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19 pages, 6387 KiB

Open AccessArticle

Performance Analysis of the C/C Composite Cylindrical Reverse Inter-Shaft Gas Film Seal

by Hua Su, Shuaike Zhao and Xiaofei Yang

Lubricants 2023, 11(5), 214; https://doi.org/10.3390/lubricants11050214 - 9 May 2023

Viewed by 1942

Abstract

The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft [...] Read more.

The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft seal structure and carries out a performance simulation analysis based on bidirectional fluid–solid coupling technology. The results show that the cylindrical reverse inter-shaft gas film seal with double-layer C/C composite sealing rings with different material mesoscopic parameters can balance seal leakage and friction power consumption and is beneficial to improving the comprehensive performance of the seal. As the mesoscopic parameters of the inner sealing ring material increase in warp and weft density, the sealing leakage rate decreases, and the gas film force and gas friction power consumption all increase. As the pressure difference increases, the sealing leakage rate and gas film force increase. As the rotation speed of the inner and outer rotors increases, the seal leakage rate increases, and the gas film force decreases. A C/C composite sealing ring cylindrical reverse inter-shaft gas film seal has a lower leakage rate and larger gas film force than a graphite sealing ring cylindrical reverse inter-shaft seal, which confers certain performance advantages. The work in this paper can provide a reference for the design of reverse inter-shaft seals. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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19 pages, 6729 KiB

Open AccessArticle

Lubrication Film Generation with Limited Lubricant Supply and Its Tuned Oil Replenishment in a Cylinder-on-Disc Contact

by Wei Jin, Feng Guo, Shuyi Li, Zhaogang Jing and Pat Lam Wong

Lubricants 2023, 11(3), 93; https://doi.org/10.3390/lubricants11030093 - 21 Feb 2023

Cited by 4 | Viewed by 3311

Abstract

Limited lubricant supply (LLS) with tuned dosage is an emerging approach to reduce friction and energy consumption. However, LLS can cause severe starvation when the oil supply is insufficient. Therefore, how to effectively replenish oil to the lubricated contact in LLS operation is [...] Read more.

Limited lubricant supply (LLS) with tuned dosage is an emerging approach to reduce friction and energy consumption. However, LLS can cause severe starvation when the oil supply is insufficient. Therefore, how to effectively replenish oil to the lubricated contact in LLS operation is very important. Using a custom-made optical slider bearing test rig, this work experimentally revealed some characteristics of LLS lubrication in a cylinder-on-disc contact, and proposed two wettability gradient patterns, namely stripe wettability and interlaced wettability, to regulate the lubricant supply to improve the lubricating properties of LLS. The effect of these two wettability patterns was evaluated experimentally according to the lubricating film thickness. The interferograms of the bearing contact under LLS show that the two patterns can augment the oil replenishment through unidirectional lubricant transport by the unbalanced interfacial force via the wettability gradient. Moreover, the interlaced wettability pattern is more effective due to the discontinuous distribution of lubricant from its hydrophilic/hydrophobic region intervals and the transfer of the hydrophobic film to the hydrophilic regions. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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11 pages, 2244 KiB

Open AccessArticle

Modified Ni Nanoparticles as Additives in Various Greases: Assessment of Comparative Performance Potential

by Jiabei Wang, Hong Zhang, Wenjing Hu and Jiusheng Li

Lubricants 2022, 10(12), 367; https://doi.org/10.3390/lubricants10120367 - 17 Dec 2022

Cited by 6 | Viewed by 2162

Abstract

China’s rapid industrial development requires more energy consumption based on non-renewable energy resources. The energy consumption caused by unnecessary friction accounts for about 4.5% of the GDP in China. Although grease effectively lubricates machines, lubrication failure may occur under severe conditions. Nanomaterials exhibit [...] Read more.

China’s rapid industrial development requires more energy consumption based on non-renewable energy resources. The energy consumption caused by unnecessary friction accounts for about 4.5% of the GDP in China. Although grease effectively lubricates machines, lubrication failure may occur under severe conditions. Nanomaterials exhibit intriguing tribological performances and have received much attention regarding lubrication. In this study, oleylamine-modified Ni nanoparticles (OA-Ni) were synthesized and used as lubricant additive in four kinds of commonly used greases: lithium, calcium, composite calcium, and polyurea grease. The OA-Ni were uniformly dispersed in the greases through electromagnetic stirring, ultrasonic vibration, and three-roll grinding. The physicochemical properties and the structure of OA-Ni-doped grease were investigated, while the feasibility of OA-Ni as various grease additives at different contact modes was evaluated by a four-ball friction tester and a UMT-tribolab tester. Tribological tests results revealed that the friction-reducing and anti-wear properties of point-to-point contact were increased by 56.7% and 70.3% in lithium grease, respectively, while those of the point-to-face contact were increased by 59.5% and 68.9% in polyurea grease, respectively. The present work provides not only theoretical guidance of nano nickel modification but also a practical reference for the application of modified nanomaterials to various greases. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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15 pages, 37416 KiB

Open AccessArticle

Experimental Study on the Lubrication Enhancement of Slider-on-Disc Contact by Stearic Acid Adsorption under Limited Lubricant Supply

by Yusheng Jian, Zhaogang Jing, Feng Guo, Pat Lam Wong and Xinming Li

Lubricants 2022, 10(12), 353; https://doi.org/10.3390/lubricants10120353 - 6 Dec 2022

Cited by 2 | Viewed by 3678

Abstract

The optimization of the lubricant supply quantity contributes to minimizing energy losses and wastage. To enhance the performance of hydrodynamic bearings running with limited lubricant supply (LLS), this study examined the effect of stearic acid as an additive. Stearic acid is commonly used [...] Read more.

