Showing papers in "Industrial Lubrication and Tribology in 2019"

Influence of iron–aluminum alloy on the tribological performance of non-asbestos brake friction materials – a solution for copper replacement

Abstract: The purpose of this study is to investigate the influence of commercially available iron–aluminum alloy compared to copper, iron and aluminum powders on the tribological performances of friction composites. The main objective is to replace copper from the friction composite formulations.,In this study, friction composites were fabricated as of standard brake pads using commercially available iron–aluminum alloy and compared to copper powder, iron powder and aluminum powder-based without varying the other ingredients. The brake pads were developed as per the industrial procedure. The physical, mechanical and thermal properties of the developed brake pads were analyzed as per industrial standards. Tribological properties were analyzed using the chase test. Initial speed and deceleration tests in a real-time braking scenario were performed using a full-scale inertia brake dynamometer. Worn surface analysis was done using a scanning electron microscope.,The results indicate that iron–aluminum alloy (mechanomade)-based friction composites possess good physical, chemical, thermal and mechanical properties with stable fade and recovery characteristics due to its composition and flake morphology. During initial speed and deceleration braking conditions, iron–aluminum alloy also showed good tribological behavior.,This paper explains the influence of commercially available iron–aluminum alloy in friction composites in enhancing tribological performance by its composition and flake morphology, which could potentially replace copper in friction composites by solving subsequent problems.

Multi-scale surface patterning – an approach to control friction and lubricant migration in lubricated systems

Abstract: The paper aims to investigate the possibilities to control friction in lubricated systems by surface patterning, making use of a multi-scale approach. Surface patterns inside the tribological contact zone tend to directly reduce friction, whereas surface patterns located in the close proximity of the contact area can improve the tribological performance by avoiding lubricant starvation and migration. Finally, optimized surface patterns were identified by preliminary laboratory tests and transferred to a journal bearing, thus testing them under more realistic conditions.,Surface patterns on a large scale (depth > 10 µm) were fabricated by micro- and roller-coining, whereas surface patterns on a small scale (depth < 2 µm) were produced by direct laser interference patterning. The combination of both techniques resulted in multi-scale surface patterns. Tribologically beneficial surface patterns (verified in ball-on-disk laboratory tests) were transferred onto a journal bearing’s shaft and tested on a special test-rig. To characterize the lubricant spreading behavior, a new test-rig was designed, which allowed for the study of the lubricant’s motion on patterned surfaces under the influence of a precisely controlled temperature gradient.,All tested patterns accounted for a pronounced friction reduction and/or an increase in oil film lifetime. The results from the preliminary laboratory tests matched well, with results from the journal bearing test-rig, both tests showing a maximum friction reduction by a factor of 3-4. Numerical investigations, as well as experiments, have shown the possibility to actively guide lubricant over patterned surfaces. Smaller periodicities, as well as greater structural depths and widths, led to a more pronounced anisotropic spreading and/or greater spreading velocities. Multi-scale surfaces demonstrated the strongest effects regarding the lubricant’s spreading behavior.,Friction, as well as lubricant migration, can be successfully controlled by using micro-coined, laser-patterned and/or multi-scale surfaces. To the best of the authors’ knowledge, the study demonstrates for the first time the unique possibility to transfer results obtained in laboratory tests to a real machine component.

Influence of WS2/SnS2 on the tribological performance of copper-free brake pads

Abstract: Purpose The purpose of this study is to investigate the influence of solid lubricants (tungsten disulfide [WS2]/ Tin disulfide [SnS2]) on the tribological performance of brake pads. Design/methodology/approach In this study, the brake pads were developed by varying the solid lubricants (WS2/SnS2) without varying the other ingredients. The brake pads were developed as per the industrial procedure. Thermal stability was found for varying ingredients and developed pads. The physical, mechanical and thermal properties of the developed brake pads were analyzed as per the industrial standards. The tribological properties were analyzed using the Chase test. The worn surface analysis was done using scanning electron microscopy, elemental mapping and three-dimensional profile analysis. Findings The experimental results indicate that the WS2-based brake pads possess good physical, chemical and mechanical properties with stable friction and less wear rate due to its good lubrication film formation and thermal stability natures of WS2. Originality/value This paper explains the effect of solid lubricants in brake pads for enhancing the tribological performance by the shearing of crystal structure, thermal stability and tribo film properties of the lubricants.

Fabrication and tribological study of AA6061 hybrid metal matrix composites reinforced with SiC/B4C nanoparticles

