Bending and contact fatigue strength of innovative steels for large gears

Gorla, Carlo; Rosa, Francesco; Conrado, Edoardo; Albertini, Horacio

doi:10.1177/0954406213519614

Cited by 22 publications

(18 citation statements)

References 5 publications

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“…As discussed in Gorla et al, 4 by adapting the length of the fixed anvil, the same principle described above can be applied also to perform tests with an asymmetric load condition between the two loaded teeth, either in order to obtain a proper value of the applied load, with respect to the range of loads that can be applied by the machine, or to effectively perform a real ''single tooth'' test, to avoid having two teeth loaded at the same test stress.…”

Section: Bendingmentioning

confidence: 89%

“…Additionally, on the basis of the previous experiences of the authors, which have performed and published several tests on gears materials, mainly case hardened and nitriding steels (see, for example, Gorla et al 4,5 and Mariani et al 6) , it can be stated that the fatigue strength of gears is influenced by many parameters that combined can determine large variations of the effective performances. In particular the fatigue performances are influenced by defects, by the state of the surface, by the local geometry at the tooth root, by the residual stresses determined by the heat treatment and the machining process.…”

Section: Introductionmentioning

confidence: 99%

“…The analysis of the available data points out that the different existing standards provide: different value of the limits and different dependency from the specific variant of the material and/or from other properties or other post treatment; different trends for the shape of the S-N curves; some shaded areas of scattering both for the values and for the trend of the S-N curves, and in particular different assumptions concerning the region of the fatigue limit and the existence of the fatigue limit itself. Additionally, on the basis of the previous experiences of the authors, which have performed and published several tests on gears materials, mainly case hardened and nitriding steels (see, for example, Gorla et al. 4,5 and Mariani et al. 6) , it can be stated that the fatigue strength of gears is influenced by many parameters that combined can determine large variations of the effective performances.…”

Section: Introductionmentioning

confidence: 99%

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Contact and bending fatigue behaviour of austempered ductile iron gears

Gorla¹,

Conrado

Rosa

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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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.

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Section: Bendingmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Contact and bending fatigue behaviour of austempered ductile iron gears

Gorla¹,

Conrado

Rosa

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…Such arrangement is known as pulsator tests, and it has been widely adopted in various literature. [24][25][26][27][28][29] Fatigue tests were performed using a stress ratio R ¼ 0.1 and load frequencies between 2 and 20 Hz. A short stair case sequence was performed to evaluate the endurance limit at 3 million cycles, according to the position of the high-cycle knee point set by the ISO standard.…”

Section: Experimental Fatigue Testsmentioning

confidence: 99%

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

Meneghetti

Dengo²,

Conte³

2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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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.

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“…For instance, increases as large as three times load capacity can be achieved using different gear materials. For this reason, the pitting strength is an important parameter to be taken into account in the selection of new gear materials [10]. There is common agreement that contact strength is influenced by Hertz stresses, load cycles, hardness, surface roughness, temperature, and degree of lubrication [11].…”

Section: Introductionmentioning

confidence: 99%

An estimate of the pitting strength of steel materials

Osakue¹,

Anetor²,

Harris³

2021

FME Transactions

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A single expression for estimating the nominal pitting strength of steel materials, based on surface hardness, is developed from first principles for a reliability of 99% at 107 load cycles. It requires the hardness values to be measured in Vicker's hardness scale. The expression may be used for any steel material processed by hot rolling, cold drawing, quenching and tempering or case-hardening. The formulation incorporates a nominal design factor at 99% reliability which is estimated from a probabilistic model based on the lognormal probability density function. Pitting strength estimates from the expression are compared with those of American Gear Manufacturers Association (AGMA) estimates and data from other sources as indicated in Tables 3 and 4. The expression predicts lower values at low hardness but higher values at high hardness. The variance is between - 15.21% and 10.13% for through-hardened steels. For case-hardened steels, the variances range from 14.23% to 20.26% between the estimates and available data. These variances appear to be reasonable considering the many factors involved in pitting resistance. The main advantage of this study is that pitting strength of new steel materials may be estimated for initial design sizing without long and costly contact fatigue testing which of course is necessary for design validation. Also, the estimation method developed may be applied to other materials, metallic and non-metallic. Suggestions are made for estimating some pertinent pitting strength adjustment factors when considering field or service pitting strength.

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Bending and contact fatigue strength of innovative steels for large gears

Cited by 22 publications

References 5 publications

Contact and bending fatigue behaviour of austempered ductile iron gears

Contact and bending fatigue behaviour of austempered ductile iron gears

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

An estimate of the pitting strength of steel materials

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