Change search
Refine search result
12345 1 - 50 of 228
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Almqvist, Andreas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Selected papers from those presented at the 3rd International Tribology Symposium of IFToMM2014In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 26, no 5, p. 273-275Article in journal (Refereed)
  • 2.
    Armada, Sergio
    et al.
    Department of Corrosion and Tribology SINTEF, Materials and Chemistry, Trondheim.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Special issue: Selected papers from the 15th Nordic Symposium on Tribology2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, p. 809-Article in journal (Other academic)
  • 3.
    Awasthy, K. L.
    et al.
    Indian Institute of Technology, New Delhi.
    Prakash, Braham
    Experimental investigation of polymer composites for tribological applications1987In: Synopsis of the papers: Budapest, 1987, Szeptember 22-24 / [ed] Gépipari Tudományos Egyesület, Budapest: Gepipari Tudomanyos Egyesulet , 1987, p. 34-35Conference paper (Other academic)
  • 4. Baart, Pieter
    et al.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Contaminant migration in the vicinity of a grease lubricated bearing seal contact2011In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 133, no 4Article in journal (Refereed)
    Abstract [en]

    Lubricating grease is commonly used for lubricating sealed and greased for life rolling element bearings. This grease also provides an additional sealing function to protect the bearing against ingress of contaminants. In this work the sealing function of lubricating grease in the vicinity of the seal lip contact has been studied experimentally by measuring the migration of spherical fluorescent contaminant particles in the vicinity of the contact, as a function of shaft speed and lubricant type. The experimental results reveal that in some greases contaminant particles migrate towards the sealing contact where the shear rate reaches its highest value. However, for other greases, Newtonian base oils, and elastic fluids, this is not necessarily the case and contaminant particles consistently migrate away from the sealing contact. Various physical phenomena have been investigated to explain the difference in migration behavior. It is concluded that migration towards the sealing contact is driven by the viscosity gradient and migration away from the sealing contact is related to the Weissenberg number. The sealing function of grease in the vicinity of the sealing contact is due to the migration of contaminant particles. The migration reduces the probability of particles to reach the sealing and bearing contacts.

  • 5. Baart, Pieter
    et al.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Non-Newtonian effects on film formation in grease lubricated radial lip seals2009In: Society of Tribologists and Lubrication Engineers annual meeting & exhibition 2009: Lake Buena Vista, Florida, USA, 17 - 21 May 2009, Red Hook, NY: Curran Associates, Inc., 2009, p. 140-142Conference paper (Refereed)
    Abstract [en]

    This study investigates the high shear rheology of grease and determines whether the "normal stress effect" can significantly contribute to film formation in radial lip seal applications. Rheology measurements and a rheology model for the grease have been developed to model the normal stress at high shear rates. Subsequently, a seal lip model is developed to predict lift forces, generated by the normal stress effect. The model predicts lift forces over 50% of the seals specific lip force for low contact pressure bearing seals.

  • 6. Baart, Pieter
    et al.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Non-newtonian effects on film formation in grease-lubricated radial lip seals2010In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 53, no 3, p. 308-318Article in journal (Refereed)
    Abstract [en]

    In existing models, the only lubricant property used for predicting film thickness in radial lip seals is the (base) oil viscosity. Lubricating greases show non-Newtonian behavior, and additional normal stress components develop that may contribute to the load-carrying capacity. This study investigates the shear rheology of greases and determines whether this "normal stress effect" in grease can significantly contribute to film formation in radial lip seals. First, the rheological behavior of grease is studied in a rotary plate-plate rheometer at small gaps of 25-500 μ m up to shear rates of 5 · 104 s-1. The rheology measurements are used for a rheology model that predicts the first normal stress difference in the grease. Second, a seal lip model was developed to predict the lift force generated by the normal stress effect that separates the seal from the shaft. The model results show that the load-carrying capacity depends very much on the operating conditions: lip geometry, speed, and temperature. The model predicts a lift force that is over 50% of the seal specific lip force for low-contact pressure-bearing seals. The model can easily be used in existing oil seal models and makes it possible to optimize seal design by utilizing the normal stress effect.

  • 7.
    Baart, Pieter
    et al.
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the Normal Stress Effect in Grease-Lubricated Bearing Seals2015In: Tribology & Lubrication Technology, ISSN 1545-858X, Vol. 71, no 9, p. 939-943Article in journal (Refereed)
    Abstract [en]

    The film formation in lip seals, due to non-Newtonian rheology of the lubricant, has been a topic of speculation. Earlier work suggests that normal stresses in grease would be favorable for the film build-up between the seal lip and shaft or bearing ring. In the current paper we evaluate this earlier work and our earlier theoretical seal lip model with a series of experiments. We use a modified concentric cylinder geometry and a model fluid to study the fluid pressure distribution in the seal type geometry. The results are then related to grease lubricated seals and our earlier theoretical predictions. The present analysis shows that this earlier work and our earlier predictions are not correct and indicate that normal stresses in the grease pull the seal lip towards the shaft, increasing the contact pressure. However, normal stresses also ensure the presence of grease on the shaft or bearing inner ring which enhances replenishment of the sealing contact.

  • 8.
    Baart, Pieter
    et al.
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    On the Normal Stress Effect in Grease-Lubricated Bearing Seals2014In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 57, no 5, p. 939-943Article in journal (Refereed)
    Abstract [en]

    The film formation in lip seals, due to non-Newtonian rheology of the lubricant, has been a topic of speculation. Earlier work suggests that normal stresses in grease would be favorable for the film build-up between the seal lip and shaft or bearing ring. In the current paper we evaluate this earlier work and our earlier theoretical seal lip model with a series of experiments. We use a modified concentric cylinder geometry and a model fluid to study the fluid pressure distribution in the seal type geometry. The results are then related to grease lubricated seals and our earlier theoretical predictions. The present analysis shows that this earlier work and our earlier predictions are not correct and indicate that normal stresses in the grease pull the seal lip towards the shaft, increasing the contact pressure. However, normal stresses also ensure the presence of grease on the shaft or bearing inner ring which enhances replenishment of the sealing contact.

