Take a deep dive into the gear industry at AGMA's Fall Technical Meeting.
This meeting brings together top researchers from across the globe who will provide the latest information on their peer-reviewed gear industry research. Network with the industry experts, academics, and engineers; ask your burning questions; and see what is in the future of this industry.
View FTM sessions from Motion + Power Technology Expo 2019 below. Information on 2021 sessions will be available spring 2021.
Monday, October 14
1:00 pm – 5:00 pm
Technical Session I — Application, Design, and Rating
Moderator: Jason Daubert, FLSmidth, Inc.
Electric Vehicle Transmissions with Hypoid Gearset (19FTM01)
Compact electric vehicles require a cost effective and compact solution for the location of the electric motor and the transmission. This paper presents a new design concept which utilizes a super reduction hypoid with a ratio between 8 and 15. The hypoid gearset moves the eMotor away from the limited space between the front wheels to deliver a symmetrical weight distribution and heat radiation away from the wheels.
Misalignment Compensation Splines Design (19FTM02)
Crowned spline teeth are frequently used to avoid interferences between shaft and hub teeth. Currently, a precise determination of the misalignment and crowned teeth influence on spline load capacity can only be performed by finite element method, (FEM), or other powerful numerical simulations. This paper proposes an analytical model. A sensitivity study to the tooth bending stiffness influence on tooth shear stress is performed and a comparison with FEM results shows good agreement.
Spline Centering, Piloting, and Toggle: Torsional Stiffness, Shaft Bending, and Centering of Moment Loads (19FTM03)
Common practice for a splined joint is to assume that the load is theoretically transmitted along the entire length of the tooth face, but several factors, including axial spline length and the ratio of hub to shaft torsional stiffness, can impact how the load is distributed along the tooth face. Previous papers have considered the effect of pure torque and combined torque plus radial load, but few have described the impact of splines loaded with torque plus both moment and radial load. This paper describes the behavior of spline interfaces in piloted (radially offset), full toggle, half-toggle, and centered alignment states. Load conditions considered include combinations of torque, radial load, and moment load. The amount of misalignment allowed is calculated, and a chart of misalignment load factor versus torque and stiffness ratio (hub to shaft) is provided.
Optimal Polymer Gear Design: Metal-to-Plastic Conversion (19FTM04)
Unlike machined metal gears, polymer gears produced by injection molding allow for a deep optimization of gear tooth macro and microgeometry. This paper describes the optimal selection of operating pressure angle and contact ratio to maximize load sharing between the contacting tooth pairs, the root fillet optimization to minimize root stress concentration, and how optimal modification of the gear tooth flanks minimizes transmission error, accounting for tooth bending and contact deflection. This paper also presents a numerical example of a metal-to-plastic conversion.
Design of a Double Spiral Bevel Gearset (19FTM05)
The most common bevel gear geometries are straight, spiral, and helical (skew), and all these types of gearset subject the bearings to three types of forces, namely: axial, radial, and tangential. This paper presents a double spiral bevel gear design. The design minimizes radial loads and consequently, axial loads of the mating gear. Stresses on the bearings are reduced, as well as the mass of the power transmission unit. With the development of computer numerical control, (CNC), machines with five or more axes and additive manufacturing processes, the design of double spiral bevel gears is now feasible.
Specific Dynamic Behavior of Planetary Gears (19FTM06)
Gear noise is a very important contribution to the overall performance of power trans-mission systems. The actual gear mesh is the most decisive criterion for noise generation with two aspects: A) impact of gears getting into mesh with the previous mesh being defected under load (premature mesh begin/mesh interference) and B) mesh stiffness variation and hereby uneven angular velocity and torsional vibration excitation. This paper describes theory of noise generation in a gear mesh and the specific application on planetary gear systems. The results are illustrated by an example with test bench measurements.
Tuesday, October 15
8:00 am – 12:00 pm
Technical Session II — Efficiency, Lubrication, Noise, and Vibration
Moderator: Walt Weber, Flender Corporation (Retired)
Phase Management as a Strategy to Reduce Gear Whine in Idler Gear Sets (19FTM07)
Gear whine is controlled by managing transmission error. Idler gear sets affect gear whine by phasing the meshes. This paper shows how, by cleverly selecting the number of teeth on the idlers, their tooth thicknesses, and the idler location, the forces from transmission error force vectors that must be reacted by the idler bearings can be substantially reduced, thereby reducing the excitation on the gearbox that causes noise.
