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The purpose of this paper is to investigate the effect of reciprocating and unidirectional sliding motions on friction and wear of phenolic resin-based composite.

The phenolic resin-based composite was fabricated by hot press molding, and then the tribological properties were tested on a CSM tribometer with two types of friction motion modes – reciprocating friction and unidirectional friction.

The results showed that the composite exhibited low friction coefficient in unidirectional test. However, the wear factor recorded under unidirectional sliding condition was 12-16 times higher than the reciprocating friction results. The SEM and optical microscopy test results showed that changing the relative motion mode resulted in different topography of transfer film, which is responsible for the different friction and wear characteristics of the composite under reciprocating and unidirectional friction conditions.

Effect of different friction modes, reciprocating friction and unidirectional friction, on friction characteristics of the composite is sought. Different topography of transfer film formed under reciprocating and unidirectional friction conditions contributed to the different friction characteristics.

The purpose of this study is to investigate the influence of dimple radius, depth and density on the lubrication performance of the plunger.

A lubrication model was adopted to consider eccentricity and deformation during the working process of the plunger, and a rig test was performed to confirm the simulation results. The texture was fabricated using laser surface texturing.

The simulation results suggested that when dimple radius or depth increases, oil film thickness of the plunger increases before decreasing, and asperity friction displays an opposite trend. Therefore, appropriate microdimple texture could facilitate lubrication performance improvement and reduce the wear. Microdimples were then lased on the plunger surface, and a basic tribological test was conducted to validate the simulation results. The experimental results suggested that the average friction coefficient decreased from 0.18 to 0.13, a reduction of 27.8%.

The introduction of microdimple on a plunger couple to reduce friction and improve lubrication is expected to provide a new approach to developing high-performance plunger couple and improve the performance of the internal combustion engine. If applied, the surface texture could help reduce friction by around 27% and cap the cost relative to the plugger friction.

The microdimple texture was introduced into the plunger couple of a vehicle to reduce the friction and improve the performance. Findings suggested that surface texture could be used in the automotive industry to improve oil efficiency and lubrication performance.

The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-07-2020-0259.

The lateral force mode of atomic force microscopy (AFM) was applied to conduct friction tests on a filled PTFE/PPS‐composite blend. This method distinguishes between the individual phases of the blend, i.e. carbon fibers, PPS‐particles, PTFE‐matrix and graphite flakes. The relative frictional behaviours of the different filler types were compared and the law of microfriction was discussed.

This paper aims to introduce a high-temperature grease design method assisted by back propagation neural network (BPNN) and verify its application value.

First, the grease data sets were built by sorting out the base data of greases in a large number of literatures and textbooks. Second, the BPNN model was built, trained and tested. Then, the optimized BPNN model was used to search the unknown data space and find the composition of greases with excellent high-temperature performance. Finally, a grease was prepared according to the selected composition predicted by the model and the high-temperature physicochemical performance, high-temperature stability and tribological properties under different friction conditions were investigated.

Through high temperature tribology experiments, thermal gravimetric analysis and differential scanning calorimetry experiments, it is proved that the high temperature grease prepared based on BPNN has good high-temperature performance.

To the best of the authors’ knowledge, a new method of designing and exploring high-temperature greases is successfully proposed, which is useful and important for the industrial applications.

The purpose of this paper is to test and analyze the friction torque of double-row angular contact ball bearings under vacuum or ordinary pressure environment, horizontal or upright installation mode, and different rotational speeds, and to provide theoretical bases for the development of aerospace equipment.

The experiments were carried out to investigate the effects of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque. To explore the relationship between working conditions and bearing friction torque, firstly, based on the generation source of friction torque, the test principle was determined, a test system was developed and the reliability of data was verified. Secondly, the friction torque of bearing was tested, and the values under various working conditions were obtained. Finally, this paper compared and discussed the test results.

The test results show that the friction torque value of vacuum environment horizontal installation condition is the largest at different rotational speeds, and the rotational speed has the most significant influence on the friction torque.

The friction torque test system of double-row angular contact ball bearing under vacuum environment was designed and built. The influence rules of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque were obtained.

The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-08-2023-0259

The aim of this paper is to characterize some selected formulations based on castor oil and a variety of biogenic thickeners from a tribological point of view and compare them with some traditional lithium greases.

The evolution of the friction coefficient in several tribological tests performed using several ball‐on‐disc configurations and coupling materials was monitored for the different oleogels proposed as biodegradable lubricating greases. Both a rotational ball‐on‐disc classical tribometer designed at MuT laboratory and a nanotribometer were used in rotational and oscillatory modes.

Generally, the use of castor oil‐based formulations potentially applicable as biodegradable lubricating greases provides similar or lower values of the friction coefficient than traditional lithium greases, depending on the nature of thickener agent employed and tribological contact. In all cases, biodegradable formulations provide significantly lower values of the friction coefficient in tribological tests performed in the oscillatory mode. Weak oleogels like those thickened with glyceryl and sorbitan monostearates or acylated chitosan, provide the lowest values of the friction coefficient in every type of configuration or frictional test analysed. Biogrease formulations containing cellulose or chitin derivatives as thickener agents generally yield higher values of the friction coefficient, which may be comparable to those obtained with the reference lithium greases depending on the thickener and tribological configuration. In frictional tests performed in the rotational mode, the inclusion of ethyl cellulose in the formulation yields high values of the friction coefficient, which was attributed to the castor oil viscosity modification exerted by this additive. Wear results depend on the balance between the frictional behaviour, especially in the initial transient regime, and oleogel mechanical stability.