  • 9.
    Baart, Pieter
    et al.
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Review of the lubrication, sealing and pumping mechanisms in oil and grease-lubricated radial lip seals2008Conference paper (Other academic)
  • 10. Baart, Pieter
    et al.
    Lugt, Piet
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Review of the lubrication, sealing, and pumping mechanisms in oil- and grease-lubricated radial lip seals2009In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 223, no 3, p. 347-358Article in journal (Refereed)
    Abstract [en]

    Radial lip seals are successfully used since the 1940s to seal lubricated systems. Despite extensive experimental and theoretical research in the field, it is still not fully clear how these seals function. Experimental studies, found in the public literature, show that the relatively high surface roughness of the seal lip is very important for good and reliable performance. In addition, the pressure distribution under the lip seems to be a critical factor. Six fundamental hypotheses are presented on the lubrication, pumping, and sealing mechanisms to explain the working principles of these seals. It is generally accepted that lubrication results from micro-elastohydrodynamic film build up between the rough seal surface and the shaft. Non-symmetrical tangential deformations of the lip surface are observed during experiments and assumed to act like spiral groove bearings that generate a pumping action and lubricant film. Another hypothesis suggests that the lubricant will behave non-Newtonian under the very high shear rates experienced in operating conditions. This will reduce friction because of shear-thinning and enhances sealing. Macroscopic aids, like hydrodynamic pumping aids and engineered asperity patterns on the shaft, do improve seal performance. Almost all public literature discusses oil-lubricated radial lip seals while many seals are grease lubricated, especially in certain technical fields. Due to the non-Newtonian behaviour of grease, the lubrication, sealing, and pumping mechanisms are assumed to differ from the oil-lubricated seals. Lower friction and improved protection against contamination are measured, and it is expected that the interest in grease lubrication will rapidly grow in future.

  • 11. Baart, Pieter
    et al.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The sealing function of grease: contamination migration in grease lubricated radial lip seals2010In: Proceedings of the STLE/ASME International Joint Tribology Conference 2010: presented at STLE/ASME International Joint Tribology Conference, October 17-20, 2010, San Francisco, California, USA, New York: American Society of Mechanical Engineers , 2010, p. 81-83Conference paper (Refereed)
    Abstract [en]

    Lubricating grease is commonly used for lubricating `sealed and greased for life' bearings. This grease lubricates the rolling contacts. It also provides an additional sealing function to protect the bearing against ingress of contamination. The sealing function of lubricating grease in the vicinity of the seal lip contact has been studied experimentally. The effects of the lubricant rheology on the migration of ingress particles has been examined. In grease, experimental results reveal that contaminant particles consistently migrate towards the sealing contact where the shear rate reaches its highest value. In contrast, for a Newtonian base oil and a non shear thinning elastic fluid, it has been observed that the migration effect takes place in the opposite direction, and brings particles away from the sealing contact. It is concluded that the sealing function of grease in the vicinity of the sealing contact is due to the fluid rheology and more specifically to the shear thinning behaviour of the lubricant

  • 12.
    Bakshi, S. Das
    et al.
    Materials Science and Metallurgy, University of Cambridge.
    Leiro, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bhadeshia, H.K.D.H.
    Materials Science and Metallurgy, University of Cambridge.
    Dry rolling/sliding wear of nanostructured bainite2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 316, no 1-2, p. 70-78Article in journal (Refereed)
    Abstract [en]

    The abrasive wear of carbide-free bainitic steel under dry rolling/sliding conditions has been studied. It is demonstrated that this nanostructure, generated by isothermal transformation at 200 °C, has a resistance to wear that supersedes that of other carbide-free bainitic steels transformed at higher temperatures. The experimental results, in combination with a theoretical analysis of rolling/sliding indicates that under the conditions studied, the role of sliding is minimal, so that the maximum shear stresses during contact are generated below the contact surface. Thus, the hardness following testing is found to reach a maximum below the contact surface. The fine scale and associated strength of the structure combats wear during the running-in period, but the volume fraction, stability and morphology of retained austenite plays a significant role during wear, by work-hardening the surface through phase transformation into very hard martensite

  • 13.
    Bakshi, S. Das
    et al.
    Materials Science and Metallurgy, University of Cambridge.
    Leiro, Alejandro
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Bhadeshia, H.K.D.H.
    Materials Science and Metallurgy, University of Cambridge.
    Dry rolling/sliding wear of nanostructured pearlite2015In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 31, no 14, p. 1735-1744Article in journal (Refereed)
    Abstract [en]

    The dry rolling-sliding wear behaviour of pearlite that has an interlamellar spacing of just 85 nm has been characterised. Its wear resistance is found to be comparable to that of much harder bainitic steels. Microstructural observations indicate that there is substantial plastic deformation of both ferrite and cementite components of pearlite in the vicinity of the wear surface. Plasticity is not expected from Hertzian analysis that assumes a smooth contact surface. Instead, it is likely to be a consequence of exaggerated stresses due to surface roughness. The material remains ductile to shear strains in the order of 4. Diffraction data indicate that the coherent domain size is reduced to about half the interlamellar spacing and that some of the cementite may dissolve and contribute to the expansion of the lattice parameter of ferrite

  • 14.
    Bara, Özlem
    et al.
    Faculty of Engineering, Department of Mechanical Engineering, Erzincan University.
    Efeoğlu, İhsan
    Faculty of Engineering, Department of Mechanical Engineering, Erzincan University.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Adhesion and tribological properties of TiTaBN coatings with a graded interlayer deposited by pulsed DC biased and continuous dc biased magnetron sputtering2015In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 29, no 18, p. 2006-2019Article in journal (Refereed)
    Abstract [en]

    The properties of TiBN-based coatings are significantly affected by adding alloying elements and coating parameters. Therefore, in this study, TiTaBN coatings with graded interlayer (CWGIL) were deposited on D2 steel substrates by pulsed DC biased (PDCB) and continuously DC biased (CDCB) closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical, adhesion and tribological properties of the coatings were analysed with EDS, SEM, XRD, microhardness, scratch testing and a pin-on-disc tribo-tester (under various atmospheric conditions). TiTaBN CWGIL deposited by PDCB magnetron sputtering (MS) had a very dense microstructure, high hardness and a high critical load value. TiTaBN CWGIL deposited by PDCB MS had a lower friction coefficient, the wear rate and the penetration depth in all atmospheric conditions. In conclusion, the application of a PDCB substrate instead of a CDCB one dramatically increases the performance of CFUBMS-deposited TiTaBN coatings.

