Reduction In Friction Coefficient Research Articles

The optimization design for the journal-thrust couple bearing surface texture based on particle swarm algorithm

Journal-thrust coupled bearings (JTC bearings), unlike conventional journal or thrust bearings, require consideration of both reducing friction coefficient in the journal part while increasing the load-carrying capacity in the thrust part during lubrication design. This study established a thermal-elastohydrodynamic mixed lubrication model for JTC bearings considering flow, pressure, and thermal continuity conditions, validated through experiments. Based on this, the influence of texture parameters on lubrication under real heavy load conditions was preliminarily investigated. The orthogonal test design was then used to determine the texture parameter that had the greatest impact on optimization. Subsequently, particle swarm optimization (PSO) algorithm was employed for synchronous optimization design of textures for both journal and thrust parts.

Oleogel Microsphere‐Based Composite Protective Coatings with Room‐Temperature Self‐Healing Enabled by a “Soft + Hard” Hybrid Architecture

AbstractIntrinsically self‐healing coatings are compelling candidates for highly reliable anti‐corrosion technologies because of their easy implementation, low cost, and repeatable self‐healing. However, most of these coatings require intervention to initiate healing due to the locking of their chain segments under ambient conditions (to provide sufficient mechanical strength). Herein, a “soft + hard” hybrid architecture strategy of preparing oleogel‐based protective coatings with room‐temperature and repeatable self‐healing is proposed by embedding “soft” self‐healing and viscoelastic oleogel microspheres (OMs) in “hard” waterborne epoxy matrix. Such a decoupled design affords both instantaneous healing without external stimuli (crack narrowing within 10 min and protection recovered within 5 h) and good mechanical properties (improved wear resistance with an 80% reduction in friction coefficient, a 63% reduction in wear volume, as well as a maintained adhesion strength of 96%). The slippery and hydrophobic OMs also bring anti‐biofouling, interfacial water repellency, and inhibitor loading‐release features, leading to coatings with superior corrosion protection (>1010 Ω cm2 impedance modulus throughout 110 d) rather than just their self‐healing. This work demonstrates a feasible approach to integrating room‐temperature repeatable self‐healing and sufficient mechanical strength in future coating design.

Tribological and mechanical characterization of glass fiber polyamide composites under hydrothermal aging

Polymer composites are increasingly used in applications where they are subjected to abrasive wear. The bulk of prior research has focused on the performance of polymers under sliding wear conditions and in some cases resulted in a contradiction, particularly when it comes to the effect of reinforcing fibers on the wear performance. Another omission is the absence of pre-conditioning or accelerated aging which is clearly an important factor from an application standpoint. This work aims to highlight the influence of hydrothermal aging on the tribological and mechanical performance of polyamide 6 (PA6) and glass fiber-reinforced polyamide 6 (PA6-GF). The friction and abrasion wear behavior of unconditioned and conditioned PA6 and PA6-GF composites are measured against silicon carbide grinding paper on a pin-on-disk tribometer in a demineralized water medium at 60 °C. Specimens are conditioned in demineralized water at room temperature (RT) 25, 40, and 60 °C to investigate the effects of moisture and temperature. The presence of up to 25 wt.% glass fiber (GF) in PA6-based composites exhibits an increasing trend in abrasion wear mass loss and a reduction in coefficient of friction (COF). Interestingly, the mass loss of specimens conditioned to saturation does not increase compared to that of unconditioned samples. The FTIR spectroscopy is used to study the polymer degradation during hydrothermal aging.

A comparative study of the tribological performance of two oil-soluble ionic liquids as replacements for ZDDP (T204) additives in lubricants

Sustainable transportation requires energy-efficient automotive oils, and producing lubricant with more effective additives is the goal. This study investigates alternative oil-soluble ionic liquids (ILs) as substitutes for ZDDP additives in automotive gear lubricant (85 W/90) to mitigate environmental impacts. Herein, two novel halogen-free Gemini ILs (N16-2-16P4 and N16-2-16P8) were synthesized. The current study used zinc isopropyl-isooctyl-dithiophosphate (T204) at a 1 wt% concentration in 85 W/90 oil to compare the tribological and physicochemical properties of ILs. The tribological data indicate that the N16-2-16P4 and N16-2-16P8 additives reduce friction coefficient and wear volume by 9–12 % and 7–28 %, respectively, compared to the T204 additive. Eventually, this study presents ILs as eco-friendly oil additives in vehicles and mechanical systems.