Abstract: Composite materials are replacing the traditional materials because of their remarkable properties and the addition of nanoparticles making a new trend in material world. The nano addition effect on tribological properties is essential to be used in automotive and industrial applications. The current work investigates the sliding wear behavior of an aluminum alloy (AA) 6061-based hybrid metal matrix composites (HMMCs) reinforced with SiC and B4C ceramic nanoparticles.,The hybrid composites are fabricated using stir casting process. Two different compositions were fabricated by varying the weight percentage of the ceramic reinforcements. An attempt has been made to study the wear and friction behavior of the composites using pin-on-disc tribometer to consider the effects of sliding speed, sliding distance and the normal load applied.,The tribological tests are carried out and the performances were compared. Increase in sliding speed to 500 rpm resulted in the rise of temperature of the contacting tribo-surface which intensified the wear rate at 30N load for the HMMC. The presence of the ceramic particles further reduced the contact region of the mating surface thus reducing the coefficient of friction at higher sliding speeds. Oxidation, adhesion, and abrasion were identified to be the main wear mechanisms which were further confirmed using energy dispersive spectroscopy and field emission scanning electron microscopy (FESEM) of the worn out samples.,The enhancement of wear properties is achieved because of the addition of the SiC and B4C ceramic nanoparticles, in which these composites can be applied to automobile, aerospace and industrial products where the mating parts with less weight is required.,The influence of nanoparticles on the tribological performance is studied in detail comprising of two different ceramic particles which is almost new research. The sliding effect of hybrid composites with nano materials paves the way for using these materials in engineering and domestic applications.

Sustainable machining. Modeling and optimization of temperature and surface roughness in the milling of AISI D2 steel

Abstract: Sustainable machining is a global consensus and the necessity to cope up the serious environmental threats. Minimum quantity lubrication (MQL) and nanofluids-based MQL(NFMQL) are state-of-the-art sustainable lubrication modes. The purpose of this study is to investigate the effect of process parameters, such as feed rate, depth of cut and cutting fluid flow rate, on temperature and surface roughness of the manufactured pieces during face milling of the AISI D2 steel.,A statistical technique called response surface methodology with Box–Behnken Design was used to design experimental runs, and empirical modeling was presented. Analysis of variance was carried out to evaluate the model’s accuracy and the validation of the applied technique.,A comprehensive analysis revealed the superiority of implementing NFMQL in comparison to MQL within the levels of process parameters. The comparison has shown a significant reduction of temperature under NFMQL at the tool-workpiece interface from 16.2 to 34.5 per cent and surface roughness from 11.3 to 12 per cent.,This research is useful for practitioners to predict the responses in workshop and select appropriate cutting parameters. Moreover, this research will be helpful to reduce the resource which will ultimately save energy consumption and cost.,To cope with the industrial challenges and tribological issues associated with the milling of AISI D2 steel, experiments were conducted in a distinct machining mode with innovative cooling/lubrication. Until now, few studies have addressed the key lubrication effects of Al2O3-based nanofluid on the machinability of D2 steel under NFMQL lubrication condition.

Investigations on tribological behaviour of AA7075-TiO2 composites under dry sliding conditions

Abstract: Aluminium and its alloys are the most preferred material in aerospace and automotive industries because of their high strength-to-weight ratio. However, these alloys are found to be low wear resistance. Hence, the incorporation of ceramic particles with the aluminium alloy may be enhanced the mechanical and tribological properties. The purpose of this study is to optimize the specific wear rate and friction coefficient of titanium dioxide (TiO2) reinforced AA7075 matrix composites. The four wear control factors are considered, i.e. reinforcement (Wt.%), applied load (N), sliding velocity (m/s) and sliding distance (m).,The composites were fabricated through stir casting route with varying weight percentages (0, 5, 10 and 15 Wt.%) of TiO2 particulates. The mechanical properties of the composites were studied. The specific wear rate and friction coefficient of the newly prepared composites was determined by using a pin-on-disc apparatus under dry sliding conditions. Experiments were planned as per Taguchi’s L16 orthogonal design. Signal-to-noise ratio analysis was used to find the optimal combination of parameters.,The mechanical properties such as yield strength, tensile strength and hardness of the composites significantly improved with the addition of TiO2 particles. The analysis of variance result shows that the applied load and reinforcement Wt.% are the most influencing parameters on specific wear rate and friction coefficient during dry sliding conditions. The scanning electron microscope morphology of the worn surface shows that TiO2 particles protect the matrix from more removal of material at all conditions.,This paper provides a solution for optimal parameters on specific wear rate and friction coefficient of aluminium matrix composites (AMCs) using Taguchi methodology. The obtained results are useful in improving the wear resistance of the AA7075-TiO2 composites.

Investigation on tribological and corrosion characteristics of oxide-coated steel and mild steel fiber-based brake friction composites

Abstract: Purpose The purpose of this work is to investigate the effect of oxide-coated steel in comparison with mild steel fibers on the tribological and corrosion performances of friction composites. Design/methodology/approach In this study, the friction composites were developed in the form of standard brake pads by using oxide-coated steel and compared with mild steel fibers-based one without varying the other ingredients. The brake pads were developed as per the industrial procedure. The physical, mechanical, thermal properties of the developed brake pads were analyzed as per the industrial standards. The tribological properties were analyzed using the Chase test. The worn surface analysis was done using scanning electron microscope. Corrosion behavior was also analyzed in both salt and normal water conditions. Findings The experimental results indicate that the oxide-coated steel-based friction composites brake pads possess good physical, chemical, thermal, corrosion resistance and mechanical properties with stable fade and recovery characteristics because of its oxide coating and flake morphology. Originality/value This paper explains the influence of oxide-coated steel in friction composites for enhancing the tribological performance and corrosion resistance by its oxide coating and flake morphology which could potentially replace mild steel fibers-based problems in friction composites.

