Oil film thickness and the mechanism of scuffing in gear teeth

The voltage drop across thin oil films when a constant current of 1 amp is passed, i.e., the discharge voltage, is used to measure the oil-film thickness between loaded gear teeth while running. It is found that the thickness at the pitch line is between 1 and 4 × 10−4 in., which varies slightly with the viscosity and rather more strongly with load. The thickness at the tips and roots is very dependent on the tip relief. The conditions here may explain the difference between disk and gear tests. These experimental values are compared with theoretical work and are shown to be of the same order of magnitude.

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An investigation of oil film thickness between involute gear teeth

Wear ◽

10.1016/0043-1648(63)90218-7 ◽

1963 ◽

Vol 6 (5) ◽

pp. 408

Keyword(s):

Film Thickness ◽

Oil Film ◽

Gear Teeth ◽

Involute Gear

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Elastohydrodynamic Lubrication of Hypoid Gears

Journal of Mechanical Design ◽

10.1115/1.3254863 ◽

1981 ◽

Vol 103 (1) ◽

pp. 195-203 ◽

Cited By ~ 16

Author(s):

V. Simon

Keyword(s):

Film Thickness ◽

Numerical Solution ◽

Elastohydrodynamic Lubrication ◽

Operating Conditions ◽

Performance Characteristics ◽

Temperature Variations ◽

Hypoid Gears ◽

Oil Film ◽

Gear Teeth ◽

Energy Equations

The full thermal elastohydrodynamic analysis of the lubrication of hypoid gears is presented. A numerical solution of the coupled Reynolds, elasticity and energy equations for the pressure, temperature and film thickness is obtained. The temperature variations across the oil film and in the pinion and gear teeth are included. The real tooth geometry of the modified hypoid gears is treated. The effect of the operating conditions on the performance characteristics is discussed.

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The measurement of oil-film thickness in gear teeth

Wear ◽

10.1016/0043-1648(60)90024-7 ◽

1960 ◽

Vol 3 (5) ◽

pp. 406 ◽

Cited By ~ 1

Keyword(s):

Film Thickness ◽

Oil Film ◽

Gear Teeth

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Experimental Investigation of the Minimum Oil-Film Thickness in Spur Gears

Journal of Basic Engineering ◽

10.1115/1.3656647 ◽

1963 ◽

Vol 85 (3) ◽

pp. 451-455 ◽

Cited By ~ 3

Author(s):

D. W. Dareing ◽

E. I. Radzimovsky

Keyword(s):

Film Thickness ◽

Voltage Drop ◽

Planetary Gear ◽

Gear Train ◽

Spur Gears ◽

Minimum Thickness ◽

Testing Technique ◽

Oil Film ◽

Gear Teeth ◽

Gear Drive

As a pair of gears is loaded, the minimum oil-film thickness between the gear teeth decreases and can approach a magnitude equal to the magnitude of the surface roughness. Metal-to-metal contact then occurs between the microscopic peaks on both mating teeth surfaces. Therefore, the minimum thickness of the film separating the mating teeth surfaces may be considered as one of the criteria of capacity for a gear drive. A testing technique that was developed for measuring oil-film thickness between loaded gear teeth while running is presented in this paper. The voltage drop across a thin oil film that is required to cause an electrical discharge was used to determine the oil-film thickness. A specially designed machine containing a planetary gear train was used in these experiments. The relationships between the minimum oil-film thickness and the load transmitted by the gearing under certain conditions were determined using this method.

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Measurement of Oil-Film Thickness Between Disks by Electrical Conductivity

Journal of Basic Engineering ◽

10.1115/1.3662499 ◽

1960 ◽

Vol 82 (1) ◽

pp. 12-16 ◽

Cited By ~ 18

Author(s):

S. I. El-Sisi ◽

G. S. A. Shawki

Keyword(s):

Electrical Conductivity ◽

Film Thickness ◽

Testing Machine ◽

Rotating Disk ◽

Substantial Improvement ◽

Film Resistance ◽

Test Results ◽

Oil Film ◽

Gear Teeth ◽

Special Apparatus

A special apparatus is designed to measure the oil-film thickness between two stationary disks (simulating meshing gear teeth) by applying a-c or d-c potential across the film and measuring its resistance for given gap between the disks. Experiments show that the treatment of oil with additive (sodium-petroleum sulphonate in this case) may well lead to a considerable increase in its electrical conductivity, and to a substantial improvement in the independence of the oil-film resistance of the electrical history and temperature of the oil. A reliable relationship could eventually be obtained between the oil-film resistance and relevant thickness. Test results are employed in investigating the behavior of the oil film in a rotating-disk testing machine developed by the authors for studying the performance of meshing gear teeth with adequate supply of lubricant.

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