Excellent Load-carrying Capacity Research Articles

Effects of metal element doping on the lubrication behaviors and mechanisms of gallium-based liquid metals

Gallium-based liquid metals (GLMs) are a novel high-end lubricant with low friction coefficient and excellent load-carrying capacity. This paper aims to improve the lubrication properties of GLMs by regulating the frictional interfaces. Six types of GLMs doped with Zn, Mg, Bi, Cu, Ti, or Sc elements are prepared respectively, and the effects of metal element doping on the lubrication behaviors and mechanisms for AISI 440C steel self-mated pairs are investigated in the mixed lubrication regime with a ball-on-three-plate setup. Doping 1 wt% Zn or Cu elements can improve the lubrication properties, with the friction coefficient reduced by 20.3 % and the wear rate reduced by 55.1 % compared with those under eutectic Ga/In/Sn lubrication. However, doping Ti, Sc, Mg, or Bi all reduce the lubrication properties. Doping Zn improves the lubrication properties of GLMs by promoting the adsorption of gallium on the frictional interfaces. Conversely, doping Bi inhibits the adsorption of gallium. The improvement in the lubrication properties of Cu-doped GLM is attributed to the formation of low-hardness CuGa2 particles. The doping of Ti or Sc generates high-hardness TiGa3 or ScGa3 particles, causing three-body abrasive wear. The doping of Mg generates a large number of Mg2Ga5 particles, seriously disrupting the stable lubrication.

Application of machine learning models in the capacity prediction of RCFST columns.

Rectangular concrete-filled steel tubular (RCFST) columns are widely used in structural engineering due to their excellent load-carrying capacity and ductility. However, existing design equations often yield different design results for the same column properties, leading to uncertainty for engineering designers. Furthermore, basic regression analysis fails to precisely forecast the complicated relation between the column properties and its compressive strength. To overcome these challenges, this study suggests two machine learning (ML) models, including the Gaussian process (GPR) and the extreme gradient boosting model (XGBoost). These models employ a range of input variables, such as the geometric and material properties of RCFST columns, to estimate their strength. The models are trained and evaluated based on two datasets consisting of 958 axially loaded RCFST columns and 405 eccentrically loaded RCFST columns. In addition, a unitless output variable, termed the strength index, is introduced to enhance model performance. From evolution metrics, the GPR model emerged as the most accurate and reliable model, with nearly 99% of specimens with less than 20% error. In addition, the prediction results of ML models were compared with the predictions of two existing standard codes and different ML studies. The results indicated that the developed ML models achieved notable enhancement in prediction accuracy. In addition, the Shapley additive interpretation (SHAP) technique is employed for feature analysis. The feature analysis results reveal that the column length and load end-eccentricity parameters negatively impact compressive strength.

Influence of manufacturing factors on compressive behavior of soft architected composite with a 3D-printed cellular core

Soft material is widely used for energy dissipation in a diverse range of applications from shoe soles to bridge bearings. Recent advances in additive manufacturing enable more new classes of materials such as soft architected composites (SAC) with 3D-printed cores that are embedded into a soft matrix. SAC has demonstrated excellent load-carrying capacity, ductility, and energy absorption under compression compared to soft material alone, but the influence of key manufacturing factors remains unknown. In this work, we conducted experimental investigations on SAC specimens considering various manufacturing parameters, including the printing materials, volume fraction, filling pattern, and printing parameters. Notably, the SAC with the gyroid filling pattern demonstrates superior specific stiffness and specific energy absorption. The effect of the printing parameters on the SAC was non-linear, and the optimal values were influenced by the core geometries. The SAC unit filled with gyroid pattern and manufactured using optimized printing parameters exhibited significant improvement in specific stiffness and specific energy absorption over those with the same mass of reinforcing phase. These results can guide the further design of similar architected composite by considering the appropriate selection of manufacturing parameters and geometric designs. With the improved mechanical properties, the concept of SAC can be further used in developing lightweight and high-performing energy absorption and dissipation components and devices.

