Friction Behavior Research Articles

Implicit Frictional Dynamics With Soft Constraints.

Dynamics simulation with frictional contacts is important for a wide range of applications, from cloth simulation to object manipulation. Recent methods using smoothed lagged friction forces have enabled robust and differentiable simulation of elastodynamics with friction. However, the resulting frictional behavior can be inaccurate and may not converge to analytic solutions. Here we evaluate the accuracy of lagged friction models in comparison with implicit frictional contact systems. We show that major inaccuracies near the stick-slip threshold in such systems are caused by lagging of friction forces rather than by smoothing the Coulomb friction curve. Furthermore, we demonstrate how systems involving implicit or lagged friction can be correctly used with higher-order time integration and highlight limitations in earlier attempts. We demonstrate how to exploit forward-mode automatic differentiation to simplify and, in some cases, improve the performance of the inexact Newton method. Finally, we show that other complex phenomena can also be simulated effectively while maintaining smoothness of the entire system. We extend our method to exhibit stick-slip frictional behavior and preserve volume on compressible and nearly-incompressible media using soft constraints.

A first-principles calculations investigate the superlubricity and adhesion performance of structural superlubricity micro-components on polydimethylsiloxane surface

Adhesion and friction are crucial considerations in the design of microelectromechanical systems because they can directly influence the energy, dissipation and wear of the system. Current related studies are primarily conducted between graphite and hard materials, such as graphite, mica and gold, but lack the theoretical support of superlubricity on the surfaces of related flexible substrates, such as Polydimethylsiloxane (PDMS). Consequently, friction and wear at the flexible interface represent a significant challenge in the failure of microelectromechanical systems devices. In this paper, we use density functional theory to simulate the adhesion characteristics and friction behaviour of structural superlubricity micro-components on the surface of a flexible substrate in an atmospheric environment. The lower graphene layer of the structural superlubricity micro-components exhibits superior adhesion performance with the PDMS substrate. The increase in normal load is simulated by changing the spacing of layers. The interlayer bonding energy increases with increasing load. The transverse friction increases gradually with the increase in load, while the average friction coefficient decreases. Graphene can reach the superlubricity state on the PDMS substrate. The reliability of this phenomenon is verified by electrical performance. We also investigate the effect of tensile strain on the friction behaviour and electrical properties. These calculations should be combined with analysis of the mechanical properties to verify the reliability of the friction performance.

Tribo-oxidation mechanism of gradient nanostructured Inconel 625 alloy during high-temperature wear

The tribo-oxidation layer is typically formed at the contact interface of high temperature wear, which exhibits a significant effect on the friction behavior of gradient nanostructured (GNS) materials. This study systematically investigated the wear resistance, near-surface microstructure, and compositional changes of ultra-thick GNS Inconel 625 alloy subjected to surface mechanical rolling treatment (SMRT) under high-temperature sliding wear conditions. The experimental results indicated that as the temperature increased to 500 °C, a tribo-oxidation layer was formed on the surface of the GNS sample, thereby resulting in an abnormal increase in the coefficient of friction (COF) and a rapid decrease in the wear rate. The gradient nanostructures facilitated oxidation diffusion channels, promoting the formation of a protective Cr2O3 film and spinel oxides, reducing the wear rate. At lower temperatures, a rapidly formed Cr2O3 film shielded the matrix, forming a tribo-oxidation layer composed of Cr2O3 and nickel. At 800 °C, the tribo-oxidation layer exhibited complex structures, including glaze, spinel oxide, Cr2O3, and Cr2O3/Ni mixed layers. This complexity was attributable to the oxidation diffusion rate of the gradient nanostructures and tribo-oxide layers. The findings not only elucidated the tribo-oxidation mechanism of GNS nickel-based superalloys but also offered valuable insights for designing wear-resistant materials.

Improve wear resistance of C/C composites as artificial bone using diamond-like carbon coatings

In this study, diamond-like carbon (DLC) coatings and silicon-doped diamond-like (Si-DLC) coatings were prepared on the surface of C/C composites by a combination of plasma-enhanced chemical vapor deposition (PECVD) and magnetron sputtering processes. The film composition, microstructure and atomic bond structure were characterized using X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and Raman spectroscopy. The mechanical properties and friction behavior related to the Si element were investigated using nanoindentation and HT-1000 high temperature friction and wear tester. The biocompatibility of the materials was also evaluated by the MG-63 proliferation test. The results indicate that Si elements were successfully incorporated into the DLC films, bonding with C and O atoms, which altered the thermal stability and microstructure of the coatings, reduced the internal stress of the films, and increased disorder. Compared to C/C composites, all coated layers exhibited lower coefficients of friction, with the formation of transfer layers and graphitization induced by friction contributing to the excellent tribological performance. Both coatings showed no cytotoxicity and demonstrated good biocompatibility. Both coatings are effective in reducing wear and chip losses in C/C composites when used as artificial bones. This work suggests that diamond-like carbon coated C/C composites can be excellent structural materials for human body in biomedical science.

