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Random point-contact between the space bearing retainer and the rolling elements may cause wear of the space bearing retainer. The paper aims to clarify the friction and wear behaviors of polyimide bearing retainer under point-contact condition.

Space bearing retainers were cut into flat specimens and the tribological behaviors of the specimens were studied under point-contact condition using a friction and wear testing machine. Different sliding velocities and normal loads were used to simulate the running state of space bearing retainer. The wear behaviors of the space bearing retainer were analyzed by SEM and white light interferometer.

The friction coefficient of the polyimide composites decreased with increase in sliding velocity from 1  to 5 mm/s. Moreover, with increase in sliding velocity and normal load, the wear rate of the polyimide composites decreased and increased, respectively. Moreover, the wear behaviors of the polyimide composites were mainly determined by the combined actions of ploughing friction and adhesive friction. The lubricating properties of transfer film and wear debris were limited under point-contact condition.

The paper includes implications for the understanding of the wear mechanism of the polyimide composites space bearing retainer under point-contact condition and then to optimize space bearing retainer materials further.

Under point-contact condition, wear debris can hardly participate in the friction process because of limited contact area. Consequently, the wear debris has limited impact on the wear process to decrease the friction and wear.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0017/

This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.

Oil–air lubrication equations between point contact counterparts were established on the basis of volume of fluid model. The effects of oil supply and injection azimuth on oil-phase volume fraction and its pressure distribution were simulated with commercial software Fluent. Characteristics of point contact sliding wear were then tested with an MFT-3000 friction tester under oil–air lubrication condition. The influence of flow behavior on wear characteristic was investigated combined with numerical and experimental results. The wear mechanism was revealed using SEM, EDS and ferrography.

When air supply speed is constant, the oil-phase volume fraction increases with the increase in oil supply, which helps form continuous oil film and decrease the sliding wear evidently. The injection angle and distance considerably influence the oil–air flow behavior. When injecting at a certain distance and angle, the oil-phase volume fraction reaches its maximum, and the abrasion loss is minimal. Under the test conditions in this study, abrasive particles are mainly debris and a few spiral cuttings. The wear mechanism is abrasive wear.

The influence of the behavior of oil–air lubrication flow on the characteristic of point contact sliding wear is analyzed. This work provides guidance for the application of oil–air lubrication technology in point contact friction pairs.

Aiming at the problems of geometric precision misalignment and unconsidered physical constraints between large components during the measurement-assisted assembly, a self-adaptive alignment strategy based on the dynamic compliance center (DCC) is proposed in this paper, using force information to guide alignment compliantly.

First, the self-adaptive alignment process of large components is described, and its geometrical and mechanical characteristics are analyzed based on six-dimensional force/torque (F/T). The setting method of DCC is studied and the areas of DCC are given. Second, the self-adaptive alignment platform of large components driven by the measured six-dimensional F/T is constructed. Based on this platform, the key supporting technologies, including principle of self-adaptive alignment, coordinate transfer, calculation of six-dimensional F/T and alignment process control, are illustrated.

Using the presented strategy, the position and orientation of large component is adjusted adaptively responding to measured six-dimensional F/T and the changes of contact states are consistent with the strategy. Through the setting of DCC, alignment process runs smoothly without jamming.

This strategy is applied to the alignment experiment of large components muff coupling. The experimental results show that the proposed alignment strategy is correct and effective and meets the real-time requirement.

This paper proposed a novel way to apply force information in large component self-adaptive alignment, and the setting method of DCC was presented to make the alignment process more feasible.

The purpose of this study is to solve this problem. Different lubrication states play a huge role in friction, wear and service life of parts. To ensure the reliability and power of the internal combustion engine, it is necessary to ensure that the friction pair has been in the best lubrication state. One of the key problems of lubrication state and transformation characteristics is to achieve real-time measurement of lubrication state.

Previous studies show that the contact resistance method is very effective in the qualitative analysis of lubrication state test. The circuit is simple and does not require expensive test equipment. But this method could not accurately reflect the film thickness ratio. Through a combination of experimental and theoretical analysis methods, the limitation of the contact resistance method could be overcome.

The relationship between the point contact film-thickness ratio and contact resistance was established, then the film-thickness ratio could be obtained through the contact resistance, thus providing the basis for determining the point contact lubrication state.

According to existing research, the lubrication state of the friction pair mainly was determined through two methods, the friction coefficient and film-thickness ratio. But there are limitations on either using Stribeck curves or optical interference methods. The method used in this paper not only provides a verified way of design theory and model, but is also beneficial to the formation of a new design theory.

A new real-time measurement method of lubrication state based on contact resistance is established and its practicability and veracity are verified by series experiments.

In this study a numerical analysis of the elastohydrodynamic lubrication point contact problem in the unsteady state of reciprocating motion is presented. The effects of frequency, stroke length and load on film thickness and pressure variation during one operating cycle are discussed. The general tribological behavior of elastohydrodynamic lubrication during reciprocating motion is explained.

The system of equations of Reynolds, film thickness considering surface deformation and load balance equations are solved using the Newton-Raphson technique with the Gauss-Seidel iteration method. Numerical solutions were performed with a sinusoidal contact surface velocity to simulate reciprocating elastohydrodynamics. The methodology is validated using historical experimental measurements/observations and numerical predictions from other researchers.

The numerical results showed that the change in oil film during a stroke is controlled by both wedge and squeeze effects. When the surface velocity is zero at the stroke end, the squeeze effect is most noticeable. As the frequency increases, the general trend of central and minimum film thickness increases. With the same entraining speed but different stroke lengths, the properties of the oil film differ from one another, with an increase in stroke length leading to a reduction in film thickness. Finally, the numerical results showed that the overall film thickness decreases with increasing load.

General tribological behaviors of elastohydrodynamic lubricating point contact, represented by pressure and film thickness variations over time and profiles, are analyzed under reciprocating motion during one working cycle to show the effects of frequency, stroke length and applied load.

This study aims to investigate the effects of single dent on the film thickness and pressure in elastohydrodynamically lubricated (EHL) point contacts by numerical analysis.

The governing equations of single dent were established and then the variations of the film thickness and pressure induced by the applied load, the entrainment velocity and the ball radius were investigated. Meanwhile, the film thickness and pressure under smooth and dented surfaces were compared with each other.

The dent enhances both the maximum pressure and the second pressure peak. The minimum film thickness arises before the dent under certain conditions. In the meantime, the pressure decreases at the inside of the dent and the film thickness is just the reverse. The entrainment velocity remarkably affects the overall film thickness, whereas the rest of the input parameters mainly decides the details of the film curve. All input parameters remarkably affect the overall pressure, especially the maximum pressure.

This work is helpful to understanding the effect of the single dent on the lubricating properties of EHL point contacts.

This paper aims to realize the automatic assembly process for multiple rigid peg-in-hole components.

This paper develops fuzzy force control strategies for the rigid dual peg-in-hole assembly. Firstly the fuzzy force control strategies are presented. Secondly the contact states and contact forces are analyzed to prove the availability of the force control strategies.

The rigid dual peg-in-hole assembly experimental results show the effectiveness of the control strategies.

This paper proposes fuzzy force control strategies for a rigid dual peg-in-hole assembly task.

The dent is one of typical surface defects on the surfaces of the machine elements and it is not in fact inerratic. This work aims to investigate the effect of a single dent with a marginal bump on the film shape in elastohydrodynamic lubrication (EHL) point contacts.

The experimental investigations of a single dent with marginal bump were carried out using multi-beam interferometry in EHL point contacts. In the meantime, its numerical simulation was also finished using multi-level method and multilevel multi-integration