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1 Study of the Correlation Between Theoretical and Actual Gear Fatigue Test Data on a Polyamide (June 2008)

In the past two years DSM has been conducting fatigue tests on actual molded gears in order to provide design data.

2 Comparing Surface Failure Modes in Bearings and Gears: Appearances vs. Mechanisms (July/August 1992)

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.

3 Maximum Surface Temperature of the Thermoplastic Gear in a Non-Lubricated Plastic-Steel Gear Pair (August/September 1984)

One of the major problems of plastic gear design is the knowledge of their running temperature. Of special interest is the bulk temperature of the tooth to predict the fatigue life, and the peak temperature on the surface of the tooth to avert surface failure. This paper presents the results of an experimental method that uses an infrared radiometer to measure the temperature variation along the profile of a plastic gear tooth in operation. Measurements are made on 5.08, 3.17, 2.54, 2.12 mm module hob cut gears made from nylon 6-6, acetal and UHMWPE (Ultra High Molecular Weight Polyethylene). All the tests are made on a four square testing rig with thermoplastic/steel gear pairs where the plastic gear is the driver. Maximum temperature prediction curves obtained through statistical analysis of the results are presented and compared to data available from literature.

4 Loaded Behavior of Gears Made of Fiber-Reinforced PA6 (July 2014)

This paper presents an original method for computing the loaded mechanical behavior of fiber reinforced polymer gears. Although thermoplastic gears are unsuitable for application transmitting high torque, adding fibers can significantly increase their performance. The particular case of polyamide 6 + 30% glass fibers is studied in this paper.

5 Methodology for Translating Single-Tooth Bending Fatigue Data to be Comparable to Running Gear Data (March/April 2008)

A method to extrapolate running gear bending strength data from STF results for comparing bending performance of different materials and processes.

6 Effects on Rolling Contact Fatigue Performance--Part II (March/April 2007)

This is part II of a two-part paper that presents the results of extensive test programs on the RCF strength of PM steels.

7 The Fatigue Endurance Limit: A Myth (November/December 2005)

Review of "Gigacycle Fatigue in Mechanical Practice," by Claude Bathias and Paul C. Paris

8 Effects on Rolling Contact Fatigue Performance (January/February 2007)

This article summarizes results of research programs on RCF strength of wrought steels and PM steels.

9 Evaluation of Bending Strength of Carburized Gears (May/June 2004)

The aim of our research is to clearly show the influence of defects on the bending fatigue strength of gear teeth. Carburized gears have many types of defects, such as non-martensitic layers, inclusions, tool marks, etc. It is well known that high strength gear teeth break from defects in their materials, so it’s important to know which defect limits the strength of a gear.

10 Effects of Axle Deflection and Tooth Flank Modification on Hypoid Gear Stress Distribution and Contact Fatigue Life (August 2009)

As is well known in involute gearing, “perfect” involute gears never work perfectly in the real world. Flank modifications are often made to overcome the influences of errors coming from manufacturing and assembly processes as well as deflections of the system. The same discipline applies to hypoid gears.

11 Deciding When to Go Plastic (July 2014)

Can my metal gear(s) be replaced with plastic gears?

12 Talking Truth to Power: Plastic Gears Taking Back Seat to No One (March/April 2013)

Automotive industry embraces proven yet evolving technology of plastic gears.

13 Fundamental Study of Detection of Plastic Gear Failure Signs (March/April 2015)

This paper proposes a new method — using neural oscillators — for filtering out background vibration noise in meshing plastic gear pairs in the detection of signs of gear failure. In this paper these unnecessary frequency components are eliminated with a feed-forward control system in which the neural oscillator’s synchronization property works. Each neural oscillator is designed to tune the natural frequency to a particular one of the components.

14 Plastic Gearing Continues Converting the Unconverted (March/April 2016)

Plastic gears are everywhere today — throughout your car, at the oceans’ lowest depths, in deep space. The question, when is a metal gear a candidate for plastic conversion, can be addressed in three words, i.e. — what’s the application?

15 Bending Fatigue, Impact and Pitting Resistance of Ausform-Finished PM Gears (June 2010)

The powder metal (P/M) process is making inroads in automotive transmission applications due to substantially lower costs of P/M-steel components for high-volume production, as compared to wrought or forged steel parts. Although P/M gears are increasingly used in powered hand tools, gear pumps and as accessory components in automotive transmissions, P/M-steel gears are currently in limited use in vehicle transmission applications. The primary objective of this project was to develop high-strength P/M-steel gears with bending fatigue, impact resistance and pitting fatigue performance equivalent to current wrought steel gears.

