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  • 1.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Polymeric Materials for Bearing Applications: Tribological Studies in Lubricated Conditions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the most important demands in hydropower and other industries today stems from the emphasis on preserving the environment. Usage of mineral and synthetic oils in sliding bearings of hydropower plants raises concerns about the environmental impact of these lubricants in case of spillage into downstream water. These concerns have led to attempts in using water as lubricant and the concept of oil-free systems in hydropower generation. Realization of this concept however poses many challenges including the choice of bearing materials and this necessitated research pertaining to the tribological behaviour of polymers in lubricated conditions. In this work, several studies have been carried out in order to obtain an insight into polymers’ tribological performance and associated mechanisms in the presence of lubricants.Extensive tribological studies on several unfilled polymers in water lubricated contacts demonstrated the superior wear resistance of UHMWPE. It was also found that the frictional behaviour of the unfilled polymers was influenced by their water contact angle and relative energy difference with regard to water.Studies on the effect of counter surface roughness characteristics on tribological behaviour of polymeric materials revealed their significant influence on friction and wear behaviour of polymer-metal contacts. Using a small scale journal bearing configuration, it was found that dynamic friction of polymer bearings can be significantly reduced using a shaft of reduced surface roughness. However, depending on the bearing material, this can adversely affect the material’s breakaway frictional response and thereby increase the torque required for machine start-up; a critical issue in applications such as pumped storage hydropower plants. Further studies using a pin on plate configuration revealed that variations in surface roughness characteristics of the metallic counter surfaces can significantly alter the wear resistance of the polymeric materials which cannot modify the topography of the counter surfaces in a tribological contact.Investigations regarding the influence of incorporation of various micro/nano carbon based fillers/reinforcements in the polymer matrix revealed their great potential for enhancing the friction and wear behaviour of the polymer composites. However these effects have been found to be strongly influenced by presence/absence of other reinforcements in the polymer matrix and/or by alterations in the operating conditions.Application of polymers as bearing lining materials also exhibits the potential of enhancing the performance of oil lubricated bearings. Therefore a part of this work was aimed at investigating the tribological characteristics of several polytetrafluoroethylene based materials at the onset of sliding (breakaway) at various pressures and temperatures. The results of this study showed dramatic reduction in breakaway friction using PTFE based materials in comparison to the conventional Babbitt (white metal) bearing lining material utilized in oil-lubricated sliding bearings of hydropower plants.

  • 2.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of polymers in lubricated contacts2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An important issue in hydropower and other industries is the increasing demand for introduction of environment friendly solutions. Mineral oil based lubricants have long been used in various sliding bearings in hydropower stations. Their use in aqueous environments however raises concerns about the environmental impact if they leak into downstream water. This has necessitated research in replacing mineral oils with more bio-degradable lubricants and the ultimate goal of ‘oil-free’ hydropower generating machines. Replacing oil with water however poses many challenges. Due to considerably lower viscosity of water compared to that of turbine oils, the water lubricated bearings are likely to operate in boundary/mixed lubrication regime for relatively longer period. Therefore choice of the materials and their tribological performance are very important for the bearings operating in the boundary/mixed lubrication regimes. Application of compliant polymers in water lubricated bearings introduces many advantages which cannot be achieved with coatings (DLC, etc.) or ceramics. Most previous tribological studies on polymers have been carried out in dry conditions and only a few studies in presence of water have been reported. This work is thus aimed at investigating the tribological behavior of some selected polymer materials in water lubricated conditions. The results of these studies provide an insight into polymers’ tribological performance in boundary/mixed and hydrodynamic lubrication regime and associated wear mechanisms in presence of water. Polymers also enhance performance of oil lubricated bearings. Application of polymers in the oil lubricated bearings provides a smooth transition from oil lubricated Babbitt bearings to water lubricated polymer bearings. Therefore a part of this thesis is also aimed at investigating the tribological characteristics of several polytetrafluoroethylene based materials at the onset of sliding (break-away friction) at different pressures and temperatures. The results of this study show significantly lower breakaway friction of PTFE materials compared to Babbitt at all pressures and temperatures. SEM investigations revealed wear modes of the PTFE materials and the abrasive nature of hard fillers. Bronze-filled, carbon-filled and pure PTFE were found to provide lower and more stable break-away friction and generally superior properties compared to the other materials.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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)
  • 7.
    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.

  • 8. Golchin, Arash
    et al.
    Simmons, Gregory F
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Break-away friction of PTFE materials in lubricated conditions2010In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper (Refereed)
    Abstract [en]

    This study investigates the tribological characteristics at the initiation of sliding (break-away friction) of several polytetrafluoroethylene (PTFE) based materials including virgin PTFE (PP), PTFE filled with 25% black glass (PG), PTFE filled with 40% Bronze (PB), PTFE filled with 25% Carbon (PC), and PTFE filled with 20% glass fibre and 5% Molybdenum disulphide (PM), as well as standard white-metal Babbitt (BA) in lubricated sliding contact with a steel counter-face. Experiments were carried out using a reciprocating tribo-meter in the block on plate configuration with the specific goal of determining the friction characteristics at break-away under varying conditions. Apparent contact pressures of 1 to 8 MPa were applied with oil temperature levels of 25° to 85°C. Bronze- and carbon-filled PTFE and virgin PTFE were found to provide generally lower break-away friction and less variation in break-away friction over the course of testing than the other tested materials. Break-away friction tests after an extended stop under loading found bronze- and carbon-filled PTFE and virgin PTFE to be minimally affected by the extended stop whereas Babbitt produced a significant increase in break-away friction in the first cycle after stopping. Break-away friction for the four tested materials after an extended stop returned to pre-stop values after 1 stroke.