Utilizing photodeposition to fabricate micro-nano structured microcapsules for enhancing mechanical and high-temperature tribological performance of fabric composites

Fabric composite materials face significant challenges in maintaining excellent tribological properties at high temperatures. This study employed photodeposition to deposit gold (Au) and copper (Cu) nanoparticles on the surface of titanium dioxide-coated jojoba oil microcapsules (TiO2 @jojoba), yielding micro-nanostructured Au-TiO2 @jojoba and Cu-TiO2 @jojoba microcapsules. Subsequently, microcapsules participated in the in-situ polymerization of polyimide (PI), serving as crosslinking points in PEEK/PTFE fabric-reinforced composites. PEEK/PTFE-Au composites containing Au-TiO2 @jojoba microcapsules exhibited outstanding tribological and mechanical properties. Compared to microcapsule-free samples, PEEK/PTFE-Au composites showed a 30.26 % reduction in friction coefficient at 250 °C and a 24.28 % increase in tensile strength. In addition, mechanistic studies indicated that TiO2 underwent a friction chemical reaction converting to TiNF during friction accompanying by friction-induced phase transitions. The release of jojoba oil during friction and the occurrence of friction chemical reactions were the main friction reduction mechanisms of PEEK/PTFE-Au composites at high temperatures.

Superior strength and wear resistance of mechanically deformed High-Mn TWIP steel

In the present study, the mechanical and wear behaviour of the surface-mechanically treated high-manganese (high-Mn) twinning-induced plasticity (TWIP) steel were investigated. The TWIP alloy was first designed and fabricated via surface-mechanical attrition treatment (SMAT) system and the mechanical properties including strength, wear behaviour as well as the microstructural evolution were thereafter determined. Transmission electron microscopy (TEM) characterization revealed a typical dislocation as a result of the surface treatment as well as the formation of twin layers with a reduced stacking fault energy (SFE). Due to the ultra-fine grain refinement caused by plastic deformation during surface treatment, a microhardness value of 489 HV can be obtained after treatment. Likewise, the yield strength of the high-Mn TWIP steel could be enhanced from 360 MPa to 813 MPa and a reduction in elongation to failure of about 20 % can be achieved. The wear test showed that the treated TWIP steel possessed a reduced friction coefficient and improved wear resistance at different testing loads, attributed to the nanoscale refinement of grains induced during treatment. The strength, hardness, and wear resistance of the fabricated TWIP alloy improves significantly, thanks to surface treatment by SMAT.

Improved wear and friction properties by self-formed SiC layers in Mg/SiC composites

The tribological properties are evaluated using several types of Mg/SiC composites, which SiC powders with particle sizes of 20∼30 nm, 130 nm and 2∼3 μm are dispersed in up to 25 % by volume fraction. Sound and bulky Mg/SiC composites are successfully fabricated by powder-metallurgy combining extrusion process. The initial SiC particle size and their dispersed volume fraction affect the wear and friction properties. The specific wear rate increases with increasing contents of SiC particles, regardless of the initial SiC particle size. However, when the SiC particle size is larger than a certain size and its content is greater than 10 %, the friction coefficient suddenly decreases. In the surface observations after friction tested specimens, the element mapping image shows the Mg ratio relative to Si ratio (=SiC) increases with reducing friction coefficient. This indicates that good wear resistance is due to the presence of self-formed SiC layers during the friction process.

An atomic-scale insight into mechanical enhancement and frictional properties of amorphous/graphene multilayers

This study utilizes molecular dynamics simulation to explore the mechanical and friction properties of CuTa/Graphene A/GR multilayers during nanoscratching. By investigating the influence of amorphous layer thickness, substrate temperature, and scratching speed valuable insights into scratching behaviors are gained. Reducing the amorphous layer thickness enhances the normal force and contact pressure, effectively strengthening the A/GR multilayer, while decreasing the frictional force owing to the lubricating properties of graphene, resulting in a notable reduction in friction coefficient. Analysis of the deformation mechanism reveals that the graphene layer impedes shear band propagation, especially noticeable at thinner amorphous layer thicknesses. Additionally, the A/GR multilayer exhibits outstanding wear resistance at high temperature and speed, as indicated by a slightly increased wear atomic ratio.

