Journal of Tribology

Intermittent motion is a complex process that involves constant speed, deceleration, static stages, and acceleration. Theoretical analysis suggests that shortening the period of intermittent motion can increase the film thickness during static stages, thereby extending the life of the part. Currently, an increasing number of studies are focusing on small oscillatory movements or vibrations. However, the impact of intermittent motion cycles on the film thickness and wear in the contact area still needs to be investigated. Optical interference and acoustic emission (AE) were employed as experimental methods to investigate simple sliding point contact intermittent motion. The lubrication state transition of full film-starvation-wear in the contact area was observed and the experimental results confirmed the correctness of the elastohydrodynamic lubrication (EHL) theoretical analysis. Additionally, the regularity of starvation and AE signal change with time during intermittent motion were summarized. An in-depth analysis of the reasons why intermittent motion with a short period generates less wear was performed. This analysis provides novel ideas to reduce wear of intermittent motion mechanisms. Overall, this research contributes to the understanding of the wear during intermittent motion and provides essential insights for wear reduction in this area.

Mingyu Zhang

Xinqing Wang

Yiming Han

Jing Wang

C. H. Venner

Point Contact Elastohydrodynamic Lubrication and Wear in Intermittent Motion

点接触弹流润滑与间歇运动中的磨损

The transient film thickness and pressure distributions in point elastohydrodynamic lubrication (EHL) contacts during start–stop–start motion are discussed based on experimental and numerical analyses. When the machine element starts to move after the stopping, where the oil is entrapped between two surfaces, the pressure at the exit area increases very much. The pressure increase depends markedly on the overall film thickness before the stopping of the motion, but is hardly controlled by the acceleration after the stopping. It can be considered that this phenomenon affects the rolling contact fatigue damage.

P. Sperka

J. Wang

I. Krupka

M. Hartl

M. Kaneta

Occurrence of High Pressure Spike in Unidirectional Start–Stop–Start Point Contacts

单向启停点接触中高压尖峰的出现

To improve mechanical efficiency, the tribological performance of short-period intermittent motion needs to be investigated. Based on the theory of thermal elastohydrodynamic lubrication (EHL) and considering the influences of rough surface, a mixed-EHL model under point contact simple sliding intermittent motion is established. Using this model, the transition from mixed-EHL to EHL in the contact area is realized by changing the period of intermittent motion and setting the surface roughness. It is found that the thermal effect on simple sliding intermittent motion should not be ignored, and the pressure, temperature rise distribution, and friction coefficient during the stop and start-up are fluctuated obviously. Under the condition of rough surface contact, the contact area will enter the mixed-EHL state during the stop and start-up. Shortening the period of intermittent motion is beneficial to alleviate the adverse effect of the mixed-EHL.

Minglu Yao

Yong Wan

Point Contact Thermal Mixed Elastohydrodynamic Lubrication Under Short-Period Intermittent Motion

短周期间歇运动下的点接触热混合弹性流体动力润滑

A 3D graded coating/substrate model based on multigrid techniques within a finite difference frame work is presented. Localized refinement is implemented to optimize memory requirement and computing time. Validation of the solver is performed through a comparison with analytical results for (i) a homogeneous material and (ii) a graded material. The algorithm performance is analyzed through a parametric study describing the influence of layer thickness (0.01 &lt; t/a &lt; 10) and mechanical properties (0.005 &lt; Ec/Es &lt; 10) of the coating on the contact parameters (Ph, a). Three-dimensional examples are then presented to illustrate the efficiency and the large range of possibilities of the model. The influence of different gradations of Young’s modulus, constant, linear and sinusoidal, through the coating thickness on the maximum tensile stress is analyzed, showing that the sinusoidal gradation best accommodates the property mismatch of two successive layers. A final case is designed to show that full 3D spatial property variations can be accounted for. Two spherical inclusions of different size made from elastic solids with Young’s modulus and Poisson’s ratio are embedded within an elastically mismatched finite domain and the stress field is computed.