This investigation proposes different new alternatives to replace the traditional thickener agent in lubricating greases with others based on renewable resources in order to obtain a completely biodegradable formulation for different industrial applications.

This paper provides a resource of new practical friction coefficient data as well as a comparative analysis of the tribological response of these new formulations based on biogenic thickeners and other traditional lithium greases.

The purpose of this paper is to investigate the friction coefficients of aramid and acrylic fibers on brake pads.

Fiber components used in the present pads are aramid and acrylic fibers, respectively, while keeping other components, such as binders, lubricants, abrasives, fillers the same. Disk FC25 and disk FC17 are used for rotor rubbing test to investigate the friction coefficients with brake pads. The pads are tested by 1/5 scale brake dynamometer, and test mode is modified JASO C406‐P1. The results are analyzed with the friction coefficient and the temperature, transfer film, roughness, and photomicrograph of worn surface on rotors.

The friction coefficient was mainly determined by the pad material rather than the rotor material, and pads made of aramid fiber had high‐friction coefficient, while pads made of acrylic fiber had low‐friction coefficient, especially under high temperature. Temperature change during braking process was directly related to the initial speed only, and was indifferent to materials or decelerations imposed. In the fade test, the reversal of friction coefficients between the aramid fiber and acrylic fiber pads is determined by the amount of remained amount of respective fiber above 520°C.

Effect of different fiber components, aramid and acrylic fibers, on friction characteristics of pad is sought. Reversal of friction coefficients is determined by the thermal stability of fibers used for pads.

This paper aims to study the friction layer and tribological property of polyimide (PI)–matrix composites under different friction speeds.

Friction tests were conducted under friction speeds ranging from 20-120 km/h and pressure of 0.57 MPa by a pin-on-disk tribometer.

The results indicate that the friction coefficient decreases with the increasing of the friction speed. Under different friction speeds, the structure of the friction layer and debris are different, which affects the actual tribological performance of the composites. At low friction speed, the morphology of the friction layer is mainly particulate. The higher level of clenching action between the friction pair leads to a high friction coefficient, and the morphology of the particles in the particulate zone and the wear debris are mostly equiaxial particles. At high friction speed, the morphology of the friction layer is mainly a compact zone. The reduction of the surface roughness leads to a low friction coefficient. The debris collected on the counter surface at high friction speeds are mostly big sheets, and the morphology of the particles in the particulate zone is mostly rod-like. Controlling the conditions of the disk and the pin can reveal the influence of friction speed on the friction layer. The wear mechanisms at different friction speeds are also discussed.

By controlling the conditions of the disk and the pin to reveal the influence of friction speed on the friction layer, and the evolutions of the friction layer, wear debris were carefully inspected with the aim of demonstrating the relationship between friction speed and wear mechanism of PI–matrix composites.

The frictional behavior of a Mo alloy‐coated piston ring sliding against cast iron cylinder bore was recorded as a function of temperature using a reciprocating tribotester and a fully formulated synthetic engine oil, with and without a friction modifier. It was observed that, as temperature increased in a stepwise mode, friction coefficients in the presence of MoDTC exhibited two local minimal values. Only one minimal friction coefficient value at 340–355 °C (μ = 0.065) was observed in the absence of MoDTC. Chemical characterization of worn tracks of the cylinder bore using reflected FTIR spectroscopy, Raman spectroscopy and ESCA, indicated that both the base stock and the tribological additives, ZDTP and MoDTC, experienced tribochemical reactions yielding MoO₃, MoS₂ and carbonaceous species as temperature ramped up stepwise. MoO₃ and MoS₂ reaction film formation are partially responsible for the local minimal friction coefficient found at the lower temperature and the ratio of the ordered carbon species accounts partially for the other local minimal friction coefficient found at the higher temperature.

The purpose of this paper is to expand the previously published fuzzy logic controller for contact method to normal frictionless contact for solving mechanical frictional contact problems. The secondary aim is to integrate a reduction model for each component in contact to decrease the size of the global finite element contact problem.

The proposed strategy relies on the design of two fuzzy logic controllers currently used in the automation domain. These controllers are considered to link normal and tangential gaps (for sticking conditions) with normal and tangential contact loads. A direct consequence of integrating a control-based approach into the numerical solving approach is the decomposition of the non-linear problem into a set of linear problems.

With this new strategy, no tangent or coupling matrix is defined for the contact problem that allows to consider a projection matrix to reduce the size of each component in contact and subsequently to decrease the associated computational time. As in condensation techniques, this matrix is composed of both modal bases of each component in contact and static modes that capture behaviors at the contact interface. Moreover, the proposed numerical application highlights the efficiency of the proposal in terms of computation time and precision of contact data.

The developments are currently implemented in Matlab only for 2D static numerical applications. Therefore, as obtained results are very promising in terms of precision and computational time, the objective is to complete the proposed method in future research to manage frictional contact for 3D finite element models in a dynamic context.

In conclusion, this paper highlights the interest of studying mechanical frictional contact problems by considering fuzzy logic control approaches.