The influence of water polarization on slip friction at charged interfaces.

The present study employs equilibrium molecular dynamics simulations to explore the potential mechanism for controlling friction by applying electrostatic fields in nanoconfined aqueous electrolytes. The slip friction coefficient demonstrates a gradual increase corresponding to the surface charge density for pure water and aqueous electrolytes, exhibiting a similar trend across both nanochannel walls. An expression is formulated to rationalize the observed slip friction behavior, describing the effect of the electric field on the slip friction coefficient. According to this formulation, the slip friction coefficient increases proportionally to the square of the uniform electric field emanating from the charged electrode. This increase in slip friction results from the energy change due to the orientation polarization of interfacial water dipoles. The minimal variations in the empirically determined proportionality constant for pure water and aqueous electrolytes indicate that water polarization primarily governs slip friction at charged interfaces. These findings offer insights into the electrical effects on nanoscale lubrication of aqueous electrolytes, highlighting the significant role of water polarization in determining slip.

Experimental research on friction and wear behavior of dissimilar steel composite structure developed by wire arc-DED process for an automobile brake rotor application

Recent applications of dissimilar composite structures produced through the wire arc-direct energy deposition process are indispensable across various industries due to their lightweight hybrid components and superior mechanical and tribological properties. This process enables a novel way to fabricate of custom-designed, high-performance composite structures that optimize friction, wear resistance, and mechanical characteristics. The present study focuses on developing a dissimilar steel composite structure using wire arc additive manufacturing process, with tribological and microstructural investigations conducted to understand the interfacial wear properties of the alloys. Standardized specimens were prepared to assess their friction and wear behavior through pin-on-disc wear test-rig. Experimental results show that the composite specimens exhibit enhanced wear resistance even under extreme sliding conditions (50 N applied load and 2400 m sliding distance), with tribolayer formation confirmed through FESEM micrographs and EDAX analysis. The highest specific wear rate (SWR) (3.87E-04 mm³/Nm) was observed at 50 N, 6.28 m/s, and 1600 m sliding distance, with a friction coefficient of 0.26. Adhesive wear was identified as the dominant wear mechanism between the specimen and the counterpart. Taguchi's multiresponse optimization indicated that sliding distance had the most significant effect on SWR and friction coefficient, followed by applied load and sliding velocity.

Prediction of frictional behaviour through regression equations: A statistical modelling approach validated with machine learning

Prediction of frictional behaviour through regression equations: A statistical modelling approach validated with machine learning

The friction, wear, and failure behaviour of functionalized hexagonal boron nitride with Karanja oil blends

This study explores lubricants derived from Karanja seed oil (Pongamia pinnata) through chemical modification and combined with hexagonal boron nitrides (h-BN) to demonstrate improved load-bearing performance. The tribological properties of pure, chemically modified Karanja oil, and oil mixed with fatty acid functionalized h-BN (fh-BN) were assessed. Initial tests evaluated essential lubricating properties. A 50% chemically modified oil blend performed best at sliding speeds from 0.05 to 0.3 m/s. Key measurements included frictional loss, failure load, wear volume, and coefficient of friction for modified blends and fh-BN nano lubricants. The 100% modified blend (100% MKO) withstood 114% higher load before failure, while fh-BN enhanced load capacity by 107% compared to pure Karanja oil. Post run-in phase, frictional work loss was similar between 100% MKO and pure oil when tested with starvation of lubricants; however, 50% MKO and 0.025 wt% h-BN and fh-BN blends showed reduced frictional work loss. The fatty acid layer on functionalized fh-BN surfaces promotes the formation of a thin tribolayer, enhancing their overall lubrication performance.

