Contact and bending fatigue behaviour of austempered ductile iron gears

Gorla, Carlo; Conrado, Edoardo; Rosa, Francesco; Concli, Franco

doi:10.1177/0954406217695846

Cited by 34 publications

(31 citation statements)

References 11 publications

(17 reference statements)

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“…Relevant Papers Presenting STBF Tests [32,47,48] The results of the STBF and RG tests differ for two main reasons. Firstly, in STBF tests, to avoid undesired displacement of the gear, a minimum compressive load is usually present; the typical ratio between the minimum and maximum force applied to the teeth is (R = 0.1), e.g., the STBF tests conducted in [26,37,45,47,49]. Naturally, this differs from RG, where R = 0, and therefore, it alters the average stress present in the tooth [18,19,50,51].…”

Section: Normal Module M Nmentioning

confidence: 99%

“…The actual TBS obtained from tests on RG (σ FlimRG ) is exactly the value σ Flim as intended in the standard. However, to perform these kinds of tests, specific test rigs are needed, e.g., [14,26]. Moreover, the breakage of a tooth makes the gear unusable for further tests, and since each tooth is loaded once every rotation of the tested gear, the experimental campaign results are particularly long and expensive.…”

Section: Introductionmentioning

confidence: 99%

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

Concli

Fraccaroli

Maccioni

2021

Metals

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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.

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Section: Normal Module M Nmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Concli

Fraccaroli

Maccioni

2021

Metals

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“…Three planets engage with sun gear and ring. The latter is directly broached in the ductile iron [6,7] casted housing. The planets are supported by means of full-complement needle bearing [8,9].…”

Section: Planetary Gearboxmentioning

confidence: 99%

Dynamic modeling of gears: An innovative hybrid FEM–analytical approach

Concli¹,

Gorla²

2021

Int. J. CMEM

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Gearboxes are widely used in several applications ranging from the automotive to the industrial and robotic sectors. A planetary gearbox is a special kinematic gear arrangement that, taking advantage of a planet carrier, ensures high reduction ratios together with a very small design. Therefore, they are widely employed for transmissions which require a high power density. There are several fields of applications including, but not limited to, mechatronic, automation and wind power generation. To improve the design of new solutions, for performing monitoring activities on actual gearboxes and for the definition of maintenance schedules, the availability of physical models able to accurately describe the behavior of the system, both in healthy and damaged conditions, would represent a great support. Experimental and numerical studies of the behavior of gearboxes are already available in the literature. Nevertheless, while the experimental approaches are valid only for the specific configuration tested, the numerical techniques show limitations related to the computational effort required. This paper presents an innovative approach for the characterization of the behavior of two different geared transmissions. It is based on a hybrid approach that combines finite elements (FE) with analytical formulations. In detail, the solver computes separately the macro deformation of the bodies (numerical solution based on a coarse grid) and the contacts (solved analytically avoiding the need of mesh refinements). The computational effort is reduced significantly without affecting the accuracy of the results significantly. This approach was used to investigate and understand the vibro-dynamical behavior of a back-to-back test rig (typically used for the characterization of the surface fatigue strength of gears) and of an industrial planetary gearbox. The results obtained for the healthy -not damaged -gearboxes were compared with experimental measurements for both configurations in order to validate the hybrid approach. Once the models were validated, the same methodology was eventually used to study the effects of typical gear failures and in specifically surface fatigue (pitting), on the vibrational response. The capability to reproduce the effect of damages with the model of a gearbox represents the first indispensable step of a Structural Health Monitoring strategy. State-of-art and challenges are analyzed and discussed in the paper.

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“…In RG tests, test rigs have to be able to provide a given torque with proper lubrication to engaging RG [8], [14]. The specimen consists of a gear made of the material (and the treatments/finishes) to be tested.…”

Section: Introductionmentioning

confidence: 99%

Reliable Gear Design: Translation of the Results of Single Tooth Bending Fatigue Tests Through the Combination of Numerical Simulations and Fatigue Criteria

Concli

Maccioni

Bonaiti

2021

WIT Transactions on Engineering Sciences

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Establishing the actual gear root bending strength is a fundamental aspect in gear design. With this respect, gears materials can be characterized through two types of tests, i.e. on Running Gears (RG) or Single Tooth Bending Fatigue (STBF). The former is able to reproduce the loading conditions of the actual gears and, therefore, leads to the most accurate results. The latter excels in terms of efficiency and simplicity of the experimental campaign but as a drawback, tends usually to overestimate the material strength due to the different stress state histories it induces on the tooth root. Therefore, a common practice is to carry out STBF tests and apply a correction coefficient () for exploiting the results in the design of actual gears. In the present paper, an approach to estimate centered on the combination of numerical simulations and multi-axial fatigue criteria based on the critical plane capable of taking into account non-proportional loading conditions has been proposed. In particular, the same gear geometry has been simulated through Finite Element (FE) models in two conditions, i.e. STBF and RG. The outcomes of the simulations, in terms of stress histories in the tooth root region, have been analyzed with five different fatigue criteria, i.e. Findley, Matake, McDiarmid, Papadopoulos, and Susmel et al.has been calculated as the ratio between the maximum damage parameter observed in the STBF and RG conditions according to the different fatigue criteria. Results show that , calculated for three different materials (i.e. 18NiCrMo5, 42CrMoS4, 31CrMo12), differs up to 22% between the RG and the STBF conditions (depending on the criterion considered). Therefore, future studies should aim to understand which fatigue criterion is the most appropriate for this type of analysis.

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Contact and bending fatigue behaviour of austempered ductile iron gears

Cited by 34 publications

References 11 publications

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

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

Dynamic modeling of gears: An innovative hybrid FEM–analytical approach

Reliable Gear Design: Translation of the Results of Single Tooth Bending Fatigue Tests Through the Combination of Numerical Simulations and Fatigue Criteria

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