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1.	Almqvist, Torbjörn, et al. (författare) A comparison between computational fluid dynamic and Reynolds approaches for simulating transient EHL line contacts 2004 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 37:1, s. 61-69 Tidskriftsartikel (refereegranskat)abstract When simulating elastohydrodynamic lubrication (EHL), the Reynolds equation is the predominating partial differential equation for prediction of the fluid flow. Also very few attempts have been carried out using the full momentum and continuity equations separately. The aim of this investigation is to compare two different approaches for simulation of EHL line contacts where a single ridge travels through an EHL conjunction. One of the approaches is based on the Reynolds equation, addressing the coupling between the pressure and the film thickness. The solver uses the advantages of multilevel techniques to speed up the convergence rate. The other approach is based on commercial CFD software. The software uses the momentum and continuity equations in their basic form, enabling numerical simulations outside the contact regions, as well as in the thin film region to be carried out. The numerical experiments show that, under the running conditions chosen, only small deviations between the two approaches can be observed. The results are encouraging from several viewpoints: validation of the codes, the possibilities of further developments of the CFD approach and the justification of using a Reynolds approach under the running conditions chosen
2.	Almqvist, Torbjörn, et al. (författare) The Navier-Stokes approach for thermal EHL line contact solutions 2002 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 35:3, s. 163-170 Tidskriftsartikel (refereegranskat)abstract The complicated nature of the EHL-problem has so far forced researchers to develop their own computer codes. These codes are ultimately based on the Reynolds equation, and if thermal EHL-simulations are required, a simultaneous solution of the equation of energy also has to be performed. To date only a few attempts to solve the full equations of momentum and continuity as well as equations of energy have been performed. However, such an approach will give extended possibilities of simulating EHL-contacts; i.e. the computational domain can be expanded and it will be possible to simulate the flow, not only in the contact but also around the contact. Another possibility is to investigate how the altering length scales of the surface roughness influence the behaviour of the flow in the contact. However, the aim of the work presented in this paper is to investigate the possibilities of using a commercial CFD-code (computational fluid dynamics code) based on the above-mentioned equations for simulating thermal EHL. The rheology is assumed to be Newtonian and the equations of momentum and continuity are then commonly referred to as the Navier-Stokes equations (N-S equations). The geometry chosen for the simulations is a smooth line contact geometry, for which the results from the simulations show that it is possible to use the N-S equations for thermal EHL for contact pressures up to approximately 0.7 GPa. The code used in this work is the commercial CFD software (CFX 4.3 user guide). There is a limitation in the N-S approach due to a singularity that can occur in the equation of momentum when the principal shear stresses in the film become too high. However, a thermal approach makes it possible to simulate EHL-contacts at higher loads compared with an isothermal approach, due to the reduction of the viscosity in the former approach. The singularity is not present in the Reynolds approach.
3.	Björklund, Stefan (författare) The influence of surface roughness in elliptical contacts 2001 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 34:12, s. 841-845 Tidskriftsartikel (refereegranskat)abstract The influence of surface roughness on contact behaviour is of great importance in many tribological situations. In the last decade several methods to calculate the pressure distribution and the real contact area in contacts between rough surfaces have been described. A problem arising for slender elliptical contacts, such as between gear teeth, roller and raceway, cam and follower, etc., is that the size of the contact is much greater than the size of the asperities. Accordingly the number of contact nodes necessary for an accurate solution to the problem becomes excessively large. This paper describes a method to calculate the influence of three-dimensional surface roughness in contacts that are very long in one direction. The method is based on restricting the calculations to a subpart of the real contact area, while the rest of the contact is taken into account by mirroring techniques. The results show that the real contact area is very sensitive to the amplitude of the roughness, while the waviness is less important. An equation is suggested from which the real area can be calculated if the smooth case contact parameters and two roughness parameters are known.
4.	Boschkova, K., et al. (författare) Study of thin surfactant films under shear using the tribological surface force apparatus 2001 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 34:12, s. 815-822 Tidskriftsartikel (refereegranskat)abstract Static and dynamic behaviour of thin surfactant films in aqueous solution of hexadecyltrimethylammonium salicylate (C16TASal) were investigated using the tribological surface force apparatus. Normal force measurements show that 0.15 mM C16TASal builds up an innermost film of approximately 8-11 Angstrom thickness at each mica surface, indicating that the surfactant adsorbs in a flat conformation. Furthermore, the height of the force barrier at approximately 60 Angstrom is low (ca 2 mN/m) indicating that the second adsorbed layer is easily pushed out. Addition of salicylate salt to 0.15 mM C16TASal give rise to a more close packed structure, with a total thickness of 62-65 Angstrom. indicative of a micellar or bilayer arrangement at the surfaces. Furthermore, the frequency dependence of the shear modulus was investigated both at close separation at the innermost force barrier and at larger separations (up to 300-400 Angstrom). The visco-elastic measurements show that the elasticity modulus, G ', dominates over the loss modulus, G , for all studied cases, indicative of a more solid-like than liquid-like film. Finally, it is shown that shear at high contact pressures induces new aggregate structures at the surface.
5.	Glavatskih, Sergei (författare) A method of temperature monitoring in fluid film bearings 2004 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 37:2, s. 143-148 Tidskriftsartikel (refereegranskat)abstract In the present paper a method to improve temperature monitoring of fluid film bearings is described. The method is tested in an industrial tilting pad thrust bearing. Test results for steady state and transient operating conditions are reported. Temperatures monitored by a thermocouple through the utilisation of the proposed method are compared to those measured by thermocouples in the pad backing and in the collar. The method is also tested on a PTFE-faced bearing. Test results show that the proposed method improves sensitivity to thermal transients in conventional babbitted bearings and provides adequate means of temperature monitoring in the PTFE-faced bearings.
6.	Glavatskih, Sergei B., et al. (författare) Simultaneous monitoring of oil film thickness and temperature in fluid film bearings 2001 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 34:12, s. 853-857 Tidskriftsartikel (refereegranskat)
7.	Kassman Rudolphi, Åsa, et al. (författare) Stationary loading, fretting and sliding of silver coated copper contacts : Influence of corrosion films and corrosive atmosphere 1997 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 30:3, s. 165-175 Tidskriftsartikel (refereegranskat)abstract The degradation mechanisms of silver coated copper contacts were studied under stationary loading, reciprocated sliding and fretting conditions. The model contact consisted of two crossed cylinders (Ø = 10 mm) mounted in a small test chamber. Prior to performance testing corrosion films were grown in a large chamber of Battelle class III atmosphere. The tests were performed in four atmospheres, specified with respect to temperature, relative humidity and pollutant gases. The normal force was 20 or 60 N and the contacts were powered with a direct current of 10 A. The study shows that the presence of a thin pre-grown corrosion film on top of the silver coating strongly influences the contact resistance, the friction and the degradation mechanisms of the contact. Generally, the corrosion films reduced the tendencies to adhesion between the contact surfaces, which subsequently reduced the deformation. Moreover, the corrosion films had very different effects in different contact situations. While the impairing effect on the contact resistance was almost neutralized during fretting it was substantial in some sliding cases. In contrast to the pre-grown corrosion film, the test atmosphere was not found to influence the contact performance.
8.	Larsson-Kråik, Per-Olof, et al. (författare) Pressure fluctuations as grease soaps pass through an EHL contact 2000 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 33:3-4, s. 211-216 Tidskriftsartikel (refereegranskat)abstract Soap lumps entering a grease-lubricated elastohydrodynamic lubrication (EHL) contact were traced as they passed through the contact by using optical interferometry in a standard Ball & Disc apparatus and a high-speed video camera with light enhancer. One specific soap lump could be traced when it was passing through the contact and sharp images of the passing lump could be captured. This paper presents a combined experimental and numerical approach to determine what is happening when such lumps pass through the contact. From the fringe pattern, obtained by optical interferometry, a film thickness map is created by using image processing. This is done for every time step (1 ms) as the lump is passing through the contact. These maps serve as input to a numerical computation of the pressure by assuming elastic deformation theory. Consequently, no assumptions about the rheological behaviour of the grease have to be made. Two greases were studied, based on the same synthetic poly-α-olefin but thickened with Li-12-OH and Li-complex respectively. It is seen that the soap thickened lumps can cause deep elastic indentations accompanied by large pressure fluctuations. The pressure level will in some cases be more than doubled due to lumps entering the contact region. The effects on noise level and operational life are also discussed.
9.	Lundberg, Jan, et al. (författare) A new method for determining the mechanical stability of lubricating greases 2000 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 33:3-4, s. 217-223 Tidskriftsartikel (refereegranskat)abstract Mechanical stability is of central importance when dealing with the long-term service-length of grease-lubricated roller bearings. Poor stability will lead to consistency degradation of the grease, because of mechanical forces between the rolling parts of the bearing. The result can be leakage of grease through seals, or at worst a total failure of the bearing. The present investigation was initiated because present-day methods for prediction of mechanical stability show weak correlation with real service-length. The aim of the project was to develop a useful alternative. In order to fulfil this, both field tests and laboratory tests were carried out. In the field tests, nine different commercial greases were examined in the wheel bearings of five ore waggons, used for transporting ore by railroad from the Kiruna Mine in northern Sweden to Narvik in northern Norway for shipping to foreign markets. The test ore waggons travelled a distance of about 300,000 km during a period of 3 years. Small samples of greases were taken, on eight different occasions, for consistency testing. After the end of the test period, the damage on the bearings was also studied. In the laboratory tests, new undestroyed greases of the same brand as in the field tests were examined using conventional methods, such as the V2F, the Roll Stability Test and the Grease Worker. Comparisons between the field tests and these laboratory tests indicate poor correlation. In addition to these conventional methods, the relevance of the shear strength of the greases to the prediction of the mechanical stability was also tested. The shear stress τL depends on the applied pressure p, thus τL=τO+γ·p where τO is the shear stress at atmospheric pressure, γ is a property of the lubricant in the same way as viscosity or density. It was found that γ correlates well with the mechanical stability in service. Increased γ values lead to a decrease in the mechanical stability. One reasonable explanation is that high γ values correspond to high shear stresses in the grease, and thus severe conditions for the thickener.
10.	Lundberg, Jan (författare) Influence of surface roughness on normal-sliding lubrication 1995 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 28:5, s. 317-322 Tidskriftsartikel (refereegranskat)abstract Contact between machine components can involve normal, sliding and rolling motion, either singly or in combination. Combined normal and sliding motion, which occur for example in the meshing of gear teeth and in heavily-loaded rolling elements, can present problems for lubrication. The purpose of the present experimental study was to investigate how surface roughness affects the lubricant film characteristics under conditions of combined normal and sliding motion. The experimental arrangement consisted of a rotating roller which impacted a stationary ball in the presence of a lubricant. Under the same conditions of normal surface approach, increasing the surface roughness significantly decreased the level of roller sliding that could occur without breakdown of the lubricating film. This behaviour was similar to a step function. Of the several surface roughness parameters investigated, only those which involved the maximum peak-to-valley height correlated well with experimental results. In general, surface roughness had a greater effect on oil film breakdown than did either viscosity or load.
11.	Markin, D., et al. (författare) A FEM approach to simulation of tilting-pad thrust bearing assemblies 2003 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 36:11, s. 807-814 Tidskriftsartikel (refereegranskat)abstract Finite-element method (FEM) modelling is applied to analysis of the performance of hydrodynamic tilting-pad thrust bearing assemblies. A 3D model of the bearing assembly that includes the bearing pad and shaft is used to assess the influence of operating conditions on bearing parameters such as temperature and oil film distributions across the pads. The model is first applied to the investigation of a spherically pivoted-pad. Through comparison with results from experiments carried out on just such a bearing, good correlation between the model and experimental results is found for maximum oil film temperature, pressure distribution and thickness. The model is then applied to the examination of a bearing having spring-supported babbitt pads. The effect of different oil types on a spring-supported thrust bearing is analysed. Further application of the model to investigate the same spring-supported pad, this time with a resilient surface coating, is discussed.
12.	Olsson, Håkan, et al. (författare) Wear testing and specification of hydraulic fluid in industrial applications 2003 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 36:11, s. 835-841 Tidskriftsartikel (refereegranskat)abstract The aim of this paper was to investigate the possibilities to use a model test to simulate the wear between cylinder bore and piston in a radial piston hydraulic motor. The tests were performed in a reciprocating test rig where the contact geometry is of the cylinder-plate type. The influence of different types of commercially available hydraulic fluids on wear protection and friction was studied. From the study, it was concluded that the use of water glycols can cause increased wear in hydraulic motors operating in low speed applications. It was also seen that the FZG test alone appears not to be enough as a hydraulic fluid wear test, at least not in the tribological conditions present in the performed wear test.
13.	Pettersson, Anders (författare) Tribological characterization of environmentally adapted ester based fluids 2003 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 36:11, s. 815-820 Tidskriftsartikel (refereegranskat)abstract Fundamental properties of six synthetic ester base fluids, suitable for the formulation of environmentally adapted lubricants, have been investigated. High pressure viscosity data for the test fluids were obtained through experimental measurements with a high pressure Couette rheometer. The temperature, pressure and viscosity data η(p, T) were parameterized against the Roelands pressure-viscosity equation. Thermal conductivity and specific heat capacity data were obtained using a transient hotwire method, and the EHD friction coefficient, γ, was obtained experimentally as well. The results from these measurements are reported, and the correlation between thermal properties, molecular structure, and the fluid rheology parameters, of the test fluids are discussed.
14.	Pettersson, Ulrika, et al. (författare) Influence of surface texture on boundary lubricated sliding contacts 2003 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 36:11, s. 857-864 Tidskriftsartikel (refereegranskat)abstract The friction and wear behaviour of boundary lubricated sliding surfaces is influenced by the surface texture. By introducing controlled depressions and undulations in an otherwise flat surface, the tribological properties can be improved. Lubricant can then be supplied even inside the contact by the small reservoirs, resulting in a reduced friction and a prolonged lifetime of the tribological contact.In the present paper, well-defined surface textures were produced by lithography and anisotropic etching of silicon wafers. The wafers were subsequently PVD coated with thin wear resistant TiN or DLC coatings, retaining the substrate texture. The size and shape of the depressions were varied and evaluated in reciprocating sliding under dry and boundary lubricated conditions.
15.	Ukonsaari, Jan (författare) Wear and friction of synthetic esters in a boundary lubricated journal bearing 2003 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 36:11, s. 821-826 Tidskriftsartikel (refereegranskat)abstract This study concerns the case of a slow intermittent motion, conformal contact, high load bronze journal bearing against a hardened steel shaft lubricated in an oil bath at a temperature about of 13 DGC. Three synthetic esters were used: one pure and two formulated ones. Worn surfaces were examined using SEM-EDS to determine the wear mechanism. The tested lubricants were examined using ICP-AES to identify the elements present. The results show the wear rate, friction and temperature in the subsurface of the journal bearing material. An initial bronze-steel contact develops into a copper-copper contact along the sliding distance. Wear element concentration in the oil and friction surfaces departs from the elementary concentration in the journal bearing bronze base material. The copper layer thickness depended on additives in the synthetic esters, load and wear rate.
16.	Waara, Patric, et al. (författare) Additive influence on wear and friction performance of environmentally adapted lubricants 2001 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 34:8, s. 547-556 Tidskriftsartikel (refereegranskat)abstract In this paper, the influence of concentration level and chemical composition of three different additive types on friction and wear coefficient are presented for a synthetic ester base fluid and a mineral base oil. One extreme-pressure (EP), two antiwear (AW) and two yellow metal passivator (Cu-passivators) additives were used. Factorial experimental design was used as the basis for a systematic evaluation of wear rates under mixed and boundary lubrication conditions. A total of 33 different lubricant blends were tested in a Plint and Partner High Frequency Friction Machine. For the synthetic ester, the extreme-pressure (EP) additive, containing phosphorus and nitrogen, was found to be much more effective in reducing wear than either of the two antiwear (AW) additives tested. In fact, the AW and Cu-passivator additives made little or no contribution to the wear protection in most of the cases studied. A synergy effect between the three additive combinations was observed only for the reference mineral oil blend. A significant difference between the antiwear performance of the test lubricants was found. This study suggests that the traditional "AW" and "EP" labels associated with commonly used additives are poor aids when designing of ester based lubricants.
17.	Wänstrand, Olle, et al. (författare) Mechanical and tribological properties of vapour deposited low friction coatings on Ni plated substrates 2000 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 33:10, s. 737-742 Tidskriftsartikel (refereegranskat)abstract Soft steel and aluminium substrates with load-carrying layers of electroplated nickel were coated with commercially available lowfrictionvapourdepositedcoatings. The mechanical and tribologicalproperties of the coating and substrate composites were evaluated with special emphasis on the influence of the nickel layer. Two different thicknesses of the intermediate load-carrying nickel layer were tested. The samples were evaluated regarding friction and sliding wear, abrasive wear, hardness and elastic modulus, morphology and coating thickness and adhesion between substrate and coating. It was found that all the evaluated lowfrictioncoatings were possible to be successfully deposited on the intermediate nickel layer. A relatively thick intermediate nickel layer is a promising candidate for improvement of the load-carrying capacity
18.	Åhrström, Bert-Olof (författare) Investigation of frictional properties of lubricants at transient elastohydrodynamic conditions 2001 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 34:12, s. 809-814 Tidskriftsartikel (refereegranskat)abstract In the assessment of lubricant properties and in various contact applications, it is of importance to know the frictional qualities. Under quasi-static conditions, normal and transverse forces are measured using force transducers but the task is more difficult when loads are high and transient, as they often are in elastohydrodynamic conjunctions. The experimental method presented in this paper is based on analysis of propagating waves in a beam, due to an impact on its end surface, using FFT analysis. Since the impact is oblique, both non-dispersive compression waves and dispersive flexural waves are generated. The normal force originating from the axial wave is measured using straingauges, while the transverse force is derived from the FFT's of two lateral acceleration histories using Euler-Bernoulli dynamic beam theory. The relation between normal- and transverse force histories displays the frictional properties at the impact as a function of time, i.e. variations in frictional properties during loading and unloading (typically 200-400 μs in ball bearings and gears) can be observed. A variety of lubricants have been studied up to a Hertzian pressure of 2.5 GPa, and the method and results are presented.
19.	Åström, Henrik, et al. (författare) Video recordings of an EHD point contact lubricated with grease 1991 Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 24:3, s. 179-184 Tidskriftsartikel (refereegranskat)abstract Optical interferometry has been used to study the film thickness of an EHD point contact lubricated with grease. The greases used were two lithium, two lithium complex and two sodium greases, all with NLGI grade two, the most common grade. They were based on one mineral oil of naphthenic type and one synthetic polyalphaolefin. The contact was lubricated without a continuous supply of grease and thus the film thickness decreased with time as the grease was gradually squeezed away from the contact area. The film thickness fluctuated during the measurement. To overcome this problem, the contact point was recorded with a video camera and the results evaluated after the tests. The video camera proved to be a powerful help in this evaluation. The tests were run at 20°C and under pure rolling conditions at a rolling velocity of 0.055 m s-1. The results from all greases showed a decreasing film thickness that tended to stabilize on about 0.2 μm after 40 cycles. The lithium and lithium complex greases showed strong local film thickness variations inside the lubricated contact, deviating from the normally horseshoe-shaped contact, during the first 20 to 40 cycles.
20.	Abbasi, Saeed, 1973-, et al. (författare) Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel-rail contact 2013 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 60, s. 136-139 Tidskriftsartikel (refereegranskat)abstract Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of theworn-off material is transformed into airborne particles. Although such wear is well understood, few studiestreat the particles generated. We investigated friction modifiers' effects on airborne particles characteristicsgenerated in wheel-rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pinloaded by a dead weight load 40 N simulated maximum contact pressure over 550 MPa. Airborne particlecharacteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease andwater- and oil-based friction modifiers. The number of particles declined with the grease; the number ofultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.
21.	Aiso, Toshiharu, 1983-, et al. (författare) Effect of Si and Cr additions to carbon steel on material transfer in a steel/TiN coated tool sliding contact 2016 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 97, s. 337-348 Tidskriftsartikel (refereegranskat)abstract A crossed cylinders sliding test, simulating the contact between the chip and the tool in machining, is used to evaluate material transfer and friction characteristics of a TiN coating against specifically designed model steels. These include one base reference, only alloyed with C (Base steel) and two alloyed also with 1 mass% Si or Cr. When sliding against the Base steel, an Fe-O layer is formed on the coating. Against the Si and Cr alloyed steels, Fe-Si-O and Fe-Cr-O layers are formed. In these oxides, Si and Cr are enriched, i.e. preferentially transferred from the steels. Compared to the Base steel, the friction coefficient is significantly lower against the Si alloyed steel and higher against the Cr alloyed steel.
22.	Aiso, Toshiharu, 1983-, et al. (författare) Influence of Mn and Al additions to carbon steel on material transfer and coating damage mechanism in a sliding contact between steel and TiN coated HSS tool 2016 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 101, s. 414-424 Tidskriftsartikel (refereegranskat)abstract A crossed cylinders sliding test, simulating the contact between the chip and the cutting tool, is used to evaluate material transfer, friction characteristics and coating damage of a TiN coated high speed steel against specifically designed model steels. These steels include one reference with C as the only alloy element (Base steel), and two alloyed also with 1 mass% Mn or Al. When sliding against the Base steel, an Fe–O layer forms on the coating and protects it from wear. Against the Mn alloyed steel, Fe–Mn–O forms, which has no protective effect. Against the Al alloyed steel, an almost pure Al–O layer forms. This leads to the highest friction, rapidly causing substrate softening and coating fracture.
23.	Alemon, B., et al. (författare) Tribocorrosion behavior and ions release of CoCrMo alloy coated with a TiAlVCN/CNx multilayer in simulated body fluid plus bovine serum albumin 2015 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 81, s. 159-168 Tidskriftsartikel (refereegranskat)abstract While the CoCrMo biomaterial is currently employed in artificial joints, there are medical concerns regarding its metal ion release and material loss caused by tribocorrosion. In this work, a TiAlVCN/CNx multilayer coating has been employed to improve the tribocorrosion-resistance of the CoCrMo substrate. During the tribocorrosion test, with the sample immersed in a simulated body fluid containing bovine serum albumin, open-circuit potential measurements showed more noble potential as well as a reduction of both the friction coefficient and wear-rate during the sliding phase. Inductive coupled plasma results demonstrate that the multilayer coating effectively blocked the emigration of metallic ions.
24.	AlMotasem, Ahmed Tamer, et al. (författare) Adhesion between ferrite iron-€“iron/cementite countersurfaces : A molecular dynamics study 2016 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 103, s. 113-120 Tidskriftsartikel (refereegranskat)abstract The adhesive properties of Fe(110)/Fe(110) and Fe3C(001)/Fe(110) countersurfaces have been investigated by using classical molecular dynamics simulations. The simulation results show that Fe3C/Fe exhibits a relatively lower adhesion compared to the Fe/Fe. Additionally, the temperature dependence of the adhesive properties between 300â€“700Â K has been examined. The results demonstrate that, with increasing the temperature, the values of the adhesion force and the work of adhesion continuously decrease in the case of Fe3C/Fe; they initially slightly increase up to 500Â K then decrease in the case of Fe/Fe. Furthermore, the effect of lattice coherency between Fe/Fe has been examined and found to slightly reduce the adhesion. These results explain how carbides improve galling resistance of tool steel observed during dry sliding.
25.	AlMotasem, Ahmed Tamer, et al. (författare) Nanoindentation and nanoscratching of a ferrite/austenite iron bi-crystal : An atomistic study 2018 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 127, s. 231-239 Tidskriftsartikel (refereegranskat)abstract Molecular dynamics simulations are applied to investigate the wear/friction behavior of a ferrite/austenite iron bi-crystal, as a model system for duplex stainless steels. The plasticity of the ferrite phase is dominated by dislocations while both dislocations and stacking faults are the primary cause of plastic deformation of the austenite phase. Interestingly, the responses of tribological parameters vary depending on the scratch direction. For instance, the scratch hardness is increased by about 46% whereas the friction coefficient is reduced by about 22% when scratch starts from austenite to ferrite. At the interface, a local softening/hardening occurs because of dislocation-interface interaction. The present results demonstrate that martensitic phase transformation is responsible for experimentally observed high amount of ferrite of the pile-up.
26.	Almqvist, Andreas, et al. (författare) Homogenization of the unstationary incompressible Reynolds equation 2007 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40:9, s. 1344-1350 Tidskriftsartikel (refereegranskat)abstract This paper is devoted to the effects of surface roughness during hydrodynamic lubrication. In the numerical analysis a very fine mesh is needed to resolve the surface roughness, suggesting some type of averaging. A rigorous way to do this is to use the general theory of homogenization. In most works about the influence of surface roughness, it is assumed that only the stationary surface is rough. This means that the governing Reynolds type equation does not involve time. However, recently, homogenization was successfully applied to analyze a situation where both surfaces are rough and the lubricant is assumed to have constant bulk modulus. In this paper we will consider a case where both surfaces are assumed to be rough, but the lubricant is incompressible. It is also clearly demonstrated, in this case that homogenization is an efficient approach. Moreover, several numerical results are presented and compared with those corresponding to where a constant bulk modulus is assumed to govern the lubricant compressibility. In particular, the result shows a significant difference in the asymptotic behavior between the incompressible case and that with constant bulk modulus.
27.	Almqvist, Andreas, et al. (författare) On the dry elasto-plastic contact of nominally flat surfaces 2007 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40:4, s. 574-579 Tidskriftsartikel (refereegranskat)abstract A model to be used for numerical simulation of the contact of linear elastic perfectly plastic rough surfaces was developed. Energy dissipation due to plastic deformation is taken into account. Spectral theory and an FFT-techique are used to facilitate the numerical solution process. Results of simulations using four two-dimensional profiles with different topographies in contact with a rigid plane for a number loads are reported. From the results it is clear that the real area of contact (Ar) changes almost linearly with load and is only slightly affected by the difference in topography. A plasticity index is defined as the ratio of plastically deformed areaÂ (Ap) and Ar. Plastic deformation occurs even at low loads and there is a significant difference in plasticity index between the surface profiles considered. An investigation on how the spectral content of the surface profile influences the results presented is also performed. This is to ensure that the metrological limitations of the optical profilerused to measure the surfaces do not have a significant influence. It is concluded that the highest frequencies of the measured profile have a negligible influence on the real area of contact.
28.	Almqvist, Andreas, et al. (författare) The homogenization process of the Reynolds equation describing compressible liquid flow 2006 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 39:9, s. 994-1002 Tidskriftsartikel (refereegranskat)abstract This paper summarizes the homogenization process of rough, hydrodynamic lubrication problems governed by the Reynolds equation used to describe compressible liquid flow. Here, the homogenized equation describes the limiting result when the wavelength of a modeled surface roughness goes to zero. The lubricant film thickness is modeled by one part describing the geometry/shape of the bearing and a periodic part describing the surface topography/roughness. By varying the periodic part as well as its wavelength, we can try to systematically investigate the applicability of homogenization on this type of problem. The load carrying capacity is the target parameter; deterministic solutions are compared to homogenized by this measure. We show that the load carrying capacity rapidly converges to the homogenized results as the wavelength decreases, proving that the homogenized solution gives a very accurate representation of the problem when real surface topographies are considered
29.	Almqvist, Torbjörn, et al. (författare) Thermal transient rough EHL line contact simulations by aid of computational fluid dynamics 2008 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 41:8, s. 683-693 Tidskriftsartikel (refereegranskat)abstract Reynolds equation is the pre-dominantly used PDE for modelling the fluid flow or more accurately the fluid pressure in an elastohydrodynamic lubrication (EHL) contact. The equation is derived by combining the two conservation equations of momentum and continuity into a single equation for the fluid pressure. The numerical approach for theoretical investigations performed on EHL contacts in this work is somewhat different. The modelling of the fluid flow is based on a computational fluid dynamic (CFD) technique. The fluid flow is simulated by aid of the equations of momentum and continuity in a more complete form and when the thermodynamics is incorporated, the equation of energy. The aim of the investigation was to examine whether the CFD technique could be used to handle thermal transient rough EHL line contacts. It is shown that commercial CFD software can be modified to meet such requirements. The influence of thermal effects on the flow under sliding motion was investigated. The non-Newtonian model used in this work is the Ree-Eyring model. It is shown that the choice of the Eyring stress in the model influences flow in the contacts. If the thermal properties of the surrounding solids differ, it has been shown experimentally and theoretically that a dimple or increased central film thickness may appear in the EHL contacts. This work shows that the governing mechanisms that result in the dimple are also present in thermal transient rough EHL line contacts.
30.	Alvi, Sajid, et al. (författare) Tribological performance of Ti6Al4V at elevated temperatures fabricated by electron beam powder bed fusion 2021 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 153 Tidskriftsartikel (refereegranskat)abstract Electron beam powder bed fusion (EBPBF) is a beneficial processing route to fabricate Ti6Al4V alloy for aerospace applications due to its relatively low lead time and the possibility of topology optimization. The dry sliding wear behavior of EBPBF-Ti6Al4V against steel and alumina counterballs from room temperature (RT) to 500 °C was investigated to evaluate the influence of EBPBF processing and microstructure on the wear properties for broadening the application criteria of this lightweight alloy. The wear tests revealed that the wear rate decreased with increasing temperature due to formation of stable oxide glaze layer. This study reveals elevated temperature sliding wear behavior, wear mechanisms and microstructural changes below the wear track of EBPBF Ti6Al4V alloy against steel and alumina counterbodies.
31.	Anderberg, Cecilia, et al. (författare) Low friction and emission cylinder liner surfaces and the influence of surface topography and scale 2019 Ingår i: Tribology International. - Kidlington : Pergamon Press. - 0301-679X .- 1879-2464. ; 133, s. 224-229 Tidskriftsartikel (refereegranskat)abstract A low friction piston ring pack, with tangential load halved, was tested in engines with four different cylinder liner finishes. Oil consumption, oil temperature and liner surface temperature were monitored at different load and speed levels, under similar test conditions. The two smoother surfaces generally kept lower oil consumption compared to the two rougher ones. Results were correlated using an area-fractal analysis. The relative area of the surface was calculated at different scales and the result was compared with the level of oil consumption for the different liner surfaces at different engine speeds. It was found that oil consumption was strongly correlated with scale for areas of above 1000 μm2 and below 20 μm2. © 2018
32.	Andersson, Martin, et al. (författare) The effect of running-in on the efficiency of superfinished gears 2016 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 93, s. 71-77 Tidskriftsartikel (refereegranskat)abstract Reduced gear contact losses are necessary to keep operating temperatures, as well as fuel consumption low. In this work, an FZG gear test rig was used to investigate the effect of running-in on superfinished gears with respect to efficiency. This was compared to ground gears where a higher contact pressure yielded higher efficiency. No difference was found between the two running-in procedures when analysing superfinished gears. The effect of running-in on gears decreased when the initial surface roughness was reduced, which initially had an Ra, Rz and Rpk value of 0.08, 0.75 and 0.08 μm respectively. Superfinished gears showed an overall higher efficiency; however, a distinctly lower efficiency was present below 2 m/s when compared to ground gears.
33.	Andersson, Sören, et al. (författare) Frictions models for sliding dry, boundary and mixed lubricated contacts 2007 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40, s. 580-587 Tidskriftsartikel (refereegranskat)abstract Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are:center dot friction models for transient sliding under dry, boundary and mixed lubrication conditions,center dot friction models for micro-displacements of engineering surfaces subjected to transient sliding,center dot friction models often used in the simulation and control of technical systems,center dot combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems,center dot friction models that take into account the stochastic nature of interacting surface asperities
34.	Bakoglidis, Konstantinos, et al. (författare) Rolling contact fatigue of bearing components coated with carbon nitride thin films 2016 Ingår i: Tribology International. - : ELSEVIER SCI LTD. - 0301-679X .- 1879-2464. ; 98, s. 100-107 Tidskriftsartikel (refereegranskat)abstract Bearing rollers were coated with CNx films using high power impulse magnetron sputtering deposition in order to reduce their rolling-contact fatigue as investigated using a Micro-Pitting Rig tribometer under poly-alpha-olefin lubricated conditions. Coated rollers with a similar to 15 nm thick W adhesion layer to the substrate, exhibit the best performance, presenting mild wear and no fatigue after 700 kcycles. The steady-state friction coefficient was similar to 0.05 for both uncoated and coated rollers. Uncoated rollers show run-in friction in the first 50 kcycles, because of steel-to-steel contact, which is absent for coated rollers. Analytical transmission electron microscopy and X-ray photoelectron spectroscopy show that the presence of a CNx coating prevents steel-to-steel contact of the counterparts, prior to the elastohydrodynamic lubrication, reducing their wear and increasing the lifetime expectancy. (C) 2016 Elsevier Ltd. All rights reserved.
35.	Bakoglidis, Konstantinos, et al. (författare) Rolling performance of carbon nitride-coated bearing components in different lubrication regimes 2017 Ingår i: Tribology International. - : Pergamon Press. - 0301-679X .- 1879-2464. ; 114, s. 141-151 Tidskriftsartikel (refereegranskat)abstract The performance of carbon nitride (CN) coated roller bearings is investigated, using a micropitting rig. The rolling performance is evaluated using Stribeck test, with a continuously varying rolling speed (0.2 - 2 m/s). Rolling contact fatigue tests with constant speeds (0.5, 1, 2, and 3.5 m/s) are also conducted in order to study the high-cycle performance of the rollers. The obtained Stribeck curve shows that the presence of coatings eliminates run-in, resulting in low friction coefficients (similar to 0.08). Raman spectroscopy, performed at the wear tracks, reveals that CNx maintain stable chemical state. Coatings show abrasion although the wear rate is not detrimental for the performance of the rollers, since a CNx to-steel contact is retained during the entire rolling contact fatigue test.
36.	Bejjani, Roland, et al. (författare) Multi-scale study of initial tool wear on textured alumina coating, and the effect of inclusions in low-alloyed steel 2016 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 100, s. 204-212 Tidskriftsartikel (refereegranskat)abstract When turning low-alloyed steel with hard inclusions, scores and grooves have been observed in the wear of the alumina coating in CVD coated cutting tools. This study focuses on detailed understanding of flank wear in the textured alumina coating and the relation to the workpiece's inclusions. For chip formation studies, a quick stop device has been used. A topography analysis for the worn coating was performed in the micro scale. Studies at lower scales were performed using TEM. This allowed the study of wear on the coating crystalline structure and the embedment of workpiece material on its surface. Based on the results, the mechanism behind the initial wear was analyzed and an abrasion wear model is proposed.
37.	Bergseth, Ellen, et al. (författare) Influence of real surface topography on the contact area ratio in differently manufactured spur gears 2012 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 56, s. 72-80 Tidskriftsartikel (refereegranskat)abstract Surface topography measurements from spur gears produced using four different manufacturing methods were used as input to a contact analysis programme. All test gears were case-hardened, two gears were machined in the hardened state using honing and grinding respectively, and two gears were machined in the non-hardened state using hobbing and hobbing followed by green-shaving respectively. The results show that the surface topography caused by the manufacturing methods has a large influence on the real contact area in the early life of the gear. The green-shaved gear surfaces and the honed gear surfaces have the highest contact area ratio after manufacturing (as-manufactured), which could be advantageous for future gear life with respect to e.g. the running-in process.
38.	Bergstedt, Edwin, et al. (författare) Gear micropitting initiation of ground and superfinished gears : Wrought versus pressed and sintered steel 2021 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 160 Tidskriftsartikel (refereegranskat)abstract This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with CPT gears. The materials are wrought steel (16MnCr5) and a commercial powder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding and superfinishing. Experimental results show that the superfinishing prevented micropitting, but led to premature failure due to cracks in the root caused by tip-to-root interference. Micropitting was initiated at a higher load stage for the powder metallurgical steel compared to the ground wrought steel. The failure mechanisms were similar between materials with the same surface finish. The powder metallurgical steel showed subsurface initiated fatigue compared to the wrought ground steel having surface-initiated fatigue. Testing new finishing methods and materials, one has to be aware of the influence of the gear micro geometry.
39.	Bergstedt, Edwin, 1986-, et al. (författare) Gear Micropitting Initiation of Ground and Superfinished Gears: Wrought versus Pressed and Sintered Steel Ingår i: Tribology International. - 0301-679X .- 1879-2464. Tidskriftsartikel (refereegranskat)abstract This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercialpowder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding andsuperfinishing. Experimental results show that the superfinishing prevented micropitting, but ledto premature failure due to cracks in the root caused by tip-to-root interference. Micropitting wasinitiated at load stage 8, and 9 for the ground wrought, and powder metallurgical steel respectively.The failure mechanisms were similar between materials with the same surface finish. The powdermetallurgical steel showed subsurface initiated fatigue compared to the wrought groundsteel having surface-initiated fatigue. Testing new finishing methods and materials, onehas to be aware of the influence of the gear micro geometry.
40.	Björling, Marcus, et al. (författare) The correlation between gear contact friction and ball on disc friction measurements 2015 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 83, s. 114-119 Tidskriftsartikel (refereegranskat)abstract Running experiments with full-size gearboxes from the actual application has the advantage of giving realistic results in terms of power losses. The drawback is extensive costs, lengthy testing, and the difficulty in differentiating between load dependent and load independent losses, and which losses are coming from the gears, seals, bearings or synchronizers. In this work, the correlation between friction measurements conducted in a ball-on-disc machine and friction measurements conducted in a back-to-back gear rig is investigated. The correlation between the gear tests and the ball-on-disc tests were reasonably good in terms of absolute values, and the shape of the friction curves were similar, indicating that the ball-on-disc measurements to a large extent are capturing the behavior of the gear contact
41.	Björling, Marcus, et al. (författare) Towards the true prediction of EHL friction 2013 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 66, s. 19-26 Tidskriftsartikel (refereegranskat)abstract The capability to predict elastohydrodynamic film-thickness and friction from primary measurements of transport properties of liquid has been an elusive goal for tribologists for 50 years. Most comparisons between predictions and experiments involve some amount of tuning of the model in order to match the experimental results. In true prediction, this cannot be done since there are normally no experimental results to compare to. Primary measurements of lubricant transport properties of Squalane were performed, and used in a numerical friction prediction model. Afterwards, friction was measured in a ball-on-disc tribotester. No tuning of the lubricant properties, model or test setup were applied. The current work on EHL-friction is therefore a true representation of the current level of EHL-friction prediction.
42.	Cadario, Alessandro, et al. (författare) Fretting fatigue experiments and analyses with a spherical contact in combination with constant bulk stress 2006 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 39:10, s. 1248-1254 Tidskriftsartikel (refereegranskat)abstract A fretting experiment with separate control of bulk stress, normal and tangential contact loads is presented. For the initial test series, constant normal and bulk loads were combined with a cyclic tangential load. Both the spherical indenter and the plane specimen were manufactured from alpha + beta titanium alloys. Strain gauges and acoustic emission measurements were employed for the determination of the time to crack initiation and the propagation life. The fretting cracks always initiated inside the slip zone at positions that were spread over the whole slip zone. Crack nucleation was investigated with five multiaxial fatigue criteria. It was concluded that macroscale stresses from the contact and bulk load alone could not explain all aspects of crack initiation. A possible explanation was found in the fretting-induced roughness. The growth of the fretting crack was simulated numerically by a parametrical description. It was noted that a cyclic bulk load was required to drive the crack growth through the specimen to final failure.