  • 15.
    Baran, Ö
    et al.
    Erzincan University.
    Efeoglu, I
    Atatürk University.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Structural, mechanical and tribological properties of TiTaBN composite graded coatings deposited by CFUBNS technique2012In: International Conference : Metallurgical Coatings & Thin Films, 39th ICMCTF: Programme, Technical Sessions, Abstracts, Exhibition, 2012, p. 99-Conference paper (Refereed)
  • 16.
    Baran, Özlem
    et al.
    Erzincan University, Faculty of Engineering, Department of Mechanical Engineering, Erzincan University.
    Efoğlu, İhsan
    Atatürk University, Faculty of Engineering, Department of Mechanical Engineering, Erzurum.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mechanical and Tribological Properties of TiTaBN Graded-Composite Coatings Deposited Using the CFUBMS Technique2016In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 59, no 6, p. 1089-1097Article in journal (Refereed)
    Abstract [en]

    In this study, TiTaBN graded-composite coatings were deposited utulizing different process parameters on D2 steel and glass substrates using pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS). The morphology and structure of the coatings were analyzed using SEM, EDS, XPS and Raman spectroscopy. The hardness and critical load values of the coatings were determined using a microhardness tester and scratch tester, respectively. The tribological properties of the coatings were analyzed in different testing environments using a pin-on-disc tribometer. The properties of the coatings were found to be strongly affected by the coating parameters. The maximum thickness and hardness were obtained at the lowest nitrogen flow rate and highest frequency. Critical load values of coatings were increased with increased nitrogen flow rate. The low nitrogen flow rate and high frequency across the coatings caused enhanced tribological properties.

  • 17.
    Burkhart, Christoph
    et al.
    Institute of Machine Elements, Gears & Transmissions (MEGT), University of Kaiserslautern.
    Johansson, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Uukonsari, Jan
    R&D, Vattenfall AB.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Performance of lubricating oils for wind turbine gear boxes and bearings2018In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 1, p. 62-72Article in journal (Refereed)
    Abstract [en]

    In this study, the friction and wear properties of six different new and used wind turbine gear oils (ISO VG 320), with different base oil formulations and additives packages, were investigated. For that purpose, a four-ball tribometer and an Optimol SRV were used. Moreover, the lubricants extreme pressure properties were also evaluated, using the same four-ball tribometer. The study also includes a characterization of the lubricants. The main objective was to compare the new and used gear oils in order to identify performance differences and predict oil change intervals. The results indicate that a use of 3 to 4 years is within the lifetime of the lubricant.

  • 18. Carlevi, Jens
    et al.
    Lundmark, Jonas
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological performance of different functional surfaces of piston and cylinder bore2005In: Book of Abstracts: International Tribology Conference KOBE / [ed] N. Ohmae; H. Ishigaki, Tokyo: Japan Society of Tribologists , 2005, p. 211-Conference paper (Other academic)
  • 19.
    Courbon, Cedric
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Fallqvust, M.
    R&D Materials and Technology Development, Seco Tools AB, Fagersta.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    M'Saoubi, R.
    R&D Materials and Technology Development, Seco Tools AB, Fagersta.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Adhesion tendency of PVD TiAlN coatings at elevated temperatures during reciprocating sliding against carbon steel2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 330-331, p. 209-222Article in journal (Refereed)
    Abstract [en]

    This work focussed on assessing the contact conditions driving the adhesion tendency of PVD TiAlN coated cemented carbide during reciprocating sliding against a normalized AISI 4137 carbon steel. A special emphasis is given to the surface topography of the coating. Results are analysed in terms of friction and material transfer over a large range of temperatures (up to 800 °C) and contact pressures. The post-test surface analysis of the specimens is conducted in order to understand the tribological behaviour and elucidate the formation mechanisms of transfer layers. A numerical model is developed to assess the amount of heat effectively transmitted into the first bodies and the temperature of the surfaces in contact.Whereas temperatures close to 400 °C ensure the formation of a stable tribofilm reducing friction, the highest temperatures lead to unstable frictional behaviour. Coating surface topography has been seen to be a major parameter driving material transfer during the first stages of the contact and the formation of a transfer layer. Thin and homogeneous layers are almost instantaneously formed with a polished surface whereas some time is required with a rougher one to form a film. A large amount of the frictional power is dissipated into these layers and high temperatures can be reached at the surface due to frictional heating. Contact pressure is found to be a parameter promoting transfer and oxidation

  • 20.
    Courbon, Cedric
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Fallqvust, M.
    R&D Materials and Technology Development, Seco Tools AB, Fagersta.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saoubi, R.M.
    R&D Materials and Technology Development, Seco Tools AB, Fagersta.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of temperature and surface topography on friction and adhesion tendency of PVD TiAIN coating2014Conference paper (Refereed)
  • 21.
    Das, Sanjeev
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of static and dynamic ageing on friction and wear behaviour of aluminium 6082 alloy2012In: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Conference paper (Refereed)
    Abstract [en]

    In recent past, warm forming processes have been used successfully to increase the strength of age-hardenable alloys by dynamic precipitation. However, the influence of dynamic age hardening on the wear and friction behaviour of age-hardenable aluminium alloy is not clear. Therefore, in the present investigation the effect of static and dynamic ageing on the friction and wear behaviour of aluminium 6082 alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The aluminium samples used in the present study were in as-cast, solitionised and peak aged conditions. Optical microscope revealed the presence of dendritic structure in both as-cast and solitionised samples. Scanning electron microscope analysis of the debris and worn surfaces revealed the wear mechanism and role of precipitates on the friction and wear results. At low temperature (40 C), the frictional behaviour of as-cast, solitionised and peak aged samples were similar. The wear rates at 40 C increased with increase in the amount of strain inside the specimens due to fine precipitations. At 180 C, a significant variation in the frictional behaviour of different specimens was observed. The wear rate of solitionised specimens at 180 C is higher compared to as-cast and aged specimens. The absence of hard phases at initial stage of the test and subsequent dynamic precipitates restricted to a thin layer were responsible for the increase in wear rate.