The optimization of the lubricant supply quantity contributes to minimizing energy losses and wastage. To enhance the performance of hydrodynamic bearings running with limited lubricant supply (LLS), this study examined the effect of stearic acid as an additive. Stearic acid is commonly used for boundary lubrication as an organic friction modifier. How the stearic acid adsorption affects the hydrodynamic lubrication of a slider-on-disc contact under LLS was investigated using interferometry measurement and fluorescence observation in this study. Firstly, the oil reservoir of PAO10 with stearic acid adsorption was observed at the slider entrance. Secondly, the film thickness versus speed of PAO10 and PAO10 with 0.1% and 0.3% stearic acid, respectively, were measured. Finally, the morphology and surface properties of the glass and steel blocks with stearic acid adsorption were characterized by atomic force microscopy and Fourier transform infrared spectroscopy. The results show that the stearic acid adsorption layer weakens the wettability of the lubrication track and induces the ‘dewetting’ phenomenon of the lubricating oil. Thus, discrete oil distribution in the form of stripe or droplet can be generated, which leads to the accumulation of lubricating oil at the slider entrance to form a reservoir. An additional inlet pressure that is generated by the oil reservoir due to surface tension increases the oil film formation capacity. Furthermore, the morphologies of the adsorbed stearic acid layer on the glass and the steel blocks are, respectively, characterized by the nano-sized granular bulge and brush structure. This study reveals a new role of stearic acid adsorption in promoting LLS lubrication. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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15 pages, 4685 KiB

Open AccessArticle

Tribological Properties of Polydopamine-Modified Ag as Lubricant Oil Additives

by Yanxin Zhang, Jun Cheng, Changfeng Lu, Hao Chen, Guoxin Xie, Lin Zhang and Jianbin Luo

Lubricants 2022, 10(12), 343; https://doi.org/10.3390/lubricants10120343 - 1 Dec 2022

Cited by 1 | Viewed by 2315

Abstract

Nanoparticles agglomerate easily because of their high surface energy, which seriously reduces their tribological properties as lubricant additives. In this work, the core-shell nanoparticles Ag@polydopamine (PDA) were successfully prepared by the self-oxidation of dopamine hydrochloride on the surface of Ag nanoparticles and the [...] Read more.

Nanoparticles agglomerate easily because of their high surface energy, which seriously reduces their tribological properties as lubricant additives. In this work, the core-shell nanoparticles Ag@polydopamine (PDA) were successfully prepared by the self-oxidation of dopamine hydrochloride on the surface of Ag nanoparticles and the dispersion of Ag nanoparticles in PAO6 was improved to promote anti-wear behaviors. The tribological properties of Ag@PDA nanocomposites as additives in poly alpha olefin (PAO) oil were studied under different concentrations, pressure and speed conditions by UMT-5 tribometer. It was demonstrated that the strong electrostatic repulsion of the PDA structure made the Ag nanoparticles better dispersed in PAO oil, thus playing a better lubricating role. When the concentration of the modified nanoparticles was 0.25 wt%, the friction coefficient of the lubricating oil decreased by 18.67% and no obvious wear was observed on the friction pair surface. When the Ag@PDA content was higher than 0.25 wt%, the tribological performance of the lubricating oil was weakened, which may be due to excessive Ag@PDA acting as an abrasive on the friction surface, thereby increasing friction and wear. The friction coefficient of the lubricating oil containing Ag@PDA decreased with the increase in load, but hardly changed with the increase in frequency. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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9 pages, 2996 KiB

Open AccessArticle

Elastic Contact Analysis of Shot-Peened Rough Surfaces

by Wanlin Dai, Weike Yuan and Gangfeng Wang

Lubricants 2022, 10(12), 331; https://doi.org/10.3390/lubricants10120331 - 24 Nov 2022

Viewed by 1840

Abstract

Shot peening can effectively improve the mechanical performance of metal components, and thus has been widely employed in the engineering field. During the processing, the surface roughness of treated components will be completely changed, which could strongly affect their tribological behavior. However, few [...] Read more.

Shot peening can effectively improve the mechanical performance of metal components, and thus has been widely employed in the engineering field. During the processing, the surface roughness of treated components will be completely changed, which could strongly affect their tribological behavior. However, few of the existing contact models are directed toward the rough surfaces generated by shot peening. In this study, the normal contact response between a shot-peened surface and a rigid plane is investigated based on the finite element method and the recently developed incremental contact model. The elastic contacts of the rough surfaces experimentally measured on three different shot-peened specimens are considered. Contrary to the conventional rough contact models, it is found that the dependence of the external load on the real contact area for the shot-peened surfaces is not at all linear, even for light loads. The slope of the area–load curve significantly varies at two transition points, which are intrinsically linked to the special structure of shot-peened surfaces. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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15 pages, 5725 KiB

Open AccessArticle

The Partial Derivative Method for Dynamic Stiffness and Damping Coefficients of Supercritical CO₂ Foil Bearings

by Dongjiang Han and Chunxiao Bi

Lubricants 2022, 10(11), 307; https://doi.org/10.3390/lubricants10110307 - 13 Nov 2022

Cited by 4 | Viewed by 2117

Abstract

Supercritical CO₂ foil bearings are promising bearing technology for supercritical CO₂ high-speed turbomachinery. The partial derivative method including complete variable perturbation of the compressible turbulent lubrication Reynolds equation is effective to predict the frequency dependent dynamic stiffness and damping coefficients of [...] Read more.

