Search results

1 – 10 of 21
Content available
Article
Publication date: 8 February 2011

John Taylor and Jorge Seabra

Abstract

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Ramiro Martins, Cristiano Locatelli and Jorge Seabra

The purpose of this paper is to get a better understanding of roughness evolution and micropitting initiation on the tooth flank, as well as the evolution of surface…

Abstract

Purpose

The purpose of this paper is to get a better understanding of roughness evolution and micropitting initiation on the tooth flank, as well as the evolution of surface topography during the test load stages in a modified DGMK short micropitting test procedure.

Design/methodology/approach

A modified DGMK short micropitting test procedure was performed, using an increased number of surface observations (three times more) in order to understand the evolution of the surface during each load stage performed. Each of these surface observations consists in the evaluation of surface roughness, surface topography, visual inspection and also weigh measurements as well as lubricant analysis.

Findings

This work showed that the larger modifications on surface took place in the beginning of tests, especially during load stage K3 (lowest load, considered as running‐in) and on the first period of load stage K6, that is, during the first 200,000 cycles of the test. The 3D roughness parameters (St and Sv), obtained from the surface topographies, gave a more precise indication about surface roughness evolution and micropitting generation than the 2D parameters, especially in what concerns to inferring the depth of micropits and the reduction of roughness. Tooth flank topography allows to identify local changes on the surface and the appearance of first micropits.

Research limitations/implications

This work was performed with gears holding a high surface roughness and with a ester‐based lubricant. It was interesting to see the differences observed for surface evolution, for other base oils and also for gears with lower roughness.

Practical implications

The main implication of this work is the understanding that major changes in the surface took place in the first cycles, indicating that the running‐in procedure could be very important for the surface fatigue life. This work also showed that micropitting depends on local contact conditions. Depending on the roughness of the counter surface, micropitting can appear on the bottom of the deep valleys and/or do not appear on the tip of the roughness peaks. The surface topography, and implicitly 3D roughness parameters, is very useful for the observation of surface evolution.

Originality/value

This paper shows in detail the evolution of the tooth surface during a micropitting test. The micropits generation and evolution and also surface wear evolution are presented.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Luis Magalhaes, Ramiro Martins, Cristiano Locateli and Jorge Seabra

The purpose of this paper is to develop innovative geometry for gears aiming low power loss and easy manufacturing.

Abstract

Purpose

The purpose of this paper is to develop innovative geometry for gears aiming low power loss and easy manufacturing.

Design/methodology/approach

New gear profiles were developed and studied, and gears were built accordingly and then tested using an FZG machine.

Findings

Results from the experimental tests revealed the influence of the profile modifications on the operating temperature, thus on the efficiency of gears (in terms of power loss).

Research limitations/implications

Studied cases were limited to experimental gear models compliant to the FZG machine.

Practical implications

Low‐loss gears can be produced using common technologies and tools. Its design includes power loss minimization besides mechanical strength. The new gears are more environmentally friendly and can operate with lower power consumption, lower temperature, increasing gear and gear oil life.

Originality/value

This work contributes to the development of the “low‐loss gears” concept, adapting it to low‐cost manufacturing technologies. Finally, more efficient gears and gearboxes can be produced only by performing simple geometrical modifications to standard gears.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Markus Klein, Bernd‐Robert Höhn, Klaus Michaelis and Rainer Annast

A failure mode called “flank breakage” is increasingly observed in cylindrical and bevel gears. Up to now, there was no calculation method available to determine the…

Abstract

Purpose

A failure mode called “flank breakage” is increasingly observed in cylindrical and bevel gears. Up to now, there was no calculation method available to determine the load‐carrying capacity related to flank breakage in bevel gears. Therefore, a research project was initiated to investigate the described failure mode in bevel gears and to develop a calculation method to predict the risk of flank breakage of such gears. The purpose of this paper is to describe this project.

Design/methodology/approach

The presented research project contained: determination of the decisive influence parameters in experimental investigations with bevel gears; development of a model to explain flank breakage in bevel gears; and development of a calculation method and design rules to avoid flank breakage.

Findings

In systematic tests, the influenced parameters of flank breakage were investigated. Besides the load torque, especially the case depth and the core hardness turned out as decisive parameters. A higher sulfur concentration in the material does not seem to be critical. The analysis of damage patterns of test and practical gears showed that the initiating crack always started below the surface in the region of the transition from case to core. For unidirectional loading, the crack propagates to the active flank on the one side and to the tooth root on the other side. On the basis of these findings, a local and a simplified calculation method were developed to estimate the risk of flank breakage.