16 Bending Fatigue Tests of Helicopter Case Carburized Gears: Influence on Material, Design and Manufacturing Parameters (November/December 2009)

A single tooth bending (STB) test procedure has been developed to optimally map gear design parameters. Also, a test program on case-carburized, aerospace standard gears has been conceived and performed in order to appreciate the influence of various technological parameters on fatigue resistance and to draw the curve shape up to the gigacycle region.

17 Gear Fault Detection Effectiveness as Applied to Tooth Surface Pitting Fatigue Damage (November/December 2010)

A study was performed to evaluate fault detection effectiveness as applied to gear-tooth pitting-fatigue damage. Vibration and oil-debris monitoring (ODM) data were gathered from 24 sets of spur pinion and face gears run during a previous endurance evaluation study.

18 Design Formulas for Evaluating Contact Stress in Generalized Gear Pairs (May/June 2001)

A very important parameter when designing a gear pair is the maximum surface contact stress that exists between two gear teeth in mesh, as it affects surface fatigue (namely, pitting and wear) along with gear mesh losses. A lot of attention has been targeted to the determination of the maximum contact stress between gear teeth in mesh, resulting in many "different" formulas. Moreover, each of those formulas is applicable to a particular class of gears (e.g., hypoid, worm, spiroid, spiral bevel, or cylindrical - spur and helical). More recently, FEM (the finite element method) has been introduced to evaluate the contact stress between gear teeth. Presented below is a single methodology for evaluating the maximum contact stress that exists between gear teeth in mesh. The approach is independent of the gear tooth geometry (involute or cycloid) and valid for any gear type (i.e., hypoid, worm, spiroid, bevel and cylindrical).

19 Austempered Gears and Shafts: Tough Solutions (March/April 2001)

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.

20 Design Against Tooth Interior Fatigue Fracture (November/December 2000)

In a modern truck, the gear teeth are among the most stressed parts. Failure of a tooth will damage the transmission severely. Throughout the years, gear design experience has been gained and collected into standards such as DIN (Ref. 1) or AGMA (Ref. 2). Traditionally two types of failures are considered in gear design: tooth root bending fatigue, and contact fatigue. The demands for lighter and more silent transmissions have given birth to new failure types. One novel failure type, Tooth Interior Fatigue Fracture (TIFF), has previously been described by MackAldener and Olsson (Refs. 3 & 4) and is further explored in this paper.

21 Consideration of Moving Tooth Load in Gear Crack Propagation Predictions (January/February 2002)

Effective gear designs balance strength, durability, reliability, size, weight, and cost. Even effective designs, however, can have the possibility of gear cracks due to fatigue. In addition, truly robust designs consider not only crack initiation, but also crack propagation trajectories. As an example, crack trajectories that propagate through the gear tooth are the preferred mode of failure compared to propagation through the gear rim. Rim failure will lead to catastrophic events and should be avoided. Analysis tools that predict crack propagation paths can be a valuable aid to the designer to prevent such catastrophic failures.

22 Characterizaton of Retained Austenite in Case Carburized Gears and Its Influence on Fatigue Performance (May/June 2003)

Carburized helical gears with high retained austenite were tested for surface contact fatigue. The retained austenite before test was 60% and was associated with low hardness near the case's surface. However, the tested gears showed good pitting resistance, with fatigue strength greater than 1,380 MPa.

23 Knowing When Enough Is Enough (November/December 2015)

Detection of impending gear tooth failure is of interest to every entity that utilizes geared transmissions. However, it is of particular significance at the Gear Research Institute (GRI), where sponsored efforts are conducted to establish gear material endurance limits, utilizing gear fatigue tests. Consequently, knowing when a gear is about to fail in each and every test, in a consistent manner, is essential for producing reliable and useful data for the gear industry.

24 Setting Load Parameters for Viable Fatigue Testing of Gears in Powertrain Axles Part I: Single-Reduction Axles (August 2014)

This presentation introduces a new procedure that - derived from exact calculations - aids in determining the parameters of the validation testing of spiral bevel and hypoid gears in single-reduction axles.