Simple and facile fabrication of carboxymethylated cellulose nanofibrils one-side-coated cotton non-woven fabrics for beauty facial mask sheets

In this study, we developed eco-friendly beauty facial mask sheets with improved absorbency and performance using a simple textile finishing process. Carboxymethyl cellulose nanofibrils (c-CNFs) were bar-coated onto cotton non-woven fabrics (COFs), transforming them into sheet-shaped structures. The resulting sheets exhibited enhanced tensile strength, water absorption, and durability. The weight of the sheets increased proportionally with the amount of coated c-CNFs, while their thickness decreased due to compression during the process. The addition of c-CNFs improved absorption capabilities, despite the formation of a non-porous structure. Furthermore, the sheets demonstrated longer drying times, reduced friction coefficients, and improved mechanical properties. Cytotoxicity evaluation confirmed the biocompatibility of the sheets. This study highlights the feasibility of producing eco-friendly beauty facial mask sheets with enhanced performance through a simplified textile finishing process using c-CNFs, offering potential applications in the cosmetics industry.

Evaluation of the effects of the application of Ti−C:H DLC coatings obtained by PVD techniques in the kinematic pairs of internal combustion engines and powertrain systems.

The article attempts to analyze the possible effects of using Ti−C:H DLC carbon coatings produced by pulsed magnetron sputtering (PVD) to reduce friction coefficient and wear in kinematic pairs found in internal combustion engines and powertrain systems used in automotive vehicles. The aim of such action is primarily to reduce internal losses in the aforementioned units. The coatings were deposited on heat-treated bearing steel 100Cr6, examined using a scanning electron microscope FEI Quanta 200 Mark II with the chemical analyzer EDS EDAX Genesis XM 2i, tribotester T−01M examining the friction coefficient in the ball-disc correlation and Hommel Werke T8000 profilometers, additionally, in order to check the coating thickness, studies were carried out using the Calotest method. The results obtained indicate that both the friction coefficient and wear are drastically reduced in relation to samples on which no DLC coatings were applied.

The influence of laser texturing on the tribological behavior of titanium alloy Ti6Al4V in medical applications

This paper analyzes the tribological behavior of the Ti6Al4V ELI alloy subjected to laser texturization for medical purposes. Laser texturing enables one to observe specific patterns of the material surface at established depths. Microtexturing of the samples was performed using a 355 nm picosecond laser. The influence of the microtexturing process (depending on the process parameters) on the geometric parameters of the proposed laser texturing pattern was evaluated. Selected samples were subjected to tribological testing using the ball-on-plate technique in dry and lubricant-sliding methods (in Ringer solution). The wear properties were evaluated by comparing the coefficient friction, wear volumes, and wear ratio. A scanning electron microscope characterized the morphologies of the wear scar and the wear mechanism. The experimental results show that the surface texturing and the changes in microgrooves can reduce wear. The results indicate, that samples after laser texturing were characterized by 15% higher microhardness, compared to those in the initial state. It was found, a 26% reduction in friction coefficient and 29% in the wear volume compared to the smooth, untextured surface samples under lubricated conditions. The decrease in value of the coefficient friction and wear volume for the samples after the laser texturing process is an effect of synergistic of entrapped wear debris in micro-grooves and increased hardness for samples after laser textured.

