Wear

TECHNICAL ARTICLES | 2024-02-16

Morphology of Wear on Tapered-Roller Bearing Roller Ends and Thrust Ribs

This report investigates the wear morphology on the large end of tapered rollers and the inner ring's large end rib on a planet carrier TRB from a multi-megawatt wind turbine gearbox. The literature on abrasive wear has many classifications, including 2-body abrasion, 3-body abrasion, scratches, grooving abrasion, rolling abrasion, cutting abrasion, and plowing abrasion. For this analysis, we have selected grooving abrasion, a common problem in wind turbine gearboxes and a prominent failure mode on many bearings, particularly planetary carrier bearings and planet bearings. Grooving abrasion is frequently observed on cylindrical roller bearings (CRB) and tapered roller bearings (TRB). Fitzsimmons and Clevenger conducted tests on roller end/rib wear for TRBs with contaminated gear oil, and they provided an excellent explanation of the mechanism.

TECH TALK | 2023-04-14

Fail Better

This month's issue of Gear Technology covers a subject engineers love to learn about from others but hate to learn about through firsthand experience: gear failure. In a broad sense, all engineering is concerned with failure. Eventually, all parts fail, so engineers need to determine the limits of their design and ensure that it will meet the requirements of the particular application.

PRODUCT NEWS | 2022-08-31

Exact Metrology Exhibits at Coordinate Metrology Society Conference

Exact Metrology recently exhibited at the Coordinate Metrology Society Conference (CMSC) with their sister division, OASIS Alignment Services: A Division of In-Place Machining Company.

INDUSTRY NEWS | 2022-08-03

Capture 3D Joins OMIC R&D

The Oregon Manufacturing Innovation Center Research and Development (OMIC R&D) recently welcomed Capture 3D, a Zeiss company, as a member of the collaboration, now at 41 members. Headquartered in Santa Ana, California, Capture 3D is a leader in innovative optical 3D metrology solutions, including accurate blue light 3D scanners, precision photogrammetry systems, comprehensive inspection software, and high-tech automated inspection systems.

TECHNICAL ARTICLES | 2022-05-19

Defining the Tooth Flank Temperature in High-Speed Gears

The objective of this paper is to improve the methodology for determining the tooth flank temperature. Two methods are proposed for assessing scuffing risk when applying AGMA 925 for high-speed gears. Both methods provide similar results.

GEAR TALK WITH CHUCK | 2020-10-14

Closing the Gap

We left the gear tribe arguing over how to solve the problems that were cropping up with the new-fangled double helical or herringbone designs. Fas...

TECHNICAL ARTICLES | 2020-01-01

Grinding Wheel Wear, Dressing, Tip Advance and Work Phase Angle Adjustment after Corrections

Are there rules to aid in grinding process optimization?

TECHNICAL ARTICLES | 2019-11-01

A Comparative Study of Polymer Gears Made of Five Materials

The wear behavior of polymer gears made of five different materials has been investigated using an existing polymer gear test rig. Step loading tests at a constant speed of 1,000 rpm were performed. Significant differences in failure modes and performance have been observed for the five polymer gear materials for gear engagements of gears, with the same material as each other.

GEAR TALK WITH CHUCK | 2018-10-04

Repairing Gears

Deadlines and budgets do not always allow for “first class” gearbox rebuilds. The challenge for rebuild shops is to find the fastest and most econo...

TECHNICAL ARTICLES | 2018-01-01

Analysis of the Influence of the Working Angles on the Tool Wear in Gear Hobbing

A calculation method is developed to estimate tool wear on hobs.

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 | 2015-01-01

On the Correlation of Specific Film Thickness and Gear Pitting Life

The effect of the lubrication regime on gear performance has been recognized, qualitatively, for decades. Often the lubrication regime is characterized by the specific film thickness defined as the ratio of lubricant film thickness to the composite surface roughness. It can be difficult to combine results of studies to create a cohesive and comprehensive data set. In this work gear surface fatigue lives for a wide range of specific film values were studied using tests done with common rigs, speeds, lubricant temperatures, and test procedures.

ASK THE EXPERT | 2014-08-01

Additives: Anti-Wear vs Anti-Scuff

A reader asks: While I have read a reasonable amount of the literature on the pros and cons of anti-wear and anti-scuff additives, I find that the more I read, the more confused I become. I could use some clarity in my life.

ASK THE EXPERT | 2013-06-01

Worn Gear Contact Analysis

How does one perform a contact analysis for worn gears? Our expert responds.

TECHNICAL ARTICLES | 2011-09-01

Size and Material Influence on the Tooth Root, Pitting, Scuffing and Wear Load-Carrying Capacity of Fine-Module Gears

In this study, limiting values for the load-carrying-capacity of fine-module gears within the module range 0.3–1.0 mm were determined and evaluated by comprehensive, experimental investigations that employed technical, manufacturing and material influence parameters.

TECHNICAL ARTICLES | 2011-01-01

Point-Surface-Origin Macropitting Caused by Geometric Stress Concentration

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.

