Discussion: "The Critical Temperature of Oil With Point and Line Contact Machines" (Matveevsky, R. M., 1965, ASME J. Basic Eng., 87, pp. 754–759)

R. S. Fein
1965 Journal of Basic Engineering  
Several papers and discussions have been presented at this conference on the critical or transition-temperature concept. They have generally covered the dependence of critical temperatures on operating variables of speed and load, machine configuration, lubricants, and ferrous-metal bearing materials. The purpose of this discussion is to focus attention on the similarities and differences among the experimental data of the various investigators. Matveevsky, at low sliding speed with a four-ball
more » ... machine, found that the critical temperature for an oil was independent of load with a hard steel. However, with a soft steel, the critical temperature decreased with increasing load. This discusser, also with a four-ball machine when using oik containing naphthenic or aromatic rings, found the same effect of load and steel £19] 5 at low sliding speed; however, Matveevsky's hard-steel lowspeed critical temperatures decrease with increasing oil viscosity, as shown in Fig. 8 , while those of this discusser increase. This may be the result of oil diff erences (such as additives or degree of refining) or differences in operating procedure. COMPARISON OF LOW-SPEED HARD-STEEL CRITICAL TEMPERATURES O MATVEEVSKY • FEIN 400r Id a I-300 2 111 I-J 200 O F E o 100 Most of the experimental data which have been presented at this conference were obtained at high sliding speeds where frictional heating is important. All investigators used the Blok equations to calculate surface temperature. Under these conditions, this discusser found that the critical temperature for a given oil increases from the constant low-speed value with increasing speed or decreasing load. On the other hand, Mat-4 Research and Technical Departments, Texaco, Inc., Beacon, N. Y. 5 Numbers in brackets designate Additional References at end of Discussion. veevsky and Kelley and Leach [20] found that the critical temperature is independent of these operating variables. Further, Kelley and Leach found no dependence of the critical temperature on oil viscosity, while Matveevsky and this discusser found the same contradicting trends as at low speed. An additional difference in critical-temperature results among investigators was reported in the discussion following Kelley and Leach's paper. Alexander and Fein, using the same type of hardened test specimens in a disk machine essentially identical to that of Kelley and Leach, indicated that transition temperatures increase with sliding speed and decrease with velocity ratio between the disks. Kelley and Leach closed with a report of tests showing critical temperature to be independent of sliding speed with the same lubricant tested by Alexander and Fein. The preceding summary of results leads to the conclusion that critical temperatures reported to date are a function of both the investigator-machine combination and the lubricant-metal combination. In view of the potential practical value of the criticaltemperature concept for machine-design and lubricant-selection purposes, future studies should be aimed at resolving the investigator-machine differences. Toward this end, effects of operating procedures, minor machine and instrumentation variations, and other similar parameters need to be studied. To permit careful investigator-machine comparisons, reports of future studies also should provide more details on apparatus, procedure, failure criteria, surface-temperature calculations, etc., than most reports up to the present time. This paper touches on one of the more difficult problems in the field of lubrication. In it, the author presents results from a variety of lubricant test machines of varying geometry. It is the author's conclusion that the temperature at which a lubricant film fails is determined by the product of coefficient of friction, unit pressure, and sliding velocity. He points out that unit pressure must be based on actual contact area, corrected for elastic and plastic deformation as well as wear. The author's results verify that, in some test machines with specimens of given metallurgy, an oil will fail to provide a coherent film at a reasonably constant temperature under a broad range of test conditions. The relation among test machines, however, remains somewhat unclear. According to the author, machines using softer test specimens should exhibit lower failure temperatures with a given oil. This reasoning appeal's to be logical, but it does not explain all the facts. For example, it would appear from Fig. 3 that Oil B has a transition temperature of 200 C in the cone-roller machine, with specimens of hardness 200 DPH. When compared with the other results on this oil (140 C in two four-ball machines with specimens of hardness 1000 DPH), it is apparent that some other factors must be operative. Figs. 3, 4, and 7 . Experiments with the cone-roller machine (Fig. 3) and the crossed-cylinder and disk machines (Fig. 4) all show reasonably constant transition temperatures with soft specimens. Fig. 7 shows data obtained in a fourball configuration with soft specimens; here the measured transition temperatures are far from constant. Another indication that other factors must be considered is found in comparing Three factors that require consideration are the geometry of the system, the nature of the oil, and its interaction with the metal. The effect of geometry may be to permit more or less plastic deformation for a given load, in line with the author's
doi:10.1115/1.3650673 fatcat:6ewju3hzpjdldhyzfwz7vfciym