Analysis on suitability of HVOF sprayed Ni-20Al, Ni-20Cr and Al-20Ti coatings in coal-ash slurry conditions using artificial neural network model

Abstract: The purpose of this study is to analyze the slurry erosion failure of Ni-20Cr (Ni-Cr2O3), Ni-20Al (Ni-Al2O3) and Al-20Ti (Al2O3-TiO2) coatings deposited on SS316L by the high-velocity oxy-fuel process.,Slurry erosion experiments were conducted using a pot type erosion tester at different velocities 1.81, 2.71, 3.61 and 4.59 m/s for the time duration of 90-180 minutes. Fly ash and bottom ash were used as erodent media; the concentration of mass flux was taken as 30-60 wt. per cent. Artificial neural network (ANN) method was used to simulate the slurry erosion for thermally sprayed coatings.,Slurry erosion of coatings increases non-linearly with an increase in experimental durations, mass flux and velocity. Slurry erosion of Ni-20Cr and Ni-20Al layers was found to be maximum at 60° impingement angle, whereas 30° for SS316L and 45° for Al-20Ti coating. Slurry erosion performance of SS316L was improved by 2.56-3.19 times by depositing Ni-20Cr and Ni-20Al layers, whereas it improved 1.15-1.75 times by Al-20Ti coating. The slurry erosion SS316L was found almost 1.35 ± 1.28 times greater than that of the Ni-20Al coating, whereas it was to be 1.12 ± 1.36 times greater than Al-20Ti. Ni-20Al-coated SS316L showed a lower value of slurry erosion than Al-20Ti-coated SS316L.,Stainless Steel SS316L is widely used in hydraulic machinery (such as turbines, pumps, valves, fittings, etc.) of hydraulic and thermal power plants, chemical industry and marine industry. Therefore, the deposition of ductile and brittle coatings is a better option for their durable performance.,Erosion wear of Ni-20Cr, Ni-20Al and Al-20Ti coatings was successfully simulated by using an artificial neural network model by supplying experimental data as a target.

Erosion wear performance of Ni-Cr-O and NiCrBSiFe-WC(Co) composite coatings deposited by HVOF technique

Abstract: Purpose This study/paper aims to investigate the erosion wear performance of Ni-based coatings [Ni-Cr-O and NiCrBSiFe-WC(Co)] under sand-water slurry conditions. Design/methodology/approach A high-velocity oxy-fuel (HVOF) process was used to deposit the Ni-based coatings [Ni-Cr-O and NiCrBSiFe-WC(Co)] on the surface of stainless steel (SS 316L) substrate. A Ducom TR-41 erosion tester was used to conduct the tribological experiments on bare/HVOF coated SS 316L. The erosion wear experiments were carried out for different time durations (1.30-3.00 h) at different impact angles (0-60°) by running the pot tester at different rotational speeds (600-1,500 rev/min). The solid concentration of sand slurry was taken in the range of 30-60 Wt.%. The surface roughness of Ni-based coated surfaces was also measured along the transverse length of the specimens. Findings Results show the arithmetic mean roughness (Ra) values of Ni-Cr-O and NiCrBSiFe-WC coated SS-316L were 7.04 and 6.67 µm, respectively. The erosion wear SS-316L was almost 3.5 ± 1.5 times greater than that of the NiCrBSiFe-WC coatings. NiBCrSi-WC(Co) sprayed SS-316L showed lower erosion wear than Ni-Cr-O sprayed SS-316L. Microscopically, the eroded Ni-Cr-O coating underwent plowing, microcutting and craters. Ni-Cr-O coating have shown the ductile nature of erosion wear mechanism. NiBCrSi-WC(Co) surface underwent craters, plowing, carbide/boride pullout, fractures and intact. Erosion wear mechanisms on the eroded surface of NiBCrSi-WC(Co) were neither purely ductile nor brittle. Practical implications It is a useful technique to estimate the erosion wear of hydraulic machinery coated with Ni-based coatings imposed under mining conditions. Originality/value The erosion wear performance of HVOF-sprayed Ni-Cr-O and NiCrBSiFe-WC(Co) powders was investigated through extensive experimentation, and the results are well supported by scanning electron micrographs and 3D topology.

Experimental investigation of tribological effect on vegetable oil with CuO nanoparticles and ZDDP additives

Abstract: This paper aims to report the friction and wear characteristics of refined soybean oil (RSBO) blended with copper oxide (CuO) nanoparticles and zinc dialkyldithiophosphate (ZDDP) as additives.,Four different concentrations 0.04, 0.05, 0.1 and 0.2 Wt.% of CuO nanoparticles were added with ZDDP in RSBO. The friction and wear characteristics of lubricants have been investigated on a pin-on-disc tribotester under loads of 120 and 180 N, with rotating speeds of 1,200 and 1,500 rpm in half hour of operating time. The dispersion stability of CuO nanoparticles has been analyzed using ultraviolet visible (UV-Vis) spectroscopy. The wearout surface of pins has been examined by using a scanning electron microscope.,The results revealed that there is a reduction in the friction and wear by the addition of CuO nanoparticles and ZDDP in RSBO. Coefficient of friction increases at a high sliding speed for RSBO with ZDDP. From UV-Vis spectroscopy, it is observed that 100 ml of oleic acid surfactant per gram of CuO nanoparticles has stable dispersion in RSBO.,The addition of ZDDP and CuO nanoparticles in RSBO is more efficient to reduce the friction and wear in comparison to base oil. The optimum concentration of CuO nanoparticles in RSBO is 0.05 Wt.%.

