AGMA: American Gear Manufacturers Association

August 11, 2017

Peer-reviewed technical papers to be featured at AGMA’s Fall Technical Meeting

The AGMA Fall Technical Meeting (FTM) is the premier technical forum in the United States to hear and discuss the latest applied research in the gear industry. This year, we will have 27 presentations in five sessions: Efficiency, Lubrication, Noise, and Vibration; Manufacturing, Inspection, and Quality Control; Application, Design, and Rating; Materials and Heat Treatment; and Gear Wear and Failure. We solicited more than 50 peer reviewers from across the globe to assist us in evaluating all papers in a thorough double-blind review process. All technical papers are published by AGMA and are later indexed in Scopus, the largest abstract and citation database of peer-reviewed literature: scientific journals, books, and conference proceedings. FTM attendees will receive PDF copies of all technical papers from the sessions for which they registered.  

Some highlights for this year’s compelling research include a presentation by Dr. Franco Concli from the University of Bozen on CFD Simulation of Power Losses and Lubricant Flows in Gearboxes. His paper describes the application of computational fluid dynamics simulations of power losses and lubricant flows in gearboxes. In addition, we have Mr. Irebert Delgado, a researcher at NASA, who will present his recent test results on The Effectiveness of Shrouding on Reducing Meshed Spur Gear Power Loss. Lastly, Dr. Hermann Stadtfeld of the Gleason Corporation will present Psychoacoustic Methodology for the Noise Reduction of Bevel Gearsets.

In addition to the 24 technical papers being presented, I would like to bring attention to three invited special presentations: Dr. David Talbot from The Ohio State University will be presenting Indexing Error and Dynamic Factors of Spur Gears, focusing on the relationship between dynamic factor, gear quality, and pitch line velocity. Our second invited speaker is Dr. Peter Glaws from TimkenSteel. He will present The Link Between Steel Cleanness Measurement and Gear Life Performance. His talk may assist designers, especially because the need for light weighting and increased power are ever-present in so many of our end-user markets. Our third special guest will be Raymond J. Drago, P.E. of Drive Systems Technology Inc., Mechanical Power Transmission Consultants. Ray is a well-known presence in the gear industry and has been a prominent instructor for AGMA for many years. He will present Reverse Gear Systems Engineering — Why, When & How — Avoiding Pitfalls … and Litigation! This presentation will be relevant to many in our industry.

I would like to thank the reviewers, as well as the AGMA Technical Division Executive Committee, chaired by Todd Praneis from Cotta Transmission Company, LLC, for all its hard work over the last several months in bringing us the high-caliber presentations that have become expected of the AGMA FTM. I encourage all gear industry engineers and technical experts to attend this event. The format allows for a level of interaction between presenters and attendees that is unique to the industry. I always enjoy the Q&A periods at the end of each session, as they are very informative.

This year’s Fall Technical Meeting is October 22–24 in Columbus, Ohio, and immediately precedes Gear Expo 2017, both located at the Greater Columbus Convention Center. FTM attendees also will receive admission to the Gear Expo show floor, where they can see more than 200 exhibitors, special keynote presentations, and so much more. I look forward to seeing you in Columbus this October.

A full list of presentations is available in this AGMA section of Gear Solutions, and presenter bios also can be found on the AGMA website at

Session I

Efficiency, Lubrication, Noise, and Vibration

CFD Simulation of Power Losses and Lubricant Flows in Gearboxes

Dr. Franco Concli, University of Bozen (Italy)

This paper describes the application of Computational Fluid Dynamics simulation of power losses and lubricant flows in gearboxes based on an original global re-meshing technique. This enables accurate predictions in relatively short simulation times, compatible with the industrial design practice. The results of the practical applications used for the validation also are included and discussed in the paper.

Understanding the Dynamic Influences of Gear Oils and Radial Shaft Seals

Joe Walker, Freudenberg-NOK Sealing Technologies and Craig Desrochers, P.E., Klüber Lubrication

Approximately 40 percent of long-term gearbox leakages can be traced back to poor interaction between the Radial Shaft Seal (RSS) and the lubricant. This paper highlights the most critical interactions between the industry’s most commonly used gear oil formulations with emphasis on synthetic oils with Nitrile and Fluoroelastomers. Through an ideal combination of base oil and additives, the demand of life expectancy on the radial shaft seals can be met.

