Absence Of Lubrication Research Articles

Abrasion of rubber and the effect of lubricants

Fracture mechanics has previously been applied to relate the rate of abrasion of rubber by a blade (in the absence of lubrication) to the horizontal force on the blade and to the crack-growth characteristics of the rubber. The effect of lubrication (reported here) is to decrease the rate of abrasion by an order of magnitude or so, but the horizontal force falls by only ten or twenty percent. This apparently conflicts with the theory. It is suggested that lubricants alter the geometry of deformation, making tearing less efficient. A model deformation is proposed which largely restores agreement with the theory.

Solid state coextrusion: A new technique for ultradrawing thermoplastics illustrated with high density polyethylene

AbstractUltraoriented films of high density polyethylene (HDPE) have been prepared in continuous lengths by a new method, solid state coextrusion, through conical dies of extrusion draw ratios up to 36. Preformed HDPE billets ∽7 cm long and ∽1 cm in diameter of duPont Alathon 7050R, Mw = 59,000, Mn = 19,900, were split longitudinally into halves and then one or more wafers of the same polymer were inserted between the two sheath halves. Thereafter, the whole assembly was extruded through a conical die of 20° included entrance angle in the absence of lubricant and at temperatures substantially below the melting range yielding continuous and transparent films. The physical and mechanical properties of the HDPE films so produced were evaluated and compared with the properties of the same polymer extruded through a slit die. The high melt transition, tensile modulus and transparency confirm the effectiveness of the new method in continuously attaining ultradrawn films.

Lubricant Effects on Fatigue in a Stationary Concentrated Contact Under Vibratory Loading

Contact fatigue, brinnelling, and erosion are reported, for a stationary ball-on-flat contact, subjected to oscillatory normal load. Damage was least in the absence of lubricant, and greatest with a diester lubricant. Low-viscosity mineral oil was less severe in its effects than was a high-viscosity mineral oil. In those cases where damage was least, it could be attributed to a process of fatigue spalling. In those cases where it was severe, other processes such as fretting could be postulated, but fatigue still appeared to be the favored cause.

Paper 2: Some Effects of Lubricant and Temperature on Failure in Rolling Contact

The rolling-four-ball test has been used to carry out an exploratory investigation on materials for unlubricated and elevated-temperature rolling bearings. Besides high-speed tool and stainless steels, other hard, wearresistant materials have been compared under unlubricated conditions at ambient and elevated temperatures. A solid material, molybdenum disulphide, has been assessed as an elevated temperature lubricant. Significant differences in performance have been found between different materials. The failure mechanism varied with environmental conditions. With liquid lubrication, plastic deformation and fatigue occur. The amount of deformation, the resistance to fatigue, and the mode of failure are affected by the type of lubricant and the nature of the additives. In the absence of lubricant there was no pitting, the useful life of rolling elements being limited by wear assessed by loss of weight. The term ‘wear’, in this paper, means grooving by removal of material evenly from the surface without pitting or deformation. Use of a solid lubricant reduced the wear rate. Material combination and compatibility of mating material surfaces are particularly significant in resistance to pitting and wear. An examination of failed specimens has been carried out to obtain a better understanding of the failure processes.

An Application of Dimensional Analysis to the Characteristics of Wear in Absence of Lubricant

A theory on galling wear has been proposed by R. Holm, that is, the amount of wear is proportional to the normal pressure and sliding distance, while it is inversely proportional to the hardness of the softer of the two rubbing materials. The theory has been improved and demonstrated experimentally by several investigators. However, actual wear characteristics are apparently more complicated. The authors have attempted to find a simple theory, which reduces the complication of actual test results by the aid of dimensional considerations, and have seen that the rate of wear par unit normal pressure and sliding distance is a function of dimensionless numbers, containing PV and V, where P and V denotes normal pressure and sliding velocity respectively, and have shown that above result is formally identical with Holm's theory.