Determination of Archard’s wear coefficient and wear simulation of sliding bearings

Abstract: This paper aims to present the methodology to determine Archard’s wear coefficient. By applying this coefficient into the numerical simulation of wear, it is possible to predict wear without long lasting and usually expensive experiments.,To determine necessary particles of Archard’s equation and calculate wear coefficient K, an experimental investigation is proposed. Afterwards, the wear simulation is executed in FEM software ANSYS 18.1. Analytical method is offered to determine worn volume for cylinder-in-cylinder contact, based on “inclination” of inner cylinder.,Comparing the value of Archard’s coefficient obtained by this experimental investigation with the values from the literature for the similar materials, high correlation is noted. Furthermore, numerically calculated contact pressure is confirmed with analytical method. Trend of pressure decrease due to wearing process, as well as due to increase of contact surface is observed.,Since the prediction of the wear is closely related to the life cycle assessment of bearings, and the machines in general, it has significant practical importance for designers.,Determination of Archard’s coefficient is usually performed by conventional pin-on-disk tribometers. This methodology offers a different approach for the determination of Archard’s wear coefficient for cylinder-in-cylinder contact, which is convenient for shaft-sliding bearing contact.

Performance studies of textured race ball bearing

Abstract: The purpose of this paper is to develop an energy-efficient and dynamically improved thrust ball bearing using textured race. A texture has been used on the stationary race of the test bearing to conduct the long-duration experiment for exploring its tribological and vibrational behaviours under starved lubricating condition using micro size MoS2 blended grease. The performance behaviours of the textured race bearing have been compared with conventional bearing (i.e. having both races without textures) under the identical operating conditions for demonstrating the advantages of textured race.,Texture was created on stationary race of the test ball bearing (51308) using nano-second pulsed Nd: YAG laser. Performance parameters (frictional torque, temperature rise and vibrations) of textured ball bearings were measured under severe starved lubricating conditions for understanding the critical role of texture in the long duration of the test. S-type load cell and miniature accelerometer were used for measuring the frictional torque and vibration, respectively. Bulk temperature at stationary races (at the back side) of test bearings was measured in operating conditions using a non-contact infrared thermometer.,Significant reduction in frictional torque and decrease in amplitude of vibration with textured ball bearing were found even under the severe starved lubricating condition in comparison to conventional bearing.,There is dearth of research pertaining to the performance behaviours of ball bearings using textures on the races. Therefore, an attempt has been made in this study to explore the tribo-dynamic performance behaviours of a thrust ball bearing using a texture on its stationary race under severe starved lubricating condition for the longer duration of the test.

Friction and wear characteristics of polylactic acid (PLA) for 3D printing under reciprocating sliding condition

Abstract: This paper aims to study the different infill, printing direction against sliding direction and various load condition for the friction and wear characteristics of polylactic acid (PLA) under reciprocating sliding condition.,The tests were performed by applying the load of 1, 5, 15 and 10 N with sliding oscillation frequency of 10 Hz for the duration of 10 min at room temperature.,The results show that the friction and wear properties of PLA specimen change with a different infill density of printed parts. The oscillation frequency is 10 Hz and the infill density of plate is 50 per cent that shows the best friction and wear properties.,The potential of this research work is to investigate the tribological characteristics of three-dimensional printing parts with different infill percentage to provide a reference for any parts in contact with each other to improve friction and wear performance. There will be many opportunities exist for further research and the advancement of three-dimensional printing in the field of tribology.

Influence of natural barytes purity levels on the tribological characteristics of non-asbestos brake pads

Abstract: This paper aims to deal with the effect of natural barytes purity levels on the tribological performance of brake pads.,In this study, brake pads were developed by varying three different natural barytes without varying other ingredients. The brake pads were developed as per the standard industrial practice. The physical, mechanical and thermal properties of the developed brake pads were tested as per the industrial standards. The tribological properties were analyzed using a full-scale inertia brake dynamometer. Worn surface analysis was done using scanning electron microscope coupled with elemental mapping.,The experimental results indicate that the brake pads filled with natural barytes 95% purity had good physical, chemical and mechanical properties with stable friction and less wear rate due to reduced impurity level preventing frictional undulations.,This paper explains the effect of the purity level of natural barytes in brake pads formulation to enhance the tribological performance by altering tribofilms and preventing friction undulations.

