Disk Friction Research Articles

Ultra−fast and stable dispersion of graphene oxide in lubricant oil toward excellent tribological property

Graphene oxide (GO) nanocomposite lubricants have been verified with excellent anti−wear and anti−friction properties. However, the rapid transfer of hydrophilic GO nanosheets into hydrophobic lubricants still faces great challenges. In this work, a series of nanocomposite lubricants were successfully fabricated by a simple phase transfer process without complex chemical modification. With the assistance of ethanol and oleylamine, the GO nanosheets initially dispersed in the water phase could be quickly transferred to the mineral oil within 20 s after hand-shaking the immiscible two−phase system. Moreover, the phase−transferred GO nanosheets were greatly stable in the mineral oil for at least seven days. The tribological properties of the GO nanocomposite lubricants had been studied by a macroscopic ball−on−disk friction test. The tribological behavior of the obtained nanocomposite lubricants showed that when 0.1 mg/mL GO was dispersed into mineral oil, the minimum average friction coefficient was 0.140, which was 72% lower than that of mineral oil. The universality of the phase transfer process was verified by the reduced GO nanosheets. This physical phase transfer method must be simple, effective, and environment−friendly to prepare nanocomposite lubricants.

Comparative evaluation of wear resistance between lithium disilicates and polymer infiltrated ceramics manufactured by computer aided design (CAD) computer aided manufacturing (CAM) against natural tooth enamel

Advances in CAD/CAM technology led to development of monolithic all ceramic restorations with superior esthetics like Lithium disilicate. But the major concern of ceramic materials was its wear towards the opposing enamel. Polymer infiltrated ceramics were developed by incorporating resin polymer in ceramics to produce esthetic stability of ceramics and low abrasive nature of composites and very few studies were done on this material. A total of 30 disc specimens were fabricated by CAD/CAM .15 discs of CAD/CAM lithium disilicate (IPS E.max CAD) and 15 discs of Polymer infiltrated ceramics of dimensions 10mmx3mm. They were named as group 1 (CAD/CAM Lithium disilicate) and group 2(Polymer infiltrated ceramics). 30 tooth specimens were mounted on auto polymerising acrylic resin blocks. Tooth specimens were placed on the upper member of the two body wear testing machine (Pin on disc wear and friction test rig, Magnum) and Lithium disilicate and polymer infiltrated ceramic disc specimens were positioned on disc of wear testing apparatus under constant load of 5kg (49N). The specimens were made to rub against one another in a rotating cycle to simulate oral wear cycle. The test was run for total of 10,000 wear cycles at 30rpm on wear machine for each sample. Wear of group 1 and group 2 and enamel wear of group 1 and group 2 was measured before and after wear test by profile projector.Wilcoxon test was done to compare the groups. Results showed that wear was greater in group 1 (Polymer infiltrated ceramics) compared to group 2 (CAD/CAM Lithium disilicate) and enamel wear of group 1 was greater than enamel wear of group 2. Advances in CAD/CAM technology led to development of aesthetic all ceramic restorations with superior mechanical properties such as CAD/CAM Lithium disilicate. But the major concern of ceramic materials is wear towards the opposing enamel. To meet the above requirements polymer infiltrated ceramics are developed by incorporating resin polymer in ceramics to produce esthetic stability of ceramics and low abrasive nature of composites. The restorative materials should not cause wear to opposing enamel and also should possess wear resistance similar to enamel for its success and longevity. This study was performed to evaluate the wear resistance of CAD/CAM lithium disilicate and Polymer infiltrated ceramics against natural teeth enamel.

Effect of parasitic losses on the design optimization of inward flow radial supercritical CO2 turbines

Inward flow radial (IFR) supercritical CO2 (sCO2) turbines are smaller in size and operate at considerably higher speeds in comparison to similar capacity conventional gas or steam turbines. The compact size and high speed of IFR turbines result in significant parasitic (leakage and disk friction) losses at the rotor backface. This paper presents CFD investigations to understand the mechanism of parasitic losses of IFR turbines in the kW to MW power scales. The first part of the paper presents a parametric study to quantify the effect of backface flowpath dimensions, rotor inlet radius, and rotational speed on the magnitude of parasitic losses. Subsequently, the paper proposes the implementation of a radial labyrinth seal on the rotor backface to curtail the parasitic losses. The second part of the paper examines how the power scale of the turbine and its design parameters, specific speed and velocity ratio, influence the magnitude of parasitic losses. The investigation reveals that parasitic losses cause an efficiency drop of 8%–15% for 100 kW and 4%–9% for 1 MW IFR sCO2 turbines. In addition, IFR turbines designed for low specific speeds and high velocity ratios result in notably higher parasitic losses, leading to a decline in turbine efficiency. Finally, the paper presents optimal turbine design parameters accounting for the parasitic losses to maximize turbine efficiency.