Investigation of agricultural waste and ZrB2 nanoparticles with reinforcement in aluminum alloy matrix

Agricultural waste has the potential to serve several purposes, such as reinforcement. In recent times, researchers have incorporated agricultural waste into various materials with the aim of enhancing their qualities. By acting as a kind of reinforcement, it has the potential to decrease the quantity of agricultural waste that needs further processing. This work enhances the area of advanced materials by examining the characteristics of Al 7175 alloy reinforced with zirconium diboride (ZrB2) nanoparticles and rice husk ash, which is a byproduct of agriculture. Understanding and improving the wear resistance of composites is crucial in several industrial applications. This study involves the incorporation of ZrB2 nanoparticles into the Al 7175 alloy at three distinct concentrations, with the addition of 2.5 % rice husk. This study examines the correlation between wear parameters and responses (Cf), including friction force (FF), wear rate (Sf), and friction coefficient. Sliding distance, load, composition, and speed are among the wear parameters. The aforementioned combinations result in a load of 25.2 N, a rotational speed of 400 rpm, a sliding distance of 71.2 m, and a composition of 5 %. Taguchi signal-to-noise ratio (SNR) analysis is used to identify optimal combinations for minimizing Cf, Sf, and FF. Confirmation tests are conducted in order to ensure that the results align with the expected optimal combinations. Data scientists may also use an Artificial Neural Network (ANN) model as a valuable tool. It utilizes input data to forecast replies. The ANN model demonstrates strong performance throughout testing, validation, and training, with an overall prediction rate of 87.873 %. The study's results indicate that reducing the load and speed, while increasing the concentration of ZrB2 nanoparticles, may effectively decrease the wear rate. In addition, the use of rice husk enhances the wear resistance of the base alloy by 28 %. The alloy Al 7175 may experience a reduction in wear rate and friction coefficients by the incorporation of 2.5 % rice husk and 5 % ZrB2 nanoparticles.

Surface wettability and tribological performance of Ni-based nanocomposite moulds against polymer materials

In the mass-production of microfluidic devices through micro hot embossing/injection moulding, the longevity of mould inserts is influenced by elevated adhesion and friction between the polymer and the mould. Thus, accurate prediction of mould lifespan requires a comprehensive understanding of surface wettability and tribological performance during polymer contact. The current study addresses this gap by characterizing fabricated micro-structured Ni, Ni-WS2, and Ni-PTFE nanocomposite moulds (surface morphologies, crystal structures and microhardness) to investigate inherent lubrication mechanisms. Surface wettability of mould material was systematically studied by measuring the contact angles with eight different polymer melts. Pin-on-disk tests with polymer pins made of cyclic olefin copolymer (COC 8007), polypropylene (PP), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were conducted to elucidate the wear resistance of the nanocomposite moulds. Pressure-dependent friction coefficient and wear resistance were further explored under increasing external loads, simulating the actual moulding processes where contact pressure may vary considerably depending on the part shape. Results indicate that Ni-WS2 exhibits the highest microhardness (532 Hv), followed by Ni-PTFE (465 Hv) and Ni (198 Hv). Notably, Ni-PTFE demonstrates exceptional hydrophobicity against all polymer melts, signifying low surface energy during polymer contact. Moreover, both nanocomposite moulds exhibit reduced friction coefficients and enhanced wear resistance across various polymers. Counterintuitively, despite its lower hardness, the Ni-PTFE mould displays superior wear resistance against the COC pin under higher loads, while the Ni-WS2 mould experiences severe adhesive wear, as observed from wear morphology and profile analysis. This finding establishes the Ni-PTFE as a promising alternative as a mould insert material for precision manufacturing.

Micro-structural, electrical, and tribological properties of SiC/DLC composite coating grown by PLD on steel

Protective diamond-like carbon (DLC) composite coating was grown on cylindrical steel surface in a simple inclined pulsed laser deposition (PLD) process. Based on this kind of flexible film-synthesis method, mixed deposition was used to generate the gradient interface that could enhance adhesive strength in Ti/SiC interface, and periodic SiC/DLC layers were grown to reduce residual stress of the pure DLC film. This kind of PLD-grown SiC/DLC composite coating on the curved thin steel that was imitated as piston cylinder showed excellent adhesive property and toughness. Compared with the bare steel, DLC-filmed steel strip had a much lower friction coefficient, higher nano-hardness, and enhanced elastic modulus. Raman spectroscopies showed transform of the micro-structure in DLC layers during friction process, revealing the important reason for reducing friction coefficient. Electrical conductivity test displayed the DLC-filmed steel strip was in high resistance state, although its thickness was only 1.27 μm. Further on, good adhesive strength, excellent toughness and high resistance state of SiC/DLC composite coating could be applied in the MEMS advices.