Supercritical CO₂ foil bearings are promising bearing technology for supercritical CO₂ high-speed turbomachinery. The partial derivative method including complete variable perturbation of the compressible turbulent lubrication Reynolds equation is effective to predict the frequency dependent dynamic stiffness and damping coefficients of supercritical CO₂ bearings. In this research, the structural perturbation of foil dynamic model was introduced into this method and then the dynamic coefficients of supercritical CO₂ foil bearings were calculated. The results of parametric analysis show that the structural loss factor has little influence on the trend of dynamic coefficients changing with the dimensionless support stiffness but mainly affects the value of stiffness coefficients as well as damping coefficients. Due to the turbulence effect, the bearing number is not able to directly determine the characteristics of supercritical CO₂ foil bearings, which is different from air bearings. Compared to the bearing number, the influence of the average Reynolds number on the change of dynamic coefficients with dimensionless support stiffness is more obvious. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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17 pages, 10977 KiB

Open AccessArticle

Optimization Design of Aerostatic Bearings with Square Micro-Hole Arrayed Restrictor for the Improvement of Stability: Theoretical Predictions and Experimental Measurements

by Puliang Yu, Jiong Lu, Qiang Luo, Guanghui Li and Xianxiong Yin

Lubricants 2022, 10(11), 295; https://doi.org/10.3390/lubricants10110295 - 4 Nov 2022

Cited by 10 | Viewed by 1794

Abstract

Aerostatic bearings are widely used in ultra-precision manufacturing equipment as a crucial support component. However, turbulent vortices in the recess can induce micro-vibration of the aerostatic bearing, which can severely affect stability. To further suppress the formation of turbulent vortices and reduce the [...] Read more.

Aerostatic bearings are widely used in ultra-precision manufacturing equipment as a crucial support component. However, turbulent vortices in the recess can induce micro-vibration of the aerostatic bearing, which can severely affect stability. To further suppress the formation of turbulent vortices and reduce the micro-vibration, an aerostatic bearing with a square micro-hole arrayed restrictor (SMAR) was designed and the influences of structural parameters of the SMAR on its static and dynamic performance were investigated using numerical simulations and experiments. The transient flow characteristics of aerostatic bearings with different numbers and spacing of micro-holes were studied using 3D large eddy simulation (LES), and the formation mechanism of turbulent vortices and the law of turbulent interaction between adjacent micro-holes were analyzed. The static performance and micro-vibration of the aerostatic bearing were measured experimentally to verify the effectiveness of the SMAR. The results show that the formation of turbulent vortices and micro-vibrations can be effectively reduced by the optimized design of the SMAR, while the static performance of the bearing is basically unchanged. The micro-vibration decreases rapidly with the number of micro-holes ranging from 1 to 36 and remains steady with the number of micro-holes ranging from 36 to 100. The micro-vibration decreases rapidly with the spacing of micro-holes ranging from 2 d_n to 8 d_n and remains steady with the spacing of micro-holes ranging from 8 d_n to 10 d_n. This study contributes to further understanding the mechanism of turbulent vortex formation in aerostatic bearings with a SMAR. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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19 pages, 11267 KiB

Open AccessArticle

The Fluid-Structure-Thermal Performance Analysis of Gas Foil Thrust Bearing by Using Computational Fluid Dynamics

by Xiaomin Liu, Changlin Li and Jianjun Du

Lubricants 2022, 10(11), 294; https://doi.org/10.3390/lubricants10110294 - 3 Nov 2022

Cited by 5 | Viewed by 2638

Abstract

This paper presents a detailed three-dimensional (3D) thermo-elastic-hydrodynamic (TEHD) multi-physics model of the bump-type gas foil thrust bearing based on computational fluid dynamics (CFD). In this model, the moving mesh technology is applied in the fluid flow domain, and the new boundary condition [...] Read more.

This paper presents a detailed three-dimensional (3D) thermo-elastic-hydrodynamic (TEHD) multi-physics model of the bump-type gas foil thrust bearing based on computational fluid dynamics (CFD). In this model, the moving mesh technology is applied in the fluid flow domain, and the new boundary condition of fully developed flow is applied at the inlet and outlet boundaries, which is consistent with the continuous property of fluid flow and has better convergence performance in CFD. The groove between pads is set as the symmetry boundary. The contact pairs with Coulomb friction and contact/separation behaviors are considered in the structure deformation and heat transfer. The simulation results indicated that the boundary pressure has a significant influence on the foil deformation. It also revealed the heat flux transfer path and temperature distribution in the gas foil thrust-bearing (GFTB) system. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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13 pages, 3540 KiB

Open AccessArticle

Novel Tribometer for Coated Self-Lubricating Spherical Plain Bearings in a Vacuum

by Zhen Li, Zhinan Zhang, Qingsong Yong, Guozheng Ma, Aobo Wei and Haidou Wang

Lubricants 2022, 10(11), 291; https://doi.org/10.3390/lubricants10110291 - 2 Nov 2022

Cited by 2 | Viewed by 2215

Abstract

Coated self-lubricating spherical plain bearings (SSPBs) are a fairly key component of the space-swing mechanism. To examine the operation status and tribological properties of coated SSPBs, a tribometer with a temperature control module in a vacuum condition was developed. The tribometer was mainly [...] Read more.

Coated self-lubricating spherical plain bearings (SSPBs) are a fairly key component of the space-swing mechanism. To examine the operation status and tribological properties of coated SSPBs, a tribometer with a temperature control module in a vacuum condition was developed. The tribometer was mainly composed of a fixture system, reciprocating rotational motion system, environment control system, etc. First, the tribometer was verified with the self-made hydrogenated diamond-like carbon (H-DLC) SSPBs. The sensor signals indicated that the tribometer conformed to the design specifications. Then, the influence of friction heat on the tribological properties of H-DLC SSPBs was analyzed. The results showed that friction torque and temperature increased with the overall test time. Although the temperature had reached 48 °C, the frictional heat had little effect on the H-DLC SSPBs’ lifespans. The damage mechanism of H-DLC SSPBs was dominated by abrasive wear and fatigue wear in vacuum conditions. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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16 pages, 20798 KiB

Open AccessArticle

Occurrence of Grease Lubricated Impact-Sliding Composite Wear

by Zhendong Lv, Yiming Han, Rui Zhang and Jing Wang

Lubricants 2022, 10(11), 284; https://doi.org/10.3390/lubricants10110284 - 28 Oct 2022

Cited by 2 | Viewed by 1578

Abstract

In industrial chain drives, the sleeve slides on the pin and impact loading occurs due to the polygon effect, while the collision between the ball and cage usually produces an impact-sliding motion in the rolling element bearings. Aiming at addressing the occurrence of [...] Read more.