Originality/value

With the described calculation method, it is now possible to evaluate running gears according to their risk of flank breakage and design new gears with a sufficient safety factor to avoid this failure.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Klaus Michaelis, Bernd‐Robert Höhn and Michael Hinterstoißer

Besides other approaches, fuel savings in automotive applications and energy savings, in general, also require high‐efficiency gearboxes. Different approaches are shown…

Abstract

Purpose

Besides other approaches, fuel savings in automotive applications and energy savings, in general, also require high‐efficiency gearboxes. Different approaches are shown regarding how to further improve gearbox efficiency. This paper aims to address these issues.

Design/methodology/approach

The paper takes the following approach: theoretical and experimental investigations of bearing arrangements and gear design as well as lubricant type and lubricant supply to the components lead to efficiency optimisation.

Findings

No‐load losses can be reduced, especially at low temperatures and part‐load conditions when using low‐viscosity oils with a high viscosity index and low oil immersion depth or low spray oil supply of the components. Bearing systems can be optimised when using more efficient systems than cross‐loading arrangements with high preload. Low‐loss gears can contribute substantially to load‐dependent power loss reduction in the gear mesh. Low‐friction oils are available for further reduction of gear and bearing mesh losses. All in all, a reduction of the gearbox losses in an average of 50 per cent is technically feasible.

Originality/value

Results from different projects of the authors and from the literature are combined to quantitatively evaluate the potential of power loss reduction in gearboxes.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Bernd‐Robert Höhn, Klaus Michaelis and Hans‐Philipp Otto

The purpose of this paper is to make an attempt to evaluate the pitting load carrying capacity under increased thermal conditions. This is the basis for an estimated…

Abstract

Purpose

The purpose of this paper is to make an attempt to evaluate the pitting load carrying capacity under increased thermal conditions. This is the basis for an estimated lifetime which is one of the most important parameters defining transmission reliability.

Design/methodology/approach

Recommendations related to pitting load carrying capacity calculation of case hardened gears running at high gear bulk temperatures are formulated. These factors are based on extensive experimental data, obtained in pitting tests with high oil injection temperatures, high oil sump temperatures or high operational gear bulk temperatures due to a lack of heat dissipation caused by minimised lubrication.

Findings

Testing of gear type C‐PT on FZG back‐to‐back test rig at high gear bulk temperatures by either heating up the lubricant or caused by a lack of heat dissipation as it appears with poor lubrication conditions resulted in a decrease of up to 30 per cent of the endurance strength in various investigations. This results in a reduction of the material strength due to tempering effects and high surface shear stress due to low oil film thicknesses caused by low operating oil viscosities.

Originality/value

The present calculation method in the standard DIN/ISO is not valid for high gear bulk temperatures. Nevertheless, the present calculation algorithms of the standards DIN/ISO are valid for low and moderate thermal operating conditions when using oil temperatures of up to 80 (90)°C in the case of a sufficient cooling oil supply to the gear mesh. With the presented modifications higher gear bulk temperatures (>120°C) can be taken into account.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 26 September 2008

Ramiro Martins and Jorge Seabra

This paper's aim is to present the gear micropitting performance of two industrial gear oils: a standard mineral lubricant (CM) containing a special micropitting additive…

Abstract

Purpose

This paper's aim is to present the gear micropitting performance of two industrial gear oils: a standard mineral lubricant (CM) containing a special micropitting additive package and a biodegradable ester with low toxicity additivation.

Design/methodology/approach

Gear micropitting tests were performed on the FZG machine, using type C gears made of case carburized steel. Lubricant samples were collected during the tests for analyzing the wear particles generated during operation. Post‐test analysis included the visual inspection of the teeth flanks and the assessment of the micropitting area, the mass loss of the gear, the ferrometric analysis of the lubricant samples and the surface roughness measurement of the teeth flanks, below and above the pitch line.

Findings

The micropitting performance of the two lubricants was very similar, confirming the advantage of using the ester lubricant (CE) as an industrial gear oil, now that it is an environmentally friendly product.

Research limitations/implications

The tests were only performed on carburizing steel and refer to the tested lubricants.

Practical implications

The study confirms the appropriateness of biodegradable ester oil to industrial gear applications, allowing the replacement of environmentally harmful gear lubricants. It shows that the micropitting protection conferred is similar to that exhibited by highly additivated CMs.

Originality/value

The paper shows the applicability of biodegradable CEs to gear lubrication, mainly where it concerns micropitting protection, and shows its potential advantages, together with the biodegradability.

Details

Industrial Lubrication and Tribology, vol. 60 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 8 February 2011

Raquel Bayón, Cristina Zubizarreta, Roman Nevshupa, Juan Carlos Rodriguez, Xana Fernández, Unai Ruiz de Gopegui and Amaya Igartua

The aim of this work is the study the tribological behaviour and tribocorrosion resistance of newly developed multilayer PVD coatings Cr/CrN and CrN/ZrCN applied on…

Abstract

Purpose

The aim of this work is the study the tribological behaviour and tribocorrosion resistance of newly developed multilayer PVD coatings Cr/CrN and CrN/ZrCN applied on nitrided F1272 steel for gear applications.

Design/methodology/approach

Tribological characterization has been completed by several tribological tests performed under ball‐on‐disc configuration, extreme pressure tests to determine the maximum load before the films failure and rolling‐sliding tests under line‐contact conditions (35‐40 per cent of sliding). The response of the different coatings to sodium chloride aggressive environment has been simulated by accelerated tribocorrosion tests, combining simultaneously chemical and mechanical factors. The synergistic effect of wear on corrosion behaviour and vice versa, has been studied in order to compare the protective properties of the different PVD coatings developed.

Findings

Cr/CrN PVD coating improves wear in almost a 90 per cent compared to the nitrided substrate, presenting a similar behaviour to this one under extreme pressure conditions. CrN/ZrCN coating also improved substrate wear and especially good behaviour for this coating was observed under extreme pressure conditions. Cr/CrN coating strongly decreases micropitting and scuffing effect when it is tested under rolling‐sliding configuration. Under micro‐pitting conditions, coating protects the substrate and reduces the fatigue of uncoated discs. When adhesive wear (scuffing) is studied also Cr/CrN improves notable the nitrided steel performance. Under simultaneously corrosion‐wear conditions, Cr/CrN coating registered the lowest material loss because in this case only corrosion effect contributed to the coated surface degradation being the mechanical contribution inappreciable.

Originality/value

New multilayer coatings with improved wear performance and tribocorrosion resistance have been developed and comprehensively characterized. These coatings can be used in advanced gears for corrosive environmental conditions as well as with biodegradable lubricants.

Details

Industrial Lubrication and Tribology, vol. 63 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 1 January 2012

Jorge Rodrigues and Miguel Seabra

The aim of this paper is to investigate how the corporate board compensations as a whole, must be perceived as fair and not directly related to the short‐term results…

Abstract

Purpose

The aim of this paper is to investigate how the corporate board compensations as a whole, must be perceived as fair and not directly related to the short‐term results, thus avoiding embarrassment and misunderstanding.

Design/methodology/approach

The study analyzed the theoretical issues associated with the question of corporate board compensation and developed a research applied to two companies in the Portuguese energy sector, listed on stock exchanges.

Findings

The findings reveal that total remuneration paid to board of directors is in line with the values involved in the business, which is not always well perceived by Society.

Practical implications

The Portuguese energy sector is based on a concentrated market structure. The boards of the companies seem to be composed of independent directors, their pay systems consisting of a fixed and a variable component; this seems supported by a capitalist logic of value creation for shareholders.

Originality/value

This is the first time that corporate board compensations have been publicly revealed. The analysis of systems of remuneration of directors is made using the public information provided by the respective companies in the year 2009. The total remuneration is compared with the size of their respective companies.

Details

Management of Environmental Quality: An International Journal, vol. 23 no. 1
Type: Research Article
ISSN: 1477-7835

Keywords

To view the access options for this content please click here
Book part
Publication date: 7 February 2013

David Crowther and Shahla Seifi

Corporate entities of whatever shape or form (profit motive or not-for-profit) aspire to be successful in whatever they do. Success can come about through many means. In…

Abstract

Corporate entities of whatever shape or form (profit motive or not-for-profit) aspire to be successful in whatever they do. Success can come about through many means. In recent times, corporate entities around the world have come to realise that success can be achieved when they are perceived by their stakeholders as being socially responsible; these stakeholders tend to warm to what the entities do or stand for, which consequently makes a big difference in terms of achieving or not achieving their strategic objectives (Aras & Crowther, 2009). This has become even more apparent during the recent economic and financial crisis where the socially responsible organisation has prospered while others faltered and CSR has been adopted as a survival strategy (Crowther & Seifi, 2011). A socially responsible corporate entity takes cognisance of the impact of its actions on its communities, its stakeholders and the environment when formulating its corporate objectives and in its decision making process. It strives at all times to either minimise or totally remove the adverse effects of its activities on the environment, employees, business contacts group, suppliers of funds and credits, governments and other affected members of society. Corporate entities around the world now consider that being socially responsible is not just very ‘trendy’ but also good for business and so an essential part of their strategy, quite a dramatic change over the last decade.

Details

Education and Corporate Social Responsibility International Perspectives
Type: Book
ISBN: 978-1-78190-590-6

1 – 10 of 21