25 Gear Crack Propagation Investigations (November/December 1997)

A common design goal for gears in helicopter or turboprop power transmission is reduced weight. To help meet this goal, some gear designs use thin rims. Rims that are too thin, however, may lead to bending fatigue problems and cracks. The most common methods of gear design and analysis are based on standards published by the American Gear Manufacturers Association. Included in the standards are rating formulas for gear tooth bending to prevent crack initiation (Ref. 1). These standards can include the effect of rim thickness on tooth bending fatigue (Ref 2.). The standards, however, do not indicate the crack propagation path or the remaining life once a crack has started. Fracture mechanics has developed into a useful discipline for predicting strength and life of cracked structures.

26 Comparison of Surface Durability & Dynamic Performance of Powder Metal & Steel Gears (September/October 1995)

Surface-hardened, sintered powder metal gears are increasingly used in power transmissions to reduce the cost of gear production. One important problem is how to design with surface durability, given the porous nature of sintered gears. Many articles have been written about mechanical characteristics, such as tensile and bending strength, of sintered materials, and it is well-known that the pores existing on and below their surfaces affect their characteristics (Refs. 1-3). Power transmission gears are frequently employed under conditions of high speed and high load, and tooth surfaces are in contact with each other under a sliding-rolling contact condition. Therefore it is necessary to consider not only their mechanical, but also their tribological characteristics when designing sintered gears for surface durability.

27 Improved Gear Life Through Controlled Shot Peening (September/October 1986)

The search for greater gear life involves improvement in cost, weight and increased power output. There are many events that affect gear life, and this paper addresses those relating to fatigue, gear tooth pitting, fatigue strength losses due to the heat treating processes and shot peening technique. The capability of shot peening to increase fatigue strength and surface fatigue life eliminate machine marks which cause stress risers, and to aid in lubrication when properly controlled, suggests increased use and acceptance of the process.

28 Effect of Shot Peening on Surface Fatigue Life of Carburized and Hardened AISI 1910 Spur Gears (January/February 1986)

Gear surface fatigue endurance tests were conducted on two groups of 10 gears each of carburized and hardened AlSI 9310 spur gears manufactured from the same heat of material

29 Surface Fatigue Life on CBN and Vitreous Ground Carburized and Hardened AISA 9310 Spur Gears (January/February 1990)

Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9210 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temperature of 320 K (116 degree F), an outlet oil temperature of 350 K (170 degree F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.

30 Influence of Lubrication on Pitting and Micropitting Resistance of Gears (March/April 1990)

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.

31 EHL Film Thickness, Additives and Gear Surface Fatigue (May/June 1995)

Aircraft transmissions for helicopters, turboprops and geared turbofan aircraft require high reliability and provide several thousand hours of operation between overhauls. In addition, They should be lightweight and have very high efficiency to minimize operating costs for the aircraft.

32 Surface Pitting Fatigue Life of Noninvolute Low-Contact-Ratio Gears (May/June 1991)

Spur gear endurance tests were conducted to investigate the surface pitting fatigue life of noninvolute gears with low numbers of teeth and low contact ratios for the use in advanced application. The results were compared with those for a standard involute design with a low number of teeth. The gear pitch diameter was 8.89 cm (3.50 in.) with 12 teeth on both gear designs. Test conditions were an oil inlet temperature of 320 K (116 degrees F), a maximum Hertz stress of 1.49 GPa (216 ksi), and a speed of 10,000 rpm. The following results were obtained: The noninvolute gear had a surface pitting fatigue life approximately 1.6 times that of the standard involute gear of a similar design. The surface pitting fatigue life of the 3.43-pitch AISI 8620 noninvolute gear was approximately equal to the surface pitting fatigue life of an 8-pitch, 28-tooth AISI 9310 gear at the same load, but at a considerably higher maximum Hertz stress.

33 New Technology for Stronger Plastic Gears (August 2012)

Gleason-K2 Plastics eliminates weld lines with no machining.

34 Failure Mechanisms in Plastic Gears (January/February 2002)

Plastics as gear materials represent an interesting development for gearing because they offer high strength-to-weight ratios, ease of manufacture and excellent tribological properties (Refs. 1-7). In particular, there is a sound prospect that plastic gears can be applied for power transmission of up to 10 kW (Ref. 6).