Evaluating the impact of post-processing on the wear and friction properties of polyamide 6 carbon fiber composites produced by fused deposition modeling

The current research addresses the challenges encountered in polyamide 6 carbon fiber composites synthesized by fused deposition modeling. It specifically investigates issues such as inadequate interlaminar bonding and increased void content compared to conventionally manufactured composite components and as-built printed parts. The study focuses on printing pin samples via fused deposition modeling and explores various thermal post-processing methods to reduce void content while preserving dimensional accuracy. To evaluate wear and friction behavior, a pin-on-disc tester was used to test both as-built samples and samples post-heat-treated at 70 °C, 140 °C, and 210 °C. The results indicate that as the applied load increases from 5 to 20 N, both wear rates and friction coefficients increase across all speeds (1–5 m/s). Heating the samples to 70 °C and 140 °C strengthens the interlayer bonding. This significantly improves the maximum wear rates and friction coefficients compared to the as-built samples. However, samples heated to 210 °C do not show much of a change in wear rates or friction coefficients. Samples heated to 210 °C exhibit a decrease in wear rate of 16.87%, 15.82%, and 15.73% for loads ranging from 5 to 20 N, at speeds of 1, 3, and 5 m/s, respectively. This is likely due to pores sealing off and structures binding tightly. The worn surfaces were analyzed using a scanning electron microscope and measured the Shore D hardness of the samples before and after wear testing and documented the results for further analysis. In a scanning electron microscope, samples treated at 210 °C displayed smoother, less worn surfaces. Shore D hardness tests revealed a slightly higher hardness in samples heated to higher temperatures, followed by higher loads and sliding speeds in tribometer tests. This showed that the material was more stable. These post-processing methods significantly advance the development of functional composite elements for superior structural or dynamic performance.

Effect of bionic shield texture on friction behavior of silicon carbide under water lubrication condition

Abstract Reasonable texture parameters can effectively generate local dynamic pressure effects and promote the formation of lubrication film. The synergistic friction reduction mechanism of the shield-shaped texture on the Silicon Carbide (SiC) surface under water-based lubrication conditions between the flow pressure effect and the ‘rolling ball’ effect is investigated by combining simulation analysis and friction experiments. The effects of shield textured surface on the friction and wear characteristics of SiC surface and the characteristics of interfacial polarization electric field under different rotational speeds and different load conditions were analyzed. The results display that synergistic texture lubrication has a beneficial effect on improving tribological properties. The surface with 6% texture area occupancy showed the best tribological characteristics. The surface with a textured area occupancy of 6% displays the optimal tribological properties. Moreover, the friction reduction mechanisms under different working conditions are discussed, with the textured uniformly arranged surfaces being more suitable for high-speed and heavy load (140 N, 2000 rpm) conditions and the textured non-uniformly arranged surfaces being more suitable for low-speed and light load (40 N, 400 rpm) conditions.

Fabrication and tribological behaviors of copper fiber and carbon fiber reinforced phenol‐formaldehyde resin‐based composite for sliding current collector

AbstractTo achieve new current collector (pantograph strip, electric brush) with easy industrialization and high strength‐toughness, carbon fiber and copper fiber reinforced phenol‐formaldehyde (Cuf/Cf/PF) composite is fabricated by over‐lapping and hot‐pressing processes. Cuf/Cf/PF composite has compact structure and good interfacial bonding between fibers and resin matrix. Cuf/Cf/PF composite is superior to carbon skateboard in terms of electrical conductivity, mechanical strength, and friction behavior. As the carbon fiber content increases, fracture failure mechanism of Cuf/Cf/PF composite transforms from plastic failure into brittle fracture. Wear mechanism is studied by combining electrical contacting and sliding friction, and appropriate arc discharge (2.48%) is benefit for the resin‐based composite to form a smooth tribolayer, but high arc discharge rate (4.83%) rapidly deteriorates wear condition on the worn surface.Highlights Carbon fiber and copper fiber mixing reinforce resin‐based composite. Cuf/Cf/PF composite has high strength‐toughness and low friction. Fracture failure mode changes to brittle fracture with increasing carbon fiber. Wear mechanism includes electrical contacting and sliding friction. Appropriate arc discharge improve friction performance of resin‐based composite.