  • 9.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Simmons, Gregory F
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Break-away friction of PTFE materials in lubricated conditions2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 48, no April, p. 54-62Article in journal (Refereed)
    Abstract [en]

    This study investigates the tribological characteristics at initiation of sliding (break-away friction) of several polytetrafluoroethylene based materials. Four PTFE composites, pure PTFE, and white-metal were tested in a reciprocating tribo-meter with the block on plate configuration against a steel counter surface. Apparent contact pressure and oil temperature were varied from 1-8 MPa and 25-85\degc respectively. SEM investigations revealed wear patterns of the PTFE materials and the abrasive nature of hard fillers.Bronze-filled, carbon-filled, and pure PTFE were found to provide lower break-away friction and less variation over the course of testing and generally superior properties.

  • 10.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Simmons, Gregory F
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of polymeric materials in water lubricated contacts2012In: 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]

    The present study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a uni-directional pin-on-disc configuration with an initial apparent contact pressure of 5 MPa at room temperature. The worn surfaces were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribo-corrosion of stainless steel during sliding against polypropylene. The results from friction and wear tests show overall superior tribological performance of UHMWPE compared to the other polymeric materials in water.

  • 11.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Simmons, Gregory F
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Glavatskih, Sergei
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of polymeric materials in water-lubricated contacts2013In: 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. 811-825Article in journal (Refereed)
    Abstract [en]

    This study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a unidirectional pin-on-disc configuration with an initial apparent contact pressure of 5 MPa at room temperature. The worn surfaces were examined using scanning electron microscopy and energy dispersive spectroscopy techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribocorrosion of stainless steel during sliding against polypropylene. It is inferred that the frictional behaviour of the polymers is determined by both their wettability and solubility in water, where generally an increased hydrophobicity and relative energy difference with regard to water results in lower friction. The results from friction and wear tests show overall superior tribological performance of ultrahigh molecular weight polyethylene compared with the other polymeric materials in water.

  • 12.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Villain, Alexis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological Behaviour of Nanodiamond Reinforced UHMWPE in Water-Lubricated Contacts2017In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 110, p. 195-200Article in journal (Refereed)
    Abstract [en]

    In this study, the tribological behaviour of nanodiamond reinforced UHMWPE composites was investigated in water-lubricated sliding contacts. A significant reduction of 72% in wear and 24% in friction of UHMWPE was observed with incorporation of 1 wt% nanodiamond in the polymer matrix. Various bulk and surface characterization techniques were utilised to reveal the main mechanisms involved in the friction and wear response of the polymeric materials. The improved tribological behaviour of UHMWPE upon incorporation of various loadings of nanodiamond in the polymer matrix was mainly attributed to the boundary lubricating action of nanodiamonds and the polishing effect of the nanodiamond reinforced UHMWPE composites on the counter surfaces in water-lubricated sliding contacts.

  • 13.
    Golchin, Arash
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wikner, Alfred
    Luleå University of Technology.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    An Investigation into Tribological Behaviour of Multi-Walled Carbon Nanotube/Graphene Oxide Reinforced UHMWPE in Water Lubricated Contacts2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 95, p. 156-161Article in journal (Refereed)
    Abstract [en]

    In this study, the influence of incorporation of carbon based nano fillers, namely multi-walled carbon nanotubes and graphene oxide on the tribological behaviour of ultra-high molecular weight polyethylene was investigated in water lubricated sliding contacts. Further investigations were carried out to study the influence of γ-irradiation and hygrothermal aging on the friction and wear response of the polymeric materials. It was found that regardless of the treatment, GO/MWNT reinforced composites consistently exhibited a lower friction and higher wear resistance in comparison to the unfilled UHMWPE. This was mainly attributed to the lubricating action of the carbonaceous nano fillers in water lubricated sliding contacts.

  • 14.
    Homayoun, Mohammad-Reza
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of Hygrothermal Ageing on Tribological Behaviour of PTFE-Based Composites2018In: Lubricants, E-ISSN 2075-4442, Vol. 6, no 4, article id 103Article in journal (Refereed)
    Abstract [en]

    The present study investigates the influence of hygrothermal ageing on the tribological behaviour of polytetrafluoroethylene (PTFE) polymer composites. Three PTFE composites along with unfilled PTFE were tested in sliding contact against Inconel 625 (a Ni-based alloy) plates in both dry and water-lubricated conditions, utilising a unidirectional pin-on-disc tribometer. The tribo-tests were performed at a constant sliding speed of 0.13 m/s with a normal load of 84N providing an apparent contact pressure of 5 MPa. Hygrothermal conditioning was carried out at two different temperatures, and the water absorption evolution and kinetic parameters were estimated. Various characterisation methods were used to identify the wear mechanisms and influence of hygrothermal ageing on the degradation of the filler/matrix. The different tribological behaviour for different PTFE composites was observed within the ageing timeframe. The wear resistance of the fibre-filled samples was reduced compared to the non-aged ones over the ageing timeframe. However, the friction and wear resistance of the bronze-filled PTFE were enhanced by hygrothermal ageing.

