Change search
Link to record
Permanent link

Direct link
BETA
Nilsson, Daniel
Publications (10 of 12) Show all publications
Nilsson, D. & Prakash, B. (2013). Static/dynamic friction and wear of some selected polymeric materials for conformal tribo-pairs under boundary lubrication conditions (ed.). Paper presented at . Friction, 1(3), 232-241
Open this publication in new window or tab >>Static/dynamic friction and wear of some selected polymeric materials for conformal tribo-pairs under boundary lubrication conditions
2013 (English)In: Friction, E-ISSN 2223-7690, Vol. 1, no 3, p. 232-241Article in journal (Refereed) Published
Abstract [en]

This work is aimed at investigating the friction and wear performance of different polymeric materials having potential for hydraulic system components under lubricated sliding conditions against a steel counter face. A pin-on-disc test configuration was used for the experimental study. The different polymeric materials selected for these studies were commercial polyimides (PI), polyether ether ketone (PEEK), and flouropolymers. Some of these materials were bulk materials whereas others were used as coatings applied on to the cast iron substrate. The tribological characteristics of the polymers were compared with a reference grey cast iron. The frictional characteristics were evaluated in both static and dynamic conditions. The results have shown that by using polymeric materials it is possible to reduce breakaway friction by an order of magnitude compared to grey cast iron. However, the breakaway friction increased significantly after the wear tests. The polymeric materials having lowest breakaway friction have shown the highest wear with the exception of the PEEK-PTFE coating which showed low wear. PI with graphite fillers also showed low wear but it resulted in relatively high friction. The carbon fibre reinforced materials resulted in unstable friction as well as higher wear compared to the PI materials with graphite fillers

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-3630 (URN)10.1007/s40544-013-0020-4 (DOI)000209841300004 ()2-s2.0-84976385779 (Scopus ID)17345f3a-453d-4f19-9278-bdf826c6780c (Local ID)17345f3a-453d-4f19-9278-bdf826c6780c (Archive number)17345f3a-453d-4f19-9278-bdf826c6780c (OAI)
Note
Godkänd; 2013; 20130919 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Nilsson, D. & Prakash, B. (2012). Friction and wear of some selected polymeric materials for conformal tribopairs under boundary lubrication conditions (ed.). In: (Ed.), (Ed.), 8th International Fluid Power Conference (8. IFK): March 26 - 28, 2012 in Dresden; [conference proceedings]. Paper presented at International Fluid Power Conference : 26/03/2012 - 28/03/2012 (pp. 217-231). Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V, 2
Open this publication in new window or tab >>Friction and wear of some selected polymeric materials for conformal tribopairs under boundary lubrication conditions
2012 (English)In: 8th International Fluid Power Conference (8. IFK): March 26 - 28, 2012 in Dresden; [conference proceedings], Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V , 2012, Vol. 2, p. 217-231Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V, 2012
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-26850 (URN)01bb2160-3aee-4d37-a2cd-13ec4cdf0382 (Local ID)01bb2160-3aee-4d37-a2cd-13ec4cdf0382 (Archive number)01bb2160-3aee-4d37-a2cd-13ec4cdf0382 (OAI)
Conference
International Fluid Power Conference : 26/03/2012 - 28/03/2012
Note
Godkänd; 2012; 20121010 (brap)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-14Bibliographically approved
Nilsson, D. & Prakash, B. (2011). Influence of different surface modification technologies on friction of conformal tribopair in mixed and boundary lubrication regimes (ed.). Paper presented at . Wear, 273(1), 75-81
Open this publication in new window or tab >>Influence of different surface modification technologies on friction of conformal tribopair in mixed and boundary lubrication regimes
2011 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 75-81Article in journal (Refereed) Published
Abstract [en]