The lubrication regimes and transition laws of gallium liquid-metal

Gallium-based liquid metal is a novel lubricant for high-end equipment due to its low friction coefficient and excellent load-carrying capacity. In this work, the stribeck curve, static friction and a series of fixed-speed friction tests for steel self-mated pairs under gallium lubrication are conducted to reveal the lubrication regimes and transition laws. In the sliding speed ranging from 10−8 to 1.4 m/s and the normal load ranging from 2 to 20 N, gallium can only provide boundary and mixed lubrication. Uniformly distributed or island-like distributed gallium-rich films are formed under boundary or mixed lubrication regimes, respectively. The different formation mechanisms are revealed. The failure of the gallium-rich film is mainly related to the average contact stress of the frictional interfaces.

Experimental study on the axial compressive behaviour of steel reinforced concrete composite columns with stay-in-place ECC jacket

Steel Reinforced Concrete (SRC) column made with high strength materials features excellent load-carrying capacity and energy dissipation capacity, but the compromised ductility issue hinders the widespread application in seismic-prone areas. To overcome this weakness, this paper proposes a novel type of steel-concrete composite column by employing Engineered Cementitious Composites (ECC) as the permanent formwork of conventional SRC column. An experimental program was conducted by subjecting seven stub columns to monotonic axial compressive loading. The test variables in this study include the presence of ECC jacket, the presence of embedded structural steel, stirrup spacing and stirrup configuration. The axial performance were carefully analyzed in terms of load-carrying capacity, initial stiffness, post-peak ductility, damage pattern, as well as the full range load-deformation response. The physical tests confirm the potential of ECC jacket to be used as the permanent formwork of SRC columns as to improve both the construction efficiency and structural performance, and the comparison between the test results and analytical predictions demonstrates the applicability of design equation in EN 1994-1-1 and JGJ 138–2016 to predict the axial capacity of ECC-SRC columns.

Axial mechanical behavior of innovative inter-module connection for modular steel constructions

Modular steel construction (MSC) is a construction mode where volumetric modules are prefabricated in a factory and assembled on-site to form permanent buildings. Inter-module connections are critical to the integrity and robustness of modular steel constructions (MSCs). In this paper, the mechanical behavior of a typical corner inter-module connection under axial tensile and compressive loads was investigated. A tensile test of the inter-module connection was carried out to investigate their axial tensile behavior. The refined numerical model was established, calibrated against the test results and then used to simulate the axial tensile and compressive mechanical behaviors of the inter-module connection. The effects of key design parameters on the axial load-displacement responses of the connection, including the bolt gasket thickness, the bolt diameter and the preload were investigated. The inter-module connection was shown to exhibit excellent load-carrying capacity under axial compression and adequate performance under tension. In terms of tensile resistances, the bolt gasket thickness and the bolt diameter were shown to be the critical parameters, while the section size of the modular columns dominated the compressive load-carrying capacity. Through geometrical parameters correlation analysis, a simplified piecewise polynomial axial load-displacement model with different stiffnesses in tension and compression was employed for predicting the axial load-displacement relationship. The proposed model was shown to be capable of accurately capturing the axial resistance characteristics of the connection while maintaining simplicity, and is therefore recommended for use to represent the axial behavior of the inter-module connection in global frame modelling.

Mechanical Behavior of Special-Shaped Reinforced Concrete Composite Columns Encased with GFRP Core Columns

In order to investigate the mechanical behavior of special-shaped reinforced concrete composite columns encased with GFRP core columns (EGCSSCs) subjected to axial load, twenty-seven full-scale EGCSSCs were designed with varying parameters: axial compressive strength of core concrete (fcc), axial compressive strength of peripheral concrete (fco), thickness of GFRP tube (tgfrp), ratio of longitudinal reinforcement (ρv), stirrup ratio (ρs) and GFRP ratio in the cross-section (α). The three-dimensional finite element refined models of EGCSSCs were established by ABAQUS finite element software, and the response of EGCSSCs under axial load was studied based on the verification of finite element modeling. The influence of different parameters on the ultimate axial compressive strength (Nus), initial stiffness (K), and ductility index (µ) of EGCSSCs was obtained, and the typical failure mode of EGCSSCs was clearly described. The results showed that the main failure mode of the EGCSSCs subjected to axial load was bulging outward at the middle of the EGCSSCs, showed yielding of the longitudinal steel bars, and was crushing both ends of the peripheral concrete. When the column was damaged, the peripheral concrete reached peak stress earlier than the core concrete. All specimens exhibited excellent load-carrying capacity and good ductility. Moreover, with the existence of GFRP core columns, the Nus and µ of the columns were increased by 11.61% and 140.86%. In addition, K increased with the increase in fcc, fco, tgfrp and α, and the largest increments were 23.99%, 50.54%, 21.77%, and 34.19%, respectively. µ decreased with the increase in fcc and fco, which decreased by 14.05% and 40.28%, respectively. By using statistical regression and introducing the constraint effect coefficients and the reduction coefficient, the calculation formula for the axial compression-bearing capacity of EGCSSCs was derived, which could lay a foundation for the popularization and application of this kind of composite column in practical engineering.

