In-person Fall Technical Meeting to highlight cutting-edge, peer-reviewed research

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After more than a year of disruptions and inconsistency, now is a vital time for you and your company to stay up to date on the latest gear research and network with your peers.  AGMA is moving full-steam ahead to safely give you this opportunity at our annual face-to-face Fall Technical Meeting November 2-3 in Chicago, Illinois. Over two days, our single-track conference showcases 24 presentations of cutting-edge, peer-reviewed research in the gear industry. Formal technical questions can be posed to the presenters during question-and-answer sessions, while more relaxed networking can take place at breaks between presenters or scheduled networking breakfasts, lunches, and dinners. 

As a consequence of continued COVID travel restrictions, some presentations will be pre-recorded with the presenter making themselves available remotely for a live Q&A. These pre-recorded presentations will be made available to attendees a week ahead of the meeting to watch at their leisure, which is the same time as the peer-reviewed papers are distributed. Your time is valuable, so because of having some pre-recorded presentations, we have compressed the schedule to fit all five sessions into two days. Only live, in-person presentations will be given on site, while we expect attendees to watch the pre-recorded presentations ahead of time.

Presenters are the leaders in their fields from Europe and the U.S. representing both academia and industry. On Tuesday, November 2, we kick off the meeting with the Gear Wear and Failure session. Attendees can look forward to thorough discussions on non-conventional root profiles for the reduction of bending stresses, a method for 100 percent inspection of gears’ residual stresses, transient friction and wear simulation of worm gears during run-in, and a new testing procedure for tooth flank fracture.

After lunch, Tuesday’s second session covers Application, Design, and Rating. The presentations of this session dive deep into the application of rating standards and showcase some interesting real-world examples. Those curious about the latest design standards will be interested to see the presentations that discuss ISO 6336 parts 3 and 6. Bevel gear designers will be interested in the bevel gear strength rating presentation and the presentation on a new double differential design for electric vehicles.

The second and final day of the meeting, Wednesday, November 3, has three sessions. The day begins with the third session of the meeting, Efficiency, Lubrication, Noise, and Vibration. Three presentations cover new design methods: one for an improved method to determine tooth flank temperature in high speed gears, one covering an algorithm-based optimization of gear mesh efficiency, and one covering NVH analysis for a rear axle drive. One will present a new phyllosilicate-based surface treatment, and the final one of the session highlights a new back-to-back test rig for ultra-high cycle fatigue testing.

The fourth session of the meeting, Manufacturing, Inspection, and Quality Control, will be most interesting to attendees that know what they want to make but are looking to answer the question of how to make it. The session includes two presentations on application of power skiving, two presentations on improving process efficiency and quality with data (one a database of cutting tools and the other inspection data), and one presentation showing how a 5-axis CNC machine was used to manufacture helical gears with crowning.

The fifth and final session of the meeting is the Materials and Heat Treatment session. Whole system designers will be interested in the presentation on the effect of steel microstructure on bearing performance. We then have two presentations in the session showcasing improved heat-treating methods, and the final presentation investigates the effect of high-cleanliness steels on the tooth root capacity of case-hardened, shot-peened gears.

AGMA is proud to be a constant during this time of much uncertainty — even though there is a lot going on around us, innovation cannot stop and the FTM won’t either. For more information and to register visit www.agma.org/events/2021-fall-technical-meeting-ftm/   or contact AGMA at 703-684-0211 or tech@agma.org.

2021 Fall Technical Meeting: A Preview

Session 1
Gear Wear and Failure

Tuesday, November 2, 2021

Investigation of the Effect of Application of Non-Conventional Root Profiles for Reduction of Bending Stresses in Helical Gear Drives

Speaker: Alfonso Fuentes-Aznar | Rochester Institute of Technology | USA

Abstract: Studies of non-conventional root profiles have mainly used finite element models in which the load is applied at the highest point of single tooth contact. The adjacent pair of teeth, when they carry part of the load, cause compressive stresses on the root area. This study will provide the variation of the alternate and mean range normal stresses on the root surface in longitudinal direction of the gear teeth for tooth root profiles based on Hermite, elliptical, and Bézier curves and their comparison in terms of the mentioned stresses with those obtained for conventional root profiles. Such variation will be obtained for two cycles of meshing by considering finite element models with five pairs of teeth, so that the effect of load sharing between adjacent pairs of teeth will be considered.