In industrial chain drives, the sleeve slides on the pin and impact loading occurs due to the polygon effect, while the collision between the ball and cage usually produces an impact-sliding motion in the rolling element bearings. Aiming at addressing the occurrence of surface damage caused by the impact-sliding motion, a ball–disk test rig employing optical interference technology was designed and built to realize load variation. Two kinds of commercial grease types, Klüber Centoplex 3 and Centoplex 2EP, were used in the experiments when the glass disk slides at a constant speed while the steel ball collides into them. The sliding and impact motions were controlled by PLC programming. After the experiments, the mid-section grease film distributions were measured using DIIM software. The results show that surface damage can rapidly occur even in the first working cycle, and that the phenomenon is affected by the sliding speed, maximum load, and grease consistency. When the sliding speed is low, multiple contacts of asperity peaks occur in the interior contact region and develop into adhesive wear. When the sliding speed increases, surface wear starts to occur at the side-lobe position of the elastohydrodynamic lubrication (EHL) horseshoe shape and extends with time accompanied by obvious surface scratches. The wear mechanism investigated provides valuable visible information for the further exploration of impact-sliding composite wear. It is suggested that great attention should be paid to impact-sliding wear occurring with grease lubrication since such working conditions are very common in industrial applications. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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15 pages, 4364 KiB

Open AccessArticle

Experimental Measurement of Ice-Curling Stone Friction Coefficient Based on Computer Vision Technology: A Case Study of “Ice Cube” for 2022 Beijing Winter Olympics

by Junxing Li, Shuaiyu Li, Wenyuan Zhang, Bo Wei and Qiyong Yang

Lubricants 2022, 10(10), 265; https://doi.org/10.3390/lubricants10100265 - 18 Oct 2022

Cited by 2 | Viewed by 3492

Abstract

In the curling sport, the coefficient of friction between the curling stone and pebbled ice is crucial to predict the motion trajectory. However, the theoretical and experimental investigations on stone–ice friction are limited, mainly due to the limitations of the field measurement techniques [...] Read more.

In the curling sport, the coefficient of friction between the curling stone and pebbled ice is crucial to predict the motion trajectory. However, the theoretical and experimental investigations on stone–ice friction are limited, mainly due to the limitations of the field measurement techniques and the inadequacy of the experimental data from professional curling rinks. In this paper, on-site measurement of the stone–ice friction coefficient in a prefabricated ice rink for the Beijing Winter Olympics curling event was carried out based on computer vision technology. Firstly, a procedure to determine the location of the curling stone was proposed using YOLO-V3 (You Only Look Once, Version 3) deep neural networks and the CSRT Object tracking algorithm. Video data was recorded during the curling stone throwing experiments, and the friction coefficient was extracted. Furthermore, the influence of the sliding velocity on the friction coefficient was discussed. Comparison with published experimental data and models and verification of the obtained results, using a sensor-based method, were conducted. Results show that the coefficient of friction (ranging from 0.006 to 0.016) decreased with increasing sliding velocity, due to the presence of a liquid-like layer. Our obtained results were consistent with the literature data and the friction model of Lozowski. In addition, the experimental results of the computer vision technique method and the accelerometer sensor method showed remarkable agreement, supporting the accuracy and reliability of our proposed measurement procedure based on deep learning. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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17 pages, 4763 KiB

Open AccessArticle

Study of the Contact Characteristics of Machine Tool Spindle Bearings under Strong Asymmetric Loads and High-Temperature Lubrication Oil

by Yanfang Dong, Feifan Chen, Ming Qiu, Huijie Wang and Chuanmeng Yang

Lubricants 2022, 10(10), 264; https://doi.org/10.3390/lubricants10100264 - 18 Oct 2022

Cited by 7 | Viewed by 2393

Abstract

The contact characteristics of angular contact ball bearings are closely related to the thermal failure of high-speed spindle systems. This paper establishes a closed-loop iterative model for analyzing the ball–race contact characteristics of machine tool spindle bearings at different combined loads and oil [...] Read more.

The contact characteristics of angular contact ball bearings are closely related to the thermal failure of high-speed spindle systems. This paper establishes a closed-loop iterative model for analyzing the ball–race contact characteristics of machine tool spindle bearings at different combined loads and oil supply temperatures, based on a five-degree-of-freedom quasi-static analysis model and the finite difference method. Additionally, the accuracy of the proposed model is verified by comparing the measured values of temperature rise with the predicted values. Based on the verification of the accuracy of the model, the contact characteristics of machine tool spindle bearings under strong asymmetric loads and high-temperature lubrication oil are discussed in detail. The results show that at elevated temperatures, the internal loads of angular contact ball bearings operating under combined loads become concentrated, which will lead to reduced fatigue life of the bearings and even thermal seizure. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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29 pages, 19781 KiB

Open AccessArticle

Investigations on the Frictional Hysteresis Effect of Multi-Leaf Journal Foil Bearing: Modeling, Predictions and Validations

by Changlin Li, Jianjun Du, Jie Li and Zhenni Xu

Lubricants 2022, 10(10), 261; https://doi.org/10.3390/lubricants10100261 - 14 Oct 2022

Cited by 6 | Viewed by 2100

Abstract

Multi-leaf journal foil bearing (MLJFB) is well known for its applications in the air cycle machines (ACMs) of airplanes. However, its frictional energy dissipation mechanism of overlapped foils has not been theoretically studied and is still not clear to researchers. This paper models [...] Read more.