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, temperature etc. The overall frictional losses in machines are dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a sliding bearing/roller tribopair both in boundary and mixed lubrication regimes. A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range to enable studies in boundary and mixed lubrication regimes. The influence of application of different surface modification technologies on both the sliding bearing and the roller surfaces on friction has been studied. The rollers used in these studies were provided with five different coatings (hard DLCs and a soft self-lubricating coating). Additionally, two uncoated rollers having different surface roughness were also studied. Uncoated bearings were used in all tribopairs except two. These two bearings were coated with DLC and phosphate coatings respectively and uncoated rollers were the mating counterparts. Friction measurements were made on the new as well as the previously run-in surfaces. It was found that the rollers with self-lubricating coating resulted in lowest boundary friction closely followed by the rollers with the hardest DLC coatings. The DLC coating applied on to the bearing showed lower boundary friction after running-in. Mixed friction has been found to be mainly dependent on the surface topography characteristics of both the original and the run-in surfaces of bearings and rollers. The harder DLC coatings and the phosphated bearing showed the lowest mixed friction due to an efficient running-in of the bearing surface.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-7459 (URN)10.1016/j.wear.2011.05.002 (DOI)000297902500013 ()2-s2.0-80055108169 (Scopus ID)5d7a6f83-89fa-43ab-9381-e99702bf4b2b (Local ID)5d7a6f83-89fa-43ab-9381-e99702bf4b2b (Archive number)5d7a6f83-89fa-43ab-9381-e99702bf4b2b (OAI)
Note
Validerad; 2011; 20110515 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Nilsson, D. (2011). Investigations for enhanced tribological performance of a hydraulic motor (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Investigations for enhanced tribological performance of a hydraulic motor
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A radial piston hydraulic motor has several components that encounter sliding orrolling motion under lubricated conditions. When a hydrostatic, hydrodynamic orelastohydrodynamic oil film separates the interacting surfaces, the wear and frictionare low provided of course the hydraulic fluid is free from the presence ofcontaminants. Mixed lubrication may occur even at relatively high speed when usinglow viscosity fluids and may result in increased friction which adversely affects theoperating efficiency of the hydraulic motor. Additionally, the increased heataccumulation at different interfaces of the motor under extreme operating conditionsinvolving high pressures, high speeds and low viscosities can also lead to unstoppablethermal process resulting in seizure. At low speeds, different tribological pairs operatein boundary lubrication regime and are prone to wear. The associated high friction canalso result in low starting efficiency.The research work reported here has thus focussed on addressing the above mentionedquestions so as to improve understanding of the tribological phenomena and find waysfor improving and alleviating hydraulic motor tribological components.The results have shown that it is possible to reduce both the boundary friction and thelift-off speed through proper choice of surface modification methods and theirapplication on motor components.The running-in aspect is also very important for the satisfactory tribologicalperformance of the motor. An optimal running-in can improve surface roughness andconformity of motor components. The studies have shown that the use of DLC andphosphate coatings can be effective in accomplishing these. It may however also bekept in mind that during the initial sliding (running-in) the machine components aresusceptible to wear and roughening of the surfaces. The conformity and roughness ofthe surfaces of the sliding components are important for the lift-off speed and this alsoinfluences both the seizure resistance and overall efficiency of the motor. Threeprocesses give rise to the occurrence of seizure in a hydraulic motor and these havebeen identified as: friction heat generation during operation in mixed lubricationregime, friction heat generation during operation in full film lubrication regime andentrapment of wear particles between sliding surfaces. The initiation of scuffing on alocal scale has been found to be dependent on interface temperature rather than on thepv-value.There are several polymeric materials that are suitable for journal bearing applicationsin hydraulic motors. The PTFE based polymeric materials have the potential to reducebreak away friction by an order of magnitude. However, after running-in at 100 MPacontact pressure their low coefficients of friction have been found to increase.The simulation of a hybrid journal bearing including influence of surface roughnesshas shown good correlation with practical measurements in component test rig inlubrication regime ranging from full film down to boundary lubrication.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2011
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-16985 (URN)106b8fe2-067d-43bb-b5e1-32bb80c9fc84 (Local ID)978-91-7439-311-8 (ISBN)106b8fe2-067d-43bb-b5e1-32bb80c9fc84 (Archive number)106b8fe2-067d-43bb-b5e1-32bb80c9fc84 (OAI)
Note
Godkänd; 2011; 20110915 (dannil); DISPUTATION Ämnesområde: Maskinelement/Machine Elements Opponent: Professor Friedrich Franek, Dept Microsystem Technology, Institute of Sensor and Actuator Systems, Vienna University of Technology, Wiener Neustadt, Austria Ordförande: Professor Braham Prakash, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå Tid: Torsdag den 20 oktober 2011, kl 09.30 Plats: E231, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-01-10Bibliographically approved
Isaksson, P., Nilsson, D., Larsson, R. & Almqvist, A. (2011). The influence of surface roughness on friction in a flexible hybrid bearing (ed.). Paper presented at . Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 225(J10), 975-985
Open this publication in new window or tab >>The influence of surface roughness on friction in a flexible hybrid bearing
2011 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, no J10, p. 975-985Article in journal (Refereed) Published
Abstract [en]

The effect of surface roughness on friction in all lubrication regimes is studied for a flexible hybrid bearing of a radial piston hydraulic motor. The effect is studied by performing experiments in a specially designed test rig and numerical simulations of the real measured surface topographies of the bearings. The simulations are performed with a two-scale model where surface roughness is treated on a local asperity level by homogenized flow factors and a global scale where the bearing structure is included. Three bearings with different surface topographies are included in the study and both experimentally measured and simulated friction are analysed for each of them. Comparison of friction predicted by the model and experimentally measured friction is performed and it reveals that the model is a valuable tool for analysing the effect of surface roughness in this type of bearing