Leveraging the Complementary Strengths of Orbitless and Planetary Drives (19FTM08)
An Orbitless drive is a novel fixed-ratio epi-cyclic drive which includes a second carrier in place of a ring gear. It has been shown to have superior efficiency to a Planetary drive and is shown here to produce less vibration and noise at the expense of reduced torque capacity and ratio. A prototype 16mm Orbitless drive is constructed and compared to an off-the-shelf Planetary drive. Vibrations that occur at the Planetary tooth engagement frequency are absent from the Orbitless drive. A higher quality 32mm Orbitless prototype is evaluated in a multi-stage environment in both a stand-alone and multi-stage configuration. It is shown that sound levels are reduced, sound quality is improved, and it is concluded that an Orbitless primary stage may be mated with conventional technologies to minimize noise, vibration, and harness, (NVH), levels in multi-stage gear drives.
Reduction of the Tonality of Gear Noise by Application of Topography Scattering for Ground Bevel Gears (19FTM09)
The noise behavior of gearboxes is mainly caused by the excitation in the gear mesh. The standardized design and calculation methods for gears concentrate on the reduction of the excitation level. However, often the physical sound characteristics do not fit in with the human noise perception. In this paper, the noise behavior of bevel gears is investigated with a targeted micro geometry scattering. The excitation and noise behavior are analyzed from the excitation in tooth contact by transmission error measurements up to noise emission in the form of airborne sound. In addition, the potentials of the topography deviation for the optimization of ground bevel gears in terms of tonality reduction is shown by test results.
Computing Gear Sliding Losses (19FTM10)
Since at high power levels gear sliding losses dominate, accurately predicting frictional losses is critical for increasing gearbox efficiency. This paper evaluates eight different algorithms available in the literature for determining coefficient of friction and calculating gear sliding loss, and their applicability to commercial vehicle transmissions. The differences between predictions and measurements are discussed for each algorithm evaluated, and a recommendation is presented for improved accuracy within the application range investigated.
Opportunities of Efficiency Improvement by the Use of Hydro Lubricants (19FTM11)
The majority of industrial lubricants are based on mineral oils. Hydro Lubricants, which use water either as a base oil or as an additive, offer a more sustainable solution and are potential candidates for a wide range of industrial applications. This paper presents one such lubricant concept based on water and highlights its benefits in comparison to a conventional polyglycol (PG)-based synthetic gear lubricant.
1:30 pm – 5:00 pm
Technical Session III — Materials and Heat Treatment
Moderator: Michael He, Scot Forge
Evaluation of Steel Cleanliness by Extreme Value Statistics and its Correlation with Fatigue Performance (19FTM12)
Nonmetallic inclusions, primarily oxides, play a significant role in the fatigue performance of components, such as bearings and gears that undergo fatigue loading. Due to the advances made in steel making processes in the past decades, the oxygen level as well as inclusion size and distribution have been brought under remarkable control. Consequently, the earlier inclusion rating methods such as ASTM A534, ASTM E-45 that use a comparison with standard micrographs are insufficient to render an effective comparison of cleanliness of steels from different heats or suppliers. Extreme value analysis is a method that can surmount these limitations and it comprises of examination of a small area of steel by Optical or Scanning Electron Microscopy to predict the maximum size of inclusions which may inhabit a larger volume of steel. In this paper, the effect of inclusion size distribution on fatigue performance is investigated from the experimental data obtained using ultrasonic fatigue testing. Extreme value analysis is used to predict the characteristic size of the largest inclusion based on the metallographic observations on polished surfaces and this inclusion size is then correlated with the fatigue limit measured by ultrasonic fatigue testing, making use of the Murakami approach.
Tooth Root Testing of Steels with High Cleanliness (19FTM13)
In this paper, investigations on the tooth root load carrying capacity of steels with different cleanliness levels is presented. The investigations are carried out on a pulsator test rig with a standardized gear geometry. To determine and compare the different behaviors of the tested steels, correct force application in the test rig needs to be ensured. By this, it is possible to separate clearly the endurance strength and damage patterns for different cleanliness levels.
4D High Pressure Gas Quenching: A Leap in Performance vs. Press Quenching (19FTM14)
Thermal processing and quenching of steels for hardening is a well-established practice performed by various techniques over the centuries. A common thread has been the unpredictable nature of the size change during the quenching process, which is known as dimensional change or distortion. Material distortion is the undesired trade-off between the development of proper mechanical property and the necessity of rapidly quenching the material from elevated temperatures into a quenching media (i.e. brine, water, polymer, oil, gas, molten salt, etc.). Due to this compromise, users have been attempting to reduce part distortion because once a component is hardened, it becomes very difficult and costly to remove excess material or form the part back into its original shape. This paper will introduce the latest achievements in the advancement of distortion control by way of 4D High Pressure Gas Quenching (HPGQ) versus press quenching. The 4D HPGQ process does not subject a part to any clamping forces/liquid quenching inconsistencies.