Multi-leaf journal foil bearing (MLJFB) is well known for its applications in the air cycle machines (ACMs) of airplanes. However, its frictional energy dissipation mechanism of overlapped foils has not been theoretically studied and is still not clear to researchers. This paper models the frictional sliding/sticking behaviors between adjacent foil leaves based on the tangent gap, applying the penalty method of contact mechanics. Large foil deformations are calculated to simulate the processes of foil assembly and rotor insertion using nonlinear curve beam elements. Predictions of the frictional hysteresis characteristics of MLJFB are obtained, influenced by foil boundary conditions, leaf number, bearing radial clearance and other foil structural parameters, which correlate well with the test results. This study lays solid theoretical foundations for the static and dynamic research of MLJFB. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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12 pages, 5305 KiB

Open AccessArticle

Effect of Substrate Roughness on the Friction and Wear Behaviors of Laser-Induced Graphene Film

by Peidong Xue, Zhiquan Huang and Cheng Chen

Lubricants 2022, 10(10), 239; https://doi.org/10.3390/lubricants10100239 - 27 Sep 2022

Cited by 4 | Viewed by 2349

Abstract

A rough substrate usually induces severe detriments limiting the performance of anti-friction materials that would lead to an increase in both the friction coefficient and wear rate. In this work, we found that a laser-induced graphene (LIG) film had a good friction adaptability [...] Read more.

A rough substrate usually induces severe detriments limiting the performance of anti-friction materials that would lead to an increase in both the friction coefficient and wear rate. In this work, we found that a laser-induced graphene (LIG) film had a good friction adaptability on both mirror-polished and rough Si substrates. The friction coefficient of the LIG increased from 0.11 to 0.24 and the substrate roughness increased from 1.4 nm to 54.8 nm, while the wear life of the LIG was more than 20,000 cycles for both the mirror-polished and rough Si substrates. Optical microscope, Raman spectroscopy and scanning electron microscope analyses revealed a friction mechanism evolution of the LIG films on Si substrates with a different roughness. For the mirror-polished Si substrate, thick and dense graphene nanocrystallite transfer films could form on the counterpart balls, which guaranteed a long and stable wear. For the rough Si substrate, although the asperities on the rough surface would plough the counterpart balls and destabilize the transfer film formation, grooves could effectively store a compressed LIG, benefiting a stable anti-wear performance and reducing the abrasive wear at the friction interface. This work showed that a LIG film had outstanding friction adaptability on Si substrates with a different roughness and that it can be fabricated in a single-step economic process, indicating bright practical prospects in the solid lubrication fields. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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17 pages, 5444 KiB

Open AccessArticle

Separation and Extraction of Mixed Grinding Chips of Artificial Joints with Different Densities by Multiple Centrifugal Separations

by Cunao Feng, Yujie Zhao, Tao Zhang, Kai Chen, Xiaowei Li and Dekun Zhang

Lubricants 2022, 10(9), 226; https://doi.org/10.3390/lubricants10090226 - 19 Sep 2022

Cited by 1 | Viewed by 1840

Abstract

Aseptic loosening caused by the wear and tear of the artificial joint prosthesis after implantation is one of the main causes of artificial joint failure. Therefore, it is important to investigate the wear debris generated due to wear when developing new artificial joint [...] Read more.

Aseptic loosening caused by the wear and tear of the artificial joint prosthesis after implantation is one of the main causes of artificial joint failure. Therefore, it is important to investigate the wear debris generated due to wear when developing new artificial joint materials. Aseptic loosening is related to the size, number, and morphology of wear debris, and this study proposed the separation and extraction of mixed wear debris with different density ratios of artificial joints by centrifugation to study the characteristics of different artificial joint wear and wear debris extraction rates. The results showed that multiple centrifugations to separate the mixed wear debris were able to reintroduce the wear debris on the wall of the centrifuge tube into the solution and that the wear debris extraction rate was increased. Suspensions with different density ratios of artificially jointed mixed wear debris were effectively separated by this method. The total extraction rate of the three repeated extractions compared to the first extraction rate, the extraction rate of CoCrMo wear debris increased by 6.7%, ultra-high molecular weight polyethylene (UHMWPE) wear debris increased by 15.1–23.44%, ZrO₂ wear debris increased by 10.91%, and that of polyether ether ketone (PEEK) wear debris increased by 9.95%. This method for separating and extracting wear debris from artificial joints can realize the separation of mixed wear debris from artificial joints and obtain a high extraction rate and high-quality wear debris images, investigate the wear mechanism of artificial joint implants, and provide valuable information on the wear performance of new artificial joint implants under investigation. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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16 pages, 69120 KiB

Open AccessArticle

Effect of Cutting Parameters on Tool Chipping Mechanism and Tool Wear Multi-Patterns in Face Milling Inconel 718

by Delin Liu, Zhanqiang Liu and Bing Wang

Lubricants 2022, 10(9), 218; https://doi.org/10.3390/lubricants10090218 - 9 Sep 2022

Cited by 12 | Viewed by 2806

Abstract

Tool wear behavior is mainly influenced by cutting parameters for a given tool–workpiece pair and cutting process. Rapid tool wear increases production costs and deteriorates machining quality in manufacturing industries. Inconel 718 is prone to severe tool wear in the milling process due [...] Read more.

Tool wear behavior is mainly influenced by cutting parameters for a given tool–workpiece pair and cutting process. Rapid tool wear increases production costs and deteriorates machining quality in manufacturing industries. Inconel 718 is prone to severe tool wear in the milling process due to its high strength under elevated temperature and being prone to work hardening. The effects of cutting speed and feed rate on the tool chipping mechanism and tool wear multi-patterns in face milling Inconel 718 with cemented carbide tools are investigated in this research. Firstly, the face milling experiments of Inconel 718 were conducted with various cutting speeds and feed rates. The experimental results show that the tool wear morphology, especially the tool edge chipping on the flank face, is changed with the cutting parameters. Secondly, the tool chipping mechanism in the milling process is discussed. The effects of cutting speed and feed rate on the chipping and wear patterns of cutting tools are clarified. Finally, the ANOVA analysis is conducted to verify the effects of cutting parameters on cutting force, tool life, and tool edge chipping. This work provides an experimental basis for process parameter optimization to alleviate cutting tool wear in machining processes. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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12 pages, 2106 KiB

Open AccessArticle

Influence of Test Parameters on the Evaluation of Chocolate Silkiness Using the Tribological Method

by Zifeng Ni, Shanhua Qian, Shuai Cheng, Liang Wang and Feifei Xu

Lubricants 2022, 10(9), 217; https://doi.org/10.3390/lubricants10090217 - 8 Sep 2022

Viewed by 1846

Abstract

Silkiness is an extremely important attribute in high-end chocolate, and tribology is one of the commonly used methods of evaluating certain properties of the relevant food. In this study, based on three commercial chocolates of the same brand, the silky sensation was assessed [...] Read more.