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-4422 (URN)10.1177/1350650111417203 (DOI)000295284900002 ()2-s2.0-81255161404 (Scopus ID)25e9bafd-5d55-4ecb-a6b9-335d4dc01c72 (Local ID)25e9bafd-5d55-4ecb-a6b9-335d4dc01c72 (Archive number)25e9bafd-5d55-4ecb-a6b9-335d4dc01c72 (OAI)
Note
Validerad; 2011; 20111021 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Nilsson, D. & Prakash, B. (2010). Influence of surface modification technologies on friction of conformal tribopair in boundary and full film lubrication regimes (ed.). In: (Ed.), (Ed.), 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010. Paper presented at Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Influence of surface modification technologies on friction of conformal tribopair in boundary and full film lubrication regimes
2010 (English)In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper, Published paper (Refereed)
Abstract [en]

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, temperature etc. The overall frictional losses in machines are thus dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a conformal tribopair both in boundary and full film lubrication regimes. The conformal pair chosen is a hydrodynamic bearing with some hydrostatic lift.A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range so as to enable studies in all lubrication regimes i.e., in boundary, mixed and full-film lubrication.The influence of application of different surface modification technologies on friction has been studied. In all, rollers with five coatings (four hard DLC coatings and one self-lubricating coating) and two rollers without coating having different surface finish. Friction measurements were made on the new as well as the previously run-in components. The different coatings exhibit different levels of boundary friction, with the self-lubricating coating having lowest boundary friction, closely followed by those with hard DLC coatings. The softer amongst the hard DLC coatings showed similar boundary friction compared to that with uncoated rollers. The lift-off speed, i.e., the transition between full-film to mixed and boundary lubrication mainly governed by the surface topography characteristics. A smooth surface finish can be achieved either by polishing before the test or by effective running in of the new surface. The effectiveness of running-in of surfaces was influenced by the surface roughness and hardness of the interacting surfaces.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2010
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-35198 (URN)9a13f730-82b7-11df-ab16-000ea68e967b (Local ID)978-91-7439-124-4 (ISBN)9a13f730-82b7-11df-ab16-000ea68e967b (Archive number)9a13f730-82b7-11df-ab16-000ea68e967b (OAI)
Conference
Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010
Note
Godkänd; 2010; Bibliografisk uppgift: CD-ROM; 20100628 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-14Bibliographically approved
Nilsson, D. & Prakash, B. (2010). Investigation into the seizure of hydraulic motors (ed.). Paper presented at . Tribology International, 43(1-2), 92-99
Open this publication in new window or tab >>Investigation into the seizure of hydraulic motors
2010 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 43, no 1-2, p. 92-99Article in journal (Refereed) Published
Abstract [en]

Despite its practical significance, the occurrence of seizure in tribological systems has not been fully understood. In this work, extensive actual tests on hydraulic motors under extreme operating conditions of low viscosity, high pressure and speed have been conducted with a view to investigate and understand the seizure mechanism. Some of the motors failed and they were stopped at different stages of progressive seizure. Based on these investigations, a three stage seizure process has been suggested. Stage 1 involves the breakdown of hydrodynamic oil film between roller and piston which leads to increased friction, thermal expansion and increased leakage. In stage 2, scuffing is initiated either between roller and piston or between piston and cylinder. During stage 3 scuffing propagate to several pistons.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-15721 (URN)10.1016/j.triboint.2009.05.001 (DOI)000271776100012 ()2-s2.0-74149095038 (Scopus ID)f4613850-411e-11de-bc0c-000ea68e967b (Local ID)f4613850-411e-11de-bc0c-000ea68e967b (Archive number)f4613850-411e-11de-bc0c-000ea68e967b (OAI)
Note
Validerad; 2010; 20090515 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Nilsson, D., Isaksson, P. & Prakash, B. (2009). Effects of area ratio and nature of surfaces on scuffing in lubricated contacts (ed.). Paper presented at . Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 223(3), 445-455
Open this publication in new window or tab >>Effects of area ratio and nature of surfaces on scuffing in lubricated contacts
2009 (English)In: 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. 445-455Article in journal (Refereed) Published
Abstract [en]