Gear Tooth Strength Analysis of High Pressure Angle Cylindrical Gears

Dr. Alfonso Fuentes, Rochester Institute of Technology

In this paper, the gear tooth strength of high pressure angle gears is studied and compared with that of conventional pressure angle gears. The comparison will be performed regarding contact pressure, contact and bending stresses, loaded function of transmission errors, and comparison of errors of alignment and shift of contact pattern when mounted in similar shafts.

The Effectiveness of Shrouding on Reducing Meshed Spur Gear Power Loss — Test Results

Irebert Delgado, NASA

Reducing power losses to rotorcraft gearboxes, due to windage drag and viscous effects on rotating, meshed gear components would allow gains in areas such as vehicle payload, range, mission type, and fuel consumption. One method used in rotorcraft gearbox design attempts to reduce losses is to use close clearance walls to enclose the gears in both the axial and radial directions. This paper examines using meshed spur gears at four shroud configurations and compares the data to available data.

Session II 

Manufacturing, Inspection, and Quality Control 

Complete Measurement of Gearbox Components

Dr. Christof Gorgels, Klingelnberg

In today’s production environment, a variety of different measurement devices, such as CMMs, gear checkers, form testers, and roughness testers, are used to assess the quality and accuracy of workpieces, many of which require specialized training and environments. This paper describes how a Circular CMM (CCMM) can be integrated into a production environment. The benefits and challenges of the use of a CCMM will be discussed.

The Effect of Asymmetric Cutter Tip Radii on Gear Tooth Root Bending Stress

Dr. Nihat Yildirim, Gaziantep University (Turkey)

The tooth root fillet is where the maximum bending stress concentration region is located during torque transmission via gear pairs. An increase in gear root fillet radius provides a smooth transition from involute to trochoid, increases root critical section thickness, and the moment of inertia against bending of tooth. A 10-percent to 11-percent reduction in bending stress is obtained by using asymmetric cutter tip radii coefficients for two sides of the gear tooth profile with standard center distance and no tooth interference.

Magnetic Barkhausen Noise as an Alternative to Nital Etch for the Detection of Grinding Burn on Gears

James Thomas and Stephen Kendrish, American Stress Technologies, Inc.

Magnetic Barkhausen Noise (MBN) is quantitative, repeatable, and non-destructive. Further, the MBN method is easily automated, thus removing operator influence as seen with Nital Etch, as a variable. Using a sample set of carburized spur gears ground to varying conditions of grinding burn, the MBN method is demonstrated to match or exceed the detection effectiveness of traditional Nital Etch. Residual stress depth distributions measured with X-ray diffraction and electrochemical layer removal are utilized as a quantitative verification method.

Areal Evaluation of Involute Gear Flanks with Three-Dimensional Surface Data

Yue Peng, University of North Carolina at Charlotte

This paper presents the benefits of areal evaluation of gear flanks, mathematical approaches for areal description of involute surface, deviations and modifications, and the characterization of areal data with “3D gear deviation parameters.” Approximation and orthogonal polynomial decomposition methods are applied for surface reconstruction and parameter calculation. Both simulated and measured gear data are analyzed, and comparisons with conventional evaluation results are presented.

Standard Samples for Grinder Burn Etch Testing

Jonathan Crow, Caterpillar Inc.

This paper discusses a unique method for producing a standard sample of an acid etch system that has a consistent amount of thermal damage. Multiple degrees of burn are applied to the sample to ensure that the etch inspection can detect all levels of potential burn on the piece parts. The sample can then be reliably used to test an acid etch system and its method to ensure the proper amount of contrast for threshold levels of thermal damage.

Psychoacoustic Methodology for the Noise Reduction of Bevel Gearsets

Dr. Hermann Stadtfeld, Gleason Corporation

A rather exciting conclusion from the psychoacoustic research is the proposal of a gear transmission graph, which is a hybrid that connects different mathematical functions within the one pitch long contact area and the outside of this area. The results show that the hybrid transmission function dramatically changes the way bevel and hypoid gearsets will be optimized in the future for silent operation.