Corrosion and wear performance and mechanism study of ZrB2/AA6016

Abstract This study involved the fabrication of aluminum matrix composites reinforced with ZrB2/AA6016 particles using the KBF4-Al-K2ZrF6 reaction system， the composites were then subjected to T6 heat treatment. An investigation was conducted to examine the impact of varying friction speeds on the corrosion and wear characteristics of ZrB2/AA6016. An investigation was conducted to study the frictional wear behavior of ZrB2/AA6016 in the presence of 3.5wt. % NaCl, both before and after T6 heat treatment. The study also aimed to understand the underlying mechanism of this behavior. The results indicate that the T6 heat treatment mitigates the impact of thermal stresses and strains caused by thermal mismatch, hence enhancing the material's wear resistance. The coefficient of friction (COF) for heat-treated ZrB2/AA6016 is lower than that for unheated-treated ZrB2/AA6016. As friction increases, the pace at which the material wears down tends to decrease. At a friction wear velocity of 50 mm/s, the wear rate of the material is minimized both before and after heat treatment, measuring 0.23×10-2mm3/Nm and 0.22×10-2mm3/Nm, respectively. Through the utilization of XRD, SEM, EBSD, TEM, and XPS analytical techniques, it has been determined that the ZrB2 particles exhibit strong bonding with the Al matrix. Additionally, the particle diameters range from 50~150nm. Following the T6 heat treatment, the grain size measured 40.53μm, while the proportion of large-angle grain boundaries was found to be 66.4%. The accumulation of Cl- resulted in the formation of localized corrosion pits on the surface undergoing wear, hence hastening the deterioration of the material. The primary causes of wear failure are corrosive wear, abrasive wear, and oxidative wear.

Achieving precise graphenization of diamond coatings below the interfacial thermal stress threshold

Abstract Diamond coatings possess numerous excellent properties, making them desirable materials for high-performance surface applications. However, without a revolutionary surface modification method, the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces. This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage, without causing damage to the metal substrate. Through experiments and simulations, the influence mechanism of surface graphitization and interfacial thermal stress was elucidated, ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness. Compared to the original diamond coatings, the obtained surfaces exhibited a 63%–72% reduction in friction coefficients, all of which were below 0.1, with a minimum of 0.06, and a 59%–67% decrease in specific wear rates. Moreover, adhesive wear in the friction counterpart was significantly inhibited, resulting in a reduction in wear by 49%–83%. This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties. This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces, with the potential to significantly enhance the performance and expand the application range of diamond-coated components.

Integrating Friction Noise for In Situ Monitoring of Polymer Wear Performance: A Machine Learning Approach in Tribology

Abstract Friction and wear between mating surfaces significantly affect the efficiency and performance of mechanical systems. Traditional tribological research relies on post-observation methods, limiting the understanding of dynamic friction behavior. In contrast, in situ monitoring provides real-time insights into evolving friction dynamics. This study employs machine learning to monitor polymer wear performance through friction noise. The predictive accuracy of various machine learning methods, including Extremely Randomized Trees, Gradient-Boosting Decision Trees, AdaBoost, LightGBM, Deep Forest, and Deep Neural Networks, is compared for wear-type classification. Additionally, the LSBoost regression is selected as the optimal method for predicting polymer wear-rates across various temperatures. The results underscore the potential of using friction noise and machine learning for real-time wear monitoring, offering valuable insights for tribological system maintenance and failure prediction.

Thickness-dependent nanoscale friction across the first-order charge density wave phase transition in 1T-TaS2

The layered charge density wave (CDW) phase transition material 1T-TaS2 has garnered significant attention due to its modulable bandgap and electrical transport properties. These unique properties make 1T-TaS2 highly promising for applications in fields such as optoelectronic devices and microstructure physics devices. In various micro-/nanodevices made from quasi-two-dimensional 1T-TaS2, it is often utilized in thin layers, making the understanding of its frictional properties crucial for practical applications. However, the layer-dependent frictional properties of 1T-TaS2 have not been thoroughly investigated. In this article, we examine the CDW phase transition between the nearly commensurate (NCCDW) and commensurate (CCDW) phases in 1T-TaS2 around 183 K using atomic force microscopy, focusing on the number of layers in the samples. Our results indicate that for thicker samples with more than approximately 17 layers, a friction peak is observed during the NCCDW–CCDW phase transition. In contrast, thinner samples do not exhibit this friction peak, and their friction continuously increases as the temperature decreases. This behavior is attributed to the suppressed NCCDW–CCDW phase transition in thinner samples. These results enhance our understanding of the frictional behavior of 1T-TaS2 in the context of micro-/nano-electromechanical systems. Furthermore, our observations offer a straightforward method to identify the NCCDW–CCDW phase transition, providing an alternative to traditional, more complex techniques such as electrical resistance measurements and Raman spectroscopy.

