Closure to “Discussions of ‘Measurement of Boundary Lubricant Viscosity at Metal-Deformation Pressures (3000 Atmospheres, 20 Tons/Sq In.)’” (1967, ASME J. Lubr. Technol., 89, pp. 281–282)

1967 ◽  
Vol 89 (3) ◽  
pp. 282-282
Author(s):  
G. W. Rowe
Keyword(s):  
Boundary Lubricant ◽  
Metal Deformation ◽  
Lubricant Viscosity

Measurement of Boundary Lubricant Viscosity at Metal-Deformation Pressures (3000 Atmospheres, 20 Tons/Sq In.)

1967 ◽  
Vol 89 (3) ◽  
pp. 272-281 ◽  
Author(s):  
G. W. Rowe
Keyword(s):  
Boundary Lubrication ◽  
Flat Surface ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Wire Drawing ◽  
Average Pressure ◽  
Boundary Lubricant ◽  
Metal Deformation ◽  
Local Pressures ◽  
Lubricant Viscosity

In many metalworking operations, such as rolling and wire drawing, the average pressure acting between the workpiece and the tool will be of the order of the yield stress of the metal, usually 20–50 tons/sq in. The lubricant temperature may also rise by 60 deg C or more. Any consideration of hydrodynamic lubrication in these operations should thus take account of the large viscosity changes which may occur under such pressures and temperatures. In addition, it is probable that the rate of shear will be important [1], but this will not be considered in this paper. Local pressures of the same order are developed in typical boundary-lubrication apparatus using a hemispherical slider on a flat surface under kilogram loads [2]. Information on the pressure and temperature coefficients of viscosity for lubricants is therefore important also in studies of boundary lubrication and elastohydrodynamic lubrication [3], especially in the presence of boundary additives [4]. This paper describes a simple apparatus for viscosity measurement at temperatures up to 70 deg C and pressures up to 20 tons/sq in. (3000 atmospheres) or with future modifications up to 45 tons/sq in., together with some results for fluids with and without boundary additives.

Simulation of vibration piercing of pipe blank at press

2020 ◽  
Vol 76 (11) ◽  
pp. 1128-1138
Author(s):  
S. R. Rakhmanov
Keyword(s):  
High Frequency ◽  
Deformation Zone ◽  
Pipe Blank ◽  
Equipment Operation ◽  
Metal Deformation ◽  
Technological Tool ◽  
High Frequency Vibrations ◽  
Pipe Blanks ◽  
Wave Phenomena

In some cases, the processes of piercing or expanding pipe blanks involve the use of high-frequency active vibrations. However, due to insufficient knowledge, these processes are not widely used in the practice of seamless pipes production. In particular, the problems of increasing the efficiency of the processes of piercing or expanding a pipe blank at a piercing press using high-frequency vibrations are being solved without proper research and, as a rule, by experiments. The elaboration of modern technological processes for the production of seamless pipes using high-frequency vibrations is directly related to the choice of rational modes of metal deformation and the prediction resistance indicators of technological tools and the reliability of equipment operation. The creation of a mathematical model of the process of vibrating piercing (expansion) of an axisymmetric pipe blank at a piercing press of a pipe press facility is an actual task. A calculation scheme for the process of piercing a pipe plank has been elaborated. A dependence was obtained characterizing the speed of front of plastic deformation propagation on the speed of penetration of a vibrated axisymmetric mandrel into the pipe workpiece being pierced. The dynamic characteristics of the occurrence of wave phenomena in the metal being pierced under the influence of a vibrated tool have been determined, which significantly complements the previously known ideas about the stress-strain state of the metal in the deformation zone. The deformation fields in the zones of the disturbed region of the deformation zone were established, taking into account the high-frequency vibrations of the technological tool. It has been established that the choice of rational parameters (amplitude-frequency characteristics) of the vibration piercing process of a pipe blank results in significant increase in the efficiency of the process, the durability of the technological tool and the quality of the pierced blanks.

scholarly journals The Role of Hyaluronic Acid in Cartilage Boundary Lubrication

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1606 ◽  
Author(s):  
Weifeng Lin ◽  
Zhang Liu ◽  
Nir Kampf ◽  
Jacob Klein
Keyword(s):  
Hyaluronic Acid ◽  
Synovial Fluid ◽  
Surface Force ◽  
Force Balance ◽  
New Paradigm ◽  
Low Friction ◽  
Cartilage Surface ◽  
Boundary Lubricant ◽  
Lipid Layers

Hydration lubrication has emerged as a new paradigm for lubrication in aqueous and biological media, accounting especially for the extremely low friction (friction coefficients down to 0.001) of articular cartilage lubrication in joints. Among the ensemble of molecules acting in the joint, phosphatidylcholine (PC) lipids have been proposed as the key molecules forming, in a complex with other molecules including hyaluronic acid (HA), a robust layer on the outer surface of the cartilage. HA, ubiquitous in synovial joints, is not in itself a good boundary lubricant, but binds the PC lipids at the cartilage surface; these, in turn, massively reduce the friction via hydration lubrication at their exposed, highly hydrated phosphocholine headgroups. An important unresolved issue in this scenario is why the free HA molecules in the synovial fluid do not suppress the lubricity by adsorbing simultaneously to the opposing lipid layers, i.e., forming an adhesive, dissipative bridge between them, as they slide past each other during joint articulation. To address this question, we directly examined the friction between two hydrogenated soy PC (HSPC) lipid layers (in the form of liposomes) immersed in HA solution or two palmitoyl–oleoyl PC (POPC) lipid layers across HA–POPC solution using a surface force balance (SFB). The results show, clearly and surprisingly, that HA addition does not affect the outstanding lubrication provided by the PC lipid layers. A possible mechanism indicated by our data that may account for this is that multiple lipid layers form on each cartilage surface, so that the slip plane may move from the midplane between the opposing surfaces, which is bridged by the HA, to an HA-free interface within a multilayer, where hydration lubrication is freely active. Another possibility suggested by our model experiments is that lipids in synovial fluid may complex with HA, thereby inhibiting the HA molecules from adhering to the lipids on the cartilage surfaces.

scholarly journals Enzymatic identification of the load-bearing boundary lubricant in the joint.

Rheumatology ◽  
1998 ◽  
Vol 37 (2) ◽  
pp. 137-142 ◽  
Author(s):  
B A Hills ◽  
M K Monds
Keyword(s):  
Water Soluble ◽  
Surprising Result ◽  
Lubrication System ◽  
Load Bearing ◽  
Bovine Articular Cartilage ◽  
Boundary Lubricant ◽  
Surface Active ◽  
Per Se ◽  
Dose Dependent ◽  
Wear Tests

Abstract Bovine articular cartilage and synovial fluid (SF) were co-incubated with one of three enzymes selected to destroy each of the three major contenders for the active ingredient imparting such remarkable load-bearing lubrication to the normal joint. Destroying hyaluronic acid (HA), alias hyaluronan, with hyaluronidase, both frictional and wear tests displayed no significant change in accordance with most previous studies of SF alone. Destroying surface-active phospholipid (SAPL) with phospholipase A2, there was a highly significant dose-dependent compromise of lubrication as recorded on both tests. Trypsin produced a somewhat surprising result in that lubrication of the cartilage actually improved. This result can be interpreted as indicating that lubricin is not the lubricant per se, but, as a water-soluble, macromolecular, proteinaceous carrier for phospholipid, its destruction caused more SAPL to be deposited as the true load-bearing lubricant. These results are discussed in the context that SAPL, lubricin and HA each have specific roles in a comprehensive lubrication system.

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