43.	Calderon Salmeron, Gabriel, 1990-, et al. (författare) Greases for electric vehicle motors : thickener effect and energy saving potential 2022 Ingår i: Tribology International. - : Elsevier Ltd. - 0301-679X .- 1879-2464. ; 167, s. 107400-107400 Tidskriftsartikel (refereegranskat)abstract Electric vehicle motors in e-drivetrain are equipped with grease-lubricated bearings operating at both low and high speeds with frequent speed changes. The grease-bearing system must secure a long lifespan and low frictional torque to improve efficiency and sustainability. The present paper focuses on the influence of two types of thickener, lithium complex and polypropylene, on the grease lubrication performance under conditions typical for e-motors. The comparison of both thickeners is performed in terms of friction torque and energy consumption in eight long-duration experiments (337 hr). The results show that the polypropylene thickener provides 21.5% lower energy consumption compared to the lithium complex. Changes in grease rheology and degradation in the tests are analysed and correlated with the grease lubrication performance.
44.	Calderon Salmeron, Gabriel, 1990-, et al. (författare) Greases for electric vehicle motors: Bearing friction torque under driving cycle conditions and the thickener effect on oil release 2024 Ingår i: Tribology International. - : Elsevier Ltd. - 0301-679X .- 1879-2464. ; 198 Tidskriftsartikel (refereegranskat)abstract Performance of Lithium Complex (LiX), Polyurea (PU), and Polypropylene (PP) greases in SKF6208 bearings subjected to driving cycle conditions for 28 days (equivalent to 23,000 km of electric vehicle operation) was studied by continuously measuring bearing friction torque and temperature. The energy dissipation was correlated to the differences in oil bleeding and rheology for the three greases. Evolution of the friction torque, friction torque hysteresis, and changes in grease rheology were dominated by the oil release property. The latter was determined by the thickener system and its particular response to the conditions imposed by the driving cycle. A quantitative estimate of the carbon footprint from using these greases to lubricate bearings under driving cycle conditions is also presented.
45.	Cha, Matthew, et al. (författare) Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings 2013 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 57, s. 46-53 Tidskriftsartikel (refereegranskat)abstract The effect of pad compliance on the dynamic response of tilting pad journal bearings is investigated. Pad compliance is varied by changing pivot geometry and Young's modulus of pad backing and pad liner. Two pad support configurations are considered: one that allows only circumferential tilt and another one that allows both circumferential and axial tilts. Journal orbits, oil film pressure and oil film thickness are compared and discussed. It is shown that higher pad backing compliance significantly increases the journal orbit size and results in an increase in oil film pressure while oil film thickness is decreased. With a compliant liner, oil film pressure is decreased while oil film thickness is increased. Tapers at the pad edges are essential to increase the global minimum oil film thickness in compliant liner bearings.
46.	Cha, Matthew, et al. (författare) Nonlinear dynamic behaviour of vertical and horizontal rotors in compliant liner tilting pad journal bearings : Some design considerations 2015 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 82, s. 142-152 Tidskriftsartikel (refereegranskat)abstract Dynamic behaviour of vertical and horizontal rotors in journal bearings with line pivot pads is investigated. Two bearing designs are compared: one with white metal pads and another with compliant liner pads. The influence of elasticity of the liner on the journal orbits is investigated. Some practical aspects of the compliant liner pad design are discussed. Compliant bearing design parameters such as preload factor, pivot offset, radial clearance, viscoelasticity, and pad inclination to control the size of the journal orbit are considered.
47.	Cousseau, T., et al. (författare) Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils 2012 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 53, s. 53-60 Tidskriftsartikel (refereegranskat)abstract Three different lubricating greases and their bleed and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. The theoretical values calculated according to Hamrock's equation are in close agreement with the base oil film thickness measurements, which validates the selected experimental methodology.The grease and bleed oil film thickness under fully flooded lubrication conditions presented quite similar behaviour and levels. Therefore, the grease film thickness under full film conditions might be predicted using their bleed oil properties, namely the viscosity and pressure-viscosity coefficient. The base and bleed oil lubricant parameter LP are proportional to the measured film thickness.A relationship between grease and the corresponding bleed oil film thickness was evidenced
48.	Cupillard, Samuel, et al. (författare) 3D thermohydrodynamic analysis of a textured slider 2009 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 42:10, s. 1487-1495 Tidskriftsartikel (refereegranskat)abstract Analysis of a 3D inlet textured slider bearing with a temperature dependent fluid is performed. Numerical simulations are carried out for a laminar and steady flow. Hot and cold lubricant mixing in the groove is modelled and examined for different operating conditions. Thermohydrodynamic performance of the bearing is analysed for different texture lengths. Results show that texture has a stronger and positive influence on load carrying capacity when thermal effects are considered. This beneficial effect is at a maximum for the longest dimples with a length shorter than the pad length. Texture is also beneficial for the load carrying capacity when the sliding speed and inlet flow rate are varied. The load carrying capacity of the slider can be increased by up to 16% in severe operating conditions (high sliding speed).
49.	Das, Sanjeev, et al. (författare) Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy 2013 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 60, s. 1-9 Tidskriftsartikel (refereegranskat)abstract 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.
50.	de la Presilla, Roman José, et al. (författare) Grease lubricity in the fretting contact : Are ionic liquids the solution? 2023 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 185, s. 108509- Tidskriftsartikel (refereegranskat)abstract A statistical, energy-based approach is employed to experimentally characterize the ability of different greases to reduce friction when a point contact is subjected to repeated reciprocal displacements of smaller magnitude than the contact diameter. This approach allows the assessment of lubricant fretting performance with respect to its ability to remain within the contact and also its boundary lubrication properties. The results indicate that composition-dependent boundary lubrication properties of greases loaded with non-halogenated ionic liquids containing bis(oxalato)borate ([BOB]) and bis(mandelato)borate ([BMB]) anions can result in no detectable wear and low friction, even under conditions of moderately high pressures and where the original contact area is never fully uncovered. This discovery paves the way for the development of anti-fretting ionic greases.

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