Technological Advances for the 100% Inspection of Gears’ Residual Stress Measurement Techniques

Speaker: Navrose Handa | Sinto America | USA

Abstract: Compressive residual stress, which is induced by shot peening, and by heat treatment can increase tooth root bending stress, which in turn improves the load carrying capacity of gears. However, over-peening can result in micropitting and subsurface initiated cracks. Eddy current inspection and X-ray residual stress analysis are established methods in the non-destructive testing industry that can measure residual stress. This paper discusses several sources of defects during manufacturing processes that the tests can detect and explains a method for 100 percent inspection of gears in the manufacturing environment.

Transient Friction and Wear Simulation of Worm Gears During Running-In

Speaker: Kevin Daubach | Technical University of Kaiserslautern – Institute of Machine Elements, Gears, and Transmissions | Germany

Abstract: The load capacity of worm gears strongly depends on the size of the contact pattern. Worm wheels are often manufactured by using an oversized hob, which results in a relatively small initial contact pattern. Wear on the worm wheel with a softer material during the running-in process increases the contact pattern and thereby the load capacity. For the investigation of the continuous change of friction in the tooth contact during that process, a tribological simulation program is used. With a simplified model of the EHL-tooth contact, boundary and fluid friction are locally calculated and the tooth efficiency evaluated. The included wear model associates abrasive wear with solid friction energy occurring in the tooth contact and allows a time-dependent simulation by considering the wear-modified tooth flank in the tribological calculation. The simulative results are then compared with experimental wear studies on the running-in of worm gears.

Tooth Flank Fracture – Design Process for a New Test Gearing and First Test Results

Speaker: Daniel Müller | Technical University of Munich, Gear Research Centre (FZG) | Germany

Abstract: Tooth flank fracture (TFF) is a gear fatigue failure mode different from tooth root breakage and pitting. So far, only test gears for TFF with a center distance of 200 mm are commonly used. In this paper, experiment results from test gears with a center distance of 200 mm were used along with ISO/TS 6336-4 to design a smaller sized test gearing with a center distance of 91.5 mm. The test gear pairing is tested with a back-to-back test rig and initial test results are shown and discussed. In addition, results of further investigations regarding microstructure, hardness, and residual stresses are presented.

Session 2
Application Design & Rating

Tuesday, November 2, 2021

Effect of the ISO 6336 3:2019 Standard Update on the Specified Load Carrying Capacity Against Tooth Root Breakage of Involute Gears

Speaker: Stefan Sendlbeck | Technical University of Munich, Gear Research Centre (FZG) | Germany

Abstract: This paper provides a detailed summary of the key changes in ISO 6336-3:2019, outlines their overall effects on the basis of a calculation study, and presents a comparison of the results to the previous version of the standard, ISO 6336-3:2006. To investigate these changes and their overall effect, we vary the contact ratio by using gears with different transverse contact ratios and overlap ratios as a basis for computing the specifications of the standard. In addition, by simultaneously varying the transmission ratio and the tool tip radius, we investigate the effect on the calculation of internal gears with different tooth root geometries.

Double Differential for Electric Vehicle and Hybrid Transmissions – Sophisticated Simplicity

Speaker: Dr. Hermann Stadtfeld/Haris Ligata | Gleason Corporation | USA

Abstract: A double differential is a design with a second differential unit around a first center unit. Both units have the same axes around which they rotate with different speeds. This paper presents double differentials’ potential as ultrahigh reduction speed reducers, their suitability for high input speeds, their very high-power density, and their good efficiency results, which qualifies this new transmission type very well for the speed reduction and transmission in electric vehicles and hybrids.

Bevel Gear Strength Rating – the Appropriate Combination of FE with Rating Standards

Speaker: Juerg Langhart | KISSsoft AG | Switzerland

Abstract: The design process for bevel gearsets is challenging. Many rating methods are available that have their specific possibilities but also may give different results in stresses or safety factors. The engineer is uncertain which method to trust and how to combine the various tools to achieve the most reliable result. This paper compares the various methods of ISO and AGMA standards, as well as the loaded contact analysis, using a practical sample. A combined approach to calculate the stresses is then developed, which significantly increases the accuracy in the rating of bevel gears.