Silkiness is an extremely important attribute in high-end chocolate, and tribology is one of the commonly used methods of evaluating certain properties of the relevant food. In this study, based on three commercial chocolates of the same brand, the silky sensation was assessed by means of the professional sensation evaluation method. Artificial saliva was employed to obtain the mixed solutions with different chocolates, and their viscosity and coefficient of friction (CoF) were measured under different test parameters. The correlation of chocolate silkiness with the viscosities and average CoFs (aCoFs) are later discussed. The results showed that the silkiness of the three chocolates were negatively correlated with cocoa concentration and weakly correlated with viscosity. As the chocolate percentage decreased, the aCoF of the mixed solutions decreased, but the aCoF of the mixed solutions increased in relation to the cocoa concentration. In combination with the correlation coefficient of chocolate silkiness with the aCoFs, it was considered that 75% chocolate solutions using the Two-PDMS pair could be representative of the silkiness characteristic in oral processing at suitable operated parameters. The study results provide an insight into the rapid evaluation and development of similar attributes of high-end food. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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9 pages, 1215 KiB

Open AccessArticle

Acid Number Prediction Model of Lubricating Oil Based on Mid-Infrared Spectroscopy

by Fanhao Zhou, Kun Yang, Dayang Li and Xinfa Shi

Lubricants 2022, 10(9), 205; https://doi.org/10.3390/lubricants10090205 - 29 Aug 2022

Cited by 6 | Viewed by 2282

Abstract

The monitoring and replacement of lubricating oil has an important impact on mechanical equipment. In this study, based on the infrared spectroscopy monitoring method, an acid value index prediction model is established. The support vector machine regression method is used to quantitatively analyze [...] Read more.

The monitoring and replacement of lubricating oil has an important impact on mechanical equipment. In this study, based on the infrared spectroscopy monitoring method, an acid value index prediction model is established. The support vector machine regression method is used to quantitatively analyze the acid number of the oil sample, which verifies the stability and predictive ability of the quantitative prediction model, and we provide a theoretical basis and practical examples for the online monitoring of oil indicators. In addition, a support vector machine regression model is established by observing the changing law of the spectral absorption peak and selecting the dominant wavelength, and it is compared against the prediction algorithm of the long- and short-term memory network. By comparing the deviation relationship between the predicted value and the real chemical value, the feasibility of the infrared spectroscopy prediction model is verified. The experimental results show that the correlation coefficient between the predicted value of the model and the actual measured value reaches 0.98. This proves that the prediction effect of the prediction model based on the infrared spectrum data and the support vector machine regression method is better than that of the long- and short-term memory network trend prediction model, and the predicted results are reliable. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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21 pages, 6571 KiB

Open AccessArticle

Modified Graphene/Muscovite Nanocomposite as a Lubricant Additive: Tribological Performance and Mechanism

by Zhinan Zhao, Yujunwen Li, Wu Lei and Qingli Hao

Lubricants 2022, 10(8), 190; https://doi.org/10.3390/lubricants10080190 - 19 Aug 2022

Cited by 3 | Viewed by 1914

Abstract

Modified graphene/muscovite (MGMu) nanocomposite was synthesized with muscovite (Mu) and silane coupling agent modified graphene oxide through a simple hydrothermal method that exhibited excellent dispersion stability in oil. Compared with the base oil sample, the average friction coefficient and wear scar diameter of [...] Read more.

Modified graphene/muscovite (MGMu) nanocomposite was synthesized with muscovite (Mu) and silane coupling agent modified graphene oxide through a simple hydrothermal method that exhibited excellent dispersion stability in oil. Compared with the base oil sample, the average friction coefficient and wear scar diameter of the MGMu oil sample decreased by 64.4 and 20.0%, respectively, and the microhardness of its wear scar was increased by 16.1%. The MGMu showed better tribological performance than its individual component due to the synergetic effect between the two components. The lubrication mechanism was proposed according to the morphology, chemical composition, and microhardness of the surface of wear scars. MGMu as an oil additive could fill between the friction pairs, cling to some asperities, and occur relative sliding between unit layers, thus playing a role in lubrication. It was found that MGMu would react with the surface of the friction pair during the friction process to generate Fe₂O₃, SiO₂, SiC, and new aluminosilicate, which formed a self-repairing layer with high hardness. This chemically reactive film exhibited a lower shear strength, which made the oil sample containing MGMu have a lower coefficient of friction. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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17 pages, 3560 KiB

Open AccessArticle

Tribological Properties of Brake Disc Material for a High-Speed Train and the Evolution of Debris

by Jinnan Wang, Muhammad Qasim Zafar, Yunbo Chen, Peng Pan, Lingli Zuo, Haiyan Zhao and Xiangjun Zhang

Lubricants 2022, 10(8), 168; https://doi.org/10.3390/lubricants10080168 - 25 Jul 2022

Cited by 10 | Viewed by 3465

Abstract

The stability and reliability of braking system are essential factors for the safe operation of high-speed trains. In the proposed work, tribological properties of a newly developed brake disc material namely BD-1 were studied considering the thermal-mechanical effects, as well as the evolutions [...] Read more.