Hugo Boffy

Marie-Christine Baietto

Philippe Sainsot

Antonius A. Lubrecht

An Efficient 3D Model of Heterogeneous Materials for Elastic Contact Applications Using Multigrid Methods

使用多重网格方法的异质材料弹性接触应用高效三维模型

Abstract This article begins by describing standard bearing life models in continuous rotation before going on to explain how the bearing life can be calculated for roller and ball bearings in oscillatory applications. An oscillation factor aosc is introduced, which accounts for the oscillating and stationary ring. This can be calculated numerically as a function of the oscillation angle θ and load zone parameter ɛ as well the parameters γ = D · cos α / dm and the ball-race osculation factors. Critical angles as used by Rumbarger are also employed at low θ values. Appropriate curve-fitted relationships for both roller and ball bearings are then given for a simple calculation of aosc with an accuracy of approximately 10%. Finally, several methods are suggested for estimating the ɛ parameter using a real case with a finite element analysis load distribution accounting for structural ring deformation and ball-race contact angle variations. The results derived in this article allow the lifetime of any arbitrary oscillating ball or roller bearing to be calculated.

Luc Houpert

Oliver Menck

Bearing Life Calculations in Rotating and Oscillating Applications

旋转和摆动应用中的轴承寿命计算

Abstract The aerospace industry aims for net-zero greenhouse gas emissions by 2050, requiring gas turbine engines to reduce CO2 emissions. This will impact engine material selection due to harsher operating conditions, limiting traditional metal/alloy use. While fibre-reinforced polymers (FRP) composites are commonly used in the aerospace industry, their use in gas turbine engines is often restricted by the lower operating temperatures of the polymer matrix. However, many studies have demonstrated the tribological potential of FRP in the fan section of the engines, but little attention has been given to the potential of orienting the fibers in the normal (i.e., out-of-plane) direction relative to the wear surface to leverage the anisotropic properties of FRP composites. This study aims to investigate the impact of fiber orientation on the tribological properties of carbon fiber/PEEK (CF-PEEK) at elevated temperatures. Three CF-PEEK samples with different fiber rientations were selected for the purpose of this study (parallel, anti-parallel and normal directions), as well as a fourth sample of pure PEEK. Tribological tests were conducted using a ball-on-disk tribometer at an elevated temperature of 200°C to evaluate wear and friction behavior. The worn surfaces and counterfaces were analyzed using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and energy dispersive X-ray Spectroscopy (EDS). The findings reveal that CF-PEEK with fibers oriented in the normal direction demonstrates significantly enhanced tribological performance at elevated temperatures, achieving a 95% reduction in the friction coefficient and a 92% decrease in the wear rate compared to pure PEEK. A wear mechanism has been proposed to explain the superior wear resistance of normally oriented fibers in CF-PEEK, linking it to the development of a fiber-based interface during the run-in phase and the formation of a uniform transfer film.

Marie-Laurence Cliche

Robert Mone

Andre C. Liberati

Pantcho Stoyanov

Influence of fiber direction on the tribological behavior of carbon-reinforced PEEK at elevated temperature for application in gas turbine engines

纤维方向对碳纤维增强聚醚醚酮在高温下摩擦行为的影响及其在燃气涡轮发动机中的应用

Abstract Polyoxymethylene (POM) and its composites with excellent mechanical properties are often used as alternative materials in gear transmission design. This paper considers the practical application scenario of POM gears, using a pin-on-disk tribometer to simulate the Hertzian contact and sliding part of gear mesh. The effects of PTFE content (0%, 5%, 10%, 15%), maximum contact pressure (40MPa and 60MPa), sliding speed (0.1m/s and 0.5m/s), and ambient temperature (room temperature and 70°C) on the tribological properties of POM composites under self-mated contact are investigated. The results show that the tribological properties of the composites tend to improve with the increase of PTFE content under the two ambient temperature conditions, reaching the optimum at 15% PTFE content. However, the addition of PTFE does not improve the tribological properties of the composites under the most severe conditions of 70°C and PV value of 30MPa·m/s. At two ambient temperatures, pure POM and its composites exhibit the lowest friction coefficient at PV value of 6MPa·m/s and the smallest specific wear rate at PV value of 20MPa·m/s. The friction coefficient of composites decreases with an increase in ambient temperature from room temperature to 70°C at a sliding speed of 0.1m/s but increases at a sliding speed of 0.5m/s. ANOVA results indicate that all factors are significant, except for temperature which does not have a significant effect on the friction coefficient. Additionally, this paper analyzes the wear mechanisms of composites.

