Gear root bending strength: statistical treatment of Single Tooth Bending Fatigue tests results

2021 ◽  
Author(s):  
Luca Bonaiti ◽  
Francesco Rosa ◽  
Prasad Mahendra Rao ◽  
Franco Concli ◽  
Carlo Gorla
Keyword(s):  
Bending Strength ◽  
Statistical Treatment ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Single Tooth

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 Gear Root Bending Strength: A New Multiaxial Approach to Translate the Results of Single Tooth Bending Fatigue Tests to Meshing Gears

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 863
Author(s):  
Franco Concli ◽  
Lorenzo Fraccaroli ◽  
Lorenzo Maccioni
Keyword(s):  
Material Properties ◽  
Bending Strength ◽  
Load Ratio ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Design Data ◽  
Bending Fatigue ◽  
Relevant Effect ◽  
Accurate Design ◽  
Single Tooth

Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material properties with respect to tests conducted on Running Gears (RG). Therefore, it is common practice to use a constant correction factor fkorr, of value 0.9 to exploit STBF results to design actual gears, e.g., through ISO 6336. In this paper, the assumption that this coefficient can be considered independent from the gear material, geometry, and loading condition was questioned, and through the combination of numerical simulations with a multiaxial fatigue criterion, a method for the calculation of fkorr was proposed. The implementation of this method using different gear geometries and material properties shows that fkorr varies with the gears geometrical characteristics, the material fatigue strength, and the load ratio (R) set in STBF tests. In particular, by applying the Findley criterion, it was found that, for the same gear geometry, fkorr depends on the material as well. Specifically, fkorr increases with the ratio between the bending and torsional fatigue limits. Moreover, through this method it was shown that the characteristics related to the material and the geometry have a relevant effect in determining the critical point (at the tooth root) where the fracture nucleates.

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.

Bending Fatigue Strength of Innovative Gear Materials for Wind Turbines Gearboxes: Effect of Surface Coatings

2012 ◽  
Author(s):  
Carlo Gorla ◽  
Francesco Rosa ◽  
Franco Concli ◽  
Horacio Albertini
Keyword(s):  
Bending Strength ◽  
Test Procedure ◽  
Base Material ◽  
Fatigue Tests ◽  
Research Project ◽  
Bending Fatigue ◽  
Gear Manufacturing ◽  
Tungsten Carbide Coating ◽  
Traditional Manufacturing ◽  
Set Up

In order to better exploit the available resources, wind turbine size is constantly increasing: the need of bigger gearboxes is an obvious and immediate consequence of this evolution tendency. The traditional manufacturing methods exhibit some difficulties for a mass-production of such large and high quality gears. The aim of the XL-Gear research project is to identify an alternative gear manufacturing procedure. This procedure mainly relies on the selection of innovative and adequate materials to manufacture the gears. Two innovative materials (Jomasco and Metasco) have been identified. A common gear material has been selected to define a baseline from which variations can be evaluated. In addition, the effects of a thermal spray tungsten carbide coating on the base material will be also investigated. In the first part of this research project, the bending resistance is evaluated, while, in the second part, the pitting resistance will be evaluated. In order to assess to bending strength, adequate gear geometry has been designed and some parts manufactured with the above mentioned materials. These gears have then been used to perform STF (Single Tooth Fatigue) bending fatigue tests. In the paper, the STF test procedure design and set-up will be described and the STF tests results on the baseline and coated gear will be presented and discussed.

Mechanical Characterizations of Saxidomus purpuratus Shells

2010 ◽  
Vol 434-435 ◽  
pp. 601-604 ◽  
Author(s):  
W. Yang ◽  
Y. Jiang ◽  
G.P. Zhang ◽  
Y.S. Chao ◽  
Xiao Wu Li
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Bending Strength ◽  
Target Material ◽  
Organic Matrix ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Three Point Bending ◽  
Saxidomus Purpuratus ◽  
Scanning Electron

A sort of biological shells (Saxidomus purpuratus), which belongs to Bivalve, was selected as the target material, and hardness and dynamic three point bending fatigue tests were conducted to examine its mechanical properties. Microhardness measurements showed that the inner layer is the hardest. The indentation on the specimen with a lower bending strength was damaged more seriously by the same load. Three point bending fatigue tests demonstrated that this kind of the shells with a special structure comprising mineral and organic matrix can experience the repeated loads instead of immediate breaking. The fatigue results on a single shell investigated here indicated that the fatigue strength is usually less than the static bending strength. Most of the fatigue lives of the specimens are less than 2105 cycles. In addition, fatigue fracture surfaces are observed by scanning electron microscopy.