A Generalized Framework for the Alternate Load Path Redundancy Analysis of Steel Truss Bridges Subjected to Sudden Member Loss Scenarios

Owing to their distinct features, such as structural simplicity and excellent load-carrying capacity, steel truss bridges are widely applied as critical transportation networks. However, many previously designed steel truss bridges that are located in harsh environmental conditions are facing severe challenges of overloading and aging or deteriorating critical structural members due to increasing traffic load and corrosion problems (i.e., chloride-induced corrosion). As a consequence, these overloaded and deteriorated critical members may initialize localized damage (e.g., sudden member failure scenarios) and then trigger a disproportionate collapse (i.e., progressive collapse) of steel truss bridges. To this end, to protect the steel truss bridges from progressive collapse resulting from locally induced damages (e.g., sudden removal of a critical member), this paper proposed a generalized framework to identify the critical members and to qualify the alternate load path (ALP) redundancy of steel truss bridges subjected to sudden member loss of a critical member. Demand-to-capacity ratio (DCR) for linear elastic analysis and strain ratio (SR) for nonlinear dynamic analysis were employed as the design metrics and performance indicators to qualify the ALP redundancy of steel truss bridges. Effectiveness of the proposed framework in qualifying the ALP redundancy of steel truss bridges was demonstrated through the I-35W truss bridge under sudden member removal (MR) analyses. Results obtained from this study may provide beneficial information and could serve as good references for the protection of steel truss bridges that are vulnerable to sudden member loss scenarios.

Seismic behavior of low shear-span ratio double-skin composite wall with L-shaped connectors

A double-skin composite wall (DSCW) with innovative L-shaped connectors was proposed, which can be simply constructed and quickly assembled to promote the development of a prefabricated steel structure. To further examine the seismic capacity of the novel DSCW, five DSCWs were designed and fabricated, each with a low shear-span ratio. The testing parameters include the welding spacing, distance between connectors, and the width-to-thickness ratio of the wall-to-steel faceplate. The failure mode of each DSCW specimen was observed, while determining the load-carrying capacity, the hysteretic curve, the skeleton curve, and the displacement ductility coefficient. Moreover, the distribution and development of the boundary column strains, steel faceplate strains, and L-shaped connector strains were researched. The test results showed that the DSCWs with a low shear-span ratio had excellent load-carrying capacity and ductility, and all specimens experienced flexural-shear failure. Decreasing the welding spacing of L-shaped connectors or reducing the distance between L-shaped connectors can enhance the capacity of energy dissipation and ductility, but such a distance reduction has a slight effect on the shear strength. When the thickness of the steel faceplate on different specimens is the same, the load-carrying capacity of the DSCW specimen obviously improves as the width-to-thickness ratio of the wall-to-steel faceplate increases. Finally, shear strength calculation formulas of the novel DSCW under the low shear-span ratio were established.

Ionic Liquids Based on Chromotropic Acid: Excellent Lubricating Additives for Aqueous System

In this paper, four ionic liquids based on chromotropate (CAILs) were prepared and applied to heighten the tribological performance of aqueous system on different metal friction contacts. Taking for the potential choice for water-based lubricating additive, CAILs exhibited excellent water solubility and corrosion resistance. Tribological results showed that the CAILs, especially the phenolic hydroxyl group decorated samples (TsnN4444 and TsnP4444), demonstrating extremely effective lubricating properties with the efficient friction and wear descent (69% and 83% for Fe, 47% and 94% for Cu, 74% and 69% for Al, respectively). Especially, the excellent load-carrying capacity was also presented with the highest PB (833 N) and PD (1568 N) values for TsnP4444. It is speculated that the CAIL molecular adsorption on the interface and further generation of tribochemical films are beneficial for their lubricating effects, resulting from the systematic discussion and analysis of CA, QCM, SEM, XPS, and FIB-TEM tests. However, TsN4444 and TsP4444 showed less effective lubricating performances and poor load-carrying capacities due to tribocorrosion of hydroxyl groups at the interface.Graphical Abstract

