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Article

Michele Cerullo and Viggo Tvergaard

– The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings.

Abstract

Purpose

The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings.

Design/methodology/approach

The local stress concentrations around an inclusion are determined from a characteristic unit cell model containing a single inclusion, using the approximation of a 2D plane strain numerical analysis. The Dang Van multiaxial fatigue criterion is used for the local stresses in the matrix material, to ensure that the stresses remain within the fatigue limit. The matrix material is taken to be one of the most commonly used bearing steels, AISI 52100, and two different types of inclusions are considered. The macroscopic stress histories applied correspond to either a Hertzian or an elastohydrodynamic (EHL) contact pressure distribution under the rollers.

Findings

The paper shows that sub-surface fatigue failure due to rolling contact is more likely to develop close to the inclusion-matrix interface, at particular angles that depend on the material and on the inclusion orientation.

Originality/value

Inclusions represent an important issue in the design of wind turbine bearings, that are supposed to work in the very high cycle regime (N>109 cycles). This paper develops a micromechanical study that provides a deeper understanding on effect of inclusions on the fatigue life, according to one of the most used multiaxial fatigue criteria.

Details

International Journal of Structural Integrity, vol. 6 no. 1
Type: Research Article
ISSN: 1757-9864

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Article

Nikos P. Andrianopoulos and Aggelos Pikrakis

The purpose of this paper is to study mutual interaction between von Mises equivalent and hydrostatic stresses at the crack tip area of an elastoplastic material in order…

Abstract

Purpose

The purpose of this paper is to study mutual interaction between von Mises equivalent and hydrostatic stresses at the crack tip area of an elastoplastic material in order to obtain critical conditions for crack propagation under fatigue loading.

Design/methodology/approach

A5083-H111 aluminum alloy is used to obtain a Chaboche-type constitutive equation, which is introduced in a commercial finite elements package to evaluate stress distribution at crack tip area. A simplified three-dimensional (generalized plane strain) grid is used, resulting in fast and accurate results. Numerical simulations are performed to connect crack propagation rate with various combinations of fatigue stress amplitude, initial crack length and number of loading cycles. Distance between characteristic points of stresses distribution in the crack tip area are compared to experimental fatigue crack growth rates in order to assess the validity of the present approach.

Findings

It is found that saturation of plastic strains, i.e. maximization of von Mises equivalent stress, is a prerequisite for hydrostatic stress to take a critical-maximum value, outside the plastically saturated zone. At the point of maximum hydrostatic stress brittle fracture is initiated, driving to separation of the ligament up to crack tip, without formation of new plastic strains. The length of this ligament is defined as crack propagation step, showing good agreement with experimental data.

Originality/value

The present approach seems to constitute a reasonable and adequate method for the description of fatigue crack propagation in terms of continuum mechanics, not necessitating microscopic considerations or empirical criteria lacking theoretical or physical basis. In addition, it liberates from the notion of stress intensity factors, strongly disputed beyond linear elasticity. Improved constitutive equations and numerical models are expected to drive in a complete fatigue failure criterion similar to those of static loading.

Details

International Journal of Structural Integrity, vol. 8 no. 2
Type: Research Article
ISSN: 1757-9864

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Article

Ye Zhou, Caichao Zhu, Huaiju Liu, Chaosheng Song and Zufeng Li

Coatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions…

Abstract

Purpose

Coatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions on the pressure, the shear traction, stresses as well as the fatigue life of spur gear.

Design/methodology/approach

A numerical contact fatigue life model of a coated spur gear pair under elastohydrodynamic lubrication (EHL) is developed based on the characteristics of gear geometry and kinematics, lubrication conditions and material properties. Frequency response functions and the discrete convolute and fast Fourier transform (DC-FFT) algorithm are applied to obtain elastic deformation and stress. Mutil-axial fatigue criteria are used to evaluate the contact fatigue life based upon the predicted time-varying stress fields of coated bodies.

Findings

The maximum Mises stress decreases while the fatigue life increases as the coating modulus decreases. A thinner coating leads to a longer life and a smaller maximum Mises stress for hard coatings. The load has more significant effect on the contact fatigue life of soft coatings.

Originality/value

The developed model can be used to evaluate the contact fatigue life of coated gear under EHL and help designers analyze the effect of coating elastic modulus and thickness on the contact pressure, film thickness and stress.

Details

Industrial Lubrication and Tribology, vol. 70 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

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Article

Florian Pape, Oliver Maiss, Berend Denkena and Gerhard Poll

The efficient and economical use of natural resources is a big issue. Machine elements with a rolling contact are highly relevant because of their wide application in…

Abstract

Purpose

The efficient and economical use of natural resources is a big issue. Machine elements with a rolling contact are highly relevant because of their wide application in technical systems and a large production quantity. Innovative hard machining can reduce the friction and increase the fatigue strength of rolling element bearings. The purpose of this study is to focus on the surface properties of such parts.