CHARACTERISTICS OF A NEW TEST RIG AND METHODOLOGY FOR CYCLIC TESTING OF GEAR TOOTH BENDING FATIGUE STRENGTH

Tribologia ◽  
2019 ◽  
Vol 283 (1) ◽  
pp. 57-65
Author(s):  
Waldemar TUSZYŃSKI ◽  
Michał GIBAŁA ◽  
Marek KALBARCZYK ◽  
Eugeniusz MATRAS ◽  
Remigiusz MICHALCZEWSKI ◽  
...  
Keyword(s):  
Research Methodology ◽  
Bending Strength ◽  
Gear Tooth ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Strength Parameter ◽  
Bending Fatigue ◽  
New Device ◽  
Engineering Materials ◽  
Materials Used

Tooth fracture is the most dangerous form of gear wear that excludes the gear from further use. In order to counteract the occurrence of this type of damage, it is very important to properly design the toothed gear. To calculate the gear tooth bending strength, a strength parameter called the nominal stress number σFlim is necessary. ISO 6336-5:2003(E) and available material databases provide σFlim values for the most popular engineering materials used for gears, including those for case-hardened steels. There is, however, no data for a new generation of nanostructured engineering materials, which are the subject of research conducted at the Tribology Department of ITeE – PIB. The σFlim parameter is most often determined in cyclic fatigue tests on toothed gears with specially selected tooth geometry. In order to determine the above strength parameter, a pulsator (symbol T-32) was developed and manufactured at ITeE-PIB in Radom. The article presents a new device, research methodology, and the results of verification tests for case-hardened steel 18CrNiMo7-6, confirming the correctness of the adopted design assumptions and the developed research methodology. The results of tooth bending fatigue tests are the basis for the selection of a new engineering material dedicated to gears, which later undergoes tribological testing.

Contact and bending fatigue behaviour of austempered ductile iron gears

2017 ◽  
Vol 232 (6) ◽  
pp. 998-1008 ◽  
Author(s):  
Carlo Gorla ◽  
Edoardo Conrado ◽  
Francesco Rosa ◽  
Franco Concli
Keyword(s):  
Ductile Iron ◽  
Contact Fatigue ◽  
Research Programme ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Austempered Ductile Iron ◽  
Fatigue Properties ◽  
Bending Fatigue ◽  
Metallurgical Analysis ◽  
Single Tooth

In the present paper a research programme aimed at investigating both the bending and contact fatigue properties of an austempered ductile iron applied to gears is presented, in order to determine reliable values of the limits, which take into account the influence of the production process, to be applied in the design of gearboxes. The bending fatigue tests are performed according to the single tooth fatigue approach and the pitting tests are performed with a back-to-back rig. Metallurgical analysis is performed on the failed specimens, in order to understand the origin and the propagation of the failures and to appreciate the influence of the micro-structure on the performances obtained.

Effect of Moisture Absorption on the Residual Strength after Bending Fatigue of CFRP

2011 ◽  
Vol 415-417 ◽  
pp. 2142-2145
Author(s):  
A Ying Zhang ◽  
Di Hong Li ◽  
Cheng Li Liang ◽  
Jiu Si Jia ◽  
Dong Xing Zhang
Keyword(s):  
Moisture Content ◽  
Composite Laminates ◽  
Immersion Time ◽  
Moisture Absorption ◽  
Bending Strength ◽  
Fatigue Tests ◽  
Material Strength ◽  
Bending Fatigue ◽  
Residual Properties ◽  
Effect Of Moisture

This study investigates the effect of moisture content on the residual bending strength after bending fatigue of T300/914 composite laminates immersed in water for 7 days and 14 days. Displacement-controlled three-point bending fatigue tests were conducted on specimens. After 40,000 cycles the fatigue test was stopped and the residual properties were measured on the tested specimens. Reduction in material strength was found to depend on the level of moisture content. Experimental results reveal that the moisture content in the laminates increased with immersion time. Compared to the unaged specimens, the residual bending strength after bending fatigue decreased by 6.67% and 37.04%, respectively. The residual bending strength and strength retention decreased with increased immersion time.

An analysis of the effect of pressure angle change on bending fatigue performance in asymmetrical spur gears

2021 ◽  
pp. 146442072110266
Author(s):  
Seyit M Demet ◽  
Ali S Ersoyoğlu
Keyword(s):  
Fatigue Tests ◽  
Fatigue Performance ◽  
Spur Gears ◽  
Bending Fatigue ◽  
Pressure Angle ◽  
Angle Change ◽  
Single Tooth ◽  
Aisi 4140 ◽  
Tooth Flank ◽  
Torque Values

In this study, the fatigue performances of symmetrical and asymmetrical spur gears were analyzed by performing single tooth bending fatigue tests. The gears tested were determined to be symmetrical spur gears with a 20°/20° pressure angle, asymmetrical spur gears with a 20°/22° pressure angle, and asymmetrical spur gears with a 20°/25° pressure angle. These gears were made of AISI 4140 material. Single tooth bending fatigue tests were performed under variable loads. Considering the tests performed at the same torque values in asymmetrical spur gears with a 20°/22° pressure angle compared to symmetrical spur gears with a 20°/20° pressure angle, a statistically significant increase in performance was achieved at close to 90%. While gears with 20°/20° and 20°/22° pressure angles break at the tooth root, tooth flank fracture was observed in relatively high numbers of cycles in asymmetric spur gears with a 20°/25° pressure angle. It was observed that the formation of tooth flank damage negatively affected the fatigue performance.

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