Experimental and numerical investigation on ultimate strength of four-legged latticed columns

Latticed built-up columns are applied more extensively than solid columns in structural engineering because of their excellent load-carrying capacity and light weight. Studies on the bearing capacity of latticed columns, particularly multiple-legged latticed columns, need to be conducted in detail. In this investigation, seven four-legged latticed column specimens of different bar sections, bar distributions and loading eccentricities under compressive loads were subjected to experimental tests. The initial geometric imperfections of the legs and bars were measured and introduced into the FE numerical method. The experimental results were then compared with those of Geometrical and Material Non-Linear Analysis with Imperfection in ABAQUS software. The combined data indicate that the bar section, bar distribution and loading eccentricity significantly influenced the ultimate strength of four-legged latticed columns, producing maximum variations of 105.67%, 65.7% and 48.48%, respectively. This investigation demonstrates the influence of lacing bars and improves the results obtained from FE numerical analytical techniques.

Effect of pH on the Tribological Behavior of Eu-Doped WO3 Nanoparticle in Water-Based Fluid

Eu-doped WO3 (WO3:Eu3+) nanoparticles were prepared by Pechini method under different pH values (pH 1, 3, 5, and 7). The prepared nano-powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the average external diameter of the prepared nano-WO3:Eu3+ powders is the smallest and reaches 50 nm at pH 5. Structural transformation matrix contained different crystals of anorthic and orthorhombic structures. Eu3+ ions are located at the center of the non-inversion symmetry of WO3:Eu3+. The tribological properties of the WO3:Eu3+ as extreme pressure and wear resistance agents in water-based lubricant were investigated by a four-ball machine. The results showed that WO3:Eu3+ displays excellent load-carrying capacity, wear resistance, and friction-reducing properties in water-based lubricant, particularly in the best concentration of WO3:Eu3+ was 0.6 wt%. WSD was reduced from 0.62 to 0.35 mm and COF was decreased from 0.083 to 0.055. This was due to the formation of tribofilms with a few tens of nanometers thick, which prevented no actual metal-to-metal contact.

Preparation, characterization, tribological and lubrication performances of Eu doped CaWO4 nanoparticle as anti-wear additive in water-soluble fluid for steel strip during hot rolling

Citric acid-synthesized Eu-doped CaWO4 (CaWO4:Eu3+) nanoparticles in acidity (pH = 1) and alkalinity solutions (pH = 10) were analyzed by SEM, TEM, XRD, and Raman. The tribological and hot rolling lubrication properties of nano-CaWO4:Eu3+ as anti-wear additives in water-based rolling fluid were investigated. Results showed that CaWO4:Eu3+-pH = 10 has excellent load-carrying capacity, wear-resistance and friction-reducing properties in water-based rolling fluid, particularly in the bestconcentration was 0.5 wt%. The WSD value is decreased from 0.62 to 0.39 mm and the COF value is reduced from 0.092 to 0.070, which attributes to the formed tribofilm (~30 nm) on the worn surface is composed of Fe2O3, CaO, WO3 and Eu2O to avoid direct contact with the metals during hot rolling, thus reducing the friction coefficient and the oxide scale.

Compound Impedance Control of a Hydraulic Driven Parallel 3UPS/S Manipulator

The hydraulic parallel manipulator combines the high-power density of the hydraulic system and high rigidity of the parallel mechanism with excellent load-carrying capacity. However, the high-precision trajectory tracking control of the hydraulic parallel manipulator is challenged by the coupling dynamics of the parallel mechanism and the high nonlinearities of the hydraulic system. In this study, the trajectory control of a 3-DOF symmetric spherical parallel 3UPS/S manipulator is evaluated. Focusing on the highly coupling and nonlinear system dynamics, a compound impedance control method for a hydraulic driven parallel manipulator is proposed, which combines impedance control with the spatial motion characteristics of a parallel manipulator. The control strategy is divided into the inner and outer loops. The inner loop controls the impedance of the actuator in the joint space, and the outer loop controls the impedance of the entire platform in the task space to compensate the coupling of the actuators and improve the tracking accuracy of the moving platform. Compound impedance control does not require force or pressure sensors and is less dependent on modeling precision. The experimental results show that the compound impedance control effectively improves the tracking accuracy of the moving platform. This research proposes a compound impedance control strategy for a 3-DOF hydraulic parallel manipulator, which has high tracking precision with a simple and cheap system configuration.