Seismic performance of self-centring connections with two energy dissipation stages for reusable modular steel buildings

This paper presented a feasibility study on a self-centring connection with two energy dissipation stages for use as a combined inter-module and intra-module connection in reusable modular steel buildings. The proposed connection was equipped with shape memory alloy (SMA) disc washers and friction dampers, the former for self-centring and the latter for energy-dissipation functions. The design concept of two energy dissipation stages was to achieve structural longevity and member reuse by 1) enabling rapid recovery after small and medium earthquakes, and 2) facilitating prompt repair if at all needed after large earthquakes. A spring analytical model was proposed, wherein each connection component was symbolised as a rotational spring. Based on the model, a design methodology to meet the two-stage performance goals was derived, where the critical story drift ratio between the two stages was expressed as a function of the properties of friction dampers and SMA disc washers. Detailed finite element simulations were used to validate the proposed design concept and the spring model and to assess the influence of the friction dampers and SMA disc washers on the hysteresis behaviour of the connection. The results demonstrated that the proposed connection would facilitate the design objectives when designed based on the proposed spring model to ensure structural longevity, member reuse, and efficient recovery and repair after seismic events.

Intelligent classification of online wear particle in lubricating oil using optical direct imaging method and convolutional neural network for rotating machinery

Different types of wear particles in lubricating oil are crucial information sources for describing wear properties of rotating machinery components. Solving the problem of particle classification using artificial intelligence models depends on sufficient wear samples, though the samples are difficult to obtain, especially in lubricants with real-time online monitoring. First, a high precision particle analyzer for online acquisition of multi-particle images in the circulating oil system based on the optical direct imaging method is developed. Then, a novel hybrid convolutional neural network (CNN) model based on the visual geometry group (VGG) network feature and residual block, called VRCNN, is proposed to classify nine types of metallic and non-metallic particles, including normal, sliding, fatigue, cutting, sphere, ceramic, bubble, plastic, and fiber, using their images. Finally, a dataset produced by a pin disc friction tribometer and bearing accelerated fatigue tester is used to demonstrate the approach. The proposed VRCNN model is also compared with the typical classifiers, including AlexNet, VGG16, RestNet50, SqueezeNet, MobileNetV2, and ShuffleNetV2 models in terms of classification accuracy, standard deviation of accuracy, F1-score, and detection time. The results show that the VRCNN model has a classification accuracy of more than 95%, and its response time is superior to that of the other networks. Furthermore, the operational process of the VRCNN classifier is analyzed visually using the Grad-CAM map. This work is beneficial for improving any type of rotating machinery’s wear mechanism analysis.

Study on the influence of three-body particles on the dynamic performance of braking system

This paper investigates the influence of three-body particle intrusion on the stability of the braking system through experimental research conducted on a friction experiment machine with a friction block-rubber disc structure. This analysis aims to uncover the inherent relationship between key variables and the nonlinear vibration characteristics of the friction pair. The results indicate that the two-block three-body experiment shows weaker chaotic characteristic of the friction force signal compared to the single-block three-body experiment. The chaotic characteristics of the braking friction force signal tend to be amplified or reduced under different pressures, masses of the friction block, and radii of the friction disc. Adjusting the key tribological parameters can suppress the chaotic vibration.

Nonlinear ultrasonic techniques to quantify oxidation damage in carbon/carbon composite material

This research applies linear and nonlinear ultrasonic (NLU) techniques to quantify oxidation damage in a carbon/carbon (C/C) composite material cut from an automotive friction disc ring. The oxidation as a result of gasification of carbon at high temperatures (T >∼ 500 °C) is a major degradation mechanism in C/C composites. This is the first research to successfully use a dry-contact mediator wedge setup for nonlinear ultrasonic applications, enabling repeatable in-situ Rayleigh wave measurements on slow wave velocity materials where submersion is impractical. The samples are subjected to thermal damage by exposure to a high temperature atmosphere over multiple holding times, and the oxidation damage is visualized using scanning electron microscopy (SEM). The sample mass is recorded and both linear (velocity and attenuation) and nonlinear (β′) ultrasonic measurements are performed after each holding time. Superior sensitivity to early stage oxidation affirms the suitability of nonlinear Rayleigh wave measurements for the quantification of thermally induced oxidation damage in C/C composites, while the double mediator wedge setup is well suited for high attenuation, slow wave velocity materials, demonstrating potential applicability for in-situ condition monitoring. The results show that a systematic oxidation starts after 3 min of exposure to the temperature in this C/C composite. The oxidation induced fiber–matrix debonding, matrix defects (appearing to be microcracking), and void growth are consistently detected by the Rayleigh wave velocity and acoustic nonlinearity. In addition to the higher sensitivity, the nonlinearity parameter has the capability of selectively measuring the strength related damage such as the observed fiber–matrix debonding, while the wave velocity can detect the oxidation voids. A combined use of these two parameters can provide useful information on the microstructural evolution in C/C composites subjected to high temperatures.