The stability and reliability of braking system are essential factors for the safe operation of high-speed trains. In the proposed work, tribological properties of a newly developed brake disc material namely BD-1 were studied considering the thermal-mechanical effects, as well as the evolutions of wear debris, were particularly examined. The tribological properties were also compared with an existing commercial brake disc material namely BD-2 in text. Friction and wear tests were carried out on BD-1 and BD-2 against a commercial brake pad material (BP) to simulate the real emergence braking conditions of a 350 km/h high-speed railway. The thermal-mechanical coupling effects of the friction velocity, wear mass, temperatures and the friction coefficient were investigated. Local wear track and wear debris were analyzed by using SEM and EDS. Results show that the shape and size of wear debris evolve as the dominant wear mechanism varies during braking tests. As the sliding speed increases from 250 to 1250 rpm, the debris may become fine particles, then into a mixture of lamellar shape and flake shape, and finally becomes fine particles again at high speed. The maximum size of wear debris is first from 20 μm to 65 μm, and then down to 10 μm. As the local area temperature increased by more than 400 °C, debris adhere to the surface forming an adhesive layer that may act as a lubricant. Debris may help to form an adhesive lubrication layer and undertake plastics defor-mation at the speed range of 500–1000 rpm. The local area temperatures prompted the wear debris adhesion and oxidation. After reaching a certain speed limit, a uniform third body appears to protect the material surface from high speed and high temperature. Results suggested that the BD-1 could be a good candidate braking material for high-speed railway applications. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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12 pages, 4002 KiB

Open AccessArticle

Influence of Adsorption Characteristics of Surfactants Sodium Dodecyl Sulfate and Aerosol–OT on Dynamic Process of Water-Based Lubrication

by Jingbo Fang, Pengpeng Bai, Chuke Ouyang, Chenxu Liu, Xiangli Wen, Yuanzhe Li, Yonggang Meng, Liran Ma and Yu Tian

Lubricants 2022, 10(7), 147; https://doi.org/10.3390/lubricants10070147 - 9 Jul 2022

Cited by 2 | Viewed by 2378

Abstract

Surfactant solutions are widely used in industry, and their steady-state lubrication properties have been comprehensively explored, while the “dynamic process” between steady states attracts much less attention. In this study, the lubrication behaviors of sodium dodecyl sulfate (SDS) and sodium bis (2–ethylhexyl) sulfosuccinate [...] Read more.

Surfactant solutions are widely used in industry, and their steady-state lubrication properties have been comprehensively explored, while the “dynamic process” between steady states attracts much less attention. In this study, the lubrication behaviors of sodium dodecyl sulfate (SDS) and sodium bis (2–ethylhexyl) sulfosuccinate (Aerosol–OT, AOT) solutions were comparatively and extensively discussed. Experimental results showed that the duration of the dynamic process of AOT solution lubrication was significantly shorter than that of SDS. The essence of the dynamic process was revealed from the aspects of the running-in of solid surfaces and the adsorption process of surfactant molecules. Unlike the general recognition that the friction force evolution mainly corresponds to the running-in of surfaces, this study indicated that the dynamic adsorption behavior of surfactant molecules mainly contributes to this process. Various experiments and analyses showed that the smaller steric hindrance and lower orientation speed of SDS molecules led to longer diffusion into the confined contact zone and a longer duration of friction force decrease. This work enhances our understanding of the dynamic friction process in water-based lubrication, which could also have important implications for oil-based lubrication and its industrial applications. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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Review

Jump to: Research

20 pages, 11783 KiB

Open AccessReview

A Review of In-Situ TEM Studies on the Mechanical and Tribological Behaviors of Carbon-Based Materials

by Zelong Hu, Xue Fan and Dongfeng Diao

Lubricants 2023, 11(5), 187; https://doi.org/10.3390/lubricants11050187 - 24 Apr 2023

Cited by 1 | Viewed by 2648

Abstract

Carbon-based materials are widely applied in various devices due to their outstanding mechanical and tribological behaviors. In recent years, more attention has been paid to clarifying the nanocontact mechanisms of carbon-based materials, in order to promote nanoscale applications. The in-situ TEM method is [...] Read more.

Carbon-based materials are widely applied in various devices due to their outstanding mechanical and tribological behaviors. In recent years, more attention has been paid to clarifying the nanocontact mechanisms of carbon-based materials, in order to promote nanoscale applications. The in-situ TEM method is currently the only way that can combine contact behavior and real interface. However, there is still a lack of a systematic summary of in-situ TEM studies on carbon-based materials. Therefore, this work provides an overview of in-situ TEM mechanical and tribological studies on carbon-based materials, consisting of the quantitative actuation and detection for in-situ tests, the strength of fracture and yield, the adhesion between interfaces, the friction performance, and wear features of carbon-based materials with different nanostructures, such as carbon nanotube, graphene, graphite, amorphous, sp² nanocrystalline, and ultrananocrystalline diamond. Nanostructures play a crucial role in determining mechanical and tribological behaviors. Perspectives on current challenges and future directions are presented, with the aim of promoting the advancement of in-situ TEM research. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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14 pages, 3234 KiB

Open AccessReview

Review of the State-of-the-Art Application of the Quantitative Structure Tribo-Ability Relationship Model of Lubricants in China

by Xinlei Gao, Miaomiao Shi, Tingting Wang, Li Wu and Hao Chen

Lubricants 2023, 11(2), 36; https://doi.org/10.3390/lubricants11020036 - 19 Jan 2023

Cited by 1 | Viewed by 1738

Abstract

In recent years, lubricant research has developed from empirical to theoretical, from descriptive to rational, from qualitative to quantitative, and from macroscopic to microscopic studies. This review presents the new concept of the quantitative structure tribo-ability relationship (QSTR) derived from the basic principles [...] Read more.