Numerical study on steady state performance enhancement of partial textured hydrodynamic journal bearing

Abstract: The purpose of this paper is to provide the various steady state parameters of hydrodynamic journal bearings have been determined to get maximum performance enhancement ratio. For this, the bearings inner surface is textured with triangular shape with different texture depths and a number of textures in pressure increasing region. The textured region acts as a lubricant reservoir, which provides additional film-thickness and reduce friction. Therefore, enhance the overall performance of bearing.,In the present study, the effect of triangular shaped texture on the static performance characteristics of a hydrodynamic journal bearing has been studied. Different values of texture depths and a number of textures have been numerically simulated in pressure developing region. The static performance characteristics have been calculated by solving the fluid flow governing Reynolds equation using the finite element method, assuming iso-viscous Newtonian fluid. The performance enhancement ratio, which is the ratio of load carrying capacity (LCC) to the coefficient of friction (COF) has been calculated from results to finalized optimum design parameters.,The paper provides numerically obtained results indicate that surface texturing can improve bearing performance if the textured region is placed in the pressure increasing region. Moreover, surface texturing is the most effective at bearing performance enhancement when the bearing operates at lower eccentricity ratios and texture depth. The performance enhancement ratio, which is the ratio of LCC to the COF is found to be a maximum value of 2.198 at texture depth of 1.5, eccentricity ratio of 0.2 and the textured region located in the increasing pressure region.,The present study is based on a numerical based research approach, which has its limitations. So, researchers are encouraged to investigate the same work experimentally.,The paper includes implications to be beneficial for designers for designing better hydrodynamic journal bearings.,For the triangular shaped texture, considered in the present study, the optimum values of texture depth and texture distribution region have also been determined. While designing, designers should focus on those values of texture depth, texture region and a number of textures, which give the maximum value of performance enhancement ratio, which represents maximum LCC at the lowest value of the COF.

On the mixed EHL characteristics, friction and flash temperature in helical gears with consideration of 3D surface roughness

Abstract: Purpose The purpose of this study is to investigate the tribological performance of helical gear pairs with consideration of the properties of non-Newtonian lubricant and the real three-dimensional (3D) topography of tooth flanks. Design/methodology/approach Based on the mixed elastohydrodynamic lubrication (EHL) theory for infinite line contact, this paper proposes a complete model for involute helical gear pairs considering the real 3D topography of tooth flanks and the properties of non-Newtonian lubricant. Film thickness, contact load and contact area ratios at the mid-point of contact line are studied for each angular displacement of pinion. Both the total friction coefficient and surface flash temperature are calculated after obtaining the values of pressure and subsurface stress. Then, the influences of input parameters including rotational speed and power are investigated. Findings During the meshing process, contact load ratio and area ratio of the two rough surface cases first increase and then decrease; the maximum flash temperature rise (MFTR) on the gear is lower than that on the pinion first, but later the situation converses. For cylindrical gears, on the plane of action, there is a point or a line where the instantaneous friction reduces to a minimum value in a sudden, as the sliding–rolling ratio becomes zero. When rotational speed increases, film thickness becomes larger, and meanwhile, contact load ratio, coefficient of friction and MFTR gradually reduce. Originality/value A comprehensive analysis is conducted and a computer program is developed for meshing geometry, kinematics, tooth contact, mixed EHL characteristics, friction, FTR and subsurface stress of involute helical gear pairs. Besides, a numerical simulation model is developed, which can be used to analyze mixed lubrication with 3D machined roughness under a wide range of operating conditions.

The dynamic performance analysis of chevron shape textured hydrodynamic bearings

Abstract: This paper aims to evaluate the various dynamic performance parameters of hydrodynamic journal bearings. For this, the bearing’s inner surface is textured with chevron-shaped textures with different texture depths and number of textures in different regions/locations.,In the present study, the effect of chevron-shaped texture having different values of texture depths, locations and number of textures has been numerically simulated. The dynamic performance characteristics have been calculated by solving the fluid flow governing Reynolds equation using the finite element method, assuming iso-viscous and Newtonian fluid.,The obtained results indicate that the bearing stability can be improved with the help of surface texture. Among all the investigated texture locations, the maximum increase in stability threshold speed is observed for fully textured distribution. Moreover, for the chevron-shaped texture considered in the present study, the optimum values of texture depth and number of textures have also been determined for maximum bearing stability.,While designing, designers should focus on those optimum values of texture depth, texture location and number of textures which lead to maximum enhancement in bearing stability.,This study is useful in the appropriate selection of chevron-shaped texture parameters on bearing surface for the maximum bearing stability.

Prediction of specific grinding forces and surface roughness in machining of AL6061-T6 alloy using ANFIS technique

