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The purpose of this study is to establish an effective method for characterizing the tribological properties of friction brakes during continuous braking because they have direct influences on the reliable operation of transport vehicles and industrial equipments.

First, tribological tests were carried out with the X-DM type friction tester, and changing curves of friction coefficient and temperature were obtained. Second, a novel tribological characteristic parameter set characterizing the tribological properties of brake pair in continuous braking was extracted from some important experimental data such as friction coefficient, wear rate and temperature. Finally, the influence of law and mechanism of braking number on dynamic tribological parameters was studied through continuous braking experiments.

The extracted tribological characteristic parameter set includes two subsets: dynamic characteristic parameter subset and overall characteristic parameter subset, which is composed of ten parameters: dynamic parameters of friction coefficient (including average, trend coefficient and stability coefficient), dynamic wear rate, dynamic average temperature, dynamic temperature rise, overall average friction coefficient, overall wear rate, overall average temperature and overall temperature rise.

Conclusively, the novel tribological characteristic parameter set is more comprehensive and objective, and it can provide a theoretical basis for the study of tribological properties in continuous braking.

This study aims to explore the superiority of the compound dimple (e.g. the rectangular-rectangular dimple) and compare its tribological performance for rough parallel surfaces with those of the traditional one-layer dimple (simple dimple).

A mixed-lubrication model for a rough textured surface is established and solved using the finite difference method for film pressure and contact pressure. To accelerate the evaluation of surface deformation, the efficient Continuous convolution fast Fourier transform algorithm is applied. The effects of the compound dimple on the tribological performance for the rough parallel surfaces is numerically investigated. And these effects are compared with those of the simple dimple. Furthermore, a reciprocating friction test is conducted to verify the superiority of the compound dimple.

The compound dimple exhibits better tribological performances in comparison with the traditional simple dimple, that is, a larger load-carrying capacity and a smaller friction coefficient. To achieve the best tribological performances for the rough parallel surfaces, the depth ratio of the lower pore to the total pore of the compound dimple and the dimple interval should be reasonably chosen. For the surface with compound dimples, there exists an optimal surface roughness to simultaneously maximize the load-carrying capacity and minimize the friction coefficient. The smaller friction coefficient of the surface with compound dimples is verified by the reciprocating friction test.

The compound dimple is proposed and the superiority of this novel surface texture is confirmed. This study is expected to provide a new texturing method to improve the tribological performances of the traditional simple dimple.

The purpose of this study is to evaluate the potentials of nano-additives in enhancement of oxidation and thermal stability of biolubricants thereby, improving the resistance of dispersed nanolubricants to thermal degradation under elevated temperature.

This study evaluates the oxidation stability and tribological performance of nano-enhanced biolubricants. Graphene and maghemite nanoparticles at 0.1% volume concentration were dispersed into coconut oil. Oxidation stability was analysed using a thermal analyser to understand the effect of nano-additives on thermal degradation of lubricants under increasing temperature. In addition, tribological performance and viscosity of the tested lubricants were evaluated using a four-ball friction tester and viscometer according to American Society for Testing and Materials standards.

The results reveal that the oxidation stability of biolubricants dispersed with nano-additives improves due to delayed thermal degradation. The nano-enhanced biolubricants’ oxidation onset temperature was delayed by 18.75 °C and 37.5 °C, respectively, for maghemite (MGCO) and graphene (XGCO) nanolubricants. This improvement imparts the performance viscosity and tribological performance positively. For graphene-enhanced nanolubricant, 10.4% and 5.6% were reduced, respectively, in coefficient of friction (COF)and wear scar diameter (WSD), whereas 3.43% and 4.3% reduction in COF and WSD, respectively, for maghemite-enhanced nanolubricant compared with coconut oil. The viscosity index of nanolubricants was augmented by 7.36% and 13.85%, respectively, for maghemite and graphene nanolubricants.

The excellent performance of nanolubricants makes them suitable candidate as sustainable lubricants for machining with regard to environmental benefits and energy saving.

The effect of graphene and maghemite nanoparticles on the oxidation stability and tribological performance of biolubricants has been investigated. It is an original work and yet to be published elsewhere.

Water-lubricated bearings can significantly reduce the pollution to environment because the traditional oil lubricant is replaced by water in the bearings. The ultrahigh molecular weight polyethylene (UHMWPE) has proven to be effective and reliable for the manufacturing of water-lubricated bearings. However, limited work has been done to address the improvement of the tribological performance of the UHMWPE-based water-lubricated bearings using surface texture processing. This paper aims to investigate the effects of bar-grooved surface on the tribological performance improvement of UHMWPE-based water-lubricated bearings.

