scholarly journals Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

2007 ◽  
Author(s):  
Timothy Krantz ◽  
Brian Tufts
Keyword(s):  
Power Density ◽  
Fatigue Testing ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Surface Fatigue ◽  
Gear Steel ◽  
Single Tooth ◽  
Carburized Gear ◽  
Gear Steels

The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

A Testing Device for Fatigue Crack Propagation Experiments on Bevel and Face Gears

2003 ◽  
Author(s):  
Mauro Filippini ◽  
Carlo Gorla
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Gear Wheel ◽  
Fatigue Tests ◽  
Testing Device ◽  
Bending Fatigue ◽  
Single Tooth

A testing device for performing single tooth bending fatigue tests on bevel and face gears is presented. Basically, it works as a normal gearbox in which the pinion acts as loading element while the gear wheel is kept fixed to the frame. The entire rig is installed in a servo-hydraulic torsion fatigue testing machine, so that torque amplitudes up 2200 Nm may be applied with convenient loading frequencies. Torque amplitude is measured by connecting the testing rig to the load cell of the testing machine. It’s possible to rotate the gearwheel at fixed positions so that a large number of teeth of the same wheel may be tested. If the tests are performed on teeth weakened by pre cracking, no special pinion is requested. The proposed testing rig may be employed for testing both bevel and face gears, by simply adapting the parts that keep the gearwheel fixed with the frame and by choosing the proper meshing pinion.

Gear root bending strength: a comparison between Single Tooth Bending Fatigue Tests and meshing gears

2021 ◽  
pp. 1-17
Author(s):  
Luca Bonaiti ◽  
Ahmed Bayoumi Mahmoud Bayoumi ◽  
Franco Concli ◽  
Francesco Rosa ◽  
Carlo Gorla
Keyword(s):  
Failure Modes ◽  
Bending Strength ◽  
Gear Tooth ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Gear Design ◽  
Single Tooth ◽  
Actual Strength ◽  
Meshing Gears ◽  
Definition Of

Abstract Gear tooth breakage due to bending fatigue is one of the most dangerous failure modes of gears. Therefore, the precise definition of tooth bending strength is of utmost importance in gear design. Single Tooth Bending Fatigue (STBF) tests are usually used to study this failure mode, since they allow to test gears, realized and finished with the actual industrial processes. Nevertheless, STBF tests do not reproduce exactly the loading conditions of meshing gears. The load is applied in a pre-determined position, while in meshing gears it moves along the active flank; all the teeth can be tested and have the same importance, while the actual strength of a meshing gear, practically, is strongly influenced by the strength of the weakest tooth of the gear. These differences have to be (and obviously are) taken into account when using the results of STBF tests to design gear sets. The aim of this paper is to investigate in detail the first aspect, i.e. the role of the differences between two tooth root stress histories. In particular, this paper presents a methodology based on high-cycle multi-axial fatigue criteria in order to translate STBF test data to the real working condition; residual stresses are also taken into account

scholarly journals Bending Fatigue Behaviors Analysis and Fatigue Life Prediction of 20Cr2Ni4 Gear Steel with Different Stress Concentrations near Non-metallic Inclusions

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3443 ◽  
Author(s):  
Zhiguo Xing ◽  
Zhiyuan Wang ◽  
Haidou Wang ◽  
Debin Shan
Keyword(s):  
Fatigue Life ◽  
Quantitative Analysis ◽  
Steel Production ◽  
The State ◽  
Heavy Duty ◽  
Stress Concentrations ◽  
Bending Fatigue ◽  
Gear Steel ◽  
Gear Steels ◽  
The Relationship

To investigate the relationship between inclusions and bending fatigue behaviors in 20Cr2Ni4 steel under different stress concentrations. This paper designs a new experimental method to prefabricate different size stress concentrations near the inclusions, and then conducts a new type of bending fatigue test to study the inclusions and their surrounding stress distributions in 20Cr2Ni4 steel. A microhardness tester was combined with laser etching equipment to realize the prefabrication of different stress concentrations at arbitrary positions around any inclusion on the gear steel surface. This method provides an experimental basis for the quantitative analysis of the relationship between stress distribution and fatigue life around the inclusions of heavy-duty gear steels. We also predict the bending fatigue lives of heavy-duty gear steels with different types of inclusions, stress states, and spatial distributions. Then, based on the prefabricated notch parameters and the state of inclusions in the steel, a mathematical model of quantitative analysis is proposed, which can accurately predict the fatigue limit of heavy-duty gear steel. The research results can be applied to the actual use of heavy-duty gears and to the accurate life estimation based on the state of gear stress, thereby providing a quantitative reference model for subsequent gear steel production and gear part processing.

Bending fatigue design of case-hardened gears based on test specimens

2017 ◽  
Vol 232 (11) ◽  
pp. 1953-1969 ◽  
Author(s):  
Giovanni Meneghetti ◽  
Carlo Dengo ◽  
Fulvio Lo Conte
Keyword(s):  
Experimental Data ◽  
Fatigue Tests ◽  
Experimental Results ◽  
Sensitivity Factor ◽  
Reference Test ◽  
Iso Standard ◽  
Bending Fatigue ◽  
Notched Specimens ◽  
Fatigue Design ◽  
Gear Steel

Different design methods against bending fatigue are reported in ISO 6336 standard. The standard suggests primarily the method based on reference test gears and provides the relevant fatigue curves. Additionally, the standard suggests the use of specimens (instead of gears) to generate the reference fatigue curves, but it also advices that specimen-based methods can be used when gears are not available and that specimens are particularly useful for comparing fatigue performances of gear materials relative to one another. The purpose of the present paper is to evaluate the accuracy of the specimen-based methods mentioned in the ISO standard when applied to design gears against bending fatigue. Experimental data were generated by means of pulsator fatigue tests on case-hardened gears used in off-highway vehicles. Afterwards, experimental results were compared with theoretical estimations according to the approaches based on reference test gears (as suggested by the ISO standard) and test specimens. Concerning the latter approach, the relevant fatigue design curves were generated by testing smooth as well as notched specimens made of the same case-hardened gear steel. It was found that the specimens-based methods are as accurate as the reference gears-based method, provided that the material notch sensitivity factor is properly calibrated on the experimental results obtained from specimens.