Performance and Properties of New, Alternative Gear Steel (19FTM15)
In the ongoing strive for light weighting or power densification, high-performance clean steels are showing a significant improvement. Traditional gear steels achieve their maximum hardness after carburizing and a fast quench. A fast quench usually results in distortion as the part is unavoidably unsymmetrically cooled/quenched. For many gear applications, distortion during heat treatment of final component, can add cost and unwanted hard machining operations. With a new steel composition, that hardens by precipitation hardening (aging around 500°C/950°F) low distortion can be attained as a fast quench such as an oil quench is not necessary resulting in reduced hard machining. This type of steel can be both nitrided and carburized. Other interesting properties of this new steel that will be presented in this paper are good mechanical properties at elevated temperatures and good corrosion and oxidation properties compared to traditional gear steels.
Material Properties and Tooth Root Bending Strength of Shot Blasted, Case Carburized Gears with Alternative Microstructures (19FTM16)
Case hardening is one of the most common heat treatment processes for highly loaded shafts and gears. Due to numerous investigations and according to the material requirements for quality grade MQ and ME in part 5 of ISO 6336, a microstructure consisting of martensite with less than 30% retained austenite is favorable for a high load carrying capacity.
The question arises, how different alternative microstructures influence material properties and thus affect the tooth root bending strength of gears.
This report states the results of current investigations on material properties such as hardness depth profile, residual stress condition and amount of retained austenite as well as the tooth root bending strength of gear variants with different alternative microstructures. The gear variants are shot blasted and made out of the materials 20MnCr5 and 18CrNiMo7-6.
Wednesday, October 16
8:00 am – 12:00 pm
Technical Session IV — Manufacturing, Inspection, and Quality Control
Moderator: Mike D'Arduini, The Gleason Works
Chamfering of Gears — New Innovative Cutting Solutions for Efficient Gear Production (19FTM17)
Cylindrical gear chamfering and deburring is a rather unloved process as it implies cost but does not directly improve gear quality. However, a properly done chamfer process provides significant advantages for downstream handling and processing. Two major chamfer technologies are used: Forming and cutting technologies. While chamfer rolling is a proven forming process that has been used for decades mainly in mass production, cutting chamfer technologies are of increasing market interest due to cost reduction and increased quality requirements.
The paper will mainly cover a new chamfer cutting processes: Chamfer Contour Milling and Chamfer Hobbing. Chamfer Contour Milling uses a universal fly cutter tool with indexable carbide inserts. Chamfer Hobbing has been developed for modern gear production focusing on low tool cost per part with dry cutting and short cycle times in mass production. By comparing the advantages and limits of the mentioned chamfer processes in gear production for workpieces up to 400 mm diameter and module 8 mm, it is possible to select the right process depending on the specific requirements.
Influence of Manufacturing Variations of Spline Couplings on Gear Root and Contact Stress (19FTM18)
Involute splines are widely used in mechanical systems to connect power transmitting gears to their supporting shafts. These splines are as susceptible as gears to manufacturing variations, which change their loading pattern and may eventually lead to failures. The influence of manufacturing variations of spline teeth on performance and failure mechanisms of splined joints are available in the literature. However, the effects of manufacturing variations of spline teeth on gear tooth contact, noise, and stresses remain unknown. This study investigates how manufacturing variations of spline couplings affect gear performance. A parametric study was done to determine the amount of gear mesh misalignment caused by manufacturing variations of spline teeth. The changes in gear contact and bending stress patterns under mesh misaligned conditions were investigated.
Micro Skiving — (r)evolution of a Known Production Process (19FTM19)
The production of an internally toothed gear wheel is possible in various ways. Different techniques like gashing, broaching, or shaving make it possible to achieve these profiles. However, skiving reduces the production time for this type of gear.
This technique of internal gear cutting has been used in the industry for gears with modules greater than 0.5. Producing a gear with a module less than 0.5 is not an easy task. The profile becomes very small and requires an optimized cutting tool, which can only be manufactured on special grinding machines that manage the micron. Micro-skiving has been developed to allow users to use the skiving technique for machining inner micro-teeth. The general process is the same as for standard modules, but the constraints of shape, burr, and surface finish are higher.
Rapid and Precise Manufacturing of Special Involute Gears for Prototype Testing (19FTM20)
Due to the steadily increasing demands on the power density of mechanical transmissions, gears with special geometries such as asymmetrical gears are increasingly coming into focus. Due to their different normal pressure angles on the drive and coast flank, asymmetrical gears are particularly suitable for use in gearboxes with preferred driving direction, whereby the loaded flank can be optimized with regard to load carrying capacity. While for symmetrical gears with normal pressure angles in the range of 20 degrees, standardized calculation methods for gear design have been available for decades, mainly theoretical numerical investigations have been carried out on asymmetrical gears so far. For the qualification of any such designed asymmetrical gear geometry with increased load carrying capacity potential for use in industrial practice; however, reliable load carrying capacity values are required. In this paper, alternative methods for a fast and cost-efficient production of asymmetric gears for prototype tests are presented.