An Experimental Study to Assessing the Efficacy of Oil to Prevent Differential Stuck Pipe Incidents in Zubair Oil Field, Southern Iraq

This study focuses on the important role of drilling mud in successful drilling operations, particularly in preventing and treating differential stuck pipes. Differential pipe sticking (DSP) is a common challenge when drilling through a pay zone with water-based drilling mud containing bentonite clay. However, using oil as an additive in a water-based mud (WBM) system offers distinct advantages and can significantly improve drilling performance. The research utilizes the Fann VG meter, a self-fabricated tester, and a tester of stickance to investigate the impact of oil on water-based drilling mud (WBM) and controlling DSP to address this challenge. The empirical study demonstrates that adding oil to the drilling fluid enables it to maintain its rheological properties (PV, YP, and API fluid loss) while reducing filtration loss from 7 to 4.8 cc and friction coefficient from 0.30 to 0.05. This indicates that emulsion mud can mitigate the risks of differential sticking by maintaining the oil concentration within the recommended limit (not exceeding 3%). Balancing the maintenance of rheological properties with the reduction of friction coefficient is essential to reaching optimal drilling performance and preventing differential pipe sticking.

Atomic layer deposited TiO2 nanofilm on titanium implant for reduced the release of particles.

Objective: Titanium implants are widely used in surgeries for their biocompatibility and mechanical properties. However, excessive titanium particle release can cause implant failure. This study explores Atomic Layer Deposition (ALD) to coat commercially pure titanium (Cp-Ti) with TiO2, aiming to improve its frictional and corrosion resistance while reducing particle release. By comparing TiO2 films with varying ALD cycle numbers, we assess surface properties, particle release, friction, and corrosion performance, providing insights into mitigating particle release from implants. Methods: Cp-Ti surfaces were prepared and coated with TiO2 films of 100, 300, and 500 ALD cycles. Surface characterization involved SEM, EDX, and XRD. Friction was tested using SEM, nanoindentation, and ICP-MS. Corrosion resistance was evaluated through immersion tests and electrochemical analysis. Cytotoxicity was assessed using BMSCs. Results: Surface characterization revealed smoother surfaces with increased ALD cycles, confirming successful TiO2 deposition. Friction testing showed reduced friction coefficients with higher ALD cycles, supported by nanoindentation results. Corrosion resistance improved with increasing ALD cycles, as evidenced by electrochemical tests and reduced titanium release. Cytotoxicity studies showed no significant cytotoxic effects. Conclusion: ALD-coated TiO2 films significantly enhance frictional and corrosion resistance of titanium implants while reducing particle release. The study underscores the importance of ALD cycle numbers in optimizing film performance, offering insights for designing implants with improved properties.

Supramolecular self‐assembled nanoparticles for targeted therapy of myocardial infarction by enhancing cardiomyocyte mitophagy

AbstractMyocardial infarction accompanied by diabetes mellitus is accepted as the most serious type of coronary heart disease, and among the current treatment strategies, the precise delivery of protective drugs for inhibiting cardiomyocyte apoptosis is still a challenge. In this study, we developed a biodegradable nanoparticles‐based delivery system with excellent macrophage escape, cardiac targeting, and drug release properties to achieve targeted therapy of myocardial infarction. Specifically, a copolymer of p(DMA–MPC–CD) combining self‐adhesion, hydration lubrication, and targeting peptide binding site was successfully prepared by free radical copolymerization, and it was self‐assembled on the surface of melatonin‐loaded dendritic mesoporous silica nanoparticles (bMSNs) following the integration of adamantane‐modified cardiac homing peptide (CHP) based on supramolecular host–guest interaction. Importantly, a hydration layer formed around the zwitterionic phosphorylcholine groups of the multifunctional nanoparticles, which was confirmed by the enhancement in hydration lubrication and reduction in coefficient of friction, prevented the nanoparticles from phagocytosis by the macrophages. The in vivo bioluminescence imaging test indicated that the nanoparticles were endowed with satisfied cardiac targeting capability, and the in vivo mice study demonstrated that the intravenous injection of drug‐loaded nanoparticles (namely bMSNs–Mel@PDMC–CHP) effectively reduced cardiomyocyte apoptosis, alleviated myocardial interstitial fibrosis, and enhanced cardiac function.