  • 22.
    Das, Sanjeev
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, p. 1-9Article in journal (Refereed)
    Abstract [en]

    In the present investigation the effect of static and dynamic ageing on the wear and friction behavior of aluminum alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The AA 6082 alloy samples used in the present study were in as-cast, solutionized and peak aged conditions. Scanning electron microscope analysis of the debris and worn surfaces revealed the role of precipitates on the dry sliding wear behavior. Frictional behavior varies significantly for all the conditions at elevated temperature (180 °C) compared to room temperature (40 °C). Such response was attributed to the dynamic precipitations during elevated temperature test.

  • 23.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Development of a Tribological Test Programme Based on Press Hardening Simulations2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 2, article id 43Article in journal (Refereed)
    Abstract [en]

    Press hardening is widely utilized to form ultra-high-strength steels characterized by a high strength-to-weight ratio for automotive components. Press hardening processes include heating boron–manganese steels to austenite phase, forming the steels at a high temperature, and cooling the formed blanks until the martensite phase is reached . However, press hardening processes lead to severe contact conditions between the blank and the tools including contact pressure, relative sliding, and high temperatures, which result in tool wear and increased maintenance cost. The contact conditions that occur in the stamping tool are difficult to study on site. Additionally, simplified tests, such as pin on disc and ball on disc, are insufficient to reproduce press hardening conditions in laboratory environments . The aim of this study includes developing a tribological test with press hardening conditions in which tool steel pins continuously slide on fresh and hot boron–manganese steel strips. The test programme mimics press hardening conditions with respect to sliding distance, sliding velocity, contact pressure, and surface temperature that were studied based on finite element (FE) simulations of a press hardening experiment. Furthermore, a FE simulation of the tribological test is established and it provides contact temperature in the pin tip with a high accuracy. A tribological test is used to study friction and mass loss with variational pressures and velocities that represented typically variational contact conditions in the press hardening. The tribological test is also used to obtain correlations between the tribological behaviours and process parameters in press hardening including pressure and sliding velocity.

  • 24.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Implementation of wear models for stamping tools under press hardening conditions based on laboratory tests2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1063, p. 339-342Article in journal (Refereed)
    Abstract [en]

    Tool wear occurring in press hardening processes receives insufficient attention since its corresponding measurements and full-scale experiments are complicated and expensive. This paper presents a study of tool wear in press hardening based on laboratory experiments and FE-simulations. Two experimental laboratory setups depending on the contact conditions in press hardening build the base for the wear models implemented in the FE-simulation to predict wear depths. The highest wear depth is found at the radius of the stamping tool and the discrepancies in wear predictions based on the two different laboratory test setups are analyzed.

  • 25.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Numerical study of contact conditions in press hardening for tool wear simulation2017In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 10, no 5, p. 717-727Article in journal (Refereed)
    Abstract [en]

    In the press hardening industry, industrial and academic efforts are being directed toward predicting tool wear to realize an economical manufacturing process. Tool wear in press hardening is a tribological response to contact conditions such as pressure and sliding motion. However, these contact conditions are difficult to measure in-situ. Furthermore, press hardening involves high temperatures, and this increases the complexity of the tribo system. The present work investigated the contact conditions of press hardening with a commercial FE code (LS-DYNA) as a base for tool wear simulation. A press hardening experiment was established in industrial environments and evaluated through FE simulations. The numerical model was set up so as to approximate the manufacturing conditions as closely as possible, and the sensitivity with respect to the friction coefficients was examined. The influence of numerical factors such as the penalty value and mesh size on the contact conditions is discussed. The implementation of a modified Archard’s wear model in the FE simulation proved the possibility of tool wear simulation in press hardening. Finally, a comparison between the tool wear simulation and the measured wear depth is presented. 

  • 26.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Press-hardening thermo-mechanical conditions in the contact between blank and tool2013In: 4th International Conference Hot Sheet Metal Forming of High-performance Steel CHS: June 9-12, Luleå, Sweden : Proceedings / [ed] Mats Oldenburg; Braham Prakash; Kurt Steinhoff, Auerbach: Verlag Wissenschaftliche Scripten , 2013, p. 293-300Conference paper (Refereed)
  • 27.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Validation of tool-wear simulations based on a full-scale press hardening experiment2015In: Hot Sheet Metal Forming of High-Performance Steel 5th International Conference: May 31-June 3, Toronto, Canada : Proceedings / [ed] Kurt Steinhoff; Mats Oldenburg; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2015, p. 121-128Conference paper (Refereed)
    Abstract [en]

    To extend the service life of stamping tools for press hardening processes, tool wear prediction gradually becomes an important topic of concern in industry. However, wear simulations based on the finite element method are mainly developed in laboratory and the lack of validation of full-scale experiments restricts the proposal of an accurate wear model. The work presented in this paper aims at validating the used wear models for stamping tools through a full-scale press hardening experiment. The wear model in conjunction with finite element (FE) simulations are dependent on contact mechanics and the corresponding wear data is obtained from laboratory tests, where the test parameters are specified in ranges that accord with the contact conditions of press hardening. The full-scale press hardening experiment producing a dog-bone shaped part is run for 200 continuous strokes. Geometry updating of the stamping tool is used to investigate the influence of shape change on the pressure occurring on the tool. The results have shown that the geometry change of the stamping tool, after producing a large number of parts, causes changes in the contact pressures and therefore affects the wear simulation. In the end, the wear simulation results are compared to the preliminary result of the full-scale press hardening.