In recent years, lubricant research has developed from empirical to theoretical, from descriptive to rational, from qualitative to quantitative, and from macroscopic to microscopic studies. This review presents the new concept of the quantitative structure tribo-ability relationship (QSTR) derived from the basic principles of quantitative structure activity relationship (QSAR) theory and reviews the latest advances in research on basic problems of the QSTR of lubricants. Specifically, it highlights a series of recent studies conducted by Chinese scholars and future prospects related to these works. It is noted that the study of lubricants involves many related issues, such that there may be omissions in this review. Additionally, the research topics of the quantitative tribo-ability relationship of lubricants covered in this review are mainly mentioned to introduce various modeling methods, and there may be many similar works that are not covered in this review. Despite these limitations, it is hoped that the described QSTR method will become a useful tool and serve as a reference for tribology research groups in the future. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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23 pages, 5389 KiB

Open AccessReview

The Current Situation and Future Direction of Nanoparticles Lubricant Additives in China

by Kun Han, Yujuan Zhang, Ningning Song, Laigui Yu, Pingyu Zhang, Zhijun Zhang, Lei Qian and Shengmao Zhang

Lubricants 2022, 10(11), 312; https://doi.org/10.3390/lubricants10110312 - 17 Nov 2022

Cited by 10 | Viewed by 4190

Abstract

Nanoparticles as lubricant additives demonstrate powerful friction reduction and antiwear properties and are potential alternatives to traditional additives in line with green and environmentally friendly requirements. However, the vast majority of currently available research focuses on the tribological properties of various nanoparticles in [...] Read more.

Nanoparticles as lubricant additives demonstrate powerful friction reduction and antiwear properties and are potential alternatives to traditional additives in line with green and environmentally friendly requirements. However, the vast majority of currently available research focuses on the tribological properties of various nanoparticles in base oils at laboratory, which has a large gap with their application in engineering. To cope with the rapid economic and industrial development in China, there is a need to improve the tribological properties of nanoparticles. This paper highlights the current status and development trend of nanoparticles as lubricant additives in China. The factors influencing the tribological properties of nanoparticles, such as their composition, particle size and morphology, as well as the base stocks and their combination with other additives, are summarized. Furthermore, the research progress in the lubrication mechanism of nanoparticles is discussed, and the issues concerning the application of nanoparticles as lubricant additives as well as their future directions are discussed. This review is expected to provide an impetus to guide the design of high-performance, fully formulated lubricant systems containing nanoparticles as the lubricant additive. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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32 pages, 7438 KiB

Open AccessReview

Graphene-Based Nanomaterials as Lubricant Additives: A Review

by Qiulong Gao, Shuwen Liu, Kaiming Hou, Zhangpeng Li and Jinqing Wang

Lubricants 2022, 10(10), 273; https://doi.org/10.3390/lubricants10100273 - 21 Oct 2022

Cited by 33 | Viewed by 6789

Abstract

Reducing friction and wear by improving the tribological properties of liquid lubricants with additives is one of the most important research goals in tribology. Graphene is a typical two-dimensional (2D) nanomaterial, which has outstanding tribological performance when used as an additive in lubricants. [...] Read more.

Reducing friction and wear by improving the tribological properties of liquid lubricants with additives is one of the most important research goals in tribology. Graphene is a typical two-dimensional (2D) nanomaterial, which has outstanding tribological performance when used as an additive in lubricants. In the past decade, various graphene-based nanomaterials have been fabricated by different methods and investigated as lubricant additives. This review aims at comprehensively overviewing the state-of-the-art graphene-based nanomaterials used as lubricant additives. Firstly, the synthesis methods and material structure are reviewed. Subsequently, the possible mechanism of graphene-based nanomaterials on friction-reduction and anti-wear was briefly discussed. Secondly, tribological properties of various graphene-based nanomaterials as lubricant additives were reviewed and discussed. Additionally, the applications of graphene-based nanomaterials in different lubricating scenarios are also discussed. Finally, challenges and future prospects of graphene-based lubricant additives are proposed. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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44 pages, 16192 KiB

Open AccessReview

Research Progress of High-Speed Wheel–Rail Relationship

by Xuesong Jin

Lubricants 2022, 10(10), 248; https://doi.org/10.3390/lubricants10100248 - 30 Sep 2022

Cited by 14 | Viewed by 7038

Abstract

The research on wheel–rail relationship includes the basic theoretical models and corresponding numerical methods of wheel–rail in rolling contact, geometric parameter matching and material matching of them, friction and wear, wheel–rail rolling contact fatigue, wheel–rail adhesion and noise. They are also key theoretical [...] Read more.

The research on wheel–rail relationship includes the basic theoretical models and corresponding numerical methods of wheel–rail in rolling contact, geometric parameter matching and material matching of them, friction and wear, wheel–rail rolling contact fatigue, wheel–rail adhesion and noise. They are also key theoretical and technical problems of the high-speed train/track coupling system. The basic theoretical models of wheel–rail in rolling contact and the corresponding numerical methods are the basis and one of the basic means for solving other wheel–rail relationship problems. The other is the experimental means. Moreover, the modeling and analysis of coupling behavior of the train and track can only be realized by means of the wheel–rail rolling contact mechanics model and its corresponding numerical method. This paper mainly discusses some research work and achievements on high-speed wheel–rail relationship problems since China opened a high-speed railway system on a large scale. The discussions in this paper include the classic wheel–rail rolling contact theoretical models (analytical forms) and the modern wheel–rail rolling contact theories (numerical methods), their advantages and disadvantages, their application and future development direction of them. The reviewed research progress on the other wheel–rail relationships mainly expounds the thorny problems of the wheel–rail relationship encountered in the operation of China’s high-speed railway, how to adopt new theoretical analysis methods, test means and take effective measures to solve these problems. It also includes research results of similar important reference values performed by international peer experts in related fields. Challenging and unsolved problems in high-speed wheel–rail relationship research are also reviewed in the full text. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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