Investigation of bending fatigue strength limit of alloy steel gear teeth

2012 ◽  
Vol 226 (3) ◽  
pp. 615-625 ◽  
Author(s):  
X X Bian ◽  
G Zhou ◽  
Liwei ◽  
J Z Tan
Keyword(s):  
Alloy Steel ◽  
Endurance Limit ◽  
Statistical Data ◽  
Basic Number ◽  
Test Method ◽  
Bending Fatigue ◽  
Gear Teeth ◽  
Strength Limit ◽  
Single Tooth ◽  
Curve Extension

An experimental investigation was conducted on the single-tooth pulsating bending fatigue of 38SiMnMo alloy steel at a frequency range of 140–150 Hz. Using both up–down test method and S–N curve extension method, statistical data in terms of curves and endurance limits were analysed. The testing and analytical results indicated that the ‘platform’ of fatigue curves exists and the S–N curve cannot be extended to the cyclic basic number Nb in order to obtain the endurance limit. Furthermore, on the basis of the life distribution optimization, the three-parameter Weibull distribution was used for statistical data analysis. The statistical analysis showed that the bending endurance limit of 38SiMnMo alloy steel gears estimated at 99 per cent reliability and 95 per cent confidence was 284 MPa, which was located at the slightly low part of the mean line in the chart range illustrated in the standards ISO6336 and GB3480. The results demonstrated that the method described in this article was valuable.

Estimating the Endurance Limit of 9310, 4340M, and 4360 Steel Gears

2000 ◽  
Author(s):  
Chien Wern ◽  
Hormoz Zareh ◽  
Matt Carter ◽  
Kelly Jones ◽  
Mike Renzelmann
Keyword(s):  
Endurance Limit ◽  
Fatigue Behavior ◽  
Test Fixture ◽  
Bending Fatigue ◽  
Yield Load ◽  
Face Width ◽  
Single Tooth ◽  
Bending Fatigue Test ◽  
Number Of Cycles ◽  
Cycles To Failure

Abstract Single tooth bending fatigue behavior of three gear alloys, namely carburized 9310, induction hardened 4340M and 4360 alloys were examined. The alloys were fabricated into gears having a module of 2.12 (12 diametral pitch) with 12.7 mm (1/2 inch) face width. As the gear geometry was different from that recommended in SAE Single Tooth Gear Bending Fatigue Test standard (SAE-J1619), a test fixture was designed to accommodate these gears. The fixture has the added feature of conjugate action, not found in the SAE test standard. The gears were slowly bent in the fixture to determine the yield load. Then fatigue loads of 85%, 75%, and 65% of yield load were used to determine the number of cycles to failure. The expected endurance limit for single tooth bending fatigue was determined statistically from the finite portion of the load-cycles to failure curve.

scholarly journals Research on the Maximal Bearing Capacity Calculation of a New Double Ring Reducer Based on MATLAB

2015 ◽  
Vol 9 (1) ◽  
pp. 34-39
Author(s):  
Qiang Xu ◽  
Qi-sheng Xu ◽  
Dao-Yi Xu
Keyword(s):  
Bearing Capacity ◽  
Elastic Deformation ◽  
Gear Tooth ◽  
Bending Fatigue ◽  
Gear Teeth ◽  
Double Ring ◽  
Contact Points ◽  
Single Tooth ◽  
Capacity Calculation ◽  
Mathematical Relationships

The bearing capacity of a new double ring reducer increases with the increase of load because of the elastic deformation of the gear tooth. In order to solve the problem of its bearing capacity quantificationally, the concept of the maximal bearing capacity is put forward. Starting with that the single tooth bending stress is up to the bending fatigue strength, a mathematical model to determine the normal backlash of the gear teeth has been established, the maximal deformation of the single tooth has been determined. The mathematical relationships have also been setup between the normal backlashes of the tooth pairs, the maximal deformation and number of contact points, a corresponding MATLAB program is designed. The maximal bearing capacity of the reducer has been estimated through examples and proved by experiment. The results show that the calculation method is more effective and fully considers the factors that the elastic deformation of the gear tooth can increases its bearing capacity, so the structure of the reducer is more compact, which establishes the theory foundation for designing the reducer.

scholarly journals Bending Fatigue Behavior of 17-4 PH Gears Produced by Additive Manufacturing

2021 ◽  
Vol 11 (7) ◽  
pp. 3019
Author(s):  
Franco Concli ◽  
Luca Bonaiti ◽  
Riccardo Gerosa ◽  
Luca Cortese ◽  
Filippo Nalli ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Specific Resistance ◽  
Fatigue Behavior ◽  
Powder Bed ◽  
Bending Fatigue ◽  
Experimental Campaign ◽  
Single Tooth ◽  
Final Failure ◽  
Effective Design ◽  
Resistance Data