  • 28.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Mozgovoy, Sergej
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wear Observations on Uncoated Tool and Workpiece Surfaces from a Full-Scale Press Hardening Wear Test2017In: Advanced High Strength Steel and Press Hardening / [ed] Zhang, Y; Ma, M, Singapore: World Scientific, 2017, p. 433-437Conference paper (Refereed)
    Abstract [en]

    Tool wear in press hardening has attracted researchers' attention and recently several papers have focused on the wear observations in the laboratory tests mimicking the press hardening conditions. However, the wear observations and quantification in full-scale press hardening tests are rare in view of high costs and longtime requirements. In this work, the wear behavior in a full-scale press hardening wear test has been studied in order to understand the wear mechanisms occurring in the stamping tool. Furthermore, the wear depths in the real stamping tool were measured by using a coordinate measurement machine (CMM) that can provide the quantified wear result and serve as a base to validate the possible wear model. The present study also includes the wear observations in both the counterparts i.e., the blank (workpiece) and the stamping tool with the aim of studying the transfer material/wear particles. Two common tool steels were used in the full-scale press hardening wear test and the differences in the wear severities were observed. Since abrasion and adhesion are major wear mechanisms previously in many laboratory tests, the present study identifies the wear evolution and mechanisms on uncoated tool and workpiece surfaces in the press hardening wear test.

  • 29.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A Tribological Test under Press Hardening Conditions for Galling Research2017In: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, p. 453-460Conference paper (Refereed)
  • 30.
    Deng, Liang
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Experimental Evaluation of Galling Under Press Hardening Conditions2018In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 3, article id 93Article in journal (Refereed)
    Abstract [en]

    Severe adhesion, also referred to as galling, is a critical problem in press hardening, especially in stamping tools used for hot forming of Al–Si-coated ultra-high strength steel. Galling is known to develop rapidly on the tool surface and it negatively affects the quality of the formed products. Earlier research on this topic has focused on the galling initiation. However, studies on the galling development during extended sliding and the corresponding quantitative measurement still lack depth. In the present study, a tribological test is established to study the galling development under press hardening conditions. The tribological test set-up aims to simulate extended sliding between the Al–Si-coated boron steels and the tool die material. The contact conditions in the interface are studied by a numerical model of the tribological test. The friction coefficients and material transfer are discussed taking into account the variation of the different test conditions. Using the results from the tribological tests, the galling simulation is performed in the numerical model. A geometry-updated sample based on the galling (transferred material build-up) height is simulated and the consequent pressure fluctuation is obtained in the numerical model. This contributes to the explanation of the severe transferred material accumulation during the test.

  • 31.
    Desai, Ajay
    et al.
    CQ University.
    Chattopadhyay, Gopinath
    CQ University.
    Clegg, Richard
    CQ University.
    Howie, Alex
    QR National Ltd, Brisbane.
    Larsson-Kråik, Per-Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Experimental setup and methodology for the analysis of rail lubricant effectiveness2011In: Proceedings of the 24th International Congress on Condition Monitoring and Diagnosis Engineering Management: COMADEM 2011 / [ed] Maneesh Singh; Raj B.K.N. Rao; J.P. Liyanage, COMADEM International, 2011, p. 592-598Conference paper (Refereed)
    Abstract [en]

    Rail and wheel wear is a complex problem. Lubrication plays an important role in reducing wear and enhancing asset life. Curves and switches are the areas of major challenges. Tight curves when running dry shows wear rates higher to rapid wear, increased maintenance costs and non-availability of track due to maintenance or replacement. The economic analysis based on cut-off radius, lubricants and applicators takes a very long time using field data. Rail operators often face difficulties when selecting lubricants. Lubricant manufactures use different test standards when specifying lubricant properties. Four-ball test fails to give a meaningful indication of lubricant performance. The result is often a complex decision problem in ranking different lubricants under a particular axel load. An appropriate selection of lubricant for a particular rail application can give financial returns and extension of asset life. An experimental set up has been proposed in this paper. The experimental results are expected to be used for development of models on effective lubrication. This paper proposes experimental setups and methodology for analysis of lubrication effectiveness in heavy haul lines. Theories along with existing research to date relating to ranking of lubricants for rail applications and a criterion for the ranking is discussed. An analysis is carried out to compare lubricants used in Australian Heavy Haul lines based on manufacturer supplied specifications and experimental results.

  • 32.
    Dilawar, Nita
    et al.
    Indian Institute of Technology, New Delhi.
    Kapil, Rahul
    Indian Institute of Technology, New Delhi.
    Prakash, Braham
    Vankar, V.D.
    Indian Institute of Technology, New Delhi.
    Avasthi, D. K.
    Nuclear Science Centre, New Delhi.
    Kabiraj, D.
    Nuclear Science Centre, New Delhi.
    Mehta, G.K.
    Nuclear Science Centre, New Delhi.
    Adhesion enhancement of diamond coatings on WC tools by high energy ion irradiation1998In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 323, no 1-2, p. 163-169Article in journal (Refereed)
    Abstract [en]

    Microcrystalline diamond thin films were deposited on cemented tungsten carbide cutting tools by hot-filament chemical vapour deposition process. The coatings deposited were irradiated with 50 MeV Si7+ ions upto a dose of <1013 ions cm-2. The adhesion and wear characteristics of as-deposited and irradiated coatings were studied and it was found that irradiation induced increased adhesion of the coatings to the substrate resulting in reduced coating failure during wear tests.

  • 33.
    Efeoglu, Ihsan
    et al.
    Atatürk University.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Interfacial scratch adhesion behavior of multilayered Ti(BN):Ti(MoS2) based PVD coatings2009Conference paper (Other academic)
    Abstract [en]

    Interfacial adhesion is critical property of multilayered thin films used in micro-electromechanical systems, ceramic capacitors, wear resistant coatings. In the present investigation, Ti(BN)+Ti(MoS2) solid multilayered composite solid lubricant coatings were deposited by magnetron sputtering from separate Ti, TiB2, and MoS2 target. X-ray diffraction, microhardness tester, and scratch tester were used to evaluate structural, mechanical and interfacial adhesion properties. In the work, described here changes in the adhesion of intercoat exhibited by nine different coatings deposited under variants of deposition parameters have been investigated. It is found that the crack propagates alternatively between the two interfaces with thinning of the interlayer.

