On the Stability of Rotors in Cylindrical Journal Bearings

1962 ◽  
Vol 84 (4) ◽  
pp. 521-531 ◽  
Author(s):  
G. M. Rentzepis ◽  
B. Sternlicht
Keyword(s):  
Experimental Evidence ◽  
Carrying Capacity ◽  
Variational Equation ◽  
Equation Of Motion ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Regions Of Stability ◽  
The Stability ◽  
Linear Variational Equation

The regions of stability for plain cylindrical journal bearings have been determined analytically here. The linear “variational” equation of motion has been employed to obtain the stability regions bounded by families of load-carrying capacity and operating eccentricity curves. The results were applied to the “quasi-static” equilibrium case for gas lubricated cylindrical journal bearings of L/D = 2. They show that there exists a “minimum” in the stability curves, a prediction supported by experimental evidence. The results of this work seem to bridge together observation on stability at very small clearances and large ones.

On the Combined Effects of Lubricant Inertia and Viscous Dissipation in Long Bearings

1997 ◽  
Vol 119 (1) ◽  
pp. 76-84 ◽  
Author(s):  
E. Kim ◽  
A. Z. Szeri
Keyword(s):  
Carrying Capacity ◽  
Journal Bearings ◽  
Isothermal Flow ◽  
Nonisothermal Flow ◽  
Combined Effects ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Bearing Load ◽  
The Stability ◽  
Rate Of Dissipation

We have demonstrated earlier that for laminar, isothermal flow of the lubricant in the non-cavitating film of long journal bearings, inertia has negligible effect on the load-carrying capacity and influences only the stability characteristics of the bearing. The question we pose in the present paper is: “will these conclusions remain valid for nonisothermal flow, or will lubricant inertia and dissipation interact and result in significant changes in bearing performance?” The results obtained here assert that the effect of lubricant inertia on load-carrying capacity remains negligible, irrespective of the rate of dissipation. The stability of the bearing is, however, affected by lubricant inertia. These results, although obtained here for long bearings and noncavitating films, are believed to be applicable to some practical bearing operations and suggest that for these, bearing load may be calculated from classical, i.e., noninertial theory.

Dissimilar Metal Weld Pipe Fracture Testing: Analysis of Results and Their Implications

2012 ◽  
Author(s):  
D. Rudland ◽  
R. Lukes ◽  
P. Scott ◽  
R. Olson ◽  
A. Cox ◽  
...  
Keyword(s):  
Experimental Data ◽  
Carrying Capacity ◽  
Nuclear Industry ◽  
Load Carrying Capacity ◽  
Base Metals ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
Estimation Scheme ◽  
The Stability ◽  
J Estimation

Typically in flaw evaluation procedures, idealized crack shapes are assumed for both subcritical and critical crack analyses. Past NRC-sponsored research have developed estimation schemes for predicting the load-carrying capacity of idealized cracks in nuclear grade piping and similar metal welds at the operating conditions of nuclear power reactors. However, recent analyses have shown that growth of primary water stress corrosion cracks (PWSCC) in dissimilar metal (DM) welds is not ideal; in fact, very unusual complex crack shapes may form, i.e., a very long surface crack that has a finite length through-wall crack in the same plane. Even though some experimental data on base metals exists to demonstrate that complex shaped cracks in high toughness materials fail under limit load conditions, other experiments demonstrate that the tearing resistance is significantly reduced. At this point, no experimental data exists for complex cracks in DM welds. In addition, it is unclear whether the idealized estimation schemes developed can be used to predict the load-carrying capacity of these complex-shaped cracks, even though they have been used in past analyses by the nuclear industry. Finally, it is unclear what material strength data should be used to assess the stability of a crack in a DM weld. The NRC Office of Nuclear Regulatory Research, with their contractor Battelle Memorial Institute, has concluded an experimental program to confirm the stability behavior of complex shaped circumferential cracks in DM welds. A combination of full-scale pipe experiments and a variety of laboratory experiments were conducted. A description of the pipe test experimental results is given in a companion paper. This paper describes the ongoing analyses of those results, and the prediction of the load-carrying capacity of the circumferential cracked pipe using a variety of J-estimation scheme procedures. Discussions include the effects of constraint, appropriate base metal material properties, effects of crack location relative to the dissimilar base metals, and the limitations of the currently available J-estimation scheme procedures. This paper concludes with plans for further development of J-estimation scheme procedures for circumferential complex cracks in DM welds.