Monotonic and cyclic loading tests of reinforced concrete beam strengthened with bond-improved carbon fiber reinforced polymer (CFRP) rods of ultra-high modulus

Abstract The present study focuses on a near-surface-mounted (NSM) strengthening technique for cantilevered-reinforced concrete (RC) bridge-deck slabs subjected to wheel loads. A carbon-fiber-reinforced polymer (CFRP) rod of ultra-high modulus (455 GPa) is used in the NSM technique adopted in this study. In particular, the fatigue durability of the RC member strengthened with the NSM CFRP rods was examined. Notably, the ultra-high modulus CFRP rod has no shear-resistant ribs because of the pultrusion manufacturing process. Hence, the greatest concern in the strengthening of the NSM is the significant low-bonding property of the CFRP rod embedded in covering/filling materials, such as concrete, mortar, and epoxy-resin. The study uses the CFRP-rod attaching glass-fiber-reinforced polymer (GFRP) ribs to improve bond strength. The bond-improved CFRP rod, with a small diameter of 8–14 mm, can be embedded in the high-strength mortar replacing the upper-cover thickness of general RC slabs. In this study, 15 RC beam specimens of 160 mm thickness were prepared, which is the minimum thickness of a Japanese highway slab. Thirteen beams strengthened with NSM-CFRP rods were tested by monotonic and cyclic loadings, respectively. The flexural fatigue test confirmed that the strengthened beams endured 2 million cycle loadings, and the CFRP rods were firmly bonded in concrete, even under a repeated load. The study reveals the excellent load-carrying capacity and fatigue durability of the RC member, strengthened by NSM-CFRP rods of ultra-high modulus.

Fabrication and Mechanical Testing of Ultralight Folded Lattice-Core Sandwich Cylinders

Abstract In this research, two novel folded lattice-core sandwich cylinders were designed, manufactured, and tested. The lattice core has periodic zigzag corrugations, whose ridges and valleys are directed axially or circumferentially. Free vibration and axial compression experiments were performed to reveal the fundamental frequency, free vibration modes, bearing capacity, and failure mode of the cylinder. A folded lattice core effectively restricts local buckling by reducing the dimension of the local skin periodic cell, and improves the global buckling resistance by enhancing the shear stiffness of the sandwich core. The cylinders fail at the mode of material failure and possess excellent load-carrying capacity. An axially directed folded sandwich cylinder has greater load-carrying capacity, while a circumferentially directed folded sandwich cylinder has higher fundamental frequencies. These two types of folded lattices provide a selection for engineers when designing a sandwich cylinder requiring strength or vibration. This research also presents a feasible way to fabricate a large-dimensional folded structure and promote its engineering application.

A nano-lubrication solution for high-speed heavy-loaded spur gears and stiffness modelling

• A revised model of calculating the time-dependent oil normal stiffness and tangential stiffness is proposed. • A numerical algorithm for high-speed spur gears lubricated by nanofluids is presented. • Spherical alumina nanoparticles significantly reduce friction coefficient and maximum temperature of total contact region. • Nanoparticles of higher concentration reduce traction friction and film temperature. • Many vortexes form and move from gear surface to pinion surface in rough contact. Nanofluids have excellent mechanical and thermal properties. Serious wear and high temperatures hamper the development of high-speed gear drives, and the application of nanofluids to gear lubrication is a potential solution. The main purpose of this paper is to investigate the mechanism by which nanofluids affect the lubrication performance of high-speed gear drives. A revised model of calculating the time-dependent oil normal stiffness and tangential stiffness is proposed. The density equation and viscosity equation are revised. Firstly, the numerical algorithm for high-speed spur gears lubricated by nanofluids is validated based on the classical minimum film thickness formula of Dowson, and then the differences between smooth and rough contact are analyzed. Furthermore, the effects of nanoparticle shape and concentration on tribology performance of gear lube are comprehensively investigated. Finally, the influences of surface roughness on film velocity field distribution are discussed. The simulation results indicate that applying spherical alumina nanoparticles to gear lube as additives is beneficial to the anti-wear performance of gear teeth and the lubricating property of lubricants, which considerably decrease friction coefficient and maximum temperature of the total contact region. Moreover, film normal stiffness of spherical alumina nanoparticles is close to base oil which means it maintains excellent load-carrying capacity. Higher concentrations of nanoparticles reduce the friction coefficient and maximum temperatures of the total contact region, and cause an increase in film tangential stiffness. The surface roughness remarkably influences film velocity field and high amplitude roughness induces formation of many vortexes in the contact center, and these vortexes move from gear surface to pinion surface in a total engagement cycle.