Heavily loaded moving machine components encounter severe tribological problems. Typical examples include piston and cylinder contacts in a hydraulic motor. Piston and cylinder bore contacts invariably operate in boundary lubrication regime and the risk for seizure of these contacts is high particularly when lubricated with low-viscosity lubricants. The piston assembly in a radial piston hydraulic motor has conformal (area) contact. In this work, these contacts have been simulated in the laboratory by using a thrust washer test configuration. The influence of area ratio, nature of contacting surfaces, and speed on scuffing has been investigated by using a factorial design of experiments approach. The influence of area ratio on wear at lower speed has also been studied. The results have revealed that the surface power, or μpv-value, at scuffing varies by 3-4 times when the area ratio was increased from 8 to 72 per cent. The running-in wear tests have shown that running-in of the upper and lower specimens also varies with the area ratio. During the first 30 s the upper specimen is polished with low area ratio, whereas the lower specimen is polished with high area ratio. The surface temperature was estimated by using finite-element calculation and it was found to be similar prior to scuffing for both 8 and 72 per cent area ratios at 1.7 m/s sliding speed. The comparison of the results with the actual motor tests shows that an area ratio of 24 per cent seems to simulate the piston-cylinder contact better.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-2930 (URN)10.1243/13506501JET472 (DOI)000266387900031 ()2-s2.0-70349667237 (Scopus ID)0ab4e980-0eed-11de-b3bc-000ea68e967b (Local ID)0ab4e980-0eed-11de-b3bc-000ea68e967b (Archive number)0ab4e980-0eed-11de-b3bc-000ea68e967b (OAI)
Note
Validerad; 2009; 20090312 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Isaksson, P., Nilsson, D. & Larsson, R. (2009). Elasto-hydrodynamic simulation of complex geometries in hydraulic motors (ed.). Paper presented at . Tribology International, 42(10), 1418-1423
Open this publication in new window or tab >>Elasto-hydrodynamic simulation of complex geometries in hydraulic motors
2009 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 42, no 10, p. 1418-1423Article in journal (Refereed) Published
Abstract [en]

As many other machines, the radial piston hydraulic motor contains a lot of tribological interfaces. One important area is the piston assembly and the journal bearing contact between the piston and cam roller. There exists good models to describe the performance of simpler geometries such as journal bearings, but when put into a system or when having a more complex geometry, the models do not apply very well. To be able to predict the tribological performance of such components, it is important to have a model that is able to include the real geometry and the properties of the system.A simulation model of the piston assembly in Hägglunds Compact hydraulic motor was built using FE software which made it easy to include the complex geometries. The model includes the deformation of the piston. The hydrodynamics is solved by using Reynolds equation.Density/pressure and viscosity/pressure dependency for the oil are included.Simulation results such as friction, hydrodynamic pressure and oil leakage was compared with test results. Good agreement between simulation and tests shows that this kind of model can be a useful tool in development and optimization of tribological systems.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-8789 (URN)10.1016/j.triboint.2009.05.018 (DOI)000270126500003 ()2-s2.0-68549105967 (Scopus ID)754d7ec0-47d6-11de-93f6-000ea68e967b (Local ID)754d7ec0-47d6-11de-93f6-000ea68e967b (Archive number)754d7ec0-47d6-11de-93f6-000ea68e967b (OAI)
Note
Validerad; 2009; 20090523 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Nilsson, D. (2009). Tribology of hydraulic motor (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Tribology of hydraulic motor
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A radial piston hydraulic motor has several components involving sliding or rolling interfaces which may encounter tribological problems. Seizure is one of them and it results in complete stoppage of motion between the relatively moving components and has serious consequences in terms of the operation of a hydraulic motor. Extreme running conditions, like low viscosity and high pressure and speed can cause the rupture of lubricating films and this may lead to the seizure of hydraulic motors. The occurrence of seizure often leads to undesirable damage to the motor components and unscheduled maintenance and can prove to be highly expensive. The work reported in this thesis has focused on investigating the mechanisms of seizure and developing suitable tribo test methods for simulating the sliding interfaces of the hydraulic motor. Extensive motor tests have been performed at low viscosity, high pressure and high speed. The results of this work enabled in describing the seizure progression, namely break down of lubricant film, particle entrapment and thermal expansion. Further, tests have been carried out in a rotary tribometer by using a thrust washer conformal test configuration. In this, the influence of area ratio has been studied and this configuration appears to simulate the piston-cylinder contact effectively during boundary lubricated conditions.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2009. p. 19
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-17674 (URN)49659880-388e-11de-9b53-000ea68e967b (Local ID)978-91-86233-49-5 (ISBN)49659880-388e-11de-9b53-000ea68e967b (Archive number)49659880-388e-11de-9b53-000ea68e967b (OAI)
Note
Godkänd; 2009; 20090504 (dannil); LICENTIATSEMINARIUM Ämnesområde: Maskinelement/Machine Elements Examinator: Professor Braham Prakash, Luleå tekniska universitet Tid: Fredag den 5 juni 2009 kl 09.15 Plats: F 531, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-01-10Bibliographically approved
Organisations

Search in DiVA

Show all publications