For the first time, the bar grooves were processed on the surfaces of UHMWPE-based water-lubricated bearings. The CBZ-1 friction and wear tester have been used to test the wear and friction performance of the bearing samples. The LI laser interference surface contour graph and the digital microscope have been used to measure the surface morphology of the specimens. The tribological characteristics of the tested bearings were analyzed.

With bar grooves added on the surfaces of the specimens, the friction coefficient of the specimens were lower than that of the specimens without surface texture processing; the wear quantity of the two kinds of specimens were almost the same; by using the LI laser interference surface contour graph and the digital microscope to measure the surface morphology of the specimens, the furrows of the specimens with bar grooves were narrower and shallower than that of the specimens without bar grooves.

The paper implicates that the surface texture processing using bar grooves can reduce the friction coefficient and prolong the service life of the water-lubricated bearings in practical applications.

This paper fulfills an identified need to provide important theoretical and experimental support to the design of water-lubricated bearings in practical applications.

This study aims to improve the tribological performance of Babbitt alloy under oil lubricant condition. Thus, the surface was treated into oleophobic state by modifying with low surface energy fluorosilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane). It is believed that the oleophobic surface offered excellent wear resistance of Babbitt-based tribo-pairs.

By modifying the Babbitt alloy with low surface energy fluorosilane and measuring the oil contact angle, the wetting behavior was evaluated. Using Pin on Disk tribometer, the tribological properties of bare Babbitt and modified Babbitt were quantified. The samples after the friction test were characterized by scanning electron microscope (SEM) and the anti-wear performance was evaluated under dry and oil lubrication conditions.

Results showed that oil contact angle of modified Babbitt was109° which was tripled compared to that of prime surface, which indicates the oleophobic behavior was greatly improved. Under dry conditions, the friction coefficient of the modified surface with different load conditions is slightly lower than that of the bare surface, while the friction coefficient of the modified surface under lubrication conditions is significantly decreased compared to that of the bare surface. Interestingly, under low load and high load, the wear rate of the modified Babbitt alloy surface is only 1/4 and 1/3 of that of the bare surface, respectively.

The work proposed an effective method to improve the Babbitt tribological performances and will lighten future ideas for the Babbitt alloy bearing with high wear resistance, which is beneficial to improve the service life of sliding bearings and has huge promotion and application value in the manufacture of sliding bearings.

This paper aims to investigate the tribological performance, i.e. abrasion resistance, friction coefficient and wear rates, of self-lubricated water conditioned polyamide6/boric oxide composites.

Polyamide6 and polyamide6/boric oxide self-lubricated composites were immersed in water for 15 days to analyze the effect of water conditioning on friction, wear and abrasion resistance. Tribological testing on pin-on-disc tribometer and abrasion resistance testing on TABER abrader were performed to see the friction coefficient and wear rates of materials. The scanning electron microscopy (SEM) characterizations were performed to analyze the wear tracks.

Tribological testing results revealed the loss in abrasive resistance, but there was an improvement in frictional coefficient and wear rates with steel after water absorption. The SEM images clearly show less depth of wear tracks in water-conditioned materials than dry ones. Water conditioning was found supportive in the formation of smooth lubricating transfer film on steel disc during the tribological testing.

The tribological behaviour of polymer composites is different in dry and in high humidity or water conditions. Experiments were performed to investigate B₂O₃ solid lubricant filler effectiveness on tribological behaviour of water-conditioned polyamide composites. Bonding between polyamide6 and water molecules plus the formation of orthoboric acid was found advantageous in decreasing the friction coefficient and wear rates of composites.

This study aims to investigate the behavior of vegetable oil with two additives. Base oil’s tribological qualities can be improved with the help of several additions. In the present investigation, soybean oil is served as the foundational oil due to its eco-friendliness and status as a vegetable oil with two additives, named polytetrafluoroethylene (PTFE) and molybdenum disulfide (MoS₂).

As additives, PTFE and MoS₂ are used; PTFE is renowned for its anti-friction (AF) properties, while MoS₂ is a solid lubricant with anti-wear (AW) properties. This investigation examines the synergistic impact of AF and AW additions in vegetable oil. The lubricity of the base oil is measured by using a four-ball tester, and the wear properties of the oil at different additive amounts are determined by using a universal tribometer.

PTFE (at 5 Wt.%) and MoS₂ (at 1 Wt.%) were found to improve the tribological performance of the base oil. The weld load is significantly increased when 5 Wt.% of PTFE + MoS₂ is added to the base oil.