Design of experiments coupled with Bayesian optimisation for nanolubricant formulation

Nanoparticle-enhanced lubricants (nanolubricants) achieve tribological properties that can signficantly outperform the unmodified base oil. However, this performance enhancement is known to be extremely senstive to the concentration of nanoparticles used. Here, we introduce a new approach to optimizing nanolubricants combining design of experiments (DOE) with machine learning, addressing the challenge of determining optimal nanoparticle concentration in base oils and demonstrating significant performance improvements. Combining Box-Behnken design with Bayesian optimization, we identify an optimal concentration of 0.04 wt% copper oxide (CuO) nanoparticles in a standard engine oil (SAE 20W50), resulting in a 42% reduction in coefficient of friction (COF) relative to the base oil. Surface analysis (AFM, SEM) confirmed improvement of anti-wear and anti-friction characteristics. Signficant enhacements of thermophysical properties were observed (demonstrated by increased flash and pour points, by 10% and 7% respectively), signifying greater thermal stability. The dynamic viscosity remained consistent, with a beneficial reduction observed under conditions of high temperature and shear, which aligns with the demands of engine lubricant standards for PC-12B oils, with a reduction from 3.49 to 3.18 cP (8%). This research introduces a novel hybrid optimization technique that provides a versatile framework for optimizing nanofluids, addressing the critical challenge of determining optimal nanoparticle concentration.

Two types of quaking and shear unjamming: State diagram for soft granular particles in quasistatic shear

Understanding intermittency, a ubiquitous behavior in flows of packed grains, is pivotal for establishing the rheology of granular matter. A straightforward explanation has been missing despite the long development of theories at various levels of abstraction. Here, we propose the use of a Stribeck-Hertz model that starts with the classic Coulomb friction but takes into account the interparticle , i.e., the reduction of friction coefficient with sliding speed as is commonly observed. Our numerical experiments reveal a state diagram that covers a wide range of packing fractions and show that incorporating the tribology enables the occurrence of quaking intermittency in the midrange of a dimensionless shear rate, consistent with prior experimental observations. Further study of the discontinuities in the evolution of the mean contact number leads to our discovery of two types of quaking that are distinguished by the abrupt or of neighboring contacts and reveal different pathways of microstructural change underlying these discrete events. In contrast to the prevailing paradigm in which shear is believed to promote jamming at intermediate densities, our study demonstrates that shear can also unjam a granular system, and this occurrence depends on the shear rate. Published by the American Physical Society 2024

Bio-based lubricant with additives: tribological performances in hydrodynamic journal bearing

PurposeThe purpose of this paper is to investigate the performance of bio-based lubricants (BBL), namely, palm mid-olein (PMO) enriched with an antioxidant agent, tertiary-butylhydroquinone (TBHQ) and a viscosity improver, ethylene-vinyl acetate (EVA), in journal bearing (JB) applications.Design/methodology/approachSamples of the BBL were prepared by blending it with TBHQ and EVA at various blending ratios. The oxidative stability (OS) and viscosity of the BBL samples were examined using differential scanning calorimetry and a viscometer, respectively. Meanwhile, their performance in JB applications was evaluated through the use of a JB test rig with a 0.5 length-to-diameter ratio at various operating conditions.FindingsIt was found that the combination of PMO + TBHQ + EVA demonstrated a superior oil film pressure and load-carrying capacity, resulting in a reduced friction coefficient and a smaller attitude angle compared to the use of only PMO or VG68. However, it was observed that the addition of TBHQ and EVA to the PMO did not have a significant impact on the minimum oil film thickness.Practical implicationsThe results would be quite useful for researchers generally and designers of bearings in particular.Originality/valueThis study used PMO as the base stock, and its compatibility with TBHQ and EVA was investigated in terms of its OS and viscosity. The performance of this treated BBL was evaluated in a hydrodynamic JB.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2023-0363/