  • 15.
    Vadivel, Hari
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of carbon filled hybrid UHMWPE composites in water2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 124, p. 169-177Article in journal (Refereed)
    Abstract [en]

    In this study, newly developed hybrid composites with Ultra High Molecular Weight Polyethylene (UHMWPE) as base polymer and Graphene Oxide (GO), Nano Diamonds (ND) and Short Carbon Fibres (SCF) as fillers were manufactured. The tribological performance of these composites in a water lubricated sliding contact and the effect of inclusion of the fillers on the mechanical and thermal properties of the composites were investigated. The resulting hybrid composite formed by using the fillers and the base polymer displayed low friction coefficient and high wear resistance. Compared to unfilled UHMWPE, composite with all the fillers incorporated had 21% smaller friction coefficient and 15% less wear.

  • 16.
    Vadivel, Hari
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological performance and thermal characteristics of UHMWPE multifunctional hybrid composites2017Conference paper (Refereed)
  • 17.
    Ytrehus, Jan David
    et al.
    Sintef Petroleum AS.
    Taghipour, Ali
    Sintef Petroleum AS.
    Golchin, Arash
    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.
    Saasen, Arild
    Det Norske oljeselskap.
    The effect of different oil based drilling fluids on mechanical friction2015In: Proceedings of the ASME 34th International Conference on Ocean, Offshore and Arctic Engineering - 2015: presented at ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering; May 31 - June 5, 2015, St. John's, Newfoundland, Canada, New York: American Society of Mechanical Engineers , 2015, Vol. 10 : Petroleum technology, article id OMAE2015-41896Conference paper (Refereed)
    Abstract [en]

    A very important aspect in highly inclined wellbores is the mechanical friction. For extended reach drilling (ERD) and through tubing extended reach drilling (TTERD) this can be a limiting factor. Friction caused by the contact between the drill string and the well casing or borehole is dependent to the drilling weight and fluid properties. Drilling fluids play an important role on mechanical friction and using oil based drilling fluids with higher lubricity can reduce torque and drag behavior and minimize stick and slip. Reducing mechanical friction will improve drilling efficiency in general, and will in particular enable longer reach for ERD wells.This paper presents results from experimental laboratory tests where mechanical friction has been investigated. The experiments have been conducted as part of a project in the Tribolab at Luleå University of Technology in cooperation with Det norske Oljeselskap.Friction behavior has been investigated for different drilling fluids; water based and oil based drilling fluids both with and without solid particles. A pin on disc setup was used for these experiments where a spherical steel pin was sliding on a rotational disc made of granite. Friction force has been measured in constant sliding speed and in presence of particles in wet condition. The test results show that mechanical friction in general is smaller with oil based than water based drilling fluids in the presence of solid particles. In addition, the friction coefficient increases when solid particles were added to the lubricants.Such experiments in a tribology laboratory are important to identify the effect of drilling fluids on mechanical friction from a basic point of view and isolated from all other wellbore parameters. It is interesting to monitor if the results from this setup can have quantitative relevance also for field situations and such comparison should be done as follow up. Test results and the experimental approach could therefore be of value for any one working with drilling and well construction.

  • 18.
    Ytrehus, Jan David
    et al.
    Sintef Petroleum AS.
    Taghipour, Ali
    Sintef Petroleum AS.
    Golchin, Arash
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Saasen, Arild
    Department of Petroleum Engineering, University of Stavanger.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The Effect of Different Drilling Fluids on Mechanical Friction2017In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 139, no 3, article id 034502Article in journal (Refereed)
    Abstract [en]

    A very important aspect in highly inclined wellbores is the mechanical friction. For extended reach drilling (ERD) and through tubing extended reach drilling (TTERD) this can be a limiting factor. Friction caused by the contact between the drill string and the well casing or borehole is dependent on the drilling weight and fluid properties. Drilling fluids play an important role in determining mechanical friction. The use of oil-based drilling fluids with higher lubricity can reduce torque and drag behavior and minimize stick and slip. Reducing mechanical friction will improve drilling efficiency in general, and will in particular enable longer reach for ERD wells. This paper presents results from experimental laboratory tests where the mechanical friction has been investigated. Friction behavior was investigated for different drilling fluids; water-based and oil-based drilling fluids both with and without solid particles. A pin on disk setup was used for these experiments where a spherical ended steel pin was slid against a rotating disk made of granite. The test results show that the mechanical friction in general is smaller with oil-based than water-based drilling fluids in the presence of solid particles.

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