An Experimental Evaluation of High-Cycle Gear Tooth Bending Fatigue Lives Under Fully Reversed and Fully Released Loading Conditions With Application to Planetary Gear Sets

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Isaac J. Hong ◽  
Ahmet Kahraman ◽  
Neil Anderson
Keyword(s):  
Fatigue Life ◽  
Gear Tooth ◽  
Planetary Gear ◽  
Fatigue Tests ◽  
Experimental Methodology ◽  
Tooth Root ◽  
Loading Conditions ◽  
Bending Fatigue ◽  
Equivalent Number ◽  
Stress Ratios

Abstract High-cycle gear tooth bending fatigue lives of spur gears under fully reversed and fully released loading conditions are compared in this experimental study. The experimental methodology described in an earlier publication, (Hong et al. 2020, “A Rotating Gear Test Methodology for Evaluation of High-Cycle Tooth Bending Fatigue Lives Under Fully Reversed and Fully Released Loading Conditions,” Int. J. Fatigue, 133, p. 105432. 10.1016/j.ijfatigue.2019.105432), is employed to perform two sets of rotating, gear tooth bending fatigue tests. Statistical analyses are performed to regress stress versus life (S–N) curves under both loading conditions. These curves indicate that a gear under fully reversed loads has a shorter bending life at the same maximum tooth root stress as a gear under fully released loads. Various planetary gear set kinematic conditions with different stationary members are considered to determine the equivalent number of tooth loading cycles per revolution of the sun gear. They are combined with established S–N curves under both loading conditions to determine the ratios of allowable maximum tooth root stresses amongst the gear components of a P-planet gear set such that each gear in the set has the same bending fatigue life. A “stress-balanced” gear set designed to these stress ratios is expected to have the same bending fatigue life for its sun, ring, and planet gears, ensuring that the planetary gear set life is the longest.

The Effects of Periodic High Loads on Fretting Fatigue

1981 ◽  
Vol 103 (3) ◽  
pp. 223-228 ◽  
Author(s):  
A. Kantimathi ◽  
J. A. Alic
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Growth Retardation ◽  
Fretting Fatigue ◽  
Fatigue Tests ◽  
Constant Amplitude ◽  
Axial Loads ◽  
Prolonged Fatigue ◽  
Stress Ratios ◽  
Crack Growth Retardation

Fretting fatigue tests have been conducted on 7075-T7351 aluminum alloy coupons with fretting pads of the same material. Three different stress ratios were used, the otherwise constant amplitude axial loads being interrupted every 1000 cycles by either tensile overloads to 400 MPa or compressive underloads to −200 MPa. Tensile overloads greatly prolonged fatigue life for low stresses where the overload ratios were 1.6 and above; compressive underloads had comparatively little effect. The results are discussed in terms of crack growth retardation phenomena.

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 Influence of the Elastoplastic Strain on Fatigue Durability Determined with the Use of the Spectral Method

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 423 ◽  
Author(s):  
Michał Böhm ◽  
Mateusz Kowalski ◽  
Adam Niesłony
Keyword(s):  
Fatigue Life ◽  
Probability Density ◽  
Spectral Method ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Loading Conditions ◽  
Random Loading ◽  
Elastoplastic Deformations ◽  
Fatigue Life Assessment ◽  
Safe Side

The paper presents experimental static and fatigue tests results under random loading conditions for the bending of 0H18N9 steel. The experimental results were used in performing calculations, according to the theoretical assumptions of the spectral method of fatigue life assessment, including elastoplastic deformations. The presented solution extends the use of the spectral method for material fatigue life assessment, in terms of loading conditions, above Hooke’s law theorem. The work includes computational verification of the proposal to extend the applicability of the spectral method of determining fatigue life for the range of elastoplastic deformations. One of the aims of the proposed modification was to supplement the stress amplitudes used to calculate the probability density function of the power spectral density of the signal with correction, due to the plastic deformation and its use for notched elements. The authors have tested the method using four of the most popular probability density functions used in commercial software. The obtained results of comparisons between the experimental and calculation results show that the proposed algorithm, tested using the Dirlik, Benasciutti–Tovo, Lalanne, and Zhao–Baker models, does not overestimate fatigue life, which means that the calculations are on the safe side. The obtained results prove that the elastoplastic deformations can be applied within the frequency domain for fatigue life calculations.

Optimization of Tooth Bending Fatigue Characteristics of Spur Gear Pairs Using a Gear Dynamics-Based Approach

2015 ◽  
Author(s):  
Yalın Öztürk ◽  
Ender Ciğeroğlu ◽  
H. Nevzat Özgüven
Keyword(s):  
Fatigue Life ◽  
Gear Tooth ◽  
Spur Gear ◽  
Bending Fatigue ◽  
Gear Dynamics ◽  
Optimization Study ◽  
Fatigue Life Estimation ◽  
Fatigue Characteristics ◽  
Profile Optimization ◽  
Operational Range

A gear tooth profile optimization study is performed with the target being defined as the maximization of tooth bending fatigue life for a selected operational range, where the operating torque and speed ranges are defined along with their corresponding durations. For this purpose, a nonlinear lumped gear dynamics model is combined with the S/N curve of the gear material in order to estimate tooth bending fatigue life of the spur gear pair. The differences between the predicted lives of the optimally modified and non-modified gear pairs are presented based on example spur gear pairs. The proposed tooth bending fatigue life estimation is compared with the standard AGMA procedure.