Session III

Application, Design, and Rating

FE-based Method for Design of Robust Tooth Flank Modifications for Cylindrical and Planetary Gear Stages in Consideration of Manufacturing Tolerances

Julian Theling, M.Sc., Laboratory of Machine Tools and Production Engineering (WZL) of RWTH Aachen, Chair of Machine Tools

The authors present a method to evaluate the quality and stability of flank modifications regarding manufacturing tolerances during the design process, using an FE-based tooth contact analysis. The presented design process provides a method to examine and simulate characteristics of the excitation behavior and durability of a gear pair. This enables the engineer to choose the most robust micro-geometry in terms of quality and stability already in the design process.

Reliability, Lifetime, and Safety Factors
Dr. Stefan Beermann, KISSsoft AG

This paper uses several examples to show the practical differences in using safety factors versus reliabilities. The failure probability of all components for a specific lifetime is calculated to provide the reliability of the whole gearbox as a system of components. This provides the engineer an easier method to compare designs and identify the critical components.

A Comparison of Current AGMA, ISO, and API Gear Rating Methods

John M. Rinaldo, Atlas Copco Comptec, LLC (retired)

There are many different gear rating methods in use today, and they can give substantially different results for any given gear set. This paper will make it easy to understand the choices and the impact the choices have on gearbox design. The eight standards examined are AGMA 2001, AGMA 6011, AGMA 6013, ISO 6336, API 613, API 617, API 672, and API 677. This paper will provide a useful aid to customers who are unsure of the differences between the standards.

Prediction of Dynamic Factors for Helical Gears in a High-Speed Multi-Body Gearbox System

Niranjan Raghuraman, MS and Chad Glinsky, Romax Technology

This paper will analyze the influence of operating speed, torque, system dynamics, and gear micro-geometry on the dynamic factors of a high-speed gearbox. It will show that the dependence of dynamic factor on torque is significant and must not be ignored, and that the presence of system resonance modes increases dynamic factors. The dynamic factors calculated in this study are compared with the dynamic factor values suggested by ISO and AGMA standards.


Indexing Error and Dynamic Factors of Spur Gears

Dr. David Talbot, The Ohio State University

According to ANSI/AGMA 2001-D04, dynamic factor is directly related to gear quality and pitch line velocity. This study uses a dynamic load distribution model in order to assess the validity of this relationship and investigate its physical source. Predictions of both gear root stress and contact stress dynamic factor are considered in the study.

Session IV

Materials and Heat Treatment

Fatigue Performance and Cleanliness of Carburizing Steels for Gears

Lily Kamjou, MSc, Ovako

The cleanliness of steels used for gears is of great importance when looking to improve life of gears or increase loads. In this paper, carburizing steels with the same basic chemical composition, but with a varying cleanliness level, are compared. The investigation showed a good qualitative correlation between the fatigue performance and the inclusion assessment made by ultrasonic evaluation and SEM. The results also show that traditional micro-inclusion rating methods are not sensitive enough to give a good indication of material performance.


The Link Between Steel Cleanness Measurement and Gear Life Performance

Dr. Peter C. Glaws, TimkenSteel

Several current industry material (cleanness) standards were reviewed and found to have poor correlation to gear fatigue performance. Possible reasons for the lack of correlation are discussed. Selected advanced cleanness measurement methods and appropriate resulting metrics are offered as alternatives, providing quantitative data in a format that may be used as tools for gear designers to improve gear reliability and highlight potential for light weighting and increased power.

Predicting Life on Through Hardened Steel Rack and Pinion for Jacking Applications in the Offshore Industry

Dipl. Ing. (FH) Adrian Nowoisky, Oerlikon Fairfield

It is well known in the industry that, according to AGMA and ISO gear calculation methods, the contact stresses in rack and pinion systems for jack up applications exceed the permissible limits by a factor of 3 to 6. However, these applications have been in service without any failures for more than 20 years. This paper will outline the process of the analytical evaluation of a specific design and validate it with systems currently in service.

Four Ways Polyketone Polymers Can Improve Gear Performance

Tim Morefield, Esprix Technologies

Historically, the most commonly specified resins for plastic gears have been acetal (POM), nylon (PA 66) and polyester (PBT), with or without modifiers (PTFE, carbon fiber, glass fiber, silicone, or combinations thereof) to reduce friction and wear. Polyketone offers engineers four distinct advantages relative to other materials in meeting design challenges: 1) superior wear properties, 2) better dimensional control/stability, 3) superior creep rupture performance, and 4) quieter operation.