Xinmin Li

Laishi Nie

Wing San Tony Hung

Yonglong Wu

Zhengjie Qiu

The Effect of PTFE Content on Tribological Properties of POM Composites

PTFE含量对POM复合材料摩擦学性能的影响

Abstract This study presents comprehensive findings on the tribological and thermal behavior of polymer gears under varying loads and operating conditions. Gear tooth wear rates and thermal contact behavior were investigated for nylon (PA) and acetal (POM) materials, fabricated using machining (MC). Experimental investigations were performed under loads of 6.5 Nm, 8.5 Nm, and 9.0 Nm, while maintaining a consistent rotational velocity of 1500 rpm. The wear rates and surface temperatures were systematically monitored utilizing a linear variable differential transformer (LVDT) with a precision of 0.1 μm and a high-resolution thermal imaging apparatus. Results revealed that at 9.0 Nm, thermal stabilization reduced wear rates by 15% compared to 8.5 Nm, due to the softened material layer acting as an internal lubricant. Conversely, higher wear rates at 8.5 Nm were attributed to localized debris formation and limited thermal softening. Key findings include the identification of the glass transition temperature of PA at approximately 75°C and its effect on wear behavior. These insights provide a deeper understanding of polymer gear performance, offering guidance for material selection and operational optimization in high-performance applications.

Khalid Abdulkhaliq M Alharbi

Tribological Analysis and Thermal Behavior of Gear Tooth Flanks in Polymer Gears During Dry Operation

干运转条件下聚合物齿轮齿面摩擦学分析与热行为研究

Abstract MoSi2 coatings were prepared on 45CrNi substrate by supersonic plasma spraying. The tribocorrosion resistance of MoSi2 coating and post-treated MoSi2 coating (P-MoSi2) in the seawater environment was analyzed. After post-treatment, some new phases such as MoO3, SiO2 and Mo9O26 are generated in the P-MoSi2 coating. The electrochemical test results indicated that the P-MoSi2 coating has lower current density, larger βc and Rp values than MoSi2 coating in both static corrosion and tribocorrosion tests. The wear test results indicate that the post-treatment reduced the wear rates and the friction coefficients of the coating. The wear mechanisms of both coatings were described to explain the differences. Moreover, the mechanism of the improved tribocorrosion resistance of the coating after post-treatment was explained.

Chunhua Hu

Quanqiang Guo

Xinghao Ji

Yu Liu

The tribocorrosion resistance of post-treated supersonic plasma sprayed MoSi2 coating

经后处理的等离子喷涂MoSi2涂层的摩擦腐蚀抗力

Abstract As the demand for ultrahigh-speed bearings grows, hybrid gas-magnetic bearings (HGMBs) have emerged as a research focus due to the ability to integrate the merits of active magnetic bearings (AMBs) and gas bearings (GBs). However, HGMBs face challenges related to complex structure and manufacturing. This study emphasizes the critical role of radial clearance in HGMB design, as excessive clearance reduces GB load capacity and stability, while insufficient clearance can lead to thermal issues. This work investigates the comprehensive performance of HGMBs with varying clearances, revealing that radial clearance significantly impacts load capacity, power consumption, stability, and startup performance. Reduced clearance enhances load capacity and decreases power losses, while higher clearances lead to instability and increased vibration. Notably, HGMBs exhibit superior stability during startup. The conclusions provide valuable insights for HGMB design, promoting advancements in this technology and the engineering applications.

Qing Liu

Mingdi Wu

Ruihuan Ge

Weipei He

Ziyu Cheng

Effect of radial clearance on static and dynamic performances of single-structured hybrid gas-magnetic bearing rotor system

径向间隙对单一结构混合气体-磁悬浮轴承转子系统静态和动态性能的影响

Abbreviation	J. Tribol.
Journal Impact	2.24
Quartiles(Global)	ENGINEERING, MECHANICAL(Q2)

ISSN	0742-4787, 1528-8897
h-index	98

Publication Information	Publisher: American Society of Mechanical Engineers (ASME)，Publishing cycle: Quarterly，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 1977，Proportion of original research papers: 99.01%，Self Citation Rate:13.60%， Gold OA Rate: 2.19%
Average review cycle	网友分享经验：平均5.0个月
Average recruitment ratio	网友分享经验：约25%

Journal of Tribology

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