42CrMo Hard Surface Gear Intensity Tests and Modified Parameter Correction

2012 ◽  
Vol 246-247 ◽  
pp. 145-148
Author(s):  
Nai Gen Li ◽  
Nan Xu ◽  
Nian Jun Zhang ◽  
Meng Guo Zhu
Keyword(s):  
Fatigue Strength ◽  
Gear Tooth ◽  
Coincidence Degree ◽  
High Strength ◽  
Tooth Root ◽  
Bending Fatigue ◽  
Hard Surface ◽  
Basic Parameters ◽  
Bending Fatigue Strength ◽  
Research Intensity

Hard surface gears drive is considering mainly how to improve the tooth root bending fatigue strength and wear resistance of the teeth. Based on the analysis of sliding ratio, coincidence degree and the gear tooth root bending fatigue strength, basic parameters of gear can be modified to improve strength. Although these gears must be cut by the standard tools, high strength gears are needed in machinery. In this research, intensity experiments were conducted with 42CrMo modified and standard hard surface gears. Experiment results show that the improvements of 42CrMo gear parameters are effective and teeth strength is improved for the modified parameters of gears.

Enhancement of Fatigue Life in St37 Steels by Carburizing Process

2021 ◽  
Vol 105 ◽  
pp. 59-67
Author(s):  
Jalal Joudaki ◽  
Mehdi Safari
Keyword(s):  
Fatigue Life ◽  
Fatigue Tests ◽  
Diffusivity Coefficient ◽  
Bending Fatigue ◽  
Steel Material ◽  
Wide Range ◽  
Different Temperatures ◽  
St37 Steel ◽  
Fatigue Life Test ◽  
Carburizing Process

Carburizing is a heat treatment process, which used widely for surface hardening. In this process, the parts are placed in a concentrated atmosphere of Carbon atoms. The carbon atoms diffuse in the samples from the surface. In the present article, the effects of carburizing temperature on fatigue life will be studied. The St37 steel material is selected for study due to its wide range of usage in industry and little attention on the carburizing of this material. The samples are prepared by implementing the carburizing process at different temperatures (300, 400, 500, and 600 °C). The holding time is 1 hour for all samples. The two-point bending fatigue tests had been carried out on constant loading stresses. The results of the fatigue life test show that the fatigue life enhances the carburizing process. The fatigue life improved from about 45000 cycles to about 65000 cycles (about 44% increase) by increasing the temperature from 300°C to 600°C. Holding at higher temperatures leads to an increase in fatigue life smoothly due to the increase in the diffusivity coefficient. Also, the fracture surface demonstrates that the crack initiation starts from outer surfaces very slowly and failure happens as a brittle fracture in the samples.

Effect of Aggregate Gradation on Fatigue Life of Asphalt Concrete Mixes

1998 ◽  
Vol 1630 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Jorge B. Sousa ◽  
Jorge C. Pais ◽  
Manuel Prates ◽  
Rui Barros ◽  
Pierre Langlois ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Asphalt Concrete ◽  
Laboratory Tests ◽  
Fatigue Tests ◽  
Test Protocol ◽  
Predictive Equations ◽  
Aggregate Gradation ◽  
Bending Fatigue ◽  
Four Point Bending ◽  
Highway Research

Four-point bending fatigue tests following the Strategic Highway Research Program (SHRP) M009 test protocol were executed to investigate to what extent gradation has an effect on fatigue performance of asphalt aggregate mixes. Gradations and mixes were selected that would satisfy all volumetric Superpave designs passing below the restricted zone. Other mixes were prepared with gradations passing through and above the restricted zone. The measured fatigue lives of 130 actual laboratory tests were compared with predictions by the Shell, Asphalt Institute, and SHRP-A003A fatigue-predictive equations.

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.

Investigating Machining Impact on Fatigue Variance: A Machining Quality Perspective

2004 ◽  
Vol 127 (3) ◽  
pp. 492-502 ◽  
Author(s):  
Xiaoping Yang ◽  
C. Richard Liu
Keyword(s):  
Fatigue Life ◽  
Data Center ◽  
Room Temperature ◽  
Fatigue Tests ◽  
Machining Processes ◽  
Case Scenario ◽  
Bending Fatigue ◽  
Machining Quality ◽  
Four Point Bending ◽  
The Impact

Fatigue life of nominally identical structures under nominally identical loading conditions can scatter widely. This study has investigated the impact of machining processes on such scatters. After Ti 6Al-4V samples were surface ground and face turned, they were subject to constant amplitude four-point bending fatigue tests under room temperature. The best-case scenario of process capability ratios of fatigue for these samples were evaluated with assumed tolerances of fatigue life. Based on these ratios, the numbers of nonconforming parts were estimated. Under the machining conditions from the Machining Data Handbook (Machining Data Center, Cincinnati, 1980), up to 39% of samples due to one process are expected to be nonconforming, whereas only up to 0.6% of samples due to the other process are expected to be nonconforming. The ramifications in terms of cost for machining quality control due to the different capability ratios have been discussed. The current findings indicate an urgent need to further the study of this issue in a scientific manner.

Bending Fatigue Life Prediction of Fillet Rolled Crankshafts

2013 ◽  
Vol 275-277 ◽  
pp. 174-178 ◽  
Author(s):  
Ke Bao ◽  
Ri Dong Liao
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Three Dimensional ◽  
Local Stress ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Stress Strain ◽  
Bending Fatigue ◽  
Bending Strain ◽  
Stress Computation

The influence of residual stesses must be considered in bending fatigue life prediction of fillet rolling crankshafts. In this paper, the stress/strain distributions near fillet during fatigue tests are calculated by finite element method. In residual stress computation, the three dimensional flexible contact model is adopted, and in bending strain computation, the static analysis are selected. Then, bending fatigue life prediction is performed by local stress-strain approach based on the residual stess and bending strain amplitude, and the results agree with the bending fatigue test.

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