New High Performance Gear Steels for Rotorcraft Transmission Applications (Ferrium® C61™ and Ferrium C64™)

2013 ◽  
Author(s):  
Jason Sebastian ◽  
Jeff Grabowski ◽  
Dave Snyder
Keyword(s):  
High Temperature ◽  
High Performance ◽  
Minimum Weight ◽  
Surface Hardness ◽  
High Strength ◽  
Innovation Research ◽  
Surface Fatigue ◽  
Vacuum Carburization ◽  
Computational Materials ◽  
Gear Steels

QuesTek Innovations LLC will present an overview of its Ferrium® C61™ and Ferrium C64™ high-performance gear steels. QuesTek designed, developed and implemented these two new steels using its Materials by Design® technology, an “Integrated Computational Materials Engineering” (ICME)-type approach. Both steels are commercially available (Ferrium C61 falls under Aerospace Materials Specification [AMS] number 6517 and Ferrium C64 falls under AMS 6509) and both can significantly reduce rotorcraft weight and manufacturing costs while increasing operational robustness (including gear steel oil-out/high temperature survivability). Ferrium C61 and C64 are new high strength, secondary hardening gear steels that offer different levels of case hardness. These highly-processable steels exhibit excellent hardenability, and were explicitly designed to leverage the advantages of high-temperature vacuum carburization. Ferrium C61 (AMS 6517) exhibits both excellent surface fatigue and core properties (225 ksi yield strength, 240 ksi ultimate tensile strength, 130 ksi•?in fracture toughness), and is a good candidate for integral gear/shaft applications where maximum torque transfer with minimum weight is tantamount. Ferrium C64 (AMS 6509) exhibits excellent surface hardness (62+ HRC after vacuum carburization), with the potential for significantly better surface fatigue performance as compared to incumbent gear steels such as AISI 9310 (AMS 6265) and Pyrowear® Alloy 53 (AMS 6308). The final tempering temperatures of both C61 and C64 (482–510°C) are 200–300°C higher than most incumbent gear steels, providing excellent scoring resistance and superior thermal stability in high-temperature environments and “oil-out” emergency conditions. Rotorcraft applications underway include an evaluation of C64 by Bell Helicopter under the U.S. Army Future Advanced Rotorcraft Drive Systems (FARDS) program, and of C61 for the forward rotorshaft of Boeing’s CH-47 Chinook under a U.S. Army Small Business Innovation Research (SBIR) Phase II project.

Effect of the gear finishing process on bending fatigue crack initiation and propagation in spur gears

2001 ◽  
Vol 215 (7) ◽  
pp. 785-792 ◽  
Author(s):  
T. K. Hidayetoglu
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Bending Fatigue ◽  
Gear Steel ◽  
Finishing Process ◽  
Single Tooth ◽  
Stress Profiles ◽  
Bench Testing

The depth and stress levels of residual stress profiles are a major concern in carburized components such as transmission gears. Residual stress profiles are, among other factors, a function of the gear steel composition, the carburizing process and the gear finishing process. One of the goals of the finishing process in gears is to obtain a certain level of toughness in the gear teeth to reduce and/or eliminate bending and contact fatigue failures. This article presents a comparison of the characteristics of bending fatigue crack initiation in cubic boron nitride (CBN)-ground only and CBN-ground and shot-peened gears during single-tooth bench testing, and also a comparison of the characteristics of bending fatigue crack initiation in shot-cleaned only and CBN-ground only gears during single-tooth bench testing. The gear steel used in this study was SAE 8620/22.

scholarly journals A Newly Devised Resonance Type Rotating Bending Fatigue Testing Machine and Some Fatigue Tests

1971 ◽  
Vol 14 (76) ◽  
pp. 1013-1020
Author(s):  
Minoru KAWAMOTO ◽  
Yukihiko IBUKI ◽  
Toshinobu SHIBATA ◽  
Hiroshi ISHIKAWA
Keyword(s):  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

The Effect of Density on the Bending Fatigue of Powdered Metal Gears

2007 ◽  
Author(s):  
David A. Alven ◽  
Peter G. Imbrogno
Keyword(s):  
Significant Influence ◽  
Fatigue Testing ◽  
Fatigue Properties ◽  
Powder Metal ◽  
Bending Fatigue ◽  
Powdered Metal ◽  
Single Tooth

The bending fatigue properties of powder metal (P/M) gears as a function of density were investigated. SAE-AISI 4600 based steel gears were manufactured using various powdered metal processes. The processes used were press and sinter, double press and double sinter, surface densify, and powder forge (P/F). The resulting gears were then subjected to single tooth bending fatigue testing and compared with 4600 based wrought gears. It was found that the density of the P/M part had a significant influence on the bending fatigue properties. When compared to the wrought material, a P/M gear of equivalent density was found to have similar bending fatigue properties.

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