Abstract: Purpose Optimisation of grinding processes involves enhancing the surface quality and reducing the cost of manufacturing through reduction of power consumptions. Recent research works have indicated the minimum quantity lubrication (MQL) system is used to achieve near dry machining of alloys and hard materials. This study aims to provide an experimental analysis of the grinding process during machining of aluminium alloy (Al6061-T6). MQL nanofluid was used as the lubricant for the grinding operations. The lubricant was formed by suspending silicon dioxide nanoparticles in canola vegetable oil. The effect of input parameters (i.e. nanoparticle concentration, depth of cut, air pressure and feed rate) on the grinding forces and surface quality was studied. Adaptive neuro-fuzzy inference system (ANFIS) prediction modelling was used to predict the specific normal force, specific tangential force and surface quality, the ANFIS models were found to have prediction accuracies of 97.4, 96.6 and 98.5 per cent, respectively. Further study shows that both the specific grinding forces and surface roughness are inversely proportional to the nanofluid concentration. Also, the depth of cut and table feed rate were found to have a directly proportional relationship with both the grinding forces and surface roughness. Moreover, higher MQL air pressure was found to offer better delivery of the atomised nanofluid into the grinding region. Design/methodology/approach Grinding experiments were performed using MQL nanofluid as the lubricant. The lubricant was formed by suspending silicon dioxide nanoparticles in canola vegetable oil. The effect of input parameters (i.e. nanoparticle concentration, depth of cut, air pressure and feed rate) on the grinding forces and surface quality has been studied. Findings The grinding process parameters were optimised using Taguchi S/N ratio analysis, whereas the prediction of the response parameters was done using ANFIS modelling technique. The developed ANFIS models for predicting the specific normal force, specific tangential force and surface quality were found to have prediction accuracies of 97.4, 96.6 and 98.5 per cent, respectively. Further findings show that both the specific grinding forces and surface roughness are inversely proportional to the percentage of nanoparticle concentration in the lubricant. Also, the depth of cut and table feed rate were found to exhibit a direct proportional relationship with both the grinding forces and surface roughness, while high MQL air pressure was observed to offer more efficient delivery of the atomised nanofluid into the grinding region. Practical implications The work can applied into manufacturing industries to prevent unnecessary trials and material wastages. Originality/value The purpose of this study is to develop an artificial intelligent model for predicting the outcomes of MQL grinding of the aluminium alloy material using ANFIS modelling technique.

Influence of positive texturing on friction and wear properties of piston ring-cylinder liner tribo pair under lubricated conditions

Abstract: In an internal combustion engine, piston ring-cylinder liner tribo pair is one among the most critical rubbing pairs. Most of the energy produced by an internal combustion engine is dissipated as frictional losses of which major portion is contributed by the piston ring-cylinder liner tribo pair. Hence, proper design of tribological parameters of piston ring-cylinder liner pair is essential and can effectively reduce the friction and wear, thereby improving the tribological performance of the engine. This paper aims to use surface texturing, an effective and feasible method, to improve the tribological performance of piston ring-cylinder liner tribo pair.,In this paper, influence of positive texturing (protruding) on friction reduction and wear resistance of piston ring surfaces was studied. The square-shaped positive textures were fabricated on piston ring surface by chemical etching method, and the experiments were conducted with textured piston ring surfaces against un-textured cylinder liner surface on pin-on-disc apparatus by continuous supply of lubricant at the inlet of contact zone. The parameters varied in this study are area density and normal load at a constant sliding speed. A comparison was made between the tribological properties of textured and un-textured piston ring surfaces.,From the experimental results, the tribological performance of the textured piston ring-cylinder liner tribo pair was significantly improved over a un-textured tribo pair. A maximum friction reduction of 67.6 per cent and wear resistance of 81.6 per cent were observed with textured ring surfaces as compared to un-textured ring surfaces.,This experimental study is helpful for better understanding of the potency of positive texturing on friction reduction and wear resistance of piston ring-cylinder liner tribo pair under lubricated sliding conditions.

The influence of roughness distribution characteristic on the lubrication performance of textured cylinder liners

Abstract: Purpose The purpose of this paper is to investigate the coupling mechanism of the roughness distribution characteristic and surface textures on the cylinder liner. Design/methodology/approach The cylinder liner-piston ring lubrication model with non-Gaussian roughness distribution surface was proposed in this paper to find the optimum cylinder liner surface. The motored engine tests were carried out to verify the simulation results. Findings The calculation and experiment results show that the large negative skewness surface has the optimal lubrication performance in the un-textured liner, while in the textured liner, the small negative skewness surface is more appropriate, which means surface textures couple with small negative skewness surface can improve the lubrication performance. Originality/value Although there are some works related to liner surface roughness and textures, the combine of roughness distribution and surface textures is not usually taken into account. Therefore, this research is different from others, as the present model considers with real non-Gaussian roughness distribution liners.

Friction reduction in EHL contacts by surface microtexturing – tribological performance, manufacturing and tailored design

Abstract: Purpose This paper aims to derive tailor-made microtextures for elastohydrodynamically lubricated (EHL) contacts under consideration of manufacturing possibilities. Design/methodology/approach Component tests were used for the evaluation of the influence of surface texturing on the friction behavior in the cam/tappet contact. Furthermore, the manufacturing possibilities and limitations of a combined μEDM and micro coining process and the feasibility of integration into a forming process were studied. Finally, a methodology based on transient EHL simulations and a meta-model of optimal prognosis was exemplarily used for microtexture optimization. Findings It was found that surface texturing in EHL contacts with high amount of sliding is promising. Moreover, the combination of μEDM and micro coining and the integration into established production processes allow the manufacturing of microtextures with desirable structural parameters and sufficient accuracy. Originality/value This paper gives a holistic view on surface microtexturing over several phases of the product life cycle, from the design, over efficient manufacturing to application-related testing.