A Comparison of Surface Roughness Measurement Methods for Gear Tooth Working Surfaces (19FTM21)
Surface roughness is a critical parameter for gears operating under a variety of conditions. It directly influences friction and contact temperature, and therefore has an impact on various failure modes such as macropitting, micropitting and scuffing. Typically, gear tooth surface roughness is measured using a stylus profilometer. Stylus profilometry can produce inconsistent results if measurements are not executed correctly. This paper examines measurements from one “shop floor” and one “metrology lab” profilometer, both using two different stylus tip radii on the same gear teeth. Measurements from ground, shot peened, and superfinished surfaces are compared. In addition, this paper compares roughness measurements made using optical interferometry of gear teeth with optical interferometry of tooth replicas. Two different replication techniques are evaluated.
1:30 pm – 5:00 pm
Technical Session V — Optimization, Gear Wear, and Failure
Moderator: Frank Uherek, Rexnord Gear Group
Effects of the Load-Dependent Shift of Gear Center Distance on Calculated Load Capacity and Excitation Using Analytical Mesh Stiffness Approach (19FTM22)
The nominal center distance in cylindrical gears is defined for the non-loaded state. Under load conditions, the center distance is changing. This change leads to a reduction of the plane of contact and respectively of the length of the effective path of contact. The effective total contact ratio is also shortened. This effects the load and pressure distribution on the flank and thus the load capacity of the gears. The transmission error is also mutated, which effects the noise excitation of the gear pair.
For the analysis of these effects, we are using an analytical approach for the calculation of the local mesh stiffness.It is based on the plate theory of Schmidt and the local deformation approach of the gear tooth according to Weber-Banaschek. This paper will show the importance of considering the load-dependent change of the center distance for the calculation and layout of cylindrical gears. Furthermore, we are showing the advantages of using an analytical approach for calculating mesh stiffness.
New Standardized Calculation Method of The Tooth Flank Fracture Load Capacity of Bevel and Hypoid Gears (19FTM23)
Bevel and hypoid gears are widespread in automotive, industrial, marine, and aeronautical applications for transmitting power between crossed axles. A major aspect in the design process is the load carrying capacity regarding different failure modes. Beside typical fatigue failures like pitting and tooth root breakage, failures caused by cracks starting in greater material depth in the area of the active flank can be observed on bevel gears. The failure mode tooth flank fracture occurs particularly frequent on spiral bevel and hypoid gears because this gear type shows larger equivalent radii of curvature compared to cylindrical gears. This paper will give an overview of the subsurface failure mode tooth flank fracture, especially on bevel and hypoid gears. Further, a newly developed standardized calculation method for determining the tooth flank fracture load capacity based on the geometry of virtual cylindrical gear according to the standard ISO 10300 will be explained in detail.
Calculated Scuffing Risk: Correlating AGMA 925-A03, AGMA 6011-J14, and Original MAAG Gear Predictions (19FTM24)
Scuffing is severe adhesive wear occurring on gear tooth flanks when oil film thickness is insufficient to prevent transfer of metal from one gear tooth surface to the mating gear tooth due to welding and tearing. It usually occurs during startup of new gears thereby requiring design modification, load adjustment, or lubricant change. Predicting scuffing risk is a critical factor when designing high speed gears. This paper compares three methods for calculating scuffing risk using performance data for real gears and presents a simplified method that assures accurate prediction of scuffing risk.
Optimum Carburized and Hardened Case Depth (19FTM25)
The optimum carburized and hardened case depth for each gear failure mode must be defined at different locations on the gear tooth. Optimum case depth varies with the failure mode. Current gear rating standards do not clearly define the different locations, do not fully explain the different failure modes that must be considered, use different hardness values to define effective case depth, and provide different values for recommended case depth. This paper explains why case hardening is beneficial and the risks involved, and compares the methods for calculating and specifying case depth per the ISO 6336-5 and ANSI/AGMA 2101-D04 gear rating standards and guidelines presented in the MAAG Gear Handbook.
Sizing of Profile Modifications for Asymmetric Gears (19FTM26)
Today, the benefit of asymmetric gears is widely discussed. There are not yet many applications in the field, but companies are investigating, if reducers could be improved with this technique. This paper describes the geometric definition of asymmetric gears, presents the strength calculation of such gears executed per ISO standards, and shows how the method for the bending stress was adapted. In addition, the paper will show how power capacity of asymmetric gears can be calculated and compared with symmetric gears.
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