  • 34.
    Gebeshuber, Ille C.
    et al.
    Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia (UKM).
    Luo, Jianbin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rymuza, Zygmunt
    Institute of Micromechanics and Photonics, Warsaw University of Technology.
    Impulse talk: ecotribology – development, prospects and challenges2013In: World Tribology Congress 2013, 2013, article id Extended abstract 738Conference paper (Refereed)
  • 35.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Efeoğlu, Ihsan
    Atatürk University.
    Prakash, Braham
    Tribological properties of composite multilayer coating2010In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper (Refereed)
    Abstract [en]

    The use of surface coatings is emerging as one of the most important approaches in reducing friction and wear in various tribological applications. Even though single layer coatings have a wide range of applications, the performance of the single layer alone may not always be adequate to meet the desired tribological property requirements. Hence, coatings consisting of multi-layers to meet different property requirements in demanding applications are required. In this study, the tribological properties of a graded composite multilayer coating with a specific layer sequence of MoS2:Ti/MoS2:TiBN/TiBN/TiB2/Ti deposited on tool steel substrate have been investigated at temperatures of 40°C and 400°C respectively. The experimental results from the tests at 40°C have shown that the friction coefficient value rangesbetween 0.02 and 0.034. It was found that the deposition parameters influenced the friction and durability of the coatings. Higher substrate bias was found to result in higher friction and the coating deposited at high substrate bias and low N2 flow showed the lowest durability. The friction coefficient and durability of the coatings were found to be highly dependent on temperature. At high temperature, the friction coefficient increases almost three fold and the durability decreases significantly.

  • 36.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Efeoğlu, Ihsan
    Faculty of Engineering, Department of Mechanical Engineering, Atatürk University, Erzurum, Turkey.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological properties of composite multilayer coating2011In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 5, no 3, p. 100-106Article in journal (Refereed)
    Abstract [en]

    The use of surface coatings is emerging as one of the most important approaches in reducing friction and wear in various tribological applications. Even though single layer coatings have a wide range of applications, the performance of the single layer alone may not always be adequate to meet the desired tribological property requirements. Hence, coatings consisting of multilayers to meet different property requirements in demanding applications are required. In this study, the tribological properties of a graded composite multilayer coating, with a specific layer sequence of MoS2/Ti‐MoS2/TiBN‐TiBN‐TiB2‐Ti deposited on tool steel substrate, have been investigated at temperatures of 40 and 400°C respectively. The experimental results from the tests at 40°C have shown that the friction coefficient value ranges between 0�02 and 0�034. It was found that the deposition parameters influenced the friction and durability of the coatings. Higher substrate bias was found to result in higher friction, and the coating deposited at high substrate bias and low N2 flow showed the lowest durability. The friction coefficient and durability of the coatings were found to be highly dependent on temperature. At high temperature, the friction coefficient increases almost threefold, and the durability decreases significantly.

  • 37.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gabler, Christoph
    Austrian Excellence Center for Tribology (AC2T).
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological Compatibility of Some Selected Pb-Free Engine Bearing Materials with Different Engine Oil Formulations2018In: Tribology Online, ISSN 1881-2198, Vol. 13, no 3, p. 91-100Article in journal (Refereed)
    Abstract [en]

    In this study, friction and wear properties of Al-Sn based bearing alloy with no overlay, bronze lining coated with Al-Sn based overlay and PAI based overlay, bronze lining coated with Sn based overlay and Pb-containing bearing material have been investigated using five different engine oil formulations including pure PAO 6 base oil and different viscosity grade oils containing anti-wear additive using an Optimol SRV® high-temperature reciprocating friction and wear test machine. It has been found that when Al-Sn based lining is lubricated with plain base oil, wear is lower compared to those with oils containing additives. For the other bearing materials, oils containing additives have shown improved friction and wear performance compared with that of the pure base oil.

  • 38.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Embeddability behaviour of some Pb-free engine bearing materials2016Conference paper (Other academic)
    Abstract [en]

    An important requirement on engine bearing materials is its ability to embed dirt/abrasive particles onto the bearing surface and minimize damage to the expensive crankshaft. This property is achieved by applying an overlay onto the lining. In this work, a journal bearing test rig that operates under steady loading condition has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials in the presence of contaminant/abrasive particles in engine oil. Test materials include Pb-free bearing materials with overlay compositions of Sn, Bi, PAI containing MoS2 and graphite. Pb-based overlay has also been studied as a reference. Embeddability behaviour in terms of wear and changes in surface topography has been investigated. The damage on the shaft and the bearing surfaces were studied in order to elucidate the mechanisms involved. It has been possible to distinguish between the embeddability characteristics of different materials.

  • 39.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction and wear characteristics of different Pb-free bearing materials in mixed and boundary lubrication regimes2014Conference paper (Refereed)
    Abstract [en]

    Traditional bearing materials contain different amounts of lead (Pb) due to its friction reducing properties. However, in view of the negative health and environmental impact of Pb, there are new directives that limit the usage of Pb in engine bearings. Owing to this, new bearing materials that provide at least comparable tribological performance to that of Pb containing alloys are emerging and manufacturers have already started manufacturing Pb-free bearing materials. It is, however; still unclear how these new engine bearing materials would perform in mixed and boundary lubricated conditions. In this study, a block-on-ring test setup was employed to investigate the tribological performance of several bimetal and multi-layer Pb-free bearings with different compositions of lining and overlay materials. Pb-containing bearing material was also studied as a reference material. Friction and wear properties of these bearing materials were investigated and their wear mechanisms under lubricated conditions have been analysed.