Life calculation of angular contact ball bearings for industrial robot RV reducer

Abstract: The purpose of this paper is to analyze the force and basic rating life of angular contact ball bearings of RV reducer under the actual operating condition.,Force analysis of angular contact ball bearing under the actual operating condition, calculate the axial, radial load and internal load distribution, calculate the basic rating life of angular contact ball bearing under variable load conditions.,The external load has a great influence on the radial load of angular contact ball bearing, further affecting the basic rating life of angular contact ball bearing, which is a great influence on the overall life of RV reducer under the condition of high frequency and heavy load.,This paper provides important ideas for the design and manufacture of RV reducer in theory and experiment technology.

Effect of MWCNTs/Talc powder nanoparticles on the tribological and thermal conductivity performance of calcium grease

Abstract: The purpose of this paper is to evaluate the influence of nanoparticles as an additive on the tribological properties of calcium grease.,The nano additives in this research are with different concentration of multi carbon nanotubes (MWCNTs) and Talc powder (1, 2, 3, 3 and 5 per cent). The ratio of MWCNTs to Talc powder is 1:1. The tribological properties of hyper MWCNTs/Talc powder to calcium grease were evaluated using a pin-on-disk wear testing. The results show that the nano additives MWCNTs/Talc to calcium grease exhibit good performance in anti-wear and friction reduction. The action mechanism was estimated through analysis of the worm surface with x-ray diffraction and transmission electron microscope.,The result indicates that boundary film mainly composed of MWCNT and Talc powder, and other organic compound was formed on the worm surface during the friction test. In addition, the wear rate and coefficient of friction of nanogreases have shown excellent improvement about 80.62 and 63.44 per cent, respectively, at 4 Wt.% of MWCNTs/Talc powder. Moreover, the thermal conductivity of nanogrease increased about 51.72 per cent.,This study describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.

MD simulation of stress-assisted nanometric cutting mechanism of 3C silicon carbide

Abstract: Purpose: This paper aims to reveal the mechanism for improving ductile machinability of 3C-silicon carbide (SiC) and associated cutting mechanism in stress-assisted nanometric cutting. Design/methodology/approach: Molecular dynamics simulation of nano-cutting 3C-SiC is carried out in this paper. The following two scenarios are considered: normal nanometric cutting of 3C-SiC; and stress-assisted nanometric cutting of 3C-SiC for comparison. Chip formation, phase transformation, dislocation activities and shear strain during nanometric cutting are analyzed. Findings: Negative rake angle can produce necessary hydrostatic stress to achieve ductile removal by the extrusion in ductile regime machining. In ductile-brittle transition, deformation mechanism of 3C-SiC is combination of plastic deformation dominated by dislocation activities and localization of shear deformation. When cutting depth is greater than 10 nm, material removal is mainly achieved by shear. Stress-assisted machining can lead to better quality of machined surface. However, there is a threshold for the applied stress to fully gain advantages offered by stress-assisted machining. Stress-assisted machining further enhances plastic deformation ability through the active dislocations’ movements. Originality/value: This work describes a stress-assisted machining method for improving the surface quality, which could improve 3C-SiC ductile machining ability.

Gear fault diagnosis based on a new wavelet adaptive threshold de-noising method

Abstract: Purpose This paper aims to explore a new wavelet adaptive threshold de-noising method to resolve the shortcomings of wavelet hard-threshold method and wavelet soft-threshold method, which are usually used in gear fault diagnosis. Design/methodology/approach A new threshold function and a new determined method of threshold for each layer are proposed. The principle and the implementation of the algorithm are given. The simulated signal and the measured gear fault signal are analyzed, and the obtained results are compared with those from wavelet soft-threshold method, wavelet hard-threshold method and wavelet modulus maximum method. Findings The presented wavelet adaptive threshold method overcomes the defects of the traditional wavelet threshold method, and it can effectively eliminate the noise hidden in the gear fault signal at different decomposition scales. It provides more accurate information for the further fault diagnosis. Originality/value A new threshold function is adopted and the multi-resolution unbiased risk estimation is used to determine the adaptive threshold, which overcomes the defect of the traditional wavelet method.