Use of Duty Cycles or Measured Torque-Time Data
with AGMA Ratings

Speaker: Ulrich Kissling | KISSsoft AG | Switzerland

Abstract: In this paper, the application of torque spectra in AGMA rating procedures is described. Furthermore, a procedure to convert measured torque data into a torque spectrum according to the definition in ISO 6336-6 is described. This task is simple if the torque is always positive but quite complicated when negative torque sequences also happen. For complex loads, where the torque has both positive and negative signs, the “Rainflow method” (ISO 12110-2) should be applied. To comply with the rules of AGMA ratings, a reverse loading factor must be used to modify the admitted sat values for tooth bending. In ISO, this factor is the mean stress influence factor YM. In the final part of this paper, some practical applications presented.

Session 3
Efficiency, Lubrication, Noise, and Vibration

Wednesday, November 3, 2021

Defining the Tooth Flank Temperature in High Speed Gears

Speaker: John Amendola Sr. | Artec Machine Systems | USA

Abstract: In defining total contact temperature, the tooth flank temperature is as significant in the calculation as the flash temperature. Previous research revealed that the applied ksump multiplier value for applications with spray lubrication should be > 1.2 for high speed gears when calculating a tooth flank temperature. However, further investigation suggests variable values of ksump are required to accurately calculate the tooth flank temperature relative to pitch line velocity. Referenced documents, with supporting comprehensive test data and testing results of high-speed gears, both indicate a higher range of tooth body temperatures increasing with pitch line velocity. This paper improves the methodology for determining the tooth flank temperature. Two methods are proposed for assessing scuffing risk when applying AGMA 925 for high speed gears.

Algorithm-based Optimization of Gear Mesh Efficiency in Stepped Planetary Gear Stages for Electric Vehicles

Speaker: Christian Westphal | Laboratory for Machine Tools and Production Engineering (WZL), Chair of Machine Tools, RWTH Aachen University | Germany

Abstract: In this paper, a method is presented for an automated optimization of the macro geometry of stepped planetary gear stages to improve the gear mesh efficiency, which takes into account assembly restrictions. An FE-based tooth contact analysis is used to evaluate the design objectives acoustics, load carrying capacity, and efficiency. The influence of the weighting of the design objectives on the gear design is shown. The results of various optimizations are compared, and an efficiency-optimized variant is selected for a specific application. With the method presented in this paper, it is possible to design and optimize the macro geometry of stepped planetary gear stages for a specific application with an FE-based tooth contact analysis.

Particle-based Phyllosilicate-Additive for Efficiency Improvement and Surface Protection

Speaker: Scott Gardiner | Croda | USA

Abstract: This paper presents an innovative phyllosilicate-based surface treatment additive technology for gears and bearings. The particles with a platelet shape use lubricants as a carrier and build through their adsorption a protective phyllosilicate-based coating on the surface. The modified surface has a significantly lower surface roughness, which ensures a better load distribution and lower local pressure. Additionally, due to the special layered material structure, the particles can be sheared in the tribological contact, which leads to a significant reduction in friction. All in all, when applying the products, treated systems can run better with reduced friction, wear, surface roughness, and temperature. These effects lead to higher efficiency and longer lifetime.

Design and Simulation of a Back-to-Back Test Rig for Ultra High Cycle Fatigue Testing of Gears Under Fully Reversed Load

Speaker: Johannes Loevenich | Laboratory for Machine Tools and Production Engineering RWTH Aachen University | Germany

Abstract: Aviation planetary gearboxes can experience high dynamics over 12,000 rpm combined with a high number of load cycles under fully reversed load, N > 108. This makes load capacity tests with standardized back-to-back test rigs uneconomical or even impossible due to the extremely long testing times. To enable the Ultra High Cycle Fatigue (UHCF) testing, a high-speed back-to-back test rig was developed. In addition to the design, particular focus is placed on the thermal and dynamic simulation of the test rig. The behavior of the test rig components in the operating temperature ranges from room temperature to T > 100°C is investigated regarding the thermal expansion and the resulting tolerances. For dynamic simulation special focus is placed on the tooth mesh frequency and the natural frequencies of the components. As a result, the operating points for testing are defined, and the operational safety is ensured. In addition, to provide a basis for the investigation of aircraft transmissions, the paper provides fundamental ideas for the design of high-speed back-to-back gear test rigs.

