Finite Journal Bearing With Nonlinear Stiffness and Damping. Part 1: Improved Mathematical Models

1982 ◽  
Vol 104 (2) ◽  
pp. 397-405 ◽  
Author(s):  
E. Hashish ◽  
T. S. Sankar ◽  
M. O. M. Osman
Keyword(s):  
Mathematical Models ◽  
Reynolds Equation ◽  
Nonlinear Dynamic Analysis ◽  
Upper And Lower Bounds ◽  
Finite Element Program ◽  
Cavitation Phenomenon ◽  
Dynamic Case ◽  
Element Program ◽  
Stiffness And Damping ◽  
Film Profile

Two mathematical models for the nonlinear hydrodynamic film forces in a finite bearing are developed including a practical adaptation of the cavitation phenomenon. Using the linearity of the Reynolds equation for incompressible film, the pressure components are effectively decomposed and the Reynolds equation is rearranged for general solution by a finite element program in which only the L/d ratio and the eccentricity ratio are to be specified. The different possibilities of partial film profile location in a general dynamic case are demonstrated. The two partial film models possess the required accuracy of the finite bearing approach with the simplicity of the known long and short bearing approximations which are shown as the upper and lower bounds for the present case. The finite bearing approach presented are particularly suitable for nonlinear dynamic analysis.

Improvement of the Calculation of Hydrodynamic Systems by Considering the Dynamic Deformation Caused by Vibration

2011 ◽  
Author(s):  
Sebastian Kukla ◽  
Tim Sadek
Keyword(s):  
Reynolds Equation ◽  
Coefficient Matrix ◽  
Influence Coefficient ◽  
Finite Element Program ◽  
Hydrodynamic System ◽  
Element Program ◽  
Dynamic Components ◽  
Stiffness And Damping ◽  
Hydrodynamic Systems ◽  
Surface Dynamic

In order to improve the calculation of stiffness and damping coefficients (SDC) for hydrodynamic systems, this paper proposes the consideration of both static and dynamic deformations of the running surface. Dynamic deformations are caused by rotor vibration and corresponding unbalanced forces. A lubrication wedge was used to exemplify the significant influence of these dynamic deformations in SDC calculations. This basic hydrodynamic system was calculated considering material elasticity. First of all, an influence coefficient matrix, which describes the correlation of pressure and deformation, was calculated with the finite element program ANSYS. Using this matrix, small dynamic deformations of the running surface were considered in solving the Reynolds equation for the lubrication wedge. The analysis of the vibration response of this basic hydrodynamic system considering elastic material deformation demonstrated that both static and dynamic components of deflection significantly affect the SDC. These coefficients were also proved to be highly dependent on the stimulation frequency.

Finite Element Analysis of Grooved Gas Thrust Bearings and Grooved Gas Face Seals

1993 ◽  
Vol 115 (3) ◽  
pp. 348-354 ◽  
Author(s):  
D. Bonneau ◽  
J. Huitric ◽  
B. Tournerie
Keyword(s):  
Finite Element ◽  
Reynolds Equation ◽  
Weak Form ◽  
Oscillating Solution ◽  
Element Analysis ◽  
Finite Element Program ◽  
Thrust Bearings ◽  
Face Seals ◽  
Element Program ◽  
Gas Seals

A finite element method enabling the Reynolds equation solution for any face geometry of gas thrust bearing or of gas seal is presented. Difficulties due to thickness discontinuities are reduced by integration by parts of the terms involving derivatives. The weak form of the finite element Reynolds equation is then solved and the nonlinearity of the equation leads to the use of Newton-Raphson procedure. The process is fast convergent. The problem of oscillating solution is solved by the use of an upwind procedure. Some numerical examples show the accuracy and efficiency of the procedures. It is shown that the developed finite element program provides a numerical tool, more efficient than the method used until now, for the grooved gas seals design.

Numerical analysis and simulations of the magnetic field and hydrophobicity effect on the journal bearing dynamics

2016 ◽  
Vol 231 (5) ◽  
pp. 561-571 ◽  
Author(s):  
Simona Fialová ◽  
František Pochylý ◽  
Eduard Malenovský
Keyword(s):  
Magnetic Field ◽  
Mathematical Models ◽  
Reynolds Equation ◽  
Hydrophobic Surface ◽  
Hydrophilic Surface ◽  
Flowing Liquid ◽  
Stiffness And Damping ◽  
Bearing Dynamics ◽  
The Magnetic Field ◽  
Generalized Reynolds Equation

The article contains mathematical models of Reynolds equation with the effects of hydrophobicity of surface and magnetic field. The first section provides a new mathematical model of the solution of the generalized Reynolds equation and its application for a hydrophilic surface. It also derives a new boundary condition for the contact of a flowing liquid with a hydrophobic surface. This wettability condition is defined in dependence on the adhesion coefficient k. The second part presents mathematical models of Reynolds equation including the effect of hydrophobia and magnetic field. For all problems, the solutions are shown and the definitions of the stiffness and damping matrices of the liquid layer are outlined. From the results, it can be deduced that hydrophobic surface significantly affects the velocity profile of the liquid. It leads to a higher effect of the Lorentz force and thus of the magnetic field in comparison with a hydrophilic surface of the bearing lining.