The introduction of Additive Manufacturing (AM) is changing the way in which components and machines can be designed and manufactured. Within this context, designers are taking advantage of the possibilities of producing parts via the addition of material, defining strategies, and exploring alternative design or optimization solutions (i.e., nonviable using subtractive technologies) of critical parts (e.g., gears and shafts). However, a safe and effective design requires specific resistance data that, due to the intrinsic modernity of additive technologies, are not always present in the literature. This paper presents the results of an experimental campaign performed on gear-samples made by 17-4 PH and produced via Laser Powder Bed Fusion (PBF-LB/M). The tests were executed using the Single Tooth Bending Fatigue (STBF) approach on a mechanical pulsator. The fatigue limit was determined using two different statistical approaches according to Dixon and Little. The obtained data were compared to those reported in the ISO standard for steels of similar performance. Additional analyses, i.e., Scanning Electron Microscopy SEM, were carried out to provide a further insight of the behavior 17-4PH AM material and in order to investigate the presence of possible defects in the tested gears, responsible for the final failure.

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

Nitriding Gears

2000 ◽  
pp. 133-158
Keyword(s):  
Fatigue Life ◽  
Liquid Medium ◽  
Case Studies ◽  
Alloy Steel ◽  
Fatigue Damage ◽  
White Layer ◽  
Case Hardening ◽  
Bending Fatigue ◽  
Gas Nitriding ◽  
Hardening Process

Abstract Nitriding is a case-hardening process used for alloy steel gears and is quite similar to case carburizing. Nitriding of gears can be done in either a gas or liquid medium containing nitrogen. This chapter discusses the processes involved in gas nitriding. It reviews the effects of white layer formation in nitrided gears and presents general recommendations for nitrided gears. The chapter describes the microstructure, overload and fatigue damage, bending-fatigue life, cost, and distortion of nitrided gears. Information on nitriding steels used in Europe and the applications of nitrided gears are also provided. The chapter presents case studies on successful nitriding of a gear and on the failure of nitrided gears used in a gearbox subjected to a load with wide fluctuations.

An Energy-Based Load Distribution Approach for the Application of Gear Mesh Stiffness on Elastic Bodies

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Faysal Andary ◽  
Joerg Berroth ◽  
Georg Jacobs
Keyword(s):  
Degrees Of Freedom ◽  
Design Method ◽  
Mesh Stiffness ◽  
Gear Teeth ◽  
Gear Mesh ◽  
Elastic Bodies ◽  
Single Tooth ◽  
Traditional Approaches ◽  
Energy Based Design ◽  
Gear Mesh Stiffness

This study introduces a new potential energy-based design method for simplifying elastic gear bodies in low- to mid-range frequency applications by bridging over the gear teeth with external stiffness elements. The advantage of the introduced method over more traditional approaches, which are either based on rigid gears or on replacing the teeth, is that the complex gear body and its dynamic behavior are preserved, albeit with fewer degrees of freedom. The method is demonstrated on a gear by replacing a single tooth under load and then validated numerically against a typical flexible gear model. The simulation results show good accuracy within the chosen frequency range and with a clear reduction in calculation time compared to the unreduced model. Furthermore, the extension and optimization potential of the results is discussed.

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.

Cyclic, Monotonic and Fatigue Performance of Stabilized Stainless Steel in PWR Water and Research Laboratory

2018 ◽  
Author(s):  
Jussi Solin ◽  
Jouni Alhainen ◽  
Tommi Seppänen ◽  
H. Ertugrul Karabaki ◽  
Wolfgang Mayinger
Keyword(s):  
Stainless Steel ◽  
Endurance Limit ◽  
Elevated Temperatures ◽  
Laboratory Data ◽  
Test Method ◽  
Fatigue Performance ◽  
Austenitic Steels ◽  
Cyclic Behavior ◽  
Normal Operation ◽  
Environment Temperature

Strain controlled LCF testing extended to 10 million cycles revealed an abrupt endurance limit enforced by secondary hardening. In elevated temperatures the ε-N curve is rotated and endurance limit is lowered, but not vanished. When very low strain rates are applied at 325°C in simulated PWR environment, fatigue life is reduced, but far less than predicted according to NUREG/CR-6909. It is possible, but not probable that the difference is due to different stainless grades studied. We assume that the test method plays a more important role. We have repeatedly demonstrated in different tests campaigns that interruptions of straining with holds aiming to simulate steady state normal operation between fatigue relevant cycles can notably extend the fatigue endurance. Further proof is again presented in this paper. The suspected explanation is prevention of strain localization within the material microstructure and also in geometric strain concentrations. This actually suggests, that hold effects should be even more pronounced in real components. Cyclic behavior of austenitic steels is very complex. Transferability of laboratory data to NPP operational conditions depends on test environment, temperature, strain rate and holds in many ways not considered in current fatigue assessment procedures. In addition to penalty factors, also bonus factors are needed to improve transferability. Furthermore, it seems that the load carrying capacity of fatigued stainless steel is not compromised before the crack growth phase. Tensile tests performed after fatigue tests interrupted shortly before end-of-life condition in 325°C (N ≈ 0.85 × N25) showed strength and ductility almost identical to virgin material. This paper provides new experimental results and discusses previous observations aiming to sum up a state of the art in fatigue performance of German NPP primary loop materials.

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