NVH Analysis of an Axle Drive with Bevel Gearset

Speaker: Davide Marano | GearLab | Italy

Abstract: This paper presents the theoretical calculation of the gearbox frequency spectrum, including the explanation of sidebands and the so-called ghost frequencies. A constrained modal analysis of the system on mountings is performed to calculate its natural frequencies. The rear axle drive is modeled as a full flexible multibody system, and the forced response is calculated in time domain for a linear speed ramp of the electric motor. The effect of pinion offset of the hypoid gears on the dynamics of the system is investigated: a comparison of accelerations on virtual control points defined on the transmission housing is shown, and the housing equivalent radiated power (ERP) is calculated for all the tested configurations.

Session 4
Manufacturing, Inspection, and Quality Control

Wednesday, November 3, 2021

Integrated Optimization of Gear Design and Manufacturing

Speaker: Massimiliano Turci | Studio Tecnico Turci | Italy

Abstract: Standard cutting tools are used to reduce cost and keep available the interchange of suppliers. This paper presents design optimization techniques adopted in different companies, then presents business scenarios where production has been equipped with a software for a semi-automatic selection of hobbing and pinion type tools, starting from the main-geometry of the gear. In particular, it will look at the case where a paper database of more than 10,000 hobbing tools with different dimensioning modes has been harmonized into a single computer database. The software allows the search for a hobbing tool even with “modified rolling.” Finally, for companies that have both design and manufacturing departments, it will present a design optimization with a list of cutting tools as the main boundary.

Investigation of Gear Surface Topomorphy and Deviations in Gear Power Skiving Through Advanced CAD Modeling Based Simulation

Speaker: Nikolaos Tapoglou | International Hellenic University, Department of Industrial Engineering and Management | Greece

Abstract: The understanding of the loads applied in the cutting tool and the gear as well as the final characteristics of the gear machined through power skiving is of key importance in the optimization of the cutting process. This paper presents a novel CAD-based simulation package that is able to simulate the cutting process and predict in a reliable fashion the cutting forces and the resulting gear topomorphy. The results of the model have been experimentally validated through analytical and experimental results from literature. In-depth investigation in the quality of gears produced is presented as part of this study with a focus in the influence of key process parameters in the resulting gear quality. Through this study, a series of process maps can be drawn that assists in the selection of the most productive parameters for machining involute gears.

Power Skiving – A Step Changing Manufacturing Process Applicable to Multifunctional 5-Axis Machine Tools

Speaker: Ben Cook | Advanced Manufacturing Research Centre, The University of Sheffield | United Kingdom

Abstract: Power skiving offers great opportunities for production with step-changing productivity, particularly for internal gears, while offering high-quality finishing capabilities and being applicable on a 5-axis machine tool with its inherent flexibility and multi-functionality. The Advanced Manufacturing Research Centre’s focus is to develop and quantify the capabilities and publicize this for the benefit of industry. Software models have been developed to predict cutting forces and establish cutting parameters for new geometries in order to expedite the process development. A range of cutting parameter strategies has been employed to establish an optimal approach for enhanced quality and reduced vibration. Cutting tool life also has been established for a range of geometries and parameter sets with a view to quantifying the commercial viability of the process.

An Accurate Method of Generating Tool Paths for Helical Gears with Crowning Modifications Using a 5-Axis CNC Machine

Speaker: Luis Vega | The University of North Carolina at Charlotte | USA

Abstract: This paper proposes an accurate method to manufacture helical gears with crowning modifications using a standard 5-axis CNC machine tool. As gear roughing process, milling using an end mill was selected, where the tool movement follows the generation principle. By incorporating crowning modifications into the tool’s movement, an accurate tool path generation method was developed. A CAM software written in C++ was developed to generate, visualize, and simulate the tool path for machining the gear according to user-defined parameters. The machining results confirmed that the proposed method is feasible.

Holistic Evaluation of Involute Gears

Speaker: Anita Przyklenk | Physikalisch-Technische Bundesanstalt (PTB) (National Metrology Institute of Germany) | Germany

Abstract: Modern coordinate metrology systems such as CMMs or GMMs gather holistic information about dimension and surface form of gears with high point density and accuracy in a short time. This paper introduces a 3D evaluation strategy focused on describing the holistic evaluation of synthetic and measured data. Considering the complete gear surface in one common model allows us to a) determine deviations along the whole flank, b) obtain more relevant and stable geometrical fitting parameters, c) find correlations between gear measurements, and d) properly understand possible manufacturing errors. The paper also shows how holistic evaluated data was used to investigate gear surface harmonic analysis methods. Future development plans are also described.