A better tribological characteristic can be achieved by combining additives that amount to less than 1% of the base oil. In experiments with highly concentrated MoS₂, the adequate pressure improved dramatically, but the lubricant’s tribological characteristics did not.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0321/

This paper aims to clarify the size and morphology of transition metal dichalcogenides has an impact on lubrication performance of Cu-based composites. This study is intended to show that Cu-based electrical contact materials containing Nb_0.91Ti0.09Se₂ have better electrical and tribological properties than those containing NbSe₂. The tribological properties of Cu-based with different Ti-dopped NbSe₂ content were also discussed.

The NbSe₂ and Nb_0.91Ti_0.09Se₂ particles were fabricated by thermal solid state reaction method. The powder metallurgy technique was used to fabricate composites with varying Nb_0.91Ti_0.09Se₂ mass fraction. The phase composition of Cu-based composites was identified by X-ray diffraction, and the morphology of NbSe₂/Nb_0.91Ti_0.09Se₂ and the worn surface of composites were characterized by scanning electron microscopy and transmission electron microscopy. In addition, the tribological properties of composites were appraised using a ball-on-disk multi-functional tribometer. The data of friction coefficient and resistivity were analyzed and the corresponding conclusion was drawn.

In comparison with the pure copper, Cu-based composites containing Nb_0.91Ti_0.09Se₂/NbSe₂ had a lower friction coefficient, illustrating the Nb_0.91Ti_0.09Se₂ with nano-size particles prepared in this work is a perfect choice for the fabrication of excellent electrical contact composites. Compared to composites with NbSe₂, composites containing Nb_0.91Ti_0.09Se₂ have better tribological and electrical properties.

Because of the use of thermal solid state reaction method, the size of NbSe₂ and Nb_0.91Ti_0.09Se₂ is relatively large. Therefore, the fabrication of finer particles of Nb_0.91Ti_0.09Se₂ is encouraged.

In this paper, the authors discuss the tribological and electrical properties of Cu-based composites, and the value of optimum obtained as Nb_0.91Ti_0.09Se₂ content is 15 Wt.%.

The involvement of wear, friction and lubrication in engineering systems and industrial applications makes it imperative to study the various aspects of tribology in relation with advanced technologies and concepts. The concept of Industry 4.0 and its implementation further faces a lot of barriers, particularly in developing economies. Real-time and reliable data is an important enabler for the implementation of the concept of Industry 4.0. For availability of reliable and real-time data about various tribological systems is crucial in applying the various concepts of Industry 4.0. This paper aims to attempt to highlight the role of sensors related to friction, wear and lubrication in implementing Industry 4.0 in various tribology-related industries and equipment.

A through literature review has been done to study the interrelationships between the availability of tribology-related data and implementation of Industry 4.0 are also discussed. Relevant and recent research papers from prominent databases have been included. A detailed overview about the various types of sensors used in generating tribological data is also presented. Some studies related to the application of machine learning and artificial intelligence (AI) are also included in the paper. A discussion on fault diagnosis and cyber physical systems in connection with tribology has also been included.

Industry 4.0 and tribology are interconnected through various means and the various pillars of Industry 4.0 such as big data, AI can effectively be implemented in various tribological systems. Data is an important parameter in the effective application of concepts of Industry 4.0 in the tribological environment. Sensors have a vital role to play in the implementation of Industry 4.0 in tribological systems. Determining the machine health, carrying out maintenance in off-shore and remote mechanical systems is possible by applying online-real-time data acquisition.

The paper tries to relate the pillars of Industry 4.0 with various aspects of tribology. The paper is a first of its kind wherein the interdisciplinary field of tribology has been linked with Industry 4.0. The paper also highlights the role of sensors in generating tribological data related to the critical parameters, such as wear rate, coefficient of friction, surface roughness which is critical in implementing the various pillars of Industry 4.0.

The purpose of this study is to evaluate the effect of water contamination on ageing of lubricants.

The viscosity, total acid number and Fourier transform infrared spectrum of a series of lubricants after ageing with water were studied. The tribological performance (friction and wear) of the aged lubricants was also analyzed, followed by X-ray photoelectron spectroscopy analysis on the selected post test samples to study the tribochemical features of the tribofilm.

The results were also compared with Part I of this study, and it was found that ageing has a different impact on lubricants and tribological performances based on the physical and chemical properties when water is present in the lubricants.

This paper is a continuation of Part I of this study and gives an understanding on the impact of water on the lubricants and related tribological and tribochemical performance.