TOPICS CALENDAR BUYER'S GUIDE AGMA

Micropitting

TECHNICAL ARTICLES | 2024-12-12

Experimental and Analytical Study of the Effect of Shot Peening on Gear Micropitting and Contact Fatigue Failure

This study aims to investigate the effect of this identified type of shot peening on the micropitting resistance of the gear tooth flanks and the macropitting resistance and to compare the experimental results with the calculation results based on standard methods.

TECHNICAL ARTICLES | 2023-06-20

Results of ISO/TS 6336-22 Evaluating Full Contact Zone

This investigation reviews calculations using ISO/TS 6336-22 Method A and Method B, comparing the calculations against field results. Extensive reviews were made of geometry, surface roughness, load conditions, and lubricant conditions to best understand the influences of micropitting on each example and the applicability of the calculations to the results.

TECHNICAL ARTICLES | 2022-08-30

Nomenclature of Micropitting

An overview of the incubation, nucleation and growth, and morphology of this common failure mode, along with the appropriate terminology to describe it.

TECH TALK | 2022-05-19

Two New AGMA Publications

AGMA is happy to announce the publication of two new documents: AGMA 925-B22, Effect of Tribology and Lubrication on Gear Surface Distress, written by a subcommittee of the AGMA Helical Gear Rating Committee, and, AGMA 943-A22, Tolerances for Spur and Helical Racks, written by the AGMA Gear Accuracy Committee.

TECHNICAL ARTICLES | 2021-03-01

Case Study of ISO/TS 6336-22 Micropitting Calculation

Micropitting per ISO standard explained.

GEAR TALK WITH CHUCK | 2019-10-10

That Blank Sheet of Paper

Does nature hate a vacuum more than a designer hates a blank sheet of paper? We will never know for sure because nature is too busy to write a blog...

GEAR TALK WITH CHUCK | 2018-04-12

Moderation Instead of Modification

Few designers would feel comfortable with a face to pinion pitch diameter ratio of 2.00 anymore. Some still prefer to select face width by face con...

VOICES | 2016-03-01

Critique of the ISO 15144-1 Method to Predict the Risk of Micropitting

There exists an ongoing, urgent need for a rating method to assess micropitting risk, as AGMA considers it a "a very significant failure mode for rolling element bearings and gear teeth - especially in gearbox applications such as wind turbines."

TECHNICAL ARTICLES | 2015-06-01

Optimal Modifications on Helical Gears for Good Load Distribution and Minimal Wear

Helical gear teeth are affected by cratering wear — particularly in the regions of low oil film thicknesses, high flank pressures and high sliding speeds. The greatest wear occurs on the pinion — in the area of negative specific sliding. Here the tooth tip radius of the driven gear makes contact with the flank of the driving gear with maximum sliding speed and pressure.

TECHNICAL ARTICLES | 2014-09-01

Micropitting of Large Gearboxes: Influence of Geometry and Operating Conditions

The focus of the following presentation is two-fold: 1) on tests of new geometric variants; and 2) on to-date, non-investigated operating (environmental) conditions. By variation of non-investigated eometric parameters and operation conditions the understanding of micropitting formation is improved. Thereby it is essential to ensure existent calculation methods and match them to results of the comparison between large gearbox tests and standard gearbox test runs to allow a safe forecast of wear due to micropitting in the future.

TECHNICAL ARTICLES | 2012-11-01

Morphology of Micropitting

Understanding the morphology of micropitting is critical in determining the root cause of failure. Examples of micropitting in gears and rolling-element bearings are presented to illustrate morphological variations that can occur in practice.

TECHNICAL ARTICLES | 2012-08-01

Case Study Involving Surface Durability and Improved Surface Finish

Gear tooth wear and micropitting are very difficult phenomena to predict analytically. The failure mode of micropitting is closely correlated to the lambda ratio. Micropitting can be the limiting design parameter for long-term durability. Also, the failure mode of micropitting can progress to wear or macropitting, and then go on to manifest more severe failure modes, such as bending. The results of a gearbox test and manufacturing process development program will be presented to evaluate super-finishing and its impact on micropitting.

TECHNICAL ARTICLES | 2012-05-01

Application of the First International Calculation Method for Micropitting

The first edition of the international calculation method for micropitting—ISO TR 15144–1:2010—was just published last December. It is the first and only official, international calculation method established for dealing with micropitting. Years ago, AGMA published a method for the calculation of oil film thickness containing some comments about micropitting, and the German FVA published a calculation method based on intensive research results. The FVA and the AGMA methods are close to the ISO TR, but the calculation of micropitting safety factors is new.

VOICES | 2011-11-01

A Proposed Life Calculation for Micropitting

If you make hardened gears and have not seen any micropitting, then you haven’t looked closely enough. Micropitting is one of the modes of failure that has more recently become of concern to gear designers and manufacturers. Micropitting in itself is not necessarily a problem, but it can lead to noise and sometimes other more serious forms of failure. Predicting when this will occur is the challenge facing designers.

TECHNICAL ARTICLES | 2011-05-01

Micropitting of Big Gearboxes: Influence of Flank Modification and Surface Roughness

Most research on micropitting is done on small-sized gears. This article examines whether those results are also applicable to larger gears.

TECHNICAL ARTICLES | 2010-06-01

The Anatomy of a Micropitting-Induced Tooth Fracture Failure

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.

TECHNICAL ARTICLES | 2009-03-01

The Effect of Superfinishing on Gear Micropitting

Results from the Technical University of Munich were presented in a previous technical article (see Ref. 4). This paper presents the results of Ruhr University Bochum. Both research groups concluded that superfinishing is one of the most powerful technologies for significantly increasing the load-carrying capacity of gear flanks.

TECHNICAL ARTICLES | 2005-05-01

The Influence of Additive Chemistry on Micropitting

This article discusses the potential effects observed for different antiwear and EP chemistry on the micropitting of cylindrical gears.

TECHNICAL ARTICLES | 2004-07-01

Influence of Coatings and Surface Improvements on the Lifetime of Gears

Surface coatings or finishing processes are the future technologies for improving the load carrying capacity of case hardened gears. With the help of basic tests, the influence of different coatings and finishing processes on efficiency and resistance to wear, scuffing, micropitting, and macropitting is examined.

TECHNICAL ARTICLES | 2000-09-01

Gear Oil Micropitting Evaluation

During the last decade, industrial gear manufacturers, particularly in Europe, began to require documentation of micropitting performance before approving a gear oil for use in their equipment. The development of micropitting resistant lubricants has been limited both by a lack of understanding of the mechanism by which certain lubricant chemistry promotes micropitting and by a lack of readily available testing for evaluation of the micropitting resistance of lubricants. This paper reports results of two types of testing: (1) the use of a roller disk machine to conduct small scale laboratory studies of the effects of individual additives and combinations of additives on micropitting and (2) a helical gear test used to study micropitting performance of formulated gear oils.

TECHNICAL ARTICLES | 1990-03-01

Influence of Lubrication on Pitting and Micropitting Resistance of Gears

Pitting and micropitting resistance of case-carburized gears depends on lubricants and lubrication conditions. Pitting is a form of fatigue damage. On this account a short time test was developed. The test procedure is described. The "pitting test" was developed as a short time test to examine the influence of lubricants on micropitting. Test results showing the influence of case-carburized gears on pitting and micropitting are presented.