35 How to Achieve a Successful Molded Gear Transmission (July/August 2006)

Molded plastic gears have very little in common with machined gears other than the fact that both use the involute for conjugate action.

36 Plastic Gears--A Growing Industry Still Seeking Respect (March/April 2007)

Forty years ago, the plastics industry was practically in its embryonic phase...

37 Gear Design: Multipoint Properties are Key to Selecting Thermoplastic Materials (November/December 2006)

The palette of thermoplastic materials for gears has grown rapidly, as have the applications themselves. Designers need to be aware of key properties and attributes in selecting the right material.

38 Latest Generation of Quieter Plastic Gears Can Take the Heat (November/December 2005)

Ten years ago, most mainstream gear manufacturers didn't even consider plastics as an option, especially in higher power applications.

39 Material Integrity in Molded Plastic Gears and its Dependence on Molding Practices (June 2008)

The quality of molded plastic gears is typically judged by dimensional feature measurements only. This practice overlooks potential deficiencies in the molding process.

40 Injection Molded Innovation (June 2008)

Alternative business strategies from some alternative gear manufacturers.

41 Plastic Gear Standards: A Balancing Act (March/April 2007)

Creating standards for plastic gears calls for a deft touch. The challenge is to set uniform guidelines, yet avoid limiting the creative solutions plastic offers gear designers.

42 Tooth-Bending Effects in Plastic Spur Gears (September/October 2007)

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.

43 Non-Standard Cylindrical Gears (November/December 2004)

Curved face width (CFW) spur gears are not popular in the gear industry. But these non-metallic gears have advantages over standard spur gears: higher contact ratio, higher tooth stiffness, and lower contact and bending stresses.

44 Pushing the Envelope with Plastic (June 2007)

We were delighted to see the plastic gear set pictured on the cover of your March/April issue. UFE played the lead role in its design and manufacture.

45 The Design and Manufacture of Plastic Gears Part II (July/August 1985)

Advancements in machining and assembly techniques of thermoplastic gearing along with new design data has lead to increased useage of polymeric materials. information on state of the art methods in fabrication of plastic gearing is presented and the importance of a proper backlash allowance at installation is discussed. Under controlled conditions, cast nylon gears show 8-14 dBA. lower noise level than three other gear materials tested.

46 The Design and Manufacture of Machined Plastic Gears (May/June 1985)

The use of plastic gearing is increasing steadily in new products. This is due in part to the availability of recent design data. Fatigue stress of plastic gears as a function of diametral pitch, pressure angle, pitch line velocity, lubrication and life cycles are described based on test information. Design procedures for plastic gears are presented.

47 Load Carrying Capacity of Screw Helical Gears with Steel Pinions and Plastic Wheels (July/August 2004)

There is an increasing significance of screw helical and worm gears that combine use of steel and plastics. This is shown by diverse and continuously rising use in the automotive and household appliance industries. The increasing requirements for such gears can be explained by the advantageous qualities of such a material combination in comparison with that of the traditional steel/bronze pairing.

48 High-Temperature Testing of Stanyl Plastic Gears: A Comparison with Tensile Fatigue Data (March/April 2010)

This paper shows an experimental study on the fatigue lifetime of high-heat polyamide (Stanyl) gears running in oil at 140°C. Based on previous works (Refs. 1–2), an analysis is made correcting for tooth bending and calculating actual root stresses. A comparison with tensile bar fatigue data for the same materials at 140°C shows that a good correlation exists between gear fatigue data and tensile bar fatigue data. This insight provides a solid basis for gear designers to design plastic gears using actual material data.

49 At the PEEK of the Polymer Food Chain (June 2010)

In the hypercompetitive race to increase automobile efficiency, Metaldyne has been developing its balance shaft module line with Victrex PEEK polymer in place of metal gears. The collaborative product development resulted in significant reductions in inertia, weight and power consumption, as well as improvement in noise, vibration and harshness (NVH) performance.

50 Noise Reduction in Plastic & Powder Metal Gear Sets (July/August 1996)

The data discussed in this article was taken from an upright vacuum cleaner. This was a prototype cleaner that was self-propelled by a geared transmission. It was the first time that the manufacturer had used a geared transmission in this application.

