The Lubrication of Lightly Loaded Cylinders in Combined Rolling, Sliding, and Normal Motion—Part II: Experimental

1976 ◽  
Vol 98 (4) ◽  
pp. 517-522 ◽  
Author(s):  
P. H. Markho ◽  
D. Dowson
Keyword(s):  
Boundary Condition ◽  
Theoretical Analysis ◽  
High Speed ◽  
Squeeze Film ◽  
Theoretical Predictions ◽  
Good Agreement

This paper forms part of a wider investigation which includes the theoretical analysis given in Part I in addition to a study of the outlet cavitation boundary, using high-speed cine photography, reported elsewhere [4]. Pressure and some load measurements are presented which show good agreement with the theoretical predictions despite the well-known shortcomings of the Swift-Stieber boundary condition used in the analysis. Two sets of results have been included to cover the pure squeeze-film problem in addition to that of combined rolling, sliding and “normal” motion.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

Stability of Water-Lubricated, Hydrostatic, Conical Bearings With Spiral Grooves for High-Speed Spindles

2001 ◽  
Vol 124 (2) ◽  
pp. 398-405 ◽  
Author(s):  
S. Yoshimoto ◽  
S. Oshima ◽  
S. Danbara ◽  
T. Shitara
Keyword(s):  
High Speed ◽  
Water Pressure ◽  
Rotating Shaft ◽  
Pressurized Water ◽  
High Speeds ◽  
Theoretical Predictions ◽  
The Stability ◽  
Stability Of Water ◽  
Spiral Grooves ◽  
Good Agreement

In this paper, the stability of water-lubricated, hydrostatic, conical bearings with spiral grooves for high-speed spindles is investigated theoretically and experimentally. In these bearing types, pressurized water is first fed to the inside of the rotating shaft and then introduced into spiral grooves through feeding holes located at one end of each spiral groove. Therefore, water pressure is increased due to the effect of the centrifugal force at the outlets of the feeding holes, which results from shaft rotation. In addition, water pressure is also increased by the viscous pumping effect of the spiral grooves. The stability of the proposed bearing is theoretically predicted using the perturbation method, and calculated results are compared with experimental results. It was consequently found that the proposed bearing is very stable at high speeds and theoretical predictions show good agreement with experimental data.

A Theoretical Analysis of the Bending into Cylindrical Dies of Metal Strips

1984 ◽  
Vol 198 (2) ◽  
pp. 99-108 ◽  
Author(s):  
T X Yu ◽  
W Johnson
Keyword(s):  
Theoretical Analysis ◽  
Metal Forming ◽  
Plastic Material ◽  
Forming Process ◽  
Rigid Plastic ◽  
Rigid Plastic Material ◽  
Punch Load ◽  
Theoretical Predictions ◽  
Metal Forming Process ◽  
Good Agreement

Based on experiments on the bending of metal strips into cylindrical dies using a semi-circular ended punch (1) a theoretical analysis of this metal forming process is presented to predict the punch load—punch travel characteristic and the clearance between the punch pole and the mid-point of the strip. Elastic/plastic and rigid/plastic material idealizations are employed, and the effect of friction between the strip and the die is also considered. The theoretical predictions show good agreement with the experimental results and are useful for designers.

On the Friction Reducing Non-Newtonian Flow Around an Enclosed Disk

1974 ◽  
Vol 41 (1) ◽  
pp. 45-50 ◽  
Author(s):  
E. Bilgen ◽  
P. Vasseur
Keyword(s):  
Theoretical Analysis ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Newtonian Flow ◽  
Dilute Polymer Solutions ◽  
Theoretical Predictions ◽  
Minimum Resistance ◽  
Good Agreement

The turbulent flow characteristics of non-Newtonian dilute polymer solutions around an enclosed rotating disk have been studied both theoretically and experimentally. In the theoretical analysis, the momentum equations of the boundary layers on both rotating disk and housing have been solved numerically using appropriate velocity profiles. It is shown that the theoretical predictions for minimum resistance conditions are in good agreement with the experimental results of this study and with those in the literature.

scholarly journals A theoretical analysis of the semileptonic decays $$\eta ^{(\prime )}\rightarrow \pi ^0l^+l^-$$ and $$\eta ^\prime \rightarrow \eta l^+l^-$$

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Rafel Escribano ◽  
Emilio Royo
Keyword(s):  
Theoretical Analysis ◽  
Semileptonic Decays ◽  
Coupling Constants ◽  
Energy Spectra ◽  
Radiative Decays ◽  
Vector Meson Dominance ◽  
Decay Widths ◽  
Theoretical Predictions ◽  
First Time ◽  
Good Agreement

AbstractA complete theoretical analysis of the C- conserving semileptonic decays $$\eta ^{(\prime )}\rightarrow \pi ^0l^+l^-$$ η ( ′ ) → π 0 l + l - and $$\eta ^\prime \rightarrow \eta l^+l^-$$ η ′ → η l + l - ($$l=e$$ l = e or $$\mu $$ μ ) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $$V\rightarrow P\gamma $$ V → P γ and $$P\rightarrow V\gamma $$ P → V γ radiative decays ($$V=\rho ^0$$ V = ρ 0 , $$\omega $$ ω , $$\phi $$ ϕ and $$P=\pi ^0$$ P = π 0 , $$\eta $$ η , $$\eta ^{\prime }$$ η ′ ). The decay widths and dilepton energy spectra for the two $$\eta \rightarrow \pi ^0l^+l^-$$ η → π 0 l + l - processes obtained using this approach are compared and found to be in good agreement with other results available in the published literature. Theoretical predictions for the four $$\eta ^{\prime }\rightarrow \pi ^0l^+l^-$$ η ′ → π 0 l + l - and $$\eta ^\prime \rightarrow \eta l^+l^-$$ η ′ → η l + l - decay widths and dilepton energy spectra are calculated and presented for the first time in this work.

Experimental Investigation of Gas-Particle Flow Trajectories and Velocities in an Axial Flow Turbine Stage

1972 ◽  
Author(s):  
W. Tabakoff ◽  
A. Hamed ◽  
M. F. Hussein
Keyword(s):  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Pressure Distribution ◽  
High Speed ◽  
Axial Flow ◽  
Particle Flow ◽  
Blade Surface ◽  
Turbine Stage ◽  
Theory And Experiment ◽  
Good Agreement

This paper describes the results from an investigation of the gas-particle flow trajectories, velocities and pressure distribution in an axial flow turbine stage. A gas-particle flow cascade tunnel and high-speed photographic techniques were used to conduct the experimental investigation. The pressure distribution on the blade surface was measured and compared with the theoretical analysis, the results exhibiting good agreement between the developed theory and experiment.

Pumping Characteristics of a Herringbone-Grooved Journal Bearing Functioning as a Viscous Vacuum Pump

1999 ◽  
Vol 122 (1) ◽  
pp. 131-136 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Ito ◽  
A. Takahashi
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Slip Flow ◽  
Laser Scanner ◽  
Vacuum Pump ◽  
Chamber Pressure ◽  
Design Parameters ◽  
Theoretical Predictions ◽  
Flow Effects ◽  
Good Agreement

A laser scanner motor with low power and high speed has been developed. This scanner motor uses a herringbone-grooved journal bearing which functions as a viscous vacuum pump. The windage power loss of a polygon mirror is reduced, since the air inside the pump housing is pumped out by herringbone-grooved viscous vacuum action. In this paper, the theoretical pumping characteristic of this bearing is investigated, using the narrow-groove theory and accounting for first-order slip flow. The effects of various design parameters on the pumping characteristics are discussed. Optimum geometric design parameters were found to obtain the minimum inner chamber pressure of the housing. The theoretical predictions considering slip flow effects are in good agreement with experimental measurements. [S0742-4787(00)01801-4]

Vibration of a Spinning Rotationally Periodic Rotor

2007 ◽  
Author(s):  
Hyunchul Kim ◽  
I. Y. Shen
Keyword(s):  
Theoretical Analysis ◽  
High Speed ◽  
Experimental Studies ◽  
Mode Shapes ◽  
Integer Multiple ◽  
Numerical Studies ◽  
Theoretical Predictions ◽  
Symmetric Rotor ◽  
Unified Algorithm ◽  
Cyclic Symmetric

This paper studies the vibrations of a spinning, rotationally periodic (also known as cyclic symmetric) rotor through theoretical analysis and experimental studies. The theoretical analysis consists of two parts. The first part is Fourier analysis of mode shapes of a stationary rotor with periodicity N. A periodic mapping of the n-th mode shape shows that its k-th Fourier coefficient is generally zero, except when k ± n is an integer multiple of N. The second part is to apply the derived mode shapes through a unified algorithm developed by Shen and Kim [1] to predict primary and secondary resonances of spinning, rotationally periodic rotors. The experimental study focuses on vibration measurements of a spinning disk carrying 4 pairs of evenly spaced brackets mounted on a high-speed air-bearing spindle. Initially, experimentally measured waterfall plots do not agree well with those from theoretical predictions. Further numerical studies show that mistune of rotationally periodic rotors could substantially change their waterfall plots. After the mistune is modeled, experimental and theoretical results agree very well with a difference of only 0.8% in natural frequencies observed in the ground-based coordinates.

scholarly journals Theoretical Determination of Porpoising Instability of High-Speed Planing Boats

1978 ◽  
Vol 22 (01) ◽  
pp. 32-53 ◽  
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Theoretical Method ◽  
Theoretical Determination ◽  
Damping Characteristics ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Good Agreement

A theoretical method is derived for predicting trim angle and speed coefficient at the inception of propoising of prismatic planing hulls. Although equations are derived for the surge, pitch, and heave degrees of freedom, it is seen that the effect of surge is small at ordinary operating trim angles. Comparisons of theoretical predictions with existing experimental data on coupled pitch and heave porpoising show reasonably good agreement for a wide range of speed coefficients, load coefficients, and deadrise angles. The theory may also be used for estimating the natural frequencies and damping characteristics of prismatic hulls in the stable, high-speed planing range.

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