Complex Crack Stability in Dissimilar Metal Welds: Background and Test Plan

2011 ◽  
Author(s):  
D. Rudland ◽  
P. Scott ◽  
R. Olson ◽  
A. Cox
Keyword(s):  
Experimental Data ◽  
Base Metal ◽  
Carrying Capacity ◽  
Nuclear Industry ◽  
Load Carrying Capacity ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
Crack Stability ◽  
Complex Crack ◽  
The Stability

Typically in flaw evaluation procedures, idealized flaw shapes are assumed for both subcritical crack growth and critical crack stability analyses. Past NRC-sponsored research have developed estimation schemes for predicting the load-carrying capacity of idealized flaws in nuclear grade piping and similar metal welds at the operating conditions of nuclear power reactors. However, recent analyses have shown that growth of primary water stress corrosion cracks (PWSCC) in dissimilar metal (DM) welds is not ideal; in fact, very unusual complex crack shapes may form, i.e., a very long surface crack that has a finite length through-wall crack in the same plane. Even though some experimental data on base metal cracks exist to demonstrate that complex shaped cracks in high toughness materials fail under limit load conditions, other experiments demonstrate that the tearing resistance is significantly reduced. At this point, no experimental data exists for complex cracks in DM welds. In addition, it is unclear whether the idealized estimation schemes developed can be used to predict the load carrying capacity of these complex-shaped flaws, even though they have been used in past analyses by the nuclear industry. Finally, it is unclear what material strength data should be used to assess the stability of a crack in a DM weld. The NRC Office of Nuclear Regulatory Research (RES), with their contractor Battelle Memorial Institute, has begun an experimental program to confirm the stability behavior of these complex shaped flaws in DM welds. A combination of thirteen full-scale pipe experiments and a variety of laboratory experiments are planned. This paper will summarize the past base metal complex-cracked pipe experiments, and the current idealized flaw load carrying capacity estimation schemes. In addition, the DM weld complex cracked pipe experimental test matrix will be presented. Finally, plans for using these results to confirm the applicability of idealized flaw stability procedures are discussed.

Overall Characteristics of Bearings Lubricated With Ferrofluids

1983 ◽  
Vol 105 (3) ◽  
pp. 466-475 ◽  
Author(s):  
N. Tipei
Keyword(s):  
Boundary Conditions ◽  
Carrying Capacity ◽  
Magnetic Particle ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Pressure Center ◽  
Friction Forces ◽  
Flow Rates ◽  
Load Carrying ◽  
Side Flow

Using the results shown in some previous papers, the overall characteristics of bearings lubricated with ferrofluids are calculated. First, the load carrying capacity of infinitely long sliding and journal bearings is considered. The pressure center and the attitude angle are also determined. Then, similar characteristics of finite bearings are obtained. In both cases, the new boundary conditions and the actual film extent under magnetic stresses are taken into account. It is shown that friction forces are mainly affected by the change in viscosity due to magnetic particle suspensions, while magnetic stresses modify friction only under special conditions which usually are not met in lubrication. In addition, the flow rates and the side flow coefficients are calculated. It is shown that the lubricant leakage can be reduced and even avoided when proper measures are taken. For short bearings, diagrams are given for the film extent, the film boundaries, the load carrying capacity, and the attitude of the journal center.

scholarly journals Effect of Grouted Granular Column on the Load Carrying Capacity of the Expansive soil

2019 ◽  
Vol 8 (3) ◽  
pp. 2606-2612
Keyword(s):  
Carrying Capacity ◽  
Urban Areas ◽  
Expansive Soil ◽  
Engineering Properties ◽  
Load Carrying Capacity ◽  
Loose Soil ◽  
Load Carrying ◽  
The Stability ◽  
Lateral Reinforcement ◽  
Granular Column

Due to the scarcity of land for the construction of industrial, commercial, and transportation structures for development in urban areas, it is very necessary to use the places which have weak strata. This has become very mandatory to use the land which has poor engineering properties due to the unavailability of land. In the recent years granular columns have come under the extensive use for increasing the load carrying capacity and reducing the settlement in the expansive soil and loose sand. Nowadays to increase the stability of the foundation, granular columns are being widely used. Traditional columns are driven into the weak expansive soil stratum and maintain its stability from lateral confinement, which is generally due to the reaction from the surrounding stiffened expansive soil. However, this is not so easy to support loose soil, an additional lateral support may have to be provided to stabilize it and reduce its settlements. This study aims to overcome this weakness in soil by wrapping the granular column in geotextile layer to enhance the lateral reinforcement. In the present paper the discussion is about the variation in load carrying capacity and settlement characteristics of granular column (made up of cement fly ash and sand in a definite proportion instead of aggregates and stones) and analyzing its effect on the expansive soil by comparing its results with geotextile encased columns. In this process the study investigates the improvement of load carrying capacity of a single granular column encased with geotextile through model test.

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