Closure to “Discussion of ‘A Fast Method for Calculating Dynamic Coefficients of Finite Width Journal Bearings With Quasi Reynolds Boundary Condition’” (1989, ASME J. Tribol., 111, p. 737)

1989 ◽  
Vol 111 (4) ◽  
pp. 737-737
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Boundary Condition ◽  
Journal Bearings ◽  
Finite Width ◽  
Fast Method ◽  
Dynamic Coefficients

A Fast Method for Calculating Dynamic Coefficients of Finite Width Journal Bearings With Quasi Reynolds Boundary Condition

1988 ◽  
Vol 110 (3) ◽  
pp. 387-393 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Boundary Condition ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Boundary Line ◽  
Finite Width ◽  
Fast Method ◽  
Dynamic Coefficients ◽  
Straight Line ◽  
Time Required ◽  
Stiffness And Damping

This paper presents a fast method for calculating the dynamic coefficients of the finite width journal bearings under quasi Reynolds boundary condition in which the trailing boundary line is given by a straight line and the continuity of bulk flow across this line is ensured. Calculated linear stiffness and damping coefficients agree well with the data of Lund and Thomsen [1]. The time required by this calculation with HITAC M682H is only 0.1–0.3 seconds (about 1/100 of the time required by the ordinary FDM), which suggests the possibility of real time journal bearing designs without using the database of the dynamic coefficients.

Theoretical Condition for the Cxy=Cyx Relation in Fluid Film Journal Bearings

1989 ◽  
Vol 111 (3) ◽  
pp. 426-429 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Finite Width ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Cross Terms ◽  
Linear Damping ◽  
Theoretical Condition

A computer program for calculating dynamic coefficients of journal bearings is necessary in designing fluid film journal bearings and an accuracy of the program is sometimes checked by the relation that the cross terms of linear damping coefficients of journal bearings are equal to each other, namely “Cxy = Cyx”. However, the condition for this relation has not been clear. This paper shows that the relation “Cxy = Cyx” holds in any type of finite width journal bearing when these are calculated under the following condition: (I) The governing Reynolds equation is linear in pressure or regarded as linear in numerical calculations; (II) Film thickness is given by h = c (1 + κcosθ); and (III) Boundary condition is homogeneous such as p=0 or dp/dn=0, where n denotes a normal to the boundary.

Performance Characteristics of Finite Width Journal Bearings Under the Separation Boundary Condition

1986 ◽  
Vol 108 (2) ◽  
pp. 178-183 ◽  
Author(s):  
M. Nakai ◽  
T. Kazamaki ◽  
T. Hatake
Keyword(s):  
Boundary Condition ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Finite Width ◽  
Separation Boundary ◽  
Physical Consideration ◽  
Calculation Results

The separation boundary condition is considered to be comparatively exact in the physical consideration of the supposition. The calculated performance characteristics applied to infinite width journal bearings are related to experimental results to some extent. However, performance characteristics applied to finite width journal bearings, which might be able to explain the experimental results more precisely, have been unknown. The present paper describes the application of the separation boundary condition to finite width journal bearings, and calculation results of some performance characteristics. The results are related to well-known experimental results in several respects.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

Impermeable Crack and Permeable Crack Assumptions, Which One is More Realistic?

2004 ◽  
Vol 71 (4) ◽  
pp. 575-578 ◽  
Author(s):  
Bao-Lin Wang ◽  
Yiu-Wing Mai
Keyword(s):  
Boundary Condition ◽  
Piezoelectric Materials ◽  
Finite Width ◽  
Permeable Crack ◽  
Impermeable Crack ◽  
Electrical Boundary Conditions ◽  
Engineering Problems ◽  
Electrical Boundary Condition ◽  
Crack Faces ◽  
Impermeable Boundary

This paper investigates the applicability and effect of the crack-free electrical boundary conditions in piezoelectric fracture. By treating flaws in a medium as notches with a finite width, the results from different electrical boundary condition assumptions on the crack faces are compared. It is found that the electrically impermeable boundary is a reasonable one for engineering problems. Unless the flaw interior is filled with conductive media, the permeable crack assumption may not be directly applied to the fracture of piezoelectric materials in engineering applications.

Thermohydrodynamic analysis of finite-width journal bearings with non-Newtonian lubricants

Wear ◽  
1994 ◽  
Vol 171 (1-2) ◽  
pp. 41-49 ◽  
Author(s):  
Ju Sheau-Ming ◽  
Weng Cheng-I
Keyword(s):  
Journal Bearings ◽  
Finite Width
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