  • 40.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction and wear characteristics of different Pb-free bearing materials in mixed and boundary lubrication regimes2014Conference paper (Refereed)
    Abstract [en]

    Traditional bearing materials contain different amounts of lead (Pb) because of its friction reducing properties. However, in view of the negative health and environmental impact of Pb, there is growing emphasis on restricting the usage of Pb in engine bearings. Owing to this, new bearing materials that provide at least comparable tribological performance to that of Pb containing alloys are being developed and some new Pb-free materials are being already used in engine bearing applications. It is, however, still unclear how these newengine bearing materials would perform in mixed and boundary lubricated conditions. In this study, a block-on-ring test setup was employed to investigate the tribological performance of several bimetal and multi-layer Pb-free bearing materials with different compositions of bearing lining and overlay plating. Pb-containing bearing material was also studied as a reference material. Friction and wear properties of these bearing materials wereinvestigated and their wear mechanisms under lubricated conditions have been analysed. Bearing material with overlay of Polyamide-Imide with graphite and MoS2 exhibited better friction and wear properties than Pb-based and Al-Sn based materials. Pb-containg bearing material shows higher wear and Al-Sn based material has shown higher friction.

  • 41.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friction and wear characteristics of different Pb-free bearing materials in mixed and boundary lubrication regimes2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 340-341, p. 63-72Article in journal (Refereed)
    Abstract [en]

    Traditional bearing materials contain different amounts of lead (Pb) because of its friction reducing properties. However, in view of the negative health and environmental impact of Pb, there is growing emphasis on restricting the usage of Pb in engine bearings. Owing to this, new bearing materials that provide at least comparable tribological performance to that of Pb containing alloys are being developed and some new Pb-free materials are being already used in engine bearing applications. It is, however, still unclear how these new engine bearing materials would perform in mixed and boundary lubricated conditions. In this study, a block-on-ring test setup was employed to investigate the tribological performance of several bimetal and multi-layer Pb-free bearing materials with different compositions of bearing lining and overlay plating. Pb-containing bearing material was also studied as a reference material. Friction and wear properties of these bearing materials were investigated and their wear mechanisms under lubricated conditions have been analysed. Bearing material with Polyamide-Imide based overlay containing graphite and MoS2 exhibited better friction and wear properties than Pb-based and Al-Sn based materials. Pb-containing bearing material shows higher wear of material and Al-Sn based material has shown higher friction compared with the other test materials.

  • 42.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Investigations into Seizure Behaviour of Pb-free Engine Bearing Materials Under Dry Condition2015Conference paper (Other academic)
    Abstract [en]

    Due to new environmental regulations, Pb-free engine bearing materials are becoming more common and there is a need for studying their tribological performance. Under severe and nonideal operating conditions, failure due to seizure can occur in engine bearings. In this work, seizure behaviour of different multi-layered engine bearing materials has been studied by using a block-on-ring test set up. These materials included Al-Sn based lining with no overlay, bronze lining with Polyamide-imide (PAI) based overlay containing MoS2 and graphite, bronze lining with two overlays of Al-Sn based and PAI based overlay, bronze based lining with Sn-based overlay and bismuth (Bi) containing bronze with Sn-based overlay. Tests were performed by progressively increasing the load in a stepwise manner at a constant speed under unidirectional dry sliding conditions. Bronze based lining with a PAI based overlay containing MoS2 and graphite did not exhibit seizure up to a load of 475 N. For Al-Sn based lining without overlay, seizure occurs at relatively lower load of 125 N. In most cases, there is material transfer onto the counter surface test ring. The test materials, counter surfaces and the wear debris were analysed using SEM incorporating EDS with a view to explain the seizure mechanisms.

  • 43.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Seizure behaviour of Pb-free engine bearing materials under dry condition2018In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 2, p. 106-116Article in journal (Refereed)
    Abstract [en]

    Due to new environmental regulations, Pb-free engine bearing materials are becoming more common and there is a need for studying their tribological performance. Under severe operating conditions, failure due to seizure can occur in engine bearings. In this work, seizure behaviour of different multi-layered engine bearing materials has been studied by using a block-on-ring test setup under dry condition. These materials included Al–Sn-based lining with no overlay, bronze lining with polyamide-imide-based overlay containing MoS2 and graphite, bronze lining with two overlays of Al–Sn-based and polyamide-imide-based material, bronze-based lining with Sn-based overlay and bismuth (Bi)-containing bronze with Sn-based overlay. The tests were performed by gradually increasing the load at a specific time interval and in a stepwise manner and at a constant speed under unidirectional dry sliding conditions. The test materials, counter surfaces and the wear debris were analysed using SEM with a view to understand the seizure mechanisms. Bronze-based lining with a polyamide-imide-based overlay containing MoS2 and graphite does not exhibit seizure up to a load of 475 N. For Al–Sn-based lining without overlay, seizure occurs at a relatively lower load of 125 N. The Al–Sn-based lining with no overlay shows higher friction and the polyamide-imide-based overlay containing MoS2 and graphite shows lower friction during the seizure test. In most cases, there is material transfer onto the test ring counter surface. Material transfer onto the counter surface either due to severe adhesion or wear debris adhered and smeared on it. Al–Sn-based lining and an exposed Al–Sn-based overlay show severe adhesion that causes seizure. On the other hand, exposed Pb containing lining and Bi containing lining seize due to mechanical interlocking caused by the adhered wear debris on both surfaces.

  • 44.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Seizure behaviour of some selected Pb-free engine bearing materials under lubricated condition2017In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 111, p. 265-275Article in journal (Refereed)
    Abstract [en]

    Under severe operating conditions seizure can occur in engine bearings. Therefore it is important to study seizure behaviour of selected Pb-free bearing materials that may replace the conventional Pb-based materials. Seizure tests were carried out using a block-on-ring test configuration by stepwise increasing applied load at a constant rotational speed using base oil and also fully formulated engine oil respectively. The bearing materials are ranked in terms of friction and seizure load. Al-Sn based lining without overlay shows higher friction and lower seizure load in both oils. Polyamide-imide based overlay containing MoS2 and graphite and Pb-based material show no sign of seizure. For Sn-based overlay plated materials seizure load is higher in fully formulated engine oil than in base oil.