Simulation and measurement study of metro wheel wear based on the Archard model

Abstract: The purpose of this paper is to study the wear evolution of metro wheels under the conditions of different track sequences, track composition and vehicle load and then to predict wheel wear and to guide its maintenance.,By using the SIMPACK and MATLAB software, numerical simulation analysis of metro wheel wear is carried out based on Hertz theory, the FASTSIM algorithm and the Archard model. First of all, the vehicle dynamics model is established to calculate the motion relationship and external forces of wheel-rail in the SIMPACK software. Then, the normal force of wheel-rail is solved based on Hertz theory, and the tangential force of wheel-rail is calculated based on the FASTSIM algorithm through the MATLAB software. Next, in the MATLAB software, the wheel wear is calculated based on the Archard model, and a new wheel profile is obtained. Finally, the new wheel profile is re-input into the vehicle system dynamics model in the SIMPACK software to carry out cyclic calculation of wear.,The results show that the setting order of different curves has an obvious influence on wear when the proportion of the straight track and the curve is fixed. With the increase in running mileage, the severe wear zone is shifted from tread to flange root under the condition of the sequence-type track, but the wheel wear distribution is basically stable for the unit-type track, and their wear growth rates become closer. In the tracks with different straight-curved ratio, the more proportion the curved tracks occupy, the closer the severe wear zone is shifted to flange root. At the same time, an increase in weight of the vehicle load will aggravate the wheel wear, but it will not change the distribution of wheel wear. Compared with the measured data of one city B type metro in China, the numerical simulation results of wheel wear are nearly the same with the measured data.,These results will be helpful for metro tracks planning and can predict the trend of wheel wear, which has significant importance for the vehicle to do the repair operation. At the same time, the security risks of the vehicle are decreased economically and effectively.,At present, many scholars have studied the influence of metro tracks on wheel wear, but mainly focused on a straight line or a certain radius curve and neglected the influence of track sequence and track composition. This study is the first to examine the influence of track sequence on metro wheel wear by comparing the sequence-type track and unit-type track. The results show that the track sequence has a great influence on the wear distribution. At the same time, the influence of track composition on wheel wear is studied by comparing different straight-curve ratio tracks; therefore, wheel wear can be predicted integrally under different track conditions.

Simulation and experiment on pressure field characteristics of hydrostatic hydrodynamic hybrid thrust bearings

Abstract: This paper aims to improve the bearing capacity of hydrostatic thrust bearing under working conditions of high speed and heavy load; a new wedge-shaped structure opened on an edge of oil seal is put forward, the loss and insufficiency for hydrostatic bearing capacity are made up by using dynamic pressure, and then, hydrostatic hydrodynamic lubrication is realized.,Oil film three-dimensional models of unidirectional and bi-directional hydrostatic hydrodynamic oil pad are established by using UG. The oil film pressure fields of two kinds of oil pad are simulated by using ANSYS ICEM CFD and ANSYS CFX; the pressure fields distribution characteristics are obtained, and the effects of workbench rotary speed and bearing weight on pressure field are analyzed. Also, the experimental verification is made.,The results demonstrate that with an increase in workbench rotary speed, the oil film pressure of two kinds of hybrid oil pad increases gradually, and the maximum pressure of the bi-directional one accounts for 95 per cent of the unidirectional one when the load is constant. With an increase in load, the oil film pressure of two kinds of hybrid oil pad increases gradually, the difference between them is 9.4 per cent under the condition of load of 25 t when the rotary speed is constant.,The paper can provide theoretical basis for a structure design of hybrid thrust bearing under different rotary speed and load conditions, and compensate the shortage of static pressure-bearing capacity by using dynamic pressure, improve the stability of vertical CNC machining equipment.

The tribological performance of engineered micro-surface topography by picosecond laser on PEEK

Abstract: The purpose of this study is to investigate the effect of engineered micro-structures on the tribological properties of metal-polyetheretherketone (PEEK) surface.,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.,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.,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.

Tribological properties of ultrahigh-molecular-weight polyethylene (UHMWPE) composites reinforced with different contents of glass and carbon fibers

Abstract: This purpose of this study was to investigate the effects of carbon fiber (CF) and/or glass fiber (GF) fillers on the tribological behaviors of ultrahigh-molecular-weight polyethylene (UHMWPE) composites to develop a high-performance water-lubricated journal bearing material.,Tribological tests were conducted using a pin-on-disc tribometer using polished GCr15 steel pins against the UHMWPE composite discs under dry conditions with a contact pressure of 15 MPa and a sliding speed of 0.15 m/s. Scanning electron microscopy, laser 3D micro-imaging profile measurements and energy-dispersive X-ray spectrometry were used to analyze the morphologies and elemental distributions of the worn surfaces.,The results showed that hybrid CF and GF fillers effectively improved the wear resistance of the composites. The fiber fillers decreased the contact area, promoted transfer from the polymers and decreased the interlocking and plowing of material pairs, which contributed to the reduction of both the friction coefficient and the wear rate.,The UHMWPE composite containing 12.5 Wt.% CF and 12.5 Wt.% GF showed the best wear resistance of 2.61 × 10−5 mm3/(N·m) and the lower friction coefficient of 0.12 under heavy loading. In addition, the fillers changed the worn surface morphology and the wear mechanism of the composites.

Experimental study on the friction stability of paper-based clutches concerning groove patterns

Abstract: This paper aims to study and compare the friction stability of wet paper-based clutches with regard to the radial grooves (RG) and waffle grooves (WG).,This paper presents an experimental study of a wet clutch concerning the effect of groove patterns on the friction torque and surface temperature. The friction stabilities of RG and WG are investigated with the applied pressure, rotating speed and automatic transmission fluid (ATF) temperature taken into consideration.,The friction torque and surface temperature of WG are larger than those of RG under the same operating condition. The friction torque difference between RG and WG grows with the increase of applied pressure and narrows with the increase of ATF temperature. Additionally, their temperature difference expands via increasing the rotating speed and ATF temperature or reducing the applied pressure; in this way, not only the variable coefficient difference between RG and WG can be narrowed, but also the friction stability of the clutch can be improved dramatically.,This paper explains the thermodynamic differences between RG and WG; moreover, it is verified experimentally that WG has a better friction stability than RG.