TECHNICAL ARTICLES | 2010-05-01

Software-Based Process Design in Gear Finish Hobbing

In this paper, the potential for geometrical cutting simulations - via penetration calculation to analyze and predict tool wear as well as to prolong tool life - is shown by means of gear finish hobbing. Typical profile angle deviations that occur with increasing tool wear are discussed. Finally, an approach is presented here to attain improved profile accuracy over the whole tool life of the finishing hob.

TECHNICAL ARTICLES | 2009-01-01

Effects of Gear Surface Parameters on Flank Wear

Non-uniform gear wear changes gear topology and affects the noise performance of a hypoid gear set. The aggregate results under certain vehicle driving conditions could potentially result in unacceptable vehicle noise performance in a short period of time. This paper presents the effects of gear surface parameters on gear wear and the measurement/testing methods used to quantify the flank wear in laboratory tests.

TECHNICAL ARTICLES | 2007-09-01

Tooth-Bending Effects in Plastic Spur Gears

This paper describes the investigation of a steel-and-plastic gear transmission and presents a new hypothesis on the governing mechanism in the wear of plastic 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 | 2001-03-01

Austempered Gears and Shafts: Tough Solutions

Austempered irons and steels offer the design engineer alternatives to conventional material/process combinations. Depending on the material and the application, austempering may provide the producers of gear and shafts with the following benefits: ease of manufacturing, increased bending and/or contact fatigue strength, better wear resistance or enhanced dampening characteristics resulting in lower noise. Austempered materials have been used to improve the performance of gears and shafts in many applications in a wide range of industries.

FEATURE ARTICLES | 2000-07-01

Ferrography: A Noninvasive Method to Inspect Your Gears

Would you like to be able to see the condition of the gears in your transmissions without having to open the box and physically examine them? There is a way, and not too many people know about it. It's called Wear Particle Analysis, or ferrography, and it is just starting to get noticed.

TECHNICAL ARTICLES | 1998-05-01

Relationship Between Wear and Pitting Phenomena in Worm Gears

Worm gears display unique behavior of surfaces because of the presence of wear phenomena in addition to contact pressure phenomena.

TECHNICAL ARTICLES | 1996-09-01

Gear Wear Caused By Contaminated Oils

The diagnosis and prevention of gear tooth and bearing wear requires the discovery and understanding of the particular mechanism of wear, which in turn indicates the best method of prevention. Because a gearbox is a tribologically dependent mechanism, some understanding of gear and bearing tribology is essential for this process. Tribology is the general term for the study and practice of lubrication, friction and wear. If tribology is neglected or considered insignificant, poor reliability and short life will result.

INDUSTRY NEWS | 1993-01-01

Classification of Types of Gear Tooth Wear - Part II

The first part of this article included abrasive wear with two bodies, streaks and scoring, polishing, and hot and cold scuffing. This part will deal with three-body wear, scratches or grooves, and interference wear. Normal, moderate, and excessive wear will be defined, and a descriptive chart will be presented.

TECHNICAL ARTICLES | 1992-11-01

Classification of Types of Gear Tooth Wear - Part I

The phenomena of deterioration of surfaces are generally very complex and depend on numerous conditions which include the operating conditions, the type of load applied, the relative speeds of surfaces in contact, the temperature, lubrication, surfaces hardness and roughness, and the compatibility and nature of materials.

TECHNICAL ARTICLES | 1992-07-01

Comparing Surface Failure Modes in Bearings and Gears: Appearances vs. Mechanisms

In the 1960's and early 1970's, considerable work was done to identify the various modes of damage that ended the lives of rolling element bearings. A simple summary of all the damage modes that could lead to failure is given in Table 1. In bearing applications that have insufficient or improper lubricant, or have contaminants (water, solid particles) or poor sealing, failure, such as excessive wear or vibration or corrosion, may occur, rather than contact fatigue. Usually other components in the overall system besides bearings also suffer. Over the years, builders of transmissions, axles, and gear boxes that comprise such systems have understood the need to improve the operating environment within such units, so that some system life improvements have taken place.

TECHNICAL ARTICLES | 1991-11-01

A Rational Procedure for Designing Minimum-Weight Gears

A simple, closed-form procedure is presented for designing minimum-weight spur and helical gearsets. The procedure includes methods for optimizing addendum modification for maximum pitting and wear resistance, bending strength, or scuffing resistance.

INDUSTRY NEWS | 1991-03-01

Our Experts Discuss...

Question: I have just become involved with the inspection of gears in a production operation and wonder why the procedure specifies that four involute checks must be made on each side of the tooth of the gear being produced, where one tooth is checked and charted in each quadrant of the gear. Why is this done? These particular gears are checked in the pre-shaved, finish-shaved, and the after-heat-treat condition, so a lot of profile checking must be done.

TECHNICAL ARTICLES | 1985-11-01

Calculation of Slow Speed Wear of Lubricated Gears

On gear drives running with pitch line velocities below 0.5 m/s so called slow speed wear is often observed. To solve some problems, extensive laboratory test work was started 10 years ago. A total of circ. 300,000 h running time on FZG back-to-back test rigs have been run in this speed range.