Super antiwear properties of polytetrafluoroethylene (PTFE) induced by MeV proton irradiation

In this paper, the surface of polytetrafluoroethylene (PTFE) was modified by 1 MeV proton beam at high temperature. The changes of wear resistance and hardness of PTFE before and after irradiation were evaluated by ball/pin disk friction loss tester and nanoindentation tester, respectively. The results showed that the wear resistance of PTFE irradiated by proton at high temperature has been significantly enhanced. The mass wear rate decreases from 2.75 × 10−6 g/Nm to 0.39 × 10−6 g/Nm, and the wear depth decreases from 29.9 μm to 8.2 μm, respectively. Proton irradiation could be a simple and effective method for PTFE surface modification and can significantly improve the wear resistance. The potential chemical reaction mechanism for the improvement of wear resistance of irradiated PTFE in terms of microstructure was discussed. Crosslinking induced by proton irradiation enhanced the interaction force among PTFE molecules, thus the mechanical properties were improved.

Power Transmission Using Circular Elements Bounded by Given Central Angle in Rolling Contact

In the present study, the concept of utilizing two circular cam-track disks, of the same central angle, in combination with one circular roller is presented. The roller is restrained to move within a vertical groove, and at the same time it rotates with rolling-contact on both cam tracks. When the upper cam is fully travelled by the roller, the same occurs with the lower one, despite their different lengths. Therefore, during the rolling contact, the two cams always sweep the same central angle. The aforementioned configuration of the two circular arcs may be considered as a unit cell, which can be repeated an even number of times, and when folded forms a closed circular groove between two cam-track disks. For better understanding, a manufactured prototype and 3D CAD-models have been developed. The operation of this setup as a gearless automotive differential is demonstrated by performing two bench experiments, which are then explained by a simplified mechanical model. The latter focuses on the implementation of the principle of the inclined plane, in which an upper limit of the inclination angle is imposed in accordance with the coefficient of friction at the friction disks. Previous patents on gearless differentials are discussed and other possible applications in mechanical engineering are outlined.

Study on the Effect of ELID Grinding on corrosion wear properties of Co-Cr Alloy

Contemporary Co-Cr alloys used in artificial joints can cause health complications in long-term applications. A pin-on-disc friction and wear testing instrument was used to evaluate the corrosion and abrasion of two types of Co-Cr alloys for artificial joints under simulated body fluid conditions after surface electrolytic composite grinding. Co-materials with lower carbon content displayed superior corrosion resistance than those materials with higher carbon content. Moreover, surface processing with electrolytic composite grinding produced a stable surface modification layer, which improved the surface hardness and formed an oxide film that inhibited metal ionization. The formation of precipitates in the corrosive environment is likely to improve the friction and wear properties of the material. As such, a variety of hardness was observed for the artificial joint friction disc and pin, especially when the hardness of the disc was higher than that of the pin, which can improve the friction and wear behavior of joints.

Certain concepts and definitions of the physical process of wear of friction discs of sewing machine clutches

The article covers analytical research of the performance of the pads of the friction clutch of the sewing machine. The results of research showed that the wear resistance of the pads decreases with increasing temperature. The wear resistance of pads made of different materials tested on the same type of friction clutch of sewing machine is different. The research has been carried out to determine the maximum value of the specific work of slipping and thermal impulse which determines the characteristics of the temperature field of the friction pair which significantly affects the wear resistance of the friction interface. The wear resistance of friction clutches which are one of the main characteristics that determine the reliability and durability of the friction assembly has been studied.