Molecular dynamics study on the enhancement of high‐temperature friction and mechanical properties of perfluoroelastomers by carbon nanomaterials

AbstractThe mechanical and frictional properties of pure perfluoroelastomer, graphene (GN)/perfluoroelastomer, and carbon nanotube (CNT)/perfluoroelastomer composite systems were investigated using molecular dynamics simulations. The influence of carbon nanomaterials on the glass transition temperature, mechanical properties, and frictional behavior of perfluoroelastomers at various temperatures was evaluated. The simulation results demonstrated that the addition of GN and CNTs increased the glass transition temperature of perfluoroelastomers to varying extents. CNTs enhanced the mechanical properties of perfluoroelastomers more effectively than GN, whereas GN provided superior improvement in frictional properties compared to CNTs. Analysis of stress–strain distribution, atomic motion trajectory, interaction energy, mass density, and temperature distribution, bond orientation parameters, radial distribution function (RDF), mean square displacement (MSD), and diffusion coefficients revealed the mechanisms and differences by which GN and CNTs enhance the mechanical and frictional properties of perfluoroelastomers.Highlights Carbon nanomaterials enhance perfluoroelastomer's high‐temperature performance. CNTs provide higher mechanical strength but lower wear resistance. GN nanosheets outperform CNTs in reducing friction and wear. Molecular dynamics simulations reveal distinct enhancement mechanisms.

Simulation analysis and experimental research of friction performance between wood and cemented carbide surface with different micro-textures

ABSTRACT Reasonable micro-pit texture has been proved to be able to improve the friction characteristics between wood and cemented carbide. In this paper, the finite element simulation analysis was used to simulate the friction surface stress, the simulation model was determined, and the simulation results were combined with the friction characteristics test to study the influence of different texture types on the friction coefficient of the wood surface. The results show that the friction coefficient and the stress magnitude of friction between cemented carbide and wood surface have a good linear correlation (R 2 = 0.9414), the finite element simulation can provide a reference for the study of friction behavior in the wood cutting process. The friction coefficient can be influenced by texture parameters such as texture type, the friction length, the width of micro-texture and the angle of micro-texture. Under the condition of the same texture area occupancy, the surface friction coefficient of the micro-pit texture is the smallest; the surface friction coefficient of the micro-groove texture is the largest, and the micro-grid texture has the smaller friction coefficient with the decrease of the texture angle. This is related to the actual contact area between the texture area of the friction area and the wood surface and the main braking force generated during contact.

Understanding Electric Current Effects on Tribological Behaviors of Instantaneous Current-Carrying Pair With Recurrence Plot

Abstract Armature–rail instantaneous current-carrying friction in electromagnetic launchers refers to a sliding electric-mechanical impact friction and transition-induced arc erosion on a millisecond time scale. To reveal the electric current (50–300 A) effects on friction behavior and wear mechanism, the instantaneous current-carrying friction tests were performed with Al 1060 and Brass H62. Given the short nonlinear friction-induced signals, the friction behavior, including the time-domain information and system state, was comprehensively analyzed via frictional sound pressure (FSP), recurrence plot (RP), and recurrence quantification analysis (RQA). The wear topography was observed and characterized by the multifractal spectrum. Recurrence analyses demonstrate that as the current increases, the nonstationarity of the system state weakens, and the complexity and unpredictability enhance. Higher currents reduce the FSP amplitude, i.e., enhance the interfacial lubrication effect, but intensify electrical wear and surface roughness. This signifies a wear mechanism transition from abrasive wear and slight adhesive wear to arc ablation, fatigue wear, and severe adhesive wear. The widening spectrum width implies that the irregularity and fluctuation of the topography are enhanced with the current. RP patterns and RQA quantifiers correlate with the wear damage state. The results provide a reference for antiwear design and online degradation tracking of the rail.

Tribological Properties of 7A04 Aluminum Alloy Enhanced by Ceramic Coating

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS2 composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS2 coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10−6 mm/Nm. The MAO/MoS2 coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS2 enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries.

Probing the friction mechanism of diamond-like carbon films in aqueous environments based on molecular dynamics simulations

Abstract The frictional behavior of diamond-like carbon (DLC) films in an aqueous environment is of tremendous interest. To compare the impacts of the quantity of water molecules, sliding velocity, and loading on the friction behavior of DLC films, a molecular model of DLC films in an aqueous environment was built. The results show that the DLC film under high load and high sliding velocity leads to severe friction behavior, but the water molecules can prevent the occurrence of this severe friction behavior. Also increasing the number of water molecules can effectively reduce the increase in friction during the running-in stage and keep it at a low value. The primary explanation is that if there are enough water molecules, they will create a stable water film at the friction interface and prevent large-scale contact and distortion between the upper and lower DLC films, significantly reducing friction.