Surface 3-D lubrication structure design of Al2O3/Ni-laminated ceramics to improve tribological properties under combined environments

High-performance alumina matrix ceramics have potential applications in harsh environments such as corrosive and high-temperature conditions because of their excellent mechanical properties, corrosion-resistance, and oxidation stability. In this study, a 3-D lubrication structure was designed and prepared on the surface of Al2O3/Ni-laminated ceramics using laser surface texture technology and bonded PTFE coatings. The wear mechanisms of the materials were also studied, and the effects of the 3-D lubrication structure on the tribological properties of Al2O3/Ni-laminated ceramics under dry and aqueous conditions were investigated. Four types of micro-dimples with different diameters and bonded PTFE solid lubricating coatings were successfully prepared on the surface of Al2O3/Ni-laminated ceramics. Experimental results demonstrated that the bonded PTFE coating combined with micro-dimples on the surface of ceramics had excellent load-carrying capacities and wear-resistance under both dry and aqueous conditions. The wear life showed a marked increase under both dry and aqueous conditions because the solid lubricant that was embedded in the micro-dimples improved the bonding strength of the coating and provided secondary lubrication. The synergistic effects of the micro-texture and the bonded PTFE coating significantly improved the tribological properties of the materials.

Performance of precast segmental concrete beams posttensioned with carbon fiber-reinforced polymer (CFRP) tendons

Precast segmental prestressed concrete beams (PSBs) have been widely used in many elevated highway bridge projects around the world. Steel tendons at joint locations, however, are vulnerable to corrosion damages, which cause deteriorations and in extreme cases lead to the collapse of the whole structures. This study experimentally investigates the use of carbon fibre-reinforced polymer (CFRP) tendons as an alternative solution for the PSBs to tackle the corrosion issue. Four large-scale segmental T-shaped concrete beams with internal bonded or unbonded tendons and dry or epoxied joints were built and tested under four-point loading. The test results indicated that CFRP tendons showed satisfactory performances therefore could replace steel tendons for the use in PSBs. All the tested beams exhibited excellent load-carrying capacity and ductility. Tendon bonding condition greatly affected the flexural performance of the segmental beams. Joint type had only a slight effect on the load-carrying capacity and ductility of the beams, but significantly affected the beams’ initial stiffness. Unbonded tendons experienced an evident reduction in the tendon strength at the ultimate stage as a consequence of the loading type, harping effect and joint opening. Both AASTHO-1999 and ACI 440.4R-04 predicted well the tendon stress, thus the load-carrying capacity of the beams with bonded tendons, however, the accuracy significantly reduced for the cases with unbonded tendons. Similarly, the codes did not well estimate the deformation capacity of the prestressed beams with unbonded tendons. An empirical formula is proposed to predict the deflections of beams with unbonded tendons, which yields very close predictions to the experimental results.

Friction and wear behaviors of MoS2-multi-walled-carbonnanotube hybrid reinforced polyurethane composite coating

MoS2-multi-walled-carbon-nanotube (MWCNT) hybrids containing two-dimensional MoS2 and one-dimensional MWCNTs were synthesized through a one-step hydrothermal reaction. X-ray-diffraction and transmission-electron-microscopy results demonstrated that MoS2 nanosheets were successfully synthesized, and uniformly anchored on the MWCNTs’ surfaces. Furthermore, the effects of the MoS2-MWCNT hybrids on the tribological performances of polyurethane composite coatings were investigated using a UMT-2MT tribo-tester. Friction and wear test results revealed that the friction coefficient and wear rate of a 3 wt% MoS2-MWCNT-1 filled polyurethane composite coating were reduced by 25.6% and 65.5%, respectively. The outstanding tribological performance of the MoS2-MWCNT-1 reinforced polyurethane composite coating was attributed to the excellent load-carrying capacity of the MWCNTs and good lubricant ability of MoS2. The surface morphologies of the worn surfaces and counterpart ball surfaces were investigated to reveal the wear mechanisms.