Research on wear law of friction plate of AMT dry clutch under continuous slip wear condition

In the process of operation, because the AMT dry clutch in the process of separation and combination of the slip wear stage, this stage will cause the clutch friction plate wear, resulting in the change of the clutch power transmission performance, but also lead to the change of the clutch engagement characteristics and affect the clutch control performance. Therefore, the purpose of this paper is to study the wear law of the friction plate of the AMT dry clutch, and it is of great significance to evaluate the change in clutch transmission performance and realize the precise control of the clutch. In this paper, the ANSYS analysis software system is used to build a finite element analysis model about the wear of the friction plate of the AMT dry clutch, and a simulation of the sliding wear condition. At the same time, the method of loading heat flux is used to simulate the temperature of the sliding wear condition. The thermal deformation caused by temperature is taken as the main influence factor. To carry on the wear simulation analysis of the clutch-driven disc friction plate. Finally, the wear law of the friction plate of the AMT dry clutch is obtained.

Research on high-speed railway vehicle emergency braking control based on rail surface foreign matter identification

In order to improve the operation stability of high-speed railway vehicles, an emergency braking control method for high-speed railway vehicles based on the identification of foreign matters on the track surface is proposed. The dynamic frame scanning method is used to build the image acquisition of abnormal objects on the high-speed rail track surface, and the visual sensor and vibration sensor are used to identify and process the features of foreign objects on the high-speed rail track surface. According to the abnormal feature extraction results, the command signal in case of foreign objects is transmitted to the terminal command library of the braking control system. According to the transfer switch of the emergency braking system to display the main emergency disposal output states such as the train emergency disposal information reception, emergency disposal level, emergency disposal type and other information, the joint control method of contact pressure distribution and non-uniform heat flux is adopted, and the joint control method of control system, drive system, disc friction system and signal acquisition system is adopted. The emergency braking control module is established to realize the emergency braking control of high-speed railway vehicles according to the feature recognition results of foreign matters on the rail surface. The test results show that the control module is less affected by the vehicle wheelbase characteristics, track structure characteristics and other factors when using this method for high-speed railway vehicle emergency braking control, and has a strong ability to identify the characteristics of foreign matters on the track surface, which improves the stability and real-time performance of emergency braking.

A new raw signal fusion method using reweighted VMD for early crack fault diagnosis at spline tooth of clutch friction disc

Spline tooth root crack is a kind of critical faults for clutch friction disc. Most traditional crack diagnosis methods based on single-sensor or fusion may be degraded due to incomplete fault information or low signal-to-noise ratio (SNR). Aiming at enhancing the ratio of fault-related information in the fusion signal, a new reweighted variational mode decomposition (VMD) multi-point fusion method is proposed. With the proposed method, each measurement point vibration acceleration signal is decomposed by VMD firstly, and the intrinsic mode functions (IMFs) containing different sensitivities information are obtained. Then, correlation energy fluctuation (CEF) and confidence distance are utilized to evaluate the IMFs and raw signal respectively. A new dual-weight strategy is proposed to restructure the IMFs. Finally, convolutional neural network (CNN) is used to identify spline tooth early crack faults. Experimental results demonstrate that the proposed method has greater fault recognition rate than single point and other fusion methods.

Prospects for Manufacturing Friction Disks from Cold-Rolled Steel

Prospects for Manufacturing Friction Disks from Cold-Rolled Steel

Effect of local pressure difference caused by argon flow on properties of DLC films on rubber

The application of a diamondlike carbon (DLC) coating on rubber surfaces is a promising method to enhance the tribological properties of rubber and alleviate its poor wear resistance. However, in the preparation of DLC films, accurate pressure detection in the sputtering region is challenging due to the single detection position in common sputtering systems. In this paper, the direct current magnetic sputtering method was used to prepare DLC films on nitrile butadiene rubber (NBR). A set of Faraday beam detection device (FBDD) was employed to monitor the current density in the sputtering region. It was found that even if the pressure at the detection position of the vacuum gauge is consistent, the actual pressure in the sputtering region may be different under different rates of argon flow based on the detection results from the FBDD. The surface energy of DLC films was also calculated and researched. According to the results of FBDD, a series of analytical characterization methods were selected to explore the influence mechanism of changing the Ar flow rate on the properties of DLC films on NBR when the initial sputtering pressure remained consistent. The results of FBDD show that the density of the beam in the sputtering region increases with the increase in the Ar flow rate introduced into the vacuum chamber. The surface energy of DLC films was also calculated and evaluated by a contact angle tester. Raman and x-ray photoelectron spectroscopy results indicate that the increase in the Ar flow rate leads to an increase in pressure, which is conducive to the formation of sp3 in DLC films, and the increase in sp3 improves the surface energy of DLC films. The highest sp3 content and surface energy among as-prepared DLC films are observed when the argon flow rate was 40 SCCM. Ball-on disk friction experiment was used to characterize the tribological performance of DLC films on NBR rubber and the adhesion between DLC films and NBR rubber was evaluated by a nanoscratching test. Combining the results of tribology and nanoscratching testing, it can be inferred that the Ar flow rate plays an important role in improving the mechanical properties of DLC films on NBR rubber. Furthermore, the results of scanning electron microscopy confirmed that the sputtering atoms can effectively fill in the grooves of the rubber substrate. This finding is of significance for controlling the sputtering process of preparing DLC on rubber and improving the frictional properties of rubber.