scholarly journals H-Adaptive Methods for Nonlinear Dynamic Analysis of Shell Structures

1995 ◽  
Vol 2 (3) ◽  
pp. 193-204 ◽  
Author(s):  
Sang-Ho Lee ◽  
Ted Belytschko
Keyword(s):  
Structural Dynamics ◽  
Nonlinear Dynamic Analysis ◽  
Adaptive Methods ◽  
General Purpose ◽  
Shell Structures ◽  
Finite Element Program ◽  
Explicit Finite Element ◽  
Shell Elements ◽  
Element Program ◽  
Projection Techniques

The implementation and application of h-adaptivity in an explicit finite element program for nonlinear structural dynamics is described. Particular emphasis is placed on developing procedures for general purpose structural dynamics programs and efficiently handling adaptivity in shell elements. New projection techniques for error estimation and projecting variables on new meshes after fission or fusion are described. Several problems of severe impact are described.

Numerical study of influences of hard particles in lubricant on tribological performances of the piston ring

2007 ◽  
Vol 221 (3) ◽  
pp. 361-372 ◽  
Author(s):  
F M Meng ◽  
Y Y Zhang ◽  
Y Z Hu ◽  
H Wang
Keyword(s):  
Friction Force ◽  
Contact Stress ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Numerical Study ◽  
Cylinder Wall ◽  
Finite Element Program ◽  
Hard Particles ◽  
Element Program ◽  
Maximum Contact

Influences of hard particles lying in the lubrication region between piston ring face and cylinder wall, including the effects of a non-contact particle and contact particle, on tribological performances of the piston ringwere numerically analysed. A modified Reynolds equation incorporating a non-contact particle effect was presented. The total friction force, deformation, and contact stress of the ring, with a non-contact particle and contact particle consideration, were solved separately by using finite-element program code of the authors and software ANSYS 5.7. The numerical results show that obvious changes in the total friction force and deformation of the ring can occur, if the diameter and height across the film thickness of a non-contact particle and axial velocity difference between the non-contact particle and ring are considered. The maximum contact stress of the ring is obviously affected by the contact particle's interfering time and velocity, and hardness value of the plastically deformed particle.

Influence of effective parameters of non-orthogonal smeared crack approach in seismic response of concrete arch dams

2003 ◽  
Vol 30 (5) ◽  
pp. 890-901 ◽  
Author(s):  
Radin Espandar ◽  
Vahid Lotfi ◽  
Ghani Razaqpur
Keyword(s):  
Seismic Response ◽  
Nonlinear Dynamic Analysis ◽  
Arch Dam ◽  
Effective Parameters ◽  
Finite Element Program ◽  
Cracking Behavior ◽  
Arch Dams ◽  
Smeared Crack Approach ◽  
Element Program ◽  
Smeared Crack

A rigorous and relatively efficient algorithm based on the non-orthogonal smeared crack approach is coded in a special finite element program to study the seismic response of arch dams. The formulation is briefly presented. The 130 m high Shahid Rajaee arch dam in Iran subjected to the Friuli-Tolmezzo earthquake is selected to present a practical application of the technique. Under the same geometry and loading conditions, six nonlinear analyses with different parameters are performed, and the results are compared with each other and a linear case. The varied parameters include secant and elastic unloading–reloading options, threshold angle, and tensile strength of the material. It is concluded that the non-orthogonal smeared crack approach can redistribute the state of stresses and produces a more realistic profile of stresses in the dam. A drift in the crest displacements forms the prominent characteristics of the cracking behavior. The results also suggest that the dam can suffer significant cracking during a strong earthquake and still remain stable. Moreover, the influences of the mentioned parameters in the seismic response of the dam are comprehensively discussed.Key words: nonlinear dynamic analysis, concrete arch dam, smeared crack approach.

Friction Force and Stresses Analysis for Contact of Assembled Details

2006 ◽  
Vol 113 ◽  
pp. 334-338
Author(s):  
Z. Dreija ◽  
O. Liniņš ◽  
Fr. Sudnieks ◽  
N. Mozga
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Plastic Deformation ◽  
Friction Force ◽  
Sliding Friction ◽  
Friction Model ◽  
Contact Interface ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Element Program

The present work deals with the computation of surface stresses and deformation in the presence of friction. The evaluation of the elastic-plastic contact is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. Several factors of sliding friction model are discussed: surface roughness, mechanical properties and contact load and areas that have strong effect on the friction force. The critical interference that marks the transition from elastic to elastic- plastic and plastic deformation is found out and its connection with plasticity index. A finite element program for determination contact analysis of the assembled details and due to details of deformation that arose a normal and tangencial stress is used.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

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