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Startup Ridging Failures at Very Large Radii: The Case of Thrust Collars.

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Title: Startup Ridging Failures at Very Large Radii: The Case of Thrust Collars.
Authors: Heinrich, Christian1 (AUTHOR) heinrich@imw.tu-clausthal.de, Lohrengel, Armin1 (AUTHOR)
Source: Tribology Transactions. Mar/Apr2026, Vol. 69 Issue 2, p217-228. 12p.
Subjects: Thrust bearings, Hertzian contact stresses, Mechanical loads, Boundary lubrication, Lubricant additives, Spur gearing, Gearing machinery, Journal bearings
Abstract: Thrust collars were previously dimensioned against mixed lubrication failures using one single Hertzian pressure limit. In this paper, a striking radius dependence of permissible Hertzian pressures is found. This radius dependence can be used to connect failure limits of spur gears, hypoid gears, thrust collars, and journal bearings (ordered from low to high reduced radii). The failure load can be increased significantly by using active extreme pressure (EP) additives. This slow-speed EP additive usage is a different use case than the traditional high-speed scuffing one; the variation between additives turns out to be much higher. Phosphating and hardening likewise lead to large increases in failure load. Crowning and roughness variations are further investigated influences. The arising ridging failure mechanism is established to be mainly due to the increased interaction length of the long and low-gradient lubrication gap at high radii. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Thrust collars were previously dimensioned against mixed lubrication failures using one single Hertzian pressure limit. In this paper, a striking radius dependence of permissible Hertzian pressures is found. This radius dependence can be used to connect failure limits of spur gears, hypoid gears, thrust collars, and journal bearings (ordered from low to high reduced radii). The failure load can be increased significantly by using active extreme pressure (EP) additives. This slow-speed EP additive usage is a different use case than the traditional high-speed scuffing one; the variation between additives turns out to be much higher. Phosphating and hardening likewise lead to large increases in failure load. Crowning and roughness variations are further investigated influences. The arising ridging failure mechanism is established to be mainly due to the increased interaction length of the long and low-gradient lubrication gap at high radii. [ABSTRACT FROM AUTHOR]
ISSN:10402004
DOI:10.1080/10402004.2025.2582043