51 Effect of Web & Flange Thickness on Nonmetallic Gear Performance (November/December 1995)

Gears are manufactured with thin rims for several reasons. Steel gears are manufactured with thin rims and webs where low weight is important. Nonmetallic gears, manufactured by injection molding, are designed with thin rims as part of the general design rule to maintain uniform thickness to ensure even post-mold cooling. When a thin-rimmed gear fails, the fracture is thought the root of the gear, as shown in Fig. 1a, rather than the usual fillet failure shown in Fig. 1b.

52 Plastic Gear Design Basics (July/August 1996)

Plastic gears are serious alternatives to traditional metal gears in a wide variety of applications. The use of plastic gears has expanded from low-power, precision motion transmission into more demanding power transmission applications. As designers push the limits of acceptable plastic gear applications, more is learned about the behavior of plastics in gearing and how to take advantage of their unique characteristics.

53 Hoechst Technical Polymers to Gather Plastic Gear Materials Data (July/August 1997)

Hoechst Technical Polymers has expanded its interests in plastic gears with the introduction of the new Plastic Gear Evaluation and Research machine P-Gear. The machine is the centerpiece of the company's continuing efforts to promote and develop the use of plastic gears in higher-powered applications.

54 A Practical Guide for Molding Better Plastic Geared Transmissions (May/June 2000)

Plastic gears and transmissions require a different design approach than metal transmissions. Different tools are available to the plastic transmission designer for optimizing his geared product, and different requirements exist for inspection and testing. This paper will present some of the new technology available to the plastic gear user, including design, mold construction, inspection, and testing of plastic gears and transmissions.

55 Plastic: The Not-So-Alternative Technology (July/August 1998)

"We're taking over," says Art Milano. It's a bold statement from the engineering manager of Seitz Corporation, one of the largest manufacturers of injection molded plastic gears, but Milano has reason for his optimism. Plastic gears are big business-probably bigger than most gear industry "insiders" realize.

56 Lubricants and Lubrication of Plastic Gears (September/October 1993)

Surface measurement of any metal gear tooth contact surface will indicate some degree of peaks and valleys. When gears are placed in mesh, irregular contact surfaces are brought together in the typical combination of rolling and sliding motion. The surface peaks, or asperities, of one tooth randomly contact the asperities of the mating tooth. Under the right conditions, the asperities form momentary welds that are broken off as the gear tooth action continues. Increased friction and higher temperatures, plus wear debris introduced into the system are the result of this action.

57 Systematic Approach to Designing Plastic Spur and Helical Gears (November/December 1989)

Plastic gears are being used increasingly in applications, such as printers, cameras, small household appliances, small power tools, instruments, timers, counters and various other products. Because of the many variables involved, an engineer who designs gear trains on an occasional basis may find the design process to be somewhat overwhelming. This article outlines a systematic design approach for developing injection molded plastic spur and helical gears. The use of a computer program for designing plastic gears is introduced as an invaluable design tool for solving complex gearing equations.

58 Gear Material Risks and Rewards (August 2011)

Technology investments lead to product innovation at gear materials suppliers.

59 The Efficiency Experts (September/October 2010)

Bradley University and Winzeler Gear collaborate on the design and development of an urban light vehicle.

60 Load-Sharing Model for Polymer Cylindrical Gears (November/December 2011)

This paper presents an original method to compute the loaded mechanical behavior of polymer gears. Polymer gears can be used without lubricant, have quieter mesh, are more resistant to corrosion, and are lighter in weight. Therefore their application fields are continually increasing. Nevertheless, the mechanical behavior of polymer materials is very complex because it depends on time, history of displacement and temperature. In addition, for several polymers, humidity is another factor to be taken into account. The particular case of polyamide 6.6 is studied in this paper.

61 The Plastic Gear Pay-Off (March/April 2012)

Eliminating noise, weight and wear proves valuable in 2012.

62 The Relative Performance of Spur Gears Manufactured from Steel and PEEK (March/April 2012)

This paper seeks to compare the data generated from test rig shaft encoders and torque transducers when using steel-steel, steel-plastic and plastic-plastic gear combinations in order to understand the differences in performance of steel and plastic gears.

63 Optimizing Plastic Gear Geometry: An Inroduction to Gear Optimization (May/June 2002)

There are numerous engineering evaluations required to design gear sets for optimum performance with regard to torque capacity, noise, size and cost. How much cost savings and added gear performance is available through optimization? Cost savings of 10% to 30% and 100% added capacity are not unusual. The contrast is more pronounced if the original design was prone to failure and not fit for function.