Point-surface-origin (PSO) macropitting occurs at sites of geometric stress concentration (GSC) such as discontinuities in the gear tooth profile caused by micropitting, cusps at the intersection of the involute profile and the trochoidal root fillet, and at edges of prior tooth damage, such as tip-to-root interference. When the profile modifications in the form of tip relief, root relief, or both, are inadequate to compensate for deflection of the gear mesh, tip-to-root
interference occurs. The interference can occur at either end of the path of contact, but the damage is usually more
severe near the start-of-active-profile (SAP) of the driving gear.
A study was performed to evaluate fault detection effectiveness as applied to gear-tooth pitting-fatigue damage. Vibration and oil-debris monitoring (ODM) data were gathered from 24 sets
of spur pinion and face gears run
during a previous endurance evaluation
study.
Profile corrections on gears are a commonly used method to reduce transmission error, contact shock, and scoring risk. There are different types of profile corrections. It is a known fact that the type of profile correction used will have a strong influence on the resulting transmission error. The degree of this influence may be determined by calculating tooth loading during mesh. The current method for this calculation is very complicated and time consuming; however,
a new approach has been developed that could reduce the calculation time.
Micropitting has become a major concern in certain classes of industrial gear applications, especially wind power and other relatively highly loaded, somewhat slow-speed applications, where carburized gears are used to facilitate maximum load capacity in a compact package. While by itself the appearance of micropitting does not generally cause
much perturbation in the overall operation of a gear system, the ultimate
consequences of a micropitting failure
can, and frequently are, much more
catastrophic.
The powder metal (P/M) process is making inroads in automotive transmission applications due to substantially lower costs of P/M-steel components for high-volume production, as compared to wrought or forged steel parts. Although P/M gears are increasingly used in powered hand tools, gear pumps and as accessory components in automotive transmissions, P/M-steel gears are currently in
limited use in vehicle transmission applications. The primary objective of this project was to develop high-strength P/M-steel gears with bending fatigue, impact resistance and pitting fatigue performance
equivalent to current wrought steel gears.
In the hypercompetitive race to increase automobile efficiency,
Metaldyne has been developing its balance shaft module line with Victrex
PEEK polymer in place of metal gears.
The collaborative product development
resulted in significant reductions in
inertia, weight and power consumption,
as well as improvement in noise, vibration and harshness (NVH) performance.
This paper shows an experimental study on the fatigue lifetime of high-heat polyamide (Stanyl) gears running in oil at 140°C. Based on previous works (Refs. 1–2), an analysis is made correcting for tooth bending and calculating actual root stresses. A comparison with tensile bar fatigue data for the same materials at 140°C shows that a good correlation exists between gear fatigue data and tensile bar fatigue data. This insight provides a solid basis for gear
designers to design plastic gears using actual material data.