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The manuscript presents the synthesis and dry sliding wear performance of Al7075 alloy‐based composites. Five compositions namely Al7075 alloy, Al7075+3 vol % molybdenum disulfide, Al7075+3 vol % molybdenum disulfide+3 vol % zirconium diboride, Al7075+3 vol % molybdenum disulfide+6 vol % zirconium diboride and Al7075+3 vol % molybdenum disulfide+9 vol % zirconium diboride were stir cast and characterized for hardness, x‐ray diffraction, microstructure, and tribological properties. In‐situ formed zirconium diboride particles increase the hardness of Al7075 alloy whereas molybdenum disulfide shows the opposite trend due to its self‐lubricating nature. X‐ray diffraction analysis identifies subsequent phase particles in the matrix while microstructural images exhibit the dispersion and morphology of reinforcement particles. The wear tests and friction coefficient were analyzed with variations of sliding velocity, normal load, sliding distance, and compositions. Further, the obtained wear results were also correlated with microstructure and wear surface topography. Al7075+3 vol % molybdenum disulfide composite shows the lowest coefficient of friction because of its self‐lubricating nature. Al7075+3 vol % molybdenum disulfide+9 vol % zirconium diboride hybrid composite exhibits the lowest wear rate at high velocity as well as at high load and can be potentially used in manufacturing and tribological applications. Moreover, the use of this material may lead to the minimum requirement of external toxic lubricants that make it cost‐effective and environmentally sustainable. [ABSTRACT FROM AUTHOR]

The tribological performance of two polymeric friction modifiers, one based on an ester‐based compound and another based on an ethoxylated fatty ester and an organic friction modifier, oleamide, was studied at 50, 90 and 140°C using a Mini Traction Machine equipped with optical interferometry and electrical contact resistance. The ability to form surface film is found to vary among the friction modifiers and with temperature and rubbing duration. Despite a thinner film being formed, polymeric friction modifier (PFMs) exhibited lower friction and wear than oleamide at all the studied temperatures. Further, the PFMs reduced boundary friction more effectively at higher temperature. In accordance with lower boundary friction, a smoother surface topography characterized by low wear was exhibited by PFM lubricated surfaces at higher temperatures. Scanning electron microscopy‐energy dispersive x‐ray analysis and time‐of‐flight secondary ion mass spectrometry provided insights on the tribofilm formation. The improvement in the tribological performance of PFMs is attributed to temperature‐induced conformation transition of adsorbed polymer chains on the surface. The results are corroborated by data obtained from dynamic light scattering and gel permeation chromatography. [ABSTRACT FROM AUTHOR]

Friction is one of the main phenomena accompanying sheet metal forming methods, affecting the surface quality of products and the formability of the sheet metal. The most basic and cheapest way to reduce friction is to use lubricants, which should ensure the highest lubrication efficiency and at the same time be environmentally friendly. Due to the trend towards sustainable production, vegetable oils have been used in research as an alternative to petroleum-based lubricants. The analysis of friction in sheet metal forming requires an appropriate tribotester simulating the friction conditions in a specific area of the sheet metal being formed. Research has used a special strip drawing tribometer, enabling the determination the value of the coefficient of friction in the blankholder zone in the deep drawing process. Quantitative analysis of the friction phenomenon is necessary at the stage of designing the technological process and selecting technological parameters, including blankholder pressure. This article presents the results of friction testing of 1.0338 (DC04) steel sheets using a strip drawing test. The experimental tests involved pulling a strip of sheet metal between two countersamples with a rounded surface. The tests were carried out on countersamples with different levels of roughness for the range of contact pressures occurring in the blankholder zone in the deep drawing process (1.7–5 MPa). The values of the coefficient of friction determined under dry friction conditions were compared with the results for edible (corn, sunflower and rapeseed) and non-edible (Moringa, Karanja) vegetable lubricants. The tested oils are the most commonly used vegetable-based biolubricants in metal forming operations. Multi-layer artificial neural networks were used to determine the relationship between the value of the contact pressure, the roughness of the countersamples, the oil viscosity and density, and the value of the coefficient of friction. Rapeseed oil provided the best lubrication efficiency during friction testing for all of the tested samples, with an average surface roughness of Sa 0.44–1.34 μm. At the same time, as the roughness of the countersamples increased, a decrease in lubrication efficiency was observed. The lowest root mean squared error value was observed for the MLP-4-8-1 network trained with the quasi-Newton algorithm. Most of the analysed networks with different architectures trained using the various algorithms showed that the kinematic viscosity of the oil was the most important aspect in assessing the friction of the sheets tested. The influence of kinematic viscosity on the value of the coefficient of friction is strongly dependent on the surface roughness of the countersamples. [ABSTRACT FROM AUTHOR]

To exactly describe lubrication problems modeling micro-scale influence in rough lubricated contact is unavoidable. In this study a novel computational scheme for lubricated problem is presented based on two-scale homogenization method, which facilitates solving the two-scale problem. Homogenization model of mass fluxes is implemented at the micro-scale domain, and represents the influence of surface topography. A linearization method is developed to derive finite derivatives of mass fluxes at the micro-scale domain defined by scale separation. The key strength of the proposed procedure is the finite difference derivative coupling which represents the lubricated problem inclusive of the effect of surface topography. The effectiveness of the proposed multiscale scheme is validated by comparing with the deterministic method. The numerical results show that increasing topography amplitude can improve the performance of journal bearing in terms of load carrying capacity and friction coefficient. [ABSTRACT FROM AUTHOR]

Many devices, including touchscreens and robotic hands, involve frictional contacts. Optimizing these devices requires fine control of the interface’s friction law. We lack systematic methods to create dry contact interfaces whose frictional behavior satisfies preset specifications. We propose a generic surface design strategy to prepare dry rough interfaces that have predefined relationships between normal and friction forces. Such metainterfaces circumvent the usual multiscale challenge of tribology by considering simplified surface topographies as assemblies of spherical asperities. Optimizing the individual asperities’ heights enables specific friction laws to be targeted. Through various centimeter-scaled elastomer-glass metainterfaces, we illustrate three types of achievable friction laws, including linear laws with a specified friction coefficient and unusual nonlinear laws. This design strategy represents a scale- and material-independent, chemical-free pathway toward energy-saving and adaptable smart interfaces. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the influence of surface texture on the subsurface characteristics of contact interfaces under elastohydrodynamic lubrication condition. As a typical contact form of gears and bearings, the optimization of friction characteristics at the elastohydrodynamic lubrication (EHL) interface has attracted the attention of scholars. Laser surface texturing is a feasible optimization solution, but there have been concerns about whether the surface texture of high-pair parts will affect their fatigue life. Design/methodology/approach: To examine the impact of texture preparation on the subsurface characteristics of high-pair interfaces under EHL conditions, a point contact EHL model is developed that takes into account the effect of textured surface topography. The pressure and thickness of the oil film are calculated as input parameters under different loads and entrainment velocities. The finite element method is used to simulate the impact of textures with varying diameters, densities and depths on the subsurface characteristics of the elastohydrodynamic interface. According to ISO 25178, analyze the relationship between 3D topography parameters and subsurface characteristics and study the trend of friction characteristics and subsurface characteristics based on the results of the ball on disc friction tests. Findings: The outcomes suggest that under different rotational velocity and load conditions, the textured surfaces exhibit improved friction reduction effects; however, the creation of textures can result in significant subsurface plastic deformation and local peeling. The existence of texture makes the larger stress zone in the subsurface layer closer to the surface, leading to fatigue failure near the surface. Reasonable design parameters can help enhance the attributes of the subsurface. A smaller Sa and a Str greater than 0.5 can achieve ideal subsurface properties on the textured surface. Originality/value: This paper investigates the influence of surface texture on the friction and subsurface characteristics of EHL interfaces and analyzes the impact of surface texture on interface contact performance while achieving lubrication improvement functional characteristics. The results provide theoretical support for the optimization design and functional regulation of surface texture in EHL interfaces. Peer review: The peer review history for this article is https://publons.com/publon/10.1108/ILT-10-2023-0324/ [ABSTRACT FROM AUTHOR]

Purpose: Hydro-viscous drive (HVD) clutches are widely used in equipment requiring soft start, such as fans and pumps, to transmit torque and adjust speed by changing the gap distance between friction pairs. This paper aims to propose a novel two-parameter evaluation method for HVD during the mixed lubrication stage. The objective is to develop an effective model that establishes the relationship between these parameters and the actual surface topography. Design/methodology/approach: In the presented methods, the fractal features of the real manufacturing surface are calculated based on the power spectrum function by the ultra-depth three-dimensional microscope. After that, the hybrid friction model of the friction plate is established based on mixed elasto-hydrodynamic lubrication theory, boundary friction model and fractal theory. Then the torque and load bearing characteristics of the clutch are obtained, and the influences of the surface fractal features are investigated and discussed. Finally, the Weierstrass–Mandelbrot function is adopted for the surface topography characterization and evaluation. Findings: The results indicate that the proposed method exhibits good accuracy, while the speed difference between the friction pair exceeds 2,500 rpm. It is concluded that this paper proposed a way to evaluate the torque and loading capacity of HVD considering the real manufacturing surface topography and is helpful for surface optimization. Originality/value: The originality and value of this study lie in its development of a novel torque and load bearing capacity evaluation method for HVD in mixed lubrication stage, considering manufacturing surface topography and describing the real manufacturing surface. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to experimentally analyze the friction and wear responses of different steels to different surface films generated in oil-lubricated tribological contacts. Design/methodology/approach: Tribological experiments were conducted using a 100Cr6 bearing ball sliding against a V155 carbon steel disk and 316L stainless steel disk, respectively. Lubricants with additives known to form zinc dialkyl-dithiophosphate (ZDDP) or Ca tribofilms were used. Findings: Both of the ZDDP and Ca tribofilms helped stabilize the friction coefficient of the carbon steel and stainless steel. The ZDDP tribofilm could effectively protect the carbon steel from wear, in contrast to the stainless steel, whereas the wear of both carbon steel and stainless steel could be significantly reduced by the Ca tribofilm. In the case of neither ZDDP nor Ca tribofilms formation, the 100Cr6 ball was worn by the V155 disk and generated a special surface topography. A polishing wear mechanism was proposed to explain the wear of the 100Cr6 ball. Originality/value: This study clearly shows the different friction and wear responses of steels to the different surface films and the response is dependent on the tested steel. [ABSTRACT FROM AUTHOR]

Everyday, we interact with screens, sensors, and many other devices through contact with the skin. Experimental efforts have increased our knowledge of skin tribology but are challenged by the fact that skin has a complex structure, undergoes finite deformations, has nonlinear material response, and has properties that vary with anatomical location, age, sex, and environmental conditions. Computational models are powerful tools to dissect the individual contribution of these variables to the overall frictional response. Here, we present a three-dimensional high-fidelity multilayer skin computational model including a detailed surface topography or skin microrelief. Four variables are explored: local coefficient of friction (COF), indenter size, mechanical properties of the stratum corneum, and displacement direction. The results indicate that the global COF depends nonlinearly on the local COF, implying a role for skin deformation on the friction response. The global COF is also influenced by the ratio of the indenter size to the microrelief features, with larger indenters smoothing out the role of skin topography. Changes in stiffness of the uppermost layer of skin associated with humidity have a substantial effect on both the contact area and the reaction forces, but the overall changes in the COF are small. Finally, for the microrelief tested, the response can be considered isotropic. We anticipate that this model and results will enable the design of materials and devices for a desired interaction against skin. [ABSTRACT FROM AUTHOR]

A model hydrodynamic lubrication tribometer consisting of two hydrodynamic journal bearings working under thin film conditions was developed to investigate the mechanisms of hydrodynamic friction with low-viscosity fluids and the role of surface effects. A small nominal radial clearance of about 5 µm was considered between the two surfaces. This fully instrumented setup provides in situ information on the sheared fluid film in terms of simultaneous measurements of film thickness; localization and extension of the cavitation zone, with a resolution of 30°; nominal friction torques up to 0.5 N m, with an accuracy of 0.05 mN m; temperature; and the position of the shaft for velocities up to 12 000 rpm. To illustrate the capability of the Osiris tribometer, thin hydrodynamic film measurements were performed on smooth surfaces. The results are presented here, and the thermal effects, acceleration, and inertia contributions are discussed. Finally, the influence of the surface topography using textured surfaces was demonstrated and the role of adsorbed layers on the surface due to fluid formulation was highlighted. [ABSTRACT FROM AUTHOR]

Aluminium alloy sheets cause many problems in sheet metal forming processes owing to their tendency to gall the surface of the tool. The paper presents a method for the determination of the kinematic friction coefficient of friction pairs. The determination of coefficient of friction (COF) in sheet metal forming requires specialised devices that 'simulate' friction conditions in specific areas of the formed sheet. In this article, the friction behaviour of aluminium alloy sheets was determined using the strip drawing test. The 1-mm-thick 6082 aluminium alloy sheets in T6 temper were used as test material. Different values for nominal pressures (4.38, 6.53, 8.13, 9.47, 10.63, and 11.69 MPa) and different sliding speeds (10 and 20 mm/min.) were considered. The change of friction conditions was also realised with several typical oils (hydraulic oil LHL 32, machine oil LAN 46 and engine oil SAE 5W-40 C3) commonly used in sheet metal forming operations. Friction tests were conducted at room temperature (24 °C). The main tribological mechanisms accompanying friction (adhesion, flattening, ploughing) were identified using a scanning electron microscope (SEM). The influence of the parameters of the friction process on the value of the COF was determined using artificial neural networks. The lowest value of the COF was recorded when lubricating the sheet metal surface with SAE 5W40 C3 engine oil, which is characterised as the most viscous of all tested lubricants. In dry friction conditions, a decreasing trend of the COF with increasing contact pressure was observed. In the whole range of applied contact pressures (4.38–11.69 MPa), the value of the COF during lubrication with SAE 5W40 C3 engine oil was between 0.14 and 0.17 for a sliding speed of 10 mm/min and between 0.13 and 0.16 for a sliding speed of 20 mm/min. The value of the COF during dry friction was between 0.23 and 0.28 for a sliding speed of 10 mm/min and between 0.22 and 0.26 for a sliding speed of 20 mm/min. SEM micrographs revealed that the main friction mechanism of 6082-T6 aluminium alloys sheet in contact with cold-work tool steel flattens surface asperities. The sensitivity analysis of the input parameters on the value of COF revealed that oil viscosity has the greatest impact on the value of the COF, followed by contact pressure and sliding speed. [ABSTRACT FROM AUTHOR]

It has been widely recognized that there are influences of static friction characteristics in a bolted joint on pre-tightening and service reliability. This study proposed a static friction coefficient model of joint surfaces based on the modified three-dimensional fractal model. A method of measuring the static friction coefficient of joint surfaces was investigated to verify the accuracy of model. The results showed that calculated value of the model and measured value of experiment are highly matched. Furthermore, the influential mechanisms of material, pressure, and surface topography were investigated. The relative error between experimental results and model calculations are all less than 15%. This research provides a theoretical basis for subsequent research on the friction characteristics of joint surfaces and connection reliability of bolted joints. [ABSTRACT FROM AUTHOR]

AlSi7Mg/SiCp aluminium matrix composites (AMCs) with a high ceramic content (35 vol.%) that were produced by using the field-assisted sintering technique (FAST) were subjected to tribological preconditioning and evaluated as a potential lightweight material to substitute grey cast iron brake discs. However, since an uncontrolled running-in process of the AMC surface can lead to severe wear and thus to failure of the friction system, AMC surfaces cannot be used directly after finishing and have to be preconditioned. A defined generation of a tribologically conditioned surface (tribosurface) is necessary, as was the aim in this study. To simulate tribological conditions in automotive brake systems, the prepared AMC samples were tested in a pin-on-disc configuration against conventional brake lining material under dry sliding conditions. The influence of the surface topography generated by face turning using different indexable inserts and feeds or an additional plasma electrolytic treatment was investigated at varied test pressures and sliding distances. The results showed that the coefficient of friction remained nearly constant when the set pressure was reached, whereas the initial topography of the samples studied by SEM varied substantially. A novel approach based on analysing the material ratio determined by 3D surface measurement was developed in order to obtain quantitative findings for industrial application. [ABSTRACT FROM AUTHOR]

The effect of cylinder liners on engine performance is substantial. Typically, the cylinder surfaces were plateau honed. However, recently additional dimples or grooves were created on them. This work discusses the tribological impacts of textured cylinder liner surfaces based on a review of the literature. The results of the experimental research obtained using test rigs and fired engines were critically reviewed. In addition, the results of the modeling are shown. Circular oil pockets and grooves perpendicular to the sliding direction of piston rings of small depths were typically used. Surface texturing of the cylinder liners governs lubrication between the cylinder liner and the piston ring by an increase in oil film thickness near the reversal points leading to reductions in friction force and wear and in the fired engine to a decrease in fuel consumption and to an increase in power or torque. The correct texturing pattern ensures a decrease in the oil consumption, blow-by, and emissions of the internal combustion engine compared to plateau-honed surfaces. Considerations of future challenges are also addressed. The volume of lubricant reservoir in surface topography, called oil capacity, should be a substantial parameter characterizing textured surfaces. [ABSTRACT FROM AUTHOR]

Controlling unabridged graphene‐lubricated layers and extending their last times can extend the service life of polymer moving components. The friction reduction behaviors of graphene nanoplatelets (GNP) on the tribology performances of high‐density polyethylene (HDPE) were studied based on friction experiments. The mechanical properties, coefficient of friction (COF), surface topography, tribo‐layers wear synthetically charactered to analyses the friction reducing processes. The results showed that the GNP presented a limited friction reduction to HDPE, and it could be controlled by the mass contents of GNP, load and speed. The proper content of graphene maintained the effective GNP tribo‐layers for a long time and led to a long duration of friction reduction. Decreasing load or speed weakened the wear processes, which was useful for maintaining the effective GNP tribo‐layers for a long time, and reduced the COF. The knowledge will provide experimental support for improving the self‐lubricating performance and abrasiveness of polymers. [ABSTRACT FROM AUTHOR]

The article focuses on friction control, emphasizing its pervasive impact on daily life and machines' energy consumption. Topics include current strategies for friction tuning, such as lubrication, and a novel approach presented by Aymard et al., involving the rational design of interfaces using small bumps to create a frictional metainterface with adjustable properties.

In this study, the influence of the in-situ tribo-oxide-layer on non-lubricated tribological behaviours of LM27/SiCp composites was studied at different applied loads. For this purpose, LM27/SiCp composites were manufactured by stir casting route with reinforcement of different amounts (3–12 wt.%) and different sizes (fine: 1–20 µm and coarse: 106–125 µm) of SiCp. A comprehensive characterization of the friction and wear mechanisms ranging from mild to severe wear for oxidative and delamination at a contact pressure of 0.125–0.624 MPa was discussed. Results indicate that the friction and wear behaviour is strongly influenced by the morphology and the nature of the oxide scale on the wear track. In-situ formation of oxide layers on the contact region of the specimen supports the self-lubrication which supports better wear performance of LM27/SiCp composites. However, these study portraits that composite with 12wt. % fine size SiCp exhibits better wear performance in comparison to the other developed composites. [ABSTRACT FROM AUTHOR]

Friction is one of the most important technological phenomena and has a large influence on the flow characteristics of a deformed material. A strip drawing friction test was used to evaluate the friction characteristics of 0.8 mm thick DC04 steel sheets in a sheet forming operation. Friction tests were carried out using a specially designed friction simulator and uniaxial tensile tests were carried out to determine the mechanical properties of the specimens. In addition, measurements of the sheet surface topography were carried out to identify the tribological properties of the specimens. The friction tests were conducted under different pressure and lubrication conditions. A comparative analysis of the results of the friction tests revealed different changes in the surface topography of the test sheets which can be associated with specific friction mechanisms. It was found that the effectiveness of lubrication depends on the lubricant viscosity and nominal pressure. Increasing the nominal pressure intensifies the phenomenon of asperity flattening and reduces the volume of closed pockets of lubricant. [ABSTRACT FROM AUTHOR]

Based on the characteristics of engine working conditions, the ring/liner reciprocating friction tests were conducted to research the effects of three typical cylinder liner surface topographies (honed surface, large dimple texture and small dimple texture) on the tribological performance of production piston ring pack. The experimental results demonstrated the effects of liner textures are different between three kinds of piston rings: for the barrel‐shaped ring‐liner pair, the large or small dimple texture has its specific working condition; for the taper‐faced ring‐liner pair, the oil scraping efficiency and oil distributing stability can be improved by texturing small dimples on liner surface; while the dimple textures have little influence on the friction force of oil control ring‐liner pair. In addition, texturing micro‐dimples on liner is conducive to reducing the surface wear caused by abrasive wear, and the anti‐wear effect of small dimple texture is much better. [ABSTRACT FROM AUTHOR]

Lubricants utilized in high-end equipment must exhibit excellent tribological properties and heat dissipation. In this study, an aqueous graphene oxide (GO) solution was used to lubricate ceramic materials. Tribological experiments were performed using a silicon carbide (SiC) planar friction pair to clarify the influencing factors and mechanism of GO nanofluid lubrication. The results showed that the GO solutions were effective in reducing wear and improving lubrication. A 0.1% medium-particle-size GO solution with a coefficient of friction of 0.020 provided the most effective lubrication. Friction temperature tests showed that the thermal conductivity of the GO solution was beneficial for reducing the temperature increase of the friction pair. Furthermore, investigations of the polarized electric field at the interface revealed that the GO solution facilitated the formation of polarized electric fields on the mutually exclusive friction surfaces. Finally, lubrication and wear reduction mechanisms of the GO solution are discussed and proposed. [Display omitted] • The frictional properties of SiC plane rotating friction pairs lubricated with GO water-based lubricant are studied. • A synergistic lubrication mechanism of interfacial lubrication film and friction volt effect is proposed. • The GO particle size and the friction pair's surface topography have an optimal matching relationship. [ABSTRACT FROM AUTHOR]

Roughness metrics measured with stylus profilometry are commonly used to explain a floor's friction performance, yet these metrics inconsistently predict shoe-floor friction. While strong correlations have been shown for systematically modified flooring, the goal of this study is to address a gap regarding the predictive ability of these metrics across heterogeneous porcelain flooring products. The predictive ability of four roughness metrics on oily friction performance was assessed using 23 floors and 4 shoe designs. Roughness was moderately correlated with friction (r ranged from 0.374 to 0.760). These results are a reference point for future studies that aim to improve predictions using novel surface characterization approaches that include multiple scales. • Predictiveness of stylus-measured roughness on floor friction was evaluated. • Twenty-three floors and four shoes were included in the study. • Correlation coefficients between 0.374 and 0.760 were observed. • Incomplete predictive power motivates additional topography metrics. • Alternative metrics may improve predictions. [ABSTRACT FROM AUTHOR]

Polymeric matrix composites are important to the advancement of industries such as the automobile and medicine industries. In this study, the silicon carbide (SiC) particle-reinforced polyamide12 (PA12) matrix composites were fabricated by selective laser sintering system as well as the pure PA12. The surface topographies, mechanical, and tribological properties were further examined. The results indicated that the friction and wear resistance of the composite were improved compared with the PA12 matrix. The compressive strength increased about 8.5%, shore D hardness increased about 6%. The friction coefficient decreased about 10%, the specific wear rate decreased 20% after adding silicon carbide 10% weight to PA12. The wear mechanisms were also discussed. The deformed asperities on the worn surface can withstand more tangential load, and therefore resulted in lower specific wear rate. It was found that the content of SiC particles on the surface were reduced after friction tests. According to the analysis of SEM, EDS, and FTIR results, the wear mechanisms were considered to be the abrasive and fatigue mode. This type of PA12 matrix composite might be a promising potential in marine and energy applications. [ABSTRACT FROM AUTHOR]

The present paper introduces a tire/road friction prediction tool based on modelling the tire/road contact as dynamic, viscoelastic, rough, and lubricated. The tool takes into account a considerable part of influent parameters related to tire, road, contaminant, and contact operating conditions: For the tire, the tool takes into account its geometry and rubber material behaviour. For the road, the texture is taken into account via the surface topography. At the contact interface, dry or wet conditions are taken into account through the lubricant depth, viscosity, and density. The operating conditions are taken into account through the normal load, speed, and slip ratio of the tire. The real novelty of this tool lies in its ability to reproduce the complete curve of the tire/road friction coefficient as a function of the slip rate. The validation of the tool is initially done through parametric studies by analyzing the trends of the results, then by performing braking tests on a passenger car at various speeds on different wet roads with different textures. The tool correctly ranks the peak friction and the sliding friction on these various road surfaces. [ABSTRACT FROM AUTHOR]

Ice friction plays an important role in many engineering applications, e.g., tires on icy roads, ice breaker ship motion, or winter sports equipment. Although numerous experiments have already been performed to understand the effect of various conditions on ice friction, to reveal the fundamental frictional mechanisms is still a challenging task. This study uses in situ white light interferometry to analyze ice surface topography during linear friction testing with a rubber slider. The method helps to provide an understanding of the link between changes in the surface topography and the friction coefficient through direct visualization and quantitative measurement of the morphologies of the ice surface at different length scales. Besides surface polishing and scratching, it was found that ice melts locally even after one sweep showing the refrozen droplets. A multi-scale rubber friction theory was also applied to study the contribution of viscoelasticity to the total friction coefficient, which showed a significant level with respect to the smoothness of the ice; furthermore, the theory also confirmed the possibility of local ice melting. [ABSTRACT FROM AUTHOR]

Laser surface texturing (LST) is widely explored for modifying the surface topography of various materials. In this study, a detailed investigation of laser textured surfaces produced on austenitic stainless steel (AISI 304) was carried out. Three different textures (square, parallel, perpendicular) were produced by a Ti sapphire laser. The processed surfaces were characterized by surface morphology, phase structure, microhardness, surface roughness, and wettability. A ball-on-disk tribometer was used to study the tribological performance of both untextured and textured samples. The experimental observations demonstrate that LST improves both surface wettability and surface roughness. Average surface roughness (Ra) was increased by 350% and the contact angle was reduced from 43° to 22°. The textured surfaces show a lower coefficient of friction and better wear resistance than the untextured surface. Out of the investigated patterns, the square textures exhibited a maximum reduction of 68% in the friction coefficient and a 50% lower wear rate. [ABSTRACT FROM AUTHOR]

Micro-texturing on machined surface has been widely applied to improve surface friction and wear properties. This paper aimed at establishing a relationship among process parameters, machined surface texturing, and friction property of scaly surface fabricated by rotary ultrasonic rolling. Firstly, a kinematic model of the scaly surface topography formation was proposed based on motion analysis between the roller and workpiece. Secondly, the roller profile was considered in the proposed model to describe the scaly surface topography formation. Three-dimensional surface roughness characteristic parameters Sa, Sz, and Sq were adopted to evaluate the scaly surface topography. These three-dimensional surface roughness parameters can be theoretically predicted with the proposed kinematic model for the scaly surface fabricated by rotary ultrasonic rolling of titanium alloy Ti-6Al-4V. The theoretical predictions of Sa, Sz, and Sq were verified with the experimental results. Finally, the friction coefficients of scaly surfaces generated with various rotary ultrasonic rolling parameters were tested. The friction coefficient of the scaly surface was minimum at ultrasonic amplitude of 7 μm. The results demonstrated that the surface texturing with larger scaly ridges possessed improved frictional performance under identical test conditions. [ABSTRACT FROM AUTHOR]

The paper presents experimental analysis of relation between friction coefficient and contact pressure of MoS 2 film deposited on Ti 6 Al 4 V substrate in contact with sapphire ball during reciprocating sliding motion. It is shown that the value of friction coefficient decreases with increasing contact pressure. A microscale modeling approach is next developed to mimic the experimental observations. Representative volume element is defined based on the actual topography of outer surface of MoS 2 film. Assuming thermo-elastic material properties, the calculations on the asperity level are performed in two steps. Firstly, the mechanical contact between two surfaces is calculated. As a result, the relation between the global load and micro-stress distribution is obtained. Secondly, for a given stress load, thermal analysis is performed providing temperature fluctuation within simplified conical asperity. By assuming relation between friction coefficient and temperature on the microscale, it is possible to obtain macroscopic friction coefficient as a function of contact pressure. In the end, model results are compared with experimental data. The novel aspects of presented approach lie in the selection of three main factors on a micro-level defining macroscopic friction. They are actual surface topography, microscopic temperature and microscopic friction-temperature relation. [ABSTRACT FROM AUTHOR]

The performance of rolling bearings is often reduced due to the additional wear introduced by sliding contact. Therefore, it is very vital to study the evolution of the sliding wear process of the bearing material friction pairs. The tribological performance of the two kinds of material pairs, including GCr15–GCr15/Si3N4–GCr15, was analysed under oil-lubricated conditions with a pin-on-disc rig. The results show that with high initial surface roughness, the friction coefficients of the two pairs decrease as the load and speed increase, while in the stable wear stage, Si3N4–GCr15 friction pairs show better tribological properties than those of GCr15–GCr15 friction pairs. For lacks of information-rich studies and techniques of worn surfaces topography, an in-suit 3D microscope is adopted to obtain the topographies of friction and wear surface during the wear tests. The results prove that 3D topography can clearly characterize the wear process. 3D topography shows identical trend with the surface roughness (Ra, Sa and Sq) and the friction coefficients. Citing mixing parameter Sdr explores its feasibility for characterizing worn surfaces. The results illustrate that there is a close relationship between Sdr and 3D topography, which can reflect the friction transition of a surface from running into severe wear. A low surface roughness indicates a small Sdr. [ABSTRACT FROM AUTHOR]

In the present study, AA6082 aluminium is deposited onto AISI 4140 steel substrates via friction surfacing (FS). Aiming to understand the influence of substrate surface for the bonding mechanism during the plasticising as well as the deposition phase, three different surface topographies have been manufactured via grinding and machining. Subsequently, FS process parameter dependencies on the deposits have been investigated. The resulting optical appearance, geometry and microstructure of the deposits have been studied. A deeper surface topography was found to facilitate plasticising and therefore FS layer deposition. Defect-free layer-to-substrate (LTS) joints have been generated for all topographies showing a fine-grained recrystallized microstructure as well as flow lines in the AA6082 deposits following closely the substrate surface topography, whereas no metallurgical changes in the AISI4140 substrates have been detected. At the LTS interfaces, a correlation of flow lines to an increased occurrence of high angle grain boundaries is identified. Appearance, geometries and grain size ratios of the AA6082 deposits show a dependency on substrate surface topography. Although complete bonding was achieved in the LTS joints, no distinct diffusion zone or interfacial mixing was observed. Mechanical interlocking on the micro scale was detected only for the samples with ground substrate surfaces. • Deeper surface topography helps plasticising and homogeneous layer deposition. • No material mixing or distinct diffusion occurred at dissimilar material interface. • Deposit's microstructural flow lines closely follow substrate surface topography. • Deposit's average grain size tends to decrease with increasing surface topography. [ABSTRACT FROM AUTHOR]

Purpose: During the production of cardboard food cans, the packaging bottom and the cylindrical wall are joined in the seaming process. In order to achieve a high-quality, crack-free surface of the cardboard seam, low friction between the seaming chuck and the cardboard must be ensured. The goal of this study was to minimise the friction between the seaming chuck and the cardboard can surface. Design/methodology/approach: Tribological properties of the seaming chuck were optimised by adjusting its material properties, surface topography and surface energy followed by measurements of the resulting friction response in sliding contact with a representative paper sample. Findings: A strong correlation between the surface free energies of the tribological samples and their measured coefficients of friction was observed, indicating that in tribological tests, adhesion was the dominating friction mechanism. Furthermore, the fact that the smoother samples yielded higher friction values than the rougher ones is most likely also correlated with the higher adhesion of the smoother samples originating from their larger contact area. Research limitations/implications: The existing results indicate that for tribological optimisation of paper and cardboard contacts primarily the adhesive friction component should be considered – by either reducing the surface free energy of the counter-body or optimising its surface topography. Practical implications: By applying the selected solution concept, a friction reduction of more than 50% as compared to the benchmark was achieved. Originality/value: The present study provides a guideline for tribological optimisation of paper and cardboard contacts. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0064/ [ABSTRACT FROM AUTHOR]

Purpose: Additive manufacturing (AM) is a promising alternative to the conventional production methods (i.e., machining), providing the developers with great geometrical and topological freedom during the design and immediate prototyping customizability. However, frictional characteristics of the AM surfaces are yet to be fully explored, making the control and manufacturing of precise assembly manufactured mechanisms (i.e., robots) challenging. The purpose of this paper is to understand the tribological behavior of fused deposition modeling (FDM) manufactured surfaces and test the accuracy of existing mathematical models such as Amontons–Coulomb, Tabor–Bowden, and variations of Hertz Contact model against empirical data. Design/methodology/approach: Conventional frictional models Amontons–Coulomb and Tabor–Bowden are developed for the parabolic surface topography of FDM surfaces using variations of Hertz contact models. Experiments are implemented to measure the friction between two flat FDM surfaces at different speeds, normal forces, and surface configuration, including the relative direction of printing stripes and sliding direction and the surface area. The global maximum measured force is considered as static friction, and the average of the local maxima during the stick-slip phase is assumed as kinematic friction. Spectral analysis has been used to inspect the relationship between the chaos of vertical wobbling versus sliding speed. Findings: It is observed that the friction between the two FDM planes is linearly proportional to the normal force. However, in contrast to the viscous frictional model (i.e., Stribeck), the friction reduces asymptotically at higher speeds, which can be attributed to the transition from harmonic to normal chaotic vibrations. The phase shift is investigated through spectral analysis; dominant frequencies are presented at different pulling speeds, normal forces, and surface areas. It is hypothesized that higher speeds lead to smaller dwell-time, reducing creep and adhesive friction consequently. Furthermore, no monotonic relationship between surface area and friction force is observed. Research limitations/implications: Due to the high number of experimental parameters, the research is implemented for a limited range of surface areas, which should be expanded in future research. Furthermore, the pulling position of the jaws is different from the sliding distance of the surfaces due to the compliance involved in the contact and the pulling cable. This issue could be alleviated using a non-contact position measurement method such as LASER or image processing. Another major issue of the experiments is the planar orientation of the pulling object with respect to the sliding direction and occasional swinging in the tangential plane. Practical implications: Given the results of this study, one can predict the frictional behavior of FDM manufactured surfaces at different normal forces, sliding speeds, and surface configurations. This will help to have better predictive and model-based control algorithms for fully AM manufactured mechanisms and optimization of the assembly manufactured systems. By adjusting the clearances and printing direction, one can reduce or moderate the frictional forces to minimize stick-slip or optimize energy efficiency in FDM manufactured joints. Knowing the harmonic to chaotic phase shift at higher sliding speeds, one can apply certain speed control algorithms to sustain optimal mechanical performance. Originality/value: In this study, theoretical tribological models are developed for the specific topography of the FDM manufactured surfaces. Experiments have been implemented for an extensive range of boundary conditions, including normal force, sliding speed, and contact configuration. Frictional behavior between flat square FDM surfaces is studied and measured using a Zwick tensile machine. Spectral analysis, auto-correlation, and other methods have been developed to study the oscillations during the stick-slip phase, finding local maxima (kinematic friction) and dominant periodicity of the friction force versus sliding distance. Precise static and kinematic frictional coefficients are provided for different contact configurations and sliding directions. [ABSTRACT FROM AUTHOR]

Tribological tests are adopted to estimate the kinetic friction coefficient (COF) of the material of interest according to the American Society for Testing and Materials (ASTM) standard. Typically, for the measurement process, several replicas, as well as a postprocessing data treatment, are necessary to take into account the observed casual variability of the measurand. This article describes a statistical approach aiming to highlight the running-in phase and the most significant time intervals during the steady-state for each test replica. A two-steps procedure based on the adoption of the bootstrap method allows the automatic detection of the running-in time interval and the outlier filtering of the steady-state. Experimental activity has been carried out by performing multiple tests through the ball-on-flat tribometer in order to verify the improvement allowed by the authors’ proposal about the dry friction COF measurement in terms of both accuracy and repeatability. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the effect of engineered micro-structures on the tribological properties of metal-polyetheretherketone (PEEK) surface. Design/methodology/approach: Circular dimples with diameters of 25 and 50 µm were designed and manufactured on PEEK plate specimens using picosecond laser. Reciprocating friction and wear tests on a ball-on-flat configuration were performed to evaluate the tribological properties of the designed micro-structures in dry contacts. The loading forces of 0.9 and 3 N were applied. Findings: As a result, obvious fluctuations of coefficient of friction curve were observed in tribosystems consisting of non-textured and textured PEEK with circular dimples of 25 µm in diameter. GCr15 ball/textured PEEK plate specimens with circular dimples of 50 µm in diameter revealed a superior friction and wear property. Originality/value: Different to the existing studies in which the tribopairs consist of hard bearing couples, this study investigated the tribological properties of the engineered micro-structures on the hard-on-soft bearing couples. [ABSTRACT FROM AUTHOR]

The dynamic evolutions of friction force and worn surface profile were qualitatively analyzed by phase trajectory and recurrence plots and quantitatively characterized by fractal dimension and percent determinism. The results show that phase trajectories first shrink to a small volume, then stabilize at a minimum volume, finally expand to a large volume in the wear process. The white areas on the recurrence plots increase with the wear time. The fractal dimension first increases, then stabilizes at a high value, and finally decreases rapidly. The percent determinism first decreases, then fluctuates in a certain range, and finally increases. It demonstrates that friction force and worn surface topography derived from one tribology system evolve in a similar but not exactly the same way. They have the consistent evolution law in the wear process. Specially, friction force is much more sensitive to the variation of wear states than the worn surface. [ABSTRACT FROM AUTHOR]

Wear is a common phenomenon which most mechanical components suffer from. Available studies are mainly focused on the wear performance after contact pairs operate for a period of time. The studies on evolution of surface topography and friction coefficient resulting from the wear process under mixed lubrication conditions are still limited. Further study of this issue may have a significant influence on wear reduction and lubricating performance improvement. In the present study, surface topography and friction coefficient evolution during sliding wear in a mixed lubricated rolling-sliding contact are investigated by the method based on the numerical approach developed by Zhu.et al. [1]. The numerical results are compared with experiment results to demonstrate the efficiency and accuracy of the present wear model. The evolutions of wear track, root mean square (RMS) roughness, and friction coefficient are observed systematically during wear process. The influences of load, slide-to-roll ratio and surface orientation on these characteristics are studied as well. The simulation results are in good agreement with experimental observations. The wear track is quite different from the one under dry contact, due to the effect of oil and the contact deformation. The friction coefficient drops rapidly at first and then it keeps stable with small fluctuations with respect to wear evolution. It indicates that load and slide-to-roll ratio have a remarkable impact on wear rate, though the effect of surface topography is limited. Further, the results show that the RMS roughness deceases slightly at first and then it increases gradually during the wear process. • A point wear model of real, engineering rough surfaces has been introduced in this paper. • In the early running-in process, the wear tracks on both sides are deeper than in the middle, which is different from that under dry contact. • In the running-in process, the friction coefficient drops rapidly first and then keeps stable with small fluctuations. • Increasing load and slide-to-roll ratio can increase the wear rate. [ABSTRACT FROM AUTHOR]

Surface topography parameters significantly control physical processes which have asperity‐to‐asperity contacts in tribological components undergoing friction and wear. In this study, the effect of correlation length, maximum contact load, and surface roughness on friction coefficient and load distribution is studied. The load‐sharing concept is employed to determine friction coefficient and load distribution in the mixed‐lubrication regime. Results clearly demonstrate the effect of correlation length on friction coefficient and load distribution. It is found that the lower value of the coefficient of friction may be achieved even at low velocity for the smooth surface as compared with rough surfaces having higher surface roughness. For a particular value of velocity, the coefficient of friction decreases with an increase in maximum contact load. This work will help in predicting the coefficient of friction in the mixed‐lubrication regime for the engineering surfaces produced by processes like grinding, which is the result of an abrasive action. [ABSTRACT FROM AUTHOR]

• Interpretation of force-indentation data from AFM probes with different tip shapes. • Effect of friction on force-indentation data obtained using AFM. • Recommendation of AFM probe for elastic modulus measurement. • Dependence of friction-induced hysteresis on stiffnesses of AFM probe and specimen. Atomic force microscopy (AFM)-based indentation has been widely used to understand mechanical properties in conjunction with surface topography and structure at the nano-scale. In this work, nanomechanical properties of three different specimens were determined using four different AFM probes with spherical and flat-ended tips and conical tips with rounded apexes, to provide useful information for probe selection and for better interpretation of force-indentation data. These probes were modeled as a sphere, flat punch, and hyperboloid, respectively, after careful characterization to determine the elastic modulus based on contact models. Polyacrylic acid, polyvinylidene fluoride, and styrene-butadiene rubber were used as specimens. The results showed that the probe with a flat-ended tip was prone to misalignment between the flat end of the tip and specimen surface, which caused that the force-indentation data could not be interpreted using the contact model due to imperfect contact. Also, hysteresis was consistently observed in force-indentation data for the probes with a spherical tip and conical tips with rounded apexes, likely due to friction. This further resulted in significant differences in the elastic moduli of the specimens as large as 22–100% as determined from extension and retraction curves. The elastic moduli approximated by the mean of those from the extension and retraction curves generally agree with those from the instrumented indentation. Considering the uncertainties associated with the modeling of tip shape and force and indentation measurements, the probe with relatively large tip radius (e.g., ∼30 nm) was recommended for more accurate measurement for the specimen with a few GPa elastic modulus. Furthermore, the difference between elastic moduli determined from extension and retraction curves was found to increase as the ratio of contact stiffness to flexural stiffness of the AFM probe decreased. The outcome of this work is expected to provide useful information for obtaining accurate mechanical property measurements using an AFM based on a better understanding of the interaction between AFM probe and specimen. [ABSTRACT FROM AUTHOR]

Newly found evidence on the negative slope of the friction-velocity curve is described in terms of the contact area on the surface of brake friction materials. The tribotests were performed using two commercial friction materials with and without steel fibers. The results showed that velocity weakening friction was pronounced in the friction materials containing steel fibers, which facilitated high pressure contact areas by the agglomeration of wear debris. The size of the high pressure contact area increased as the sliding velocity decreased, which supported the correlation among velocity weakening friction, friction instability, and high pressure contact areas. The pronounced velocity dependence of the friction coefficient due to transient contact area was highly relevant to noise propensity of the friction material. • The sliding surface of a brake friction material shows wide pressure distribution. • The size of the high-pressure contact area changes with the sliding velocity. • μ-v character of the friction material is affected by high-pressure contact areas. • Large stick-slip amplitudes are germane to velocity weakening friction phenomena. • Velocity dependence of the contact area affects the friction and noise propensity. [ABSTRACT FROM AUTHOR]

The tribological behaviors of soft materials are closely related to their surface chemistry and morphology. Thus, this study investigates the effects of surface chemistry and morphology on the stick-slip friction of polydimethylsiloxane (PDMS). Air plasma treatment is conducted to modify the surface chemistry, and the bionic shark skin texture is replicated on PDMS. The synergistic effect of the bionic shark skin texture and air plasma treatment on stick-slip friction is evaluated. The results show that air plasma treatment and bionic texture decrease the friction force. Various stick-slip features are observed under different numbers of pendant chains at the contact interfaces, which increase the adhesion force. This study provides fundamental insights into the stick-slip behaviors of other soft materials. [Display omitted] • Stick-slip patterns were proposed to analyze the stick-slip friction behavior of soft material such as PDMS. • Air plasma treatment was used to change surface chemistry of PDMS and decrease the friction of PDMS. • Bionic (shark skin) structure was replicated on PDMS to reduce the friction force and stick-slip effect. • Synergistic effect of surface chemistry and topography on friction of PDMS is analyzed and explained. [ABSTRACT FROM AUTHOR]

The tribological properties of graphene have become an object of great scientific interest. However, the graphene oxide friction performance on rough surfaces remains comparatively unexplored. In this work, we focused on the effect of the multilayer graphene oxide (GO) dispersions in glycerol on the steel-steel tribosystem. Macroscale tribological tests were performed using a tribometer having a pin-on-disc configuration (normal loads 98 and 196 N, rotating speed 200 rpm). The wear samples were made of 40Cr steel with a roughness of about 110 nm. The study of the morphology of worn surfaces showed the dependence of lubricant efficiency on GO concentration. The use of 0.025 wt% GO led to the formation of a movable lubricating layer without deposition of tribofilm. The lowest friction coefficient was found at a concentration of 0.05 wt%. The decrease correlated with the formation of tribofilm on the steel surface. At high GO concentration (0.10 wt%), the agglomerated GO particles scratch the rubbing surfaces, and the friction coefficient increases significantly. • The influence of graphene oxide glycerol dispersions to lubrication of steel • AFM study of steel rubbing surface • Concentration dependence of lubricating properties of graphene oxide dispersions • Decreasing of friction coefficient in graphene oxide lubrication [ABSTRACT FROM AUTHOR]

Carbon fabric (CF) was pretreated by air-plasma bombardment and then further modified by deposition of polydopamine on the surface of the pretreated CF. Epoxy resin composites reinforced by unmodified or surface-modified carbon fabric were fabricated. The friction and wear behaviors of the resulting composites were evaluated in a ring-on-block contact mode. The flexural strength and Rockwell hardness of the composites were also evaluated. The morphologies of the worn surfaces of the unmodified and modified composites were analyzed by scanning electron microscopy. The surface treatment increased the surface roughness and changed the surface topography of the CF, which contributed to enhancing the interfacial adhesion of the composites and thus improved the mechanical properties and tribo-performance. The friction and wear properties of both the unfilled and filled composites were highly dependent on the load and sliding velocity. Moreover, the results were supplemented with scanning electron micrographs to help understand the possible wear mechanisms. [ABSTRACT FROM AUTHOR]

This work carried out a systematic analysis to help understanding how surface roughness and relative orientation between surface topography and direction of abrasive entrainment can affect particle dynamics during both pure microabrasion and microabrasion-corrosion. For that, tests were carried out in AISI 304 austenitic stainless steel test specimens using a recently developed microabrasion-corrosion tester. A 3D load cell ensures controlled application and measurement of forces during the tests. For the microabrasion tests, a slurry composed of small (ϕ=2.5 µm) silica particles dispersed in distilled water at a concentration of 20wt% was employed, whereas for the microabrasion corrosion tests the distilled water in the slurry was substituted by a corrosive solutions in distilled water (1 N H 2 SO 4). Potentiodynamic curves varying from cathodic potentials into the transpassive region were obtained within the course of duration of each microabrasion-corrosion test. The specimens were ground using two different SiC papers (#80 and #4000) to vary their surface topography and were tested with the grooves oriented perpendicular and parallel to the direction of rotation of the ball. Although the effect of surface topography was slight under pure microabrasion conditions, it was more significant under microabrasion-corrosion conditions. It was proposed that under microabrasion conditions, the formation of a low friction passive layer on the specimens made particle entrainment more difficult and therefore the relative orientation between surface topography and ball rotation had a stronger effect on the amount of abrasives that entered the contact, affecting wear rates. Grooves parallel to the rotation of the sphere increased wear rates under microabrasion-corrosion conditions when compared with grooves oriented perpendicular to the contact. Parallel grooves also resulted in higher passivation currents than perpendicular grooves, probably due to more severe damage to the passive layer caused by more abrasives into the contact [ABSTRACT FROM AUTHOR]

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. Highlights • A correlation is established between oil consumption and relative area determined by area-scale fractal analysis. • Waviness, dale and core volume parameters have a high correlation to oil consumption at engine speeds above 1200 rpm. • Functional scale analysis gives the possibility to visualize surfaces at the appropriate scale of interest. [ABSTRACT FROM AUTHOR]

Abstract Cutting fluid in machining process brings negative impacts on environment and operator health. Excessive cutting fluid is required and consumed in machining difficult-to-machine materials with high-pressure coolant supplies (HPCS). Dry cutting as clean manufacturing technology can eliminate the cutting fluid hazards. This work investigated the tool usage assessment, machining process variables, and surface topography under dry and HPCS conditions employing uncoated WC/6%Co fine tools. The Product Sustainability Index (PSI) approach was applied to establish the sustainability assessment involving machining process and surface quality. Tool life of dry cutting (v = 75 m/min, f = 0.1 mm/rev) achieved 75.8% of corresponding HPCS. Normal wear stage proportion in dry cutting was relatively larger. Higher cutting parameters exacerbated tool wear rate resulting in rapid edge damage, especially in dry cutting. The cutting forces, friction coefficient and specific cutting energy were associated with Ti-6Al-4V softened and specific tribological behaviors accompanied with different cutting parameters. The decisive factor of Sa depended on feed rates. Feed marks in dry cutting were eliminated due to heat softening and lateral pressure, resulting in Sa decreasing. The noticeable difference existed in Sdr for dry cutting while HPCS had a slight fluctuation for the whole cutting parameters. Under dry cutting (v = 75 m/min, f = 0.1 mm/rev), the highest sustainability index was obtained 70.0. The results indicated that dry cutting provided environmental friendliness, cleaner productions and helped to enhance sustainability. Graphical abstract Image 104 Highlights • Cooling methods with dry v. s. HPCS in turning Ti-6Al-4V were investigated. • Tool usage, process variables, and 3D surface topography were analyzed. • Product Sustainability Index (PSI) approach was applied to establish the sustainability assessment. • Under dry cutting (v = 75 m/min, f = 0.1 mm/rev), the highest PSI was 70.0. [ABSTRACT FROM AUTHOR]

Abstract The article examines the influence of several factors (load, moisture, velocity) on the value of the friction force. The research was conducted on three different granular materials of biological origin (peas, maize, triticale). In addition, attention was given to the geometrical surface structure of grains on contact with the structural material. The proposed mathematical model took account of four independent factors. Statistical analysis showed their significant influence on the friction force. It was also found that velocity, in the tested range (30–60 mm/min), had a negligible impact on the value of the friction force. Graphical abstract Unlabelled Image Highlights • The value of the friction force for three plant granular materials was determined. • The influence of several factors on the value of the friction force was examined. • The 3D model of the surface of the tested materials was made. • The parameters of the surface topography of the tested materials were determined. • Based on the obtained results, a mathematical model was proposed. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to investigate the influence of different finish processes on the surface integrity and tribological behaviour of cylinder running surfaces for internal combustion engines.Design/methodology/approach The cutting force during finishing and the resulting surface topography was measured for a variety of cylinder running surfaces made of EN-GJL-250, EN-GJV-400 and thermal sprayed aluminium alloy. A separate conditioning tool was developed and tested. Different analysis methods (SEM, EDX, SIMS and FIB) for the characterisation of the boundary conditions were used. By an oscillating friction wear test and a single cylinder floating liner engine, the running-in and frictional behaviour was rated.Findings It was shown that honing with low cutting forces and silicon carbide cutting material decreases the friction in operation. The characteristics of the boundary layers after running-in depend on the finish machining process. A preconditioning with a separate tool can adjust the boundary layer and running-in behaviour. Based on the experimental results, a multi-body and computational fluid dynamics simulation was developed for the floating liner engine.Originality/value The results demonstrate the potential of finishing with low process forces to reduce friction and the need for a complete consideration of the tribological system piston ring/cylinder liner surface. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the effect of frictional materials and surface texture on the energy conversion efficiency and the mechanical output performance of the ultrasonic motor (USM).Design/methodology/approach A newly designed testing system was set up to measure the mechanical output performance of the USM. The influence of different frictional materials on the output performance of the USM was studied under the same assembly process and parameters. The surface texture was fabricated by laser ablation processing. The effects of surface texture and input parameters on the energy conversion efficiency and mechanical output performance of the USM were studied.Findings The results show that polyimide (PI) composites as frictional material can significantly improve the output performance of the USM compared to polytetrafluoroethylene (PTFE) composites. When the pre-load is 240 N, the energy conversion efficiency of the USM using textured PI composites as frictional material can reach 41.93 per cent, increased by 29.21 per cent compared to PTFE composites, and the effective output range of the USM is increased to 0.7-1.1 N m. Besides, the pre-load and surface texture have a great influence on the output performance of the USM.Originality/value PI composites can improve the mechanical output performance of the USM. Surface texture can also improve the interface tribological properties and the energy conversion efficiency based on the advanced frictional materials, which will contribute to the increment of the output performance of the USM under the same input conditions. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to study the change rule of sintered iron friction properties under high temperature and establish the model to predict the friction coefficient.Design/methodology/approach The morphological measurements of sintered iron material with four different oxidation degrees are carried out. A prediction model of friction coefficient in high temperature oxide growth stage for sintered iron material is established based on the theory of flash temperature and adhesion friction. The relationship between friction coefficient and the key parameters is found through the test fitting.Findings The surface topography changes with oxidative wear. The wear debris will be compacted and sintered again to form a composite oxide layer with the temperature increasing. The validity and accuracy of proposed model are tested using the friction coefficient and temperature experiments. Results are in reasonable agreement with those obtained using values of load commonly used.Originality/value The significance lies in the change mechanism of high temperature friction characteristic is clarified. Three friction stages related to temperature of dry friction are put forward for sintered iron, and a meaningful reference is provided by the established model for high-temperature performance design of sintered iron friction material. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to investigate the effects of surface topography, including surface roughness, circumferential waviness and radial taper, on hydrodynamic performance of liquid film seals considering cavitation.Design/methodology/approach A mathematical model of liquid film seals with surface topography was established based on the mass-conservative algorithm. Liquid film governing equation was discretized by the finite control volume method and solved by the Gauss–Seidel relaxation iterative algorithm, and the hydrodynamic performance parameters of liquid film seals were obtained considering surface roughness, circumferential waviness and radial taper separately.Findings The results indicate that the values of load-carrying capacity and frication torque are affected by the surface topography in varying degrees, but the effect is limited.Originality/value The results presented in the study are expected to aid in determining the optimum value of structural parameters for the optimum seal performance because of the realistic model which considers both surface topography and cavitation. [ABSTRACT FROM AUTHOR]