Session 5
Materials and Heat Treatment

Wednesday, November 3, 2021

The Effect of Steel Microstructure on Bearing Performance

Speaker: R. Scott Hyde | The Timken Company | USA

Abstract: This paper presents a high-level overview of bearing microstructure and its impact to bearing performance to aid equipment designers in understanding the options available in the marketplace. Traditional bearing microstructures primarily consist of a martensitic structure formed using a high carbon alloy or a case hardening process. More recently, bearings have been manufactured with bainitic microstructures using a process known as austempering. The various microstructural constituents such as martensite and bainite, along with retained austenite and carbides, all contribute in different ways to bearing performance. In addition to the microstructure, residual stresses develop at and near the surface of the bearing raceways due to the combination of heat-treat process, material, and finishing processes. These residual stresses created from the bearing manufacturing influence performance and may either aid or detract from performance depending on the combination of factors present.

Enhanced Distortion Control – ISO Class 8 Gears After Case Hardening

Speaker: Volker Heuer | ALD Vacuum Technologies GmbH | Germany

Abstract: The combination of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ) offers the potential to provide better control of distortion compared to other process-combinations such as Atmospheric Carburizing with Oil Quenching. This paper analyzes distortion values of gear components from a planetary set of a six-speed automatic transmission over a long period of time. The gears were analyzed in terms of circularity, helix average, and helix variation. It is demonstrated that distortion data stays stable and predictable even over a long period of time when applying optimized heat-treatment process parameters and if the process-steps in the manufacturing chain before heat treatment are frozen and robust. The paper gives directions how this goal can be achieved by combining an advanced heat treatment process with advanced gear inspection technology.

Tooth Root Bending Strength of Shot-Peened Gears Made of High-Purity Steels Up to the VHCF Range

Speaker: Daniel Fuchs | Technical University of Munich, Gear Research Centre (FZG) | Germany

Abstract: Shot-peening achieves higher bending strength in the tooth root area of gears, but often causes a change in the crack mechanism to occur at non-metallic inclusions in the steel matrix. The hypothesis of this publication is: The higher the steel cleanliness, the fewer the non-metallic inclusions in the material, and therefore the higher the tooth root capacity of case-hardened, shot-peened gears. This working hypothesis is verified with tests on back-to-back test rigs up to the very high cycle fatigue (VHCF) range. The test gear variants were manufactured from steels with different degrees of cleanliness. The gears were also examined metallographically, with a special focus on the residual stress state in the tooth root area.

4D Quench – Taking Aerospace to New Heights

Speaker: Thomas Hart | SECO/VACUUM | ASM International | USA

Abstract: A single-piece flow (SPF) vacuum heat-treatment furnace with 4D Quench (4DQ) provides continuous flow heat treatment with low geometric distortion, environmental impact, and personal safety concerns. This system has the flexibility of operating in a batch style work cell, or it can be sized up and inserted in a continuous work cell, operating without human interference. 4DQ technology equals the speed of an oil quench and the cooling gas nozzle profile can be optimized based on actual part geometry. By controlling the direction of the cooling gas spray with part rotation, manufacturers now have the ability to control how fast or slow a part section cools providing a better quench. With this improved uniformity, larger and previously pressed quenched parts can now be processed in a 4DQ system. This paper will also summarize a half decade’s worth of research associated to SPF with 4DQ Vacuum Heat Treatment.

Calendar of Events

October 13 — Operator Hobbing and Shaping — Chicago, Illinois

October 19-21 — Gearbox System Design — Clearwater, Florida

October 22 — 3D Printing Committee Meeting — WebEx

October 26 — Robotics & Automation Committee Meeting — WebEx

November 1-3 — Fall Technical Meeting — Crowne Plaza, Chicago, Illinois

November 9-10 — Heat Treatment for Operators — Chicago, Illinois

November 16-17 — AGMA Board Meeting — Daley College

November 16-19 — Gear Failure Analysis — St. Louis, Missouri