Design/methodology/approach

A new model to predict bearing fatigue life is presented which takes compressive residual stresses in the bearing subsurface area into consideration. The investigated bearings were machined by the processes of hard turning, hard turning with subsequent deep rolling and a combination of hard turning and deep rolling (turn-rolling) in one process step. Changes in the residual stress state during bearing fatigue tests were investigated and the influence of residual stresses on the bearings fatigue life was researched.

Findings

Both combinations including the deep rolling process decrease the surface roughness and induce compressive residual stresses. As a result, the L10 fatigue life of roller bearings was increased by the factor of 2.5. Owing to the developed models, this effect can be considered within the design process.

Originality/value

In the context of the research program “Resource efficient Machine Elements (SPP1551),” machining processes of bearings were investigated regarding the bearing fatigue life. By inducing beneficial residual stresses on the bearings’ subsurface area, the fatigue life could be increased. Thus higher resource efficiency was achieved. To increase the productivity, a combination of hard turning and deep rolling was evaluated.

Details

Industrial Lubrication and Tribology, vol. 71 no. 8
Type: Research Article
ISSN: 0036-8792

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Article

Luis Reis, Bin Li and Manuel De Freitas

The purpose of this paper is to study the influence of multiaxial loading composed with different frequencies between the axial and torsional components in 42CrMo4…

Abstract

Purpose

The purpose of this paper is to study the influence of multiaxial loading composed with different frequencies between the axial and torsional components in 42CrMo4 concerning fatigue life and early crack growth orientation.

Design/methodology/approach

Biaxial fatigue tests were carried out by a biaxial servo‐hydraulic machine, considering different loading paths and different frequencies between the normal and shear stress components in 42CrMo4. Theoretical estimations for fatigue life and early crack growth orientation were performed by applying various critical plane models. In addition, fractographic analysis of the fracture surfaces was carried out. The estimated results are compared with experimental results.

Findings

Significant effects were observed of the different frequency between the axial and torsion components on fatigue life and early crack growth orientation. The critical plane models based on shear mode give better estimations when compared with experimental results.

Originality/value

The paper shows that improved fatigue design can be achieved by considering the influence of different frequencies in multiaxial loadings.

Details

International Journal of Structural Integrity, vol. 1 no. 4
Type: Research Article
ISSN: 1757-9864

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Abstract

Details

Traffic Safety and Human Behavior
Type: Book
ISBN: 978-0-08-045029-2

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Abstract

Details

Traffic Safety and Human Behavior
Type: Book
ISBN: 978-1-78635-222-4

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Article

N. Brännberg and J. Mackerle

This paper gives a review of the finite element techniques (FE)applied in the area of material processing. The latest trends in metalforming, non‐metal forming and powder…

Abstract

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming and powder metallurgy are briefly discussed. The range of applications of finite elements on the subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for the last five years, and more than 1100 references are listed.

Details

Engineering Computations, vol. 11 no. 5
Type: Research Article
ISSN: 0264-4401

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Article

ZHI‐HUA ZHONG and JAROSLAV MACKERLE

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years…

Abstract

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite element method has been widely used to solve contact problems with various grades of complexity. Great progress has been made on both theoretical studies and engineering applications. This paper reviews some of the main developments in contact theories and finite element solution techniques for static contact problems. Classical and variational formulations of the problem are first given and then finite element solution techniques are reviewed. Available constraint methods, friction laws and contact searching algorithms are also briefly described. At the end of the paper, a bibliography is included, listing about seven hundred papers which are related to static contact problems and have been published in various journals and conference proceedings from 1976.

Details

Engineering Computations, vol. 9 no. 1
Type: Research Article
ISSN: 0264-4401

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Article

Xiongfei Cao, Ahsan Ali, Abdul Hameed Pitafi, Ali Nawaz Khan and Muhammad Waqas

The purpose of this study is to extend the existing literature on knowledge management, which generally focuses on knowledge sharing. The model of this article explains…

Abstract

Purpose

The purpose of this study is to extend the existing literature on knowledge management, which generally focuses on knowledge sharing. The model of this article explains how knowledge creation and team performance can be increased through the integration of social and technological factors

Design/methodology/approach

To empirically test the model, multi-wave and multi-source data were collected from 80 teams whose members use social media as a tool for communication and interaction.

Findings

The analysis results provide insights into some interesting findings. The results show transactive memory system (TMS) as an important factor that can significantly contribute to knowledge creation in teams. Especially, the TMS strengthens the significant positive effect of enterprise social media (ESM) and insignificant positive effect of knowledge complementarity on knowledge creation. Furthermore, knowledge creation is found to be a significant predictor of team performance

Originality/value

Much of the knowledge management literature focuses on the ways to increase the quantity of accessible knowledge to organization members. Such knowledge management studies are more relevant to knowledge exchange among individual employees, teams and organizations. However, this study takes a nuanced approach to explore how knowledge creation can be increased in teams by implementing a knowledge integration mechanism. A general model of knowledge creation is proposed, but the strength of this model lies in the moderating effect of TMS which strengthens the effect of knowledge complementarity and ESM on knowledge creation in teams which eventually increases team performance.

Details

Information Technology & People, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0959-3845

Keywords

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