Effect of Non-Metallic Inclusions on Bending Fatigue Performance in High Strength 4140 Steel

Michael Burnett, TimkenSteel

This paper studies the fatigue performance of three sets of quench and tempered 4140 steel samples, representing three distinctly different inclusion populations. The inclusion populations for each of the sample sets were characterized using both an SEM-based image analysis system, primarily for the micro-inclusions, and a high-resolution UT system for the macro-inclusions. The sample sets also were evaluated using both longitudinal and transverse specimens in all the bending fatigue tests. The results of these tests will be presented.

Sensitivity Study of Press Quench Process and Concept of Tooling Design for Reduced Distortion by Modeling

Dr. Zhichao (Charlie) Li, DANTE Solutions Inc.

The press quench process includes parameters such as heating rate, austenitization temperature, applied load type, load amount, load locations from the tooling, friction between the tooling and the gear, and the quench rate. All these factors can lead to inconsistent distortion, especially for the radial size of thin-wall gears. In this paper, the effects of several critical factors on the dimensional inconsistency and tooling design are analyzed by heat treatment modeling software.

Session V

Gear Wear and Failure

Influences of the Residual Stress Condition on the Load Carrying Capacity of Case Hardened Gears

Dipl.-Ing. Christian Güntner, Gear Research Center (FZG) — Technical University of Munich

Compressive residual stresses, such as those generated by shot peening, result in an increased tooth root bending strength. The author’s investigations show that shot peening can increase the load carrying capacity of case hardened gears significantly. Correlations between the residual stress state and the load carrying capacity limits were determined. This paper will give an overview of the main results of different investigations and discuss influences of the residual stress condition on different failure modes of case hardened gears.

Calculation of Tooth Flank Fracture Load Capacity — Practical Applicability and Main Influence Parameters

Dipl.-Ing. Michael Hein, Gear Research Center (FZG) — Technical University of Munich

Due to improved material qualities, new surface finishing methods, and increased heat-treatment process reliability, flank surface damages, such as pitting or micropitting, can increasingly be prevented in a reliable manner. At the same time, this may result in an increase of unexpected flank damages such as tooth flank fracture. A computer-aided calculation of the risk of tooth flank fracture damages will be presented.

Full Contact Analysis Versus Standard Load Capacity Calculation for Cylindrical Gears

Dr.-Ing. Michael Otto, Gear Research Center (FZG) — Technical University of Munich

In this paper, local tooth contact analysis and standard calculation are used to determine the load capacity for the failure modes pitting, tooth root breakage, micropitting, and tooth flank breakage. Analogies and differences between both the local and the standard approaches are shown. The example presented demonstrates a valid possibility to optimize the gear design by using local tooth contact analysis while satisfying the requirement of documenting the load carrying capacity by standard calculations.

The Influence of a Grinding Notch on the Gear Bending Strength Rating

Dr. Ulrich Kissling, KISSsoft AG

To achieve the requested quality, most gears today are ground. If the gear is premanufactured with a tool without protuberance, then at the position where the grinding tool retracts from the flank, a grinding notch in the tooth root area is produced. A review of the formulas to calculate the effects of the grinding notch is necessary. A 3D-FEM analysis that was used to deduce an improved formula will be presented.

Gear Failure Analysis and Lessons Learned Under Unanticipated Loading Conditions

Dr. Anngwo Wang, MOOG Inc. Aircraft Group

Lessons about gear failure can be learned in the development phases under unanticipated design or manufacturing errors or unaccounted loading and operating conditions. This paper will study 10 such failure cases. Lessons learned are presented and act as reminders not to overlook lightly loaded gears, gears with deflection, or mounting problems and unexpected issues from manufacturing errors.


Reverse Gear System Engineering — Why, When & How — (Avoiding Pitfalls … and Litigation!)

Raymond J. Drago, P. E., Drive Systems Technology, Inc. Mechanical Power Transmission Consultants

Reverse engineering a gear system is a not too unusual task, thus it is easy to become complacent. Failure to fully follow best practices can result in, in the worst cases, very expensive, time consuming, and reputation damaging litigation. This presentation will rely on the experience of being an expert witness to provide information to aid the reverse engineering of a project as completely as possible.