Nanohybrid of h‐BN nanosheets supporting CeO2 enhanced epoxy composite coatings with excellent self‐lubricating performance

AbstractPolymer self‐lubricating composite coatings have been widely used on the surface of machinery to extend the life of the moving systems/parts by controlling friction and wear. In this work, epoxy nanocomposite coating with the thickness of about 60 μm was fabricated with addition of hexagonal boron nitride nanosheets (BNNSs)/CeO2 nanohybrid for enhancement in antifriction and wear resistance. The active BNNSs were first obtained by exfoliating h‐BN with alkaline solution, and then the rare earth oxide of CeO2 nanoparticles were immobilized on the surface of BNNSs through hydrothermal method. The microstructure morphology and chemical composition of as‐proposed BNNSs/CeO2 were characterized by field emission scanning electron microscopy, HRTEM, Fourier transform infrared spectroscopy, RS, X‐ray diffraction, and X‐ray photoelectron spectroscopy. And the tribological behaviors of epoxy nanocomposite coatings containing BNNSs, CeO2, and BNNSs/CeO2 were investigated comparatively using ball‐on disc friction tester (MPX‐3). And the 440C stainless‐steel ball with diameter of 8 mm was used as the counterface material. Tribological tests showed that epoxy‐BNNSs/CeO2 had the best friction and wear reduction properties, and the lowest coefficient of friction and wear rate of epoxy‐based composite coating were achieved when the content of BNNSs/CeO2 was 0.5 wt%, with 84.9% and 96.3% reduction, respectively. Moreover, the effect of sliding conditions on the tribological performance of epoxy‐BNNSs/CeO2 was investigated. The corresponding enhancing mechanisms of BNNSs/CeO2 were discussed as well.

Effects of the surface layer of steel samples after ball burnishing on friction and wear in dry reciprocating sliding

The effects of ball burnishing on tribological behaviour in dry reciprocating motion have not yet been studied. This work attempts to fill this gap. The steel disc samples after milling were ball burnished. Due to ball burnishing, the average surface height decreased to 85% and the microhardness increased to 20%. Burnishing also generated the compressive residual stresses that were responsible factor to enhance the hardness of the steel surface. Trbological tests were carried out in reciprocating motion under dry sliding conditions. A 10 mm diameter ceramic ball from WC material contacted the steel disc. Ball burnishing was found to lead to improvements in disc wear and friction of the sliding pair. The maximum decreases in friction coefficient and wear volume compared to the milled sample were 39% and 85%, respectively. Samples of the lowest amplitude and high microhardness led to the highest behaviour.

Development of designs and research of the main tribotechnical parameters of friction pairs with plasma powder friction coatings and a steel counterbody when operating in oil for friction devices

Designs are developed and studies of the main tribotechnical parameters of friction pairs with plasma powder friction coatings and a steel counterbody when operating in oil for disc and cone friction devices are carried out. The threedimensional image shows the dependence of the dynamic coefficient of friction on the sliding speeds and specific loads for the considered friction devices. Keywords: friction in oil, tribological parameters, coefficient of friction, wear, sliding speed, specific load, temperature, friction machine, new friction material, steel counterbody. au@vstu.ru

Study on the Wear Performance of Polyethylene Inner Lining Pipe under Different Load and Mineralization Conditions

This study conducted pin disc friction and wear performance tests on polyethylene-lined oil pipes and four types of centralizing materials (45# steel, nylon, polytetrafluoroethylene (PTFE), and surface alloy coating) in oil fields. The friction coefficient and wear rate were tested, and the wear mechanism was analyzed using scanning electron microscopy (SEM) and three-dimensional confocal microscopy. Using a combination of experimental testing analysis and theoretical research, a comprehensive evaluation of the current wellbore centering and anti-wear technology for oil was conducted. The experimental results indicate that the usage limit of polyethylene-lined oil pipes is 400 N, and compared to metal oil pipe materials, the wear rate of both stabilizing material and tubing material is lower, indicating that it has a certain service life. From the perspective of testing load, taking into account the factors of friction coefficient and wear rate, the recommended sequence of straightening material for polyethylene lined oil pipes is (1) surface alloy coating, (2) nylon, (3) PTFE, and (4) 45# steel.