  • 45.
    Gebretsadik, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological performance of tin-based overlay plated engine bearing materials2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 92, p. 281-289Article in journal (Refereed)
    Abstract [en]

    A block-on-ring test setup is employed to investigate tribological performance of Sn-based overlay plated bearing materials under mixed and boundary lubrication condition. Pb-containing bearing material is also studied as a reference. Sn-based and Pb-based overlays have shown similar transition in friction when rotational speed is varied. Under relatively longer test duration, Sn-based overlays exhibit comparable friction and wear properties with that of Pb-based overlay. It takes longer time to obtain steady-state friction for Sn-based overlay than Pb-based overlay. Wear behaviour of tested samples are also similar except for tests in the mixed lubrication regime where Sn-based overlays show better wear resistance. In the Sn-based overlays main wear mechanisms are adhesive and abrasive wear leading to exposure of the Ni interlayer.

  • 46.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friedrich, Klaus
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Noll, Andreas
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of Counter Surface Topography on the Tribological Behaviour of Carbon-filled PPS Composites in Water2015Conference paper (Refereed)
    Abstract [en]

    This study is aimed at investigating the influence of counter surfaces’ topography on tribological behaviour of several carbon-filled polyphenylene sulfide (PPS) composites in water lubricated contacts. The results of this study showed significant increase in wear rate of pure, graphite and/or multi-walled carbon nanotubes filled PPS composites with increase in mean slope of profile along the sliding direction (Δαy). This is while short carbon fiber (SCF) filled PPS composites exhibited 1-3 orders of magnitude lower wear rate with little dependence on counter surface roughness characteristics. Among the roughness parameters studied, Rpk and lay orientation played a more significant role in friction, and Rpk and Δαy were found to correlate best with the wear rate of the composites not containing SCF in their matrices.Keywords: Polyphenylene sulfide, Roughness; Polymer; Friction; Wear.

  • 47.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friedrich, Klaus
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Noll, Andreas
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of counter surface topography on the tribological behaviour of carbon-filled PPS composites in water2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 88, p. 209-217Article in journal (Refereed)
    Abstract [en]

    This study is aimed at investigating the influence of counter surfaces’ topography on tribological behaviour of several carbon-filled polyphenylene sulfide (PPS) composites in water lubricated contacts. The results of this study showed significant increase in wear rate of pure, graphite and/or multi-walled carbon nanotubes filled PPS composites with increase in mean slope of profile along the sliding direction (Δαy). This is while SCF filled PPS composites exhibited 1–3 orders of magnitude lower wear rate with little dependence on counter surface roughness characteristics. Among the roughness parameters studied, Rpk and lay orientation played a more significant role in friction, and Rpk and Δαy were found to correlate best with the wear rate of the composites not containing SCF in their matrices.

  • 48.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Friedrich, Klaus
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Noll, Andreas
    Institute for Composite Materials (IVW GmbH), Technical University of Kaiserslautern.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of carbon-filled PPS composites in water lubricated contacts2015In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 328-329, p. 456-463Article in journal (Refereed)
    Abstract [en]

    The present study aims at investigating the tribological behaviour of polyphenylene sulfide (PPS) composites in water lubricated sliding contact against a metallic (Inconel) counterpart. Factorial combinations of three commercially available carbon based fillers namely short carbon fibers (SCF), multi-walled carbon nanotubes (MWNT) and graphite (Gr) were utilized as single, dual- and multi-modal reinforcement.Reduction in wear of more than three orders of magnitude and a reduction in friction of more than 60% were achieved for the composite containing short carbon fibers as compared to neat PPS. However, incorporation of MWNTs and/or Gr marginally influenced the friction and wear behaviour of the PPS composites. X-ray photoelectron spectroscopy (XPS) of the worn counter surfaces confirmed the formation of a reaction layer on the Inconel counterpart. Further investigations utilizing Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) revealed the formation of nano-tribo-layers on load bearing plateaus of the Inconel counter surface.It can be concluded that the sliding wear resistance of the short carbon fibers, the enhanced polymer transfer, and the formation of a nano-tribo-layer on the counter surface are mainly responsible for the outstanding tribological behaviour of short carbon fiber reinforced PPS composites in water lubricated sliding conditions.

  • 49.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Nguyen, Tan Dat
    Ghent University.
    Baets, Patrick De
    Ghent University.
    Glavatskih, Sergei
    Kungliga tekniska högskolan, KTH.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of shaft roughness and pressure on friction of polymer bearings in water2013Conference paper (Refereed)
  • 50.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Nguyen, Tan Dat
    Department of Mechanical Construction and Production, Ghent University.
    Baets, Patrick De
    Department of Mechanical Construction and Production, Ghent University.
    Glavatskih, Sergei
    Division of Machine Design, School of Industrial Engineering and Management, Royal Institute of Technology.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of shaft roughness and pressure on friction of polymer bearings in water2014In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, no 4, p. 371-381Article in journal (Refereed)
    Abstract [en]

    In this study, the frictional behavior of selected commercially available unfilled polymers, namely, polyether ether ketone, polytetrafluoroethylene, polyethylene terephthalate, and ultra-high molecular weight polyethylene against an Inconel shaft was investigated using a journal bearing test configuration in water-lubricated sliding contact. Dynamic friction curves were obtained for various shaft roughness values and polymer combinations. The results showed a significant influence of shaft surface roughness on running-in and steady state friction in water-lubricated conditions. Contact angle measurements revealed a significant increase in wettability of Inconel counterfaces. The X-ray photoelectron spectroscopy (XPS) analysis of the surfaces suggests formation of a reaction layer on worn Inconel surfaces when sliding against the polymers. The influences of counter surface roughness and load on frictional response of polymers were studied through intermittent tests by obtaining dynamic and breakaway friction maps for different polymer materials, shaft roughness values, and pressure combinations. In general, a trend of decreasing friction was obtained with increasing contact pressure; however, the materials’ frictional responses to variations in counter surface roughness were different. These results indicate that although a reduced counter surface roughness may be beneficial for dynamic friction of polymers in all lubrication regimes, it can adversely affect the materials’ breakaway friction response.

12345 1 - 50 of 228
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf