fluid where the effects of density gradients are incorporated in the stress tensor. For a fully developed flow the equations simplify to a system of three non-linear ordinary differential equations. The equations are made dimensionless and a parametric study is performed where the effects of various dimensionless numbers representing the effects of heat conduction, viscous dissipation, etc., are presented.

Key words:

granular materials, heat transfer, fully developed inclined flow, radiation boundary condition, viscous dissipation, continuum mechanics.

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9.

CHARACTERIZATION OF THE VISCOUS BEHAVIOR OF COMPACTED CERAMIC PARTICLES UNDER SHEAR AND PRESSURE LOADS

Fuping ZHOU and S.G. ADVANI

Department of Mechanical Engineering and Center for Composite Materials
University of Delaware, Newark, Delaware 19716, U.S.A.
e-mail: advani@me.udel.edu
e-mail:zhouf@me.udel.edu

E.D. WETZEL
Army Research Laboratory, Aberdeen Proving Ground
Maryland 21005, U.S.A.

     Two different viscometer systems are designed and fabricated to characterize the behavior of ceramic particles under shear stress and high pressures. The first system is a Couette flow device with ability to exert pressure on the particles during its rotation and measure the torque and angular velocity of the system. From this information we can calculate viscosity and energy dissipation due to friction between particles as a function of the shear rate. The second system focuses on the movement of a cylinder through a bed of compacted ceramic particles. By measuring the force required to move the cylinder through the compacted bed, we can evaluate the effective resistance of the particle bed under various compaction pressures. This characterization should prove useful in understanding the shearing and dissipation mechanisms between granular particles under high pressures.

Key words:

viscous behavior; ceramic particles; shear; pressure; Couette flow, rheology, friction

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10.

CAVITATION EFFECTS ON THE DYNAMICS OF JOURNAL BEARINGS

Jerzy T. SAWICKI

D.E. Bently & A. Muszynska Endowed Chair
Rotor-Bearing Dynamics and Diagnostics Laboratory
Fenn College of Engineering
Cleveland State University
Cleveland, Ohio 44115-2425, U.S.A.
e-mail: j.sawicki@csuohio.edu

     A numerical procedure incorporating cavitation effects on the dynamics of journal bearings is presented. A two-dimensional linear stability analysis considering the fluid flow in both full film and cavitation regions for a plain cylindrical journal bearing and four multi-lobe bearings are presented. The Lund’s infinitesimal perturbation procedure is applied to Elrod’s universal equation for evaluation of unsteady pressure gradients. Based on JFO theory, the pressure distribution, film rupture, and reformation boundaries can be obtained using Elrod’s universal equation, for a given operating position of the journal. In this work, it is assumed that for infinitesimal perturbation of journal about equilibrium position, the film rupture and film reformation boundaries are same as those obtained for steady state. However, the unsteady pressure gradients in the full film region are evaluated taking into consideration the perturbed flow parameters in the cavitation region, i.e., at both rupture and reformation boundaries. The linearized stiffness and damping coefficients, whirl frequency ratio, and threshold speed for various values of eccentricity and L/D ratios are obtained for a plain cylindrical journal bearing with an axial groove along the load line. Measured data of dynamic coefficients for a 120° partial arc bearing are chosen for comparison with this work. Results show good agreement between the theoretical and experimental results. Results of stiffness and damping coefficients are presented for two-axial groove, elliptical, three-lobe and offset cylindrical bearing for various L/D and eccentricity ratios. A transient analysis of submerged journal bearing incorporating the mechanism of shear between the liquid sublayer and air cavity in the cavitation zone is also presented. Using the mass conservation principles, Elrod’s universal equation is modified to take into consideration the shear of air cavity in the cavitation zone. Results of transient response for the submerged journal bearing using the present approach are compared with the Elrod’s universal equation based on the striated flow in the cavitation region. The limit cycle journal motion using the present approach predicts higher eccentricity ratios.

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11.

ROTATIONAL INERTIA AND SURFACE ROUGHNESS EFFECTS IN CURVILINEAR THRUST BEARINGS LUBRICATED BY A COUPLE STRESS FLUID

A. WALICKA and E. WALICKI

University of Zielona Góra, Department of Mechanics
ul. Szafrana 2. P.O. Box 47, 65-016 Zielona Góra, POLAND
e-mail: a.walicka@ijame.uz.zgora.pl

     On the basis of Christensen’s stochastic model of rough surfaces, different forms of Reynolds equation with rotational inertia effect are obtained for various types of surface roughness pattern and for couple stress lubricant. As results one obtained the formulae expressing the mean film pressure distribution for externally pressurized bearings and for bearings with a squeeze film. Examples of spherical and step bearings are considered.

Key words:

Christensen stochastic model, couple stress, surface roughness, curvilinear surfaces, thrust bearings.

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