scholarly journals Discussion: “Interpretations of the Thickness of Lubricant Films in Rolling Contact—1. Examination of Measurements Obtained by X-Rays” (Kannel, J. W., and Bell, J. C., 1971, ASME J. Lubr. Technol., 93, pp. 478–484)

1972 ◽  
Vol 94 (4) ◽  
pp. 341-342
Author(s):  
T. E. Tallian
Keyword(s):  
Rolling Contact ◽  
X Rays ◽  
Lubricant Films

Interpretations of the Thickness of Lubricant Films in Rolling Contact. 2. Influence of Possible Rheological Factors

1971 ◽  
Vol 93 (4) ◽  
pp. 485-497 ◽  
Author(s):  
J. C. Bell ◽  
J. W. Kannel
Keyword(s):  
Time Delay ◽  
Film Thickness ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Rolling Contact ◽  
X Rays ◽  
Load Effect ◽  
Simple Theories ◽  
Lubricant Films ◽  
Inlet Zone

Several theories involving rarely analyzed but yet realistic rheological effects have been developed in an effort to find why lubricant film thicknesses in rolling contact, as measured by X rays for rigorous operating conditions, do not obey simple theories well, especially with respect to load effect. The analysis is based on actions in the inlet zone, using the approximate geometry implied for previous simple theories. Effects investigated include a generalized pressure variation of viscosity, a non-Newtonian rheology of Ree-Eyring form, and a time delay in pressure effect on viscosity. Simple formulas are found for the influence of all these factors on lubricant film thickness. The time delay theory is found to provide the best correlation with experimental measurements of film thickness, and it is suggested to offer an attractive field for further research embracing friction effects as well as film thickness.

Interpretations of the Thickness of Lubricant Films in Rolling Contact. 1. Examination of Measurements Obtained by X-Rays

1971 ◽  
Vol 93 (4) ◽  
pp. 478-484 ◽  
Author(s):  
J. W. Kannel ◽  
J. C. Bell
Keyword(s):  
Film Thickness ◽  
Rolling Contact ◽  
X Rays ◽  
Measuring Process ◽  
X Ray ◽  
Lubricant Films ◽  
Two Temperatures ◽  
Thickness Measurements ◽  
X Ray Absorption ◽  
Higher Sensitivity

The thickness of the film formed by each of five lubricants between a pair of disks in rolling contact has been measured by an X-ray technique for a range of loads (80,000 to 225,000 psi maximum Hertz stress), two temperatures (178 F and 250 F), and three speeds (4300 fpm to 9100 fpm). An empirical formula fitted to the X-ray data shows a much higher sensitivity of film thickness to load than is normally predicted. In order to judge whether the measurements themselves are at fault, the X-ray measuring process has been reexamined for accuracy, especially where load-dependent errors might arise. Some weaknesses are noted, such as in the amount of X-ray absorption, but these should not affect load sensitivity greatly. New experiments designed to find effects of imperfect collimation of X-rays indicate that reflection of X-rays may be significant, but these effects too do not seem to account for the anomalies of the film thickness measurements.

Observations of viscoelastic behaviour of an elastohydrodynamic lubricant film

1974 ◽  
Vol 337 (1609) ◽  
pp. 217-242 ◽  
Keyword(s):  
Point Contact ◽  
High Viscosity ◽  
Rolling Contact ◽  
Viscoelastic Behaviour ◽  
Shear Forces ◽  
Cyclic Shear ◽  
Direct Observations ◽  
Lubricant Films ◽  
Elastic Shear ◽  
Small Shear

A novel rolling-contact experiment has been devised with the object of making direct observations of viscoelastic behaviour of elastohydrodynamic lubricant films. A ‘point contact' disk machine has been used which permits the axes of the disks to be either tilted or skewed through small angles relative to each other. Tilt subjects the film to cyclic shear while skew subjects it to unidirectional shear. By measuring and comparing the resultant shear forces developed by the film in each case, its viscoelastic properties can be deduced. Experiments at 23 °C with a high-viscosity mineral oil revealed viscoelastic behaviour above a contact pressure of about 0.5 GPa. In the pressure range 1.0 to 2.0 GPa the effective elastic shear modulus of the oil was found to vary from 0.1 to 1.0 GPa. At a pressure of 0.8 GPa the oil exhibited a viscoelastic transition in the temperature range 70 to 30 °C. The investigation was restricted to small shear strains for which the behaviour is linear.

Lubricant Films in Rolling Contact of Rough Surfaces

1964 ◽  
Vol 7 (2) ◽  
pp. 109-126 ◽  
Author(s):  
T. E. Tallian ◽  
Y. P. Chiu ◽  
D. F. Huttenlocher ◽  
J. A. Kamenshine ◽  
L. B. Sibley ◽  
...  
Keyword(s):  
Rough Surfaces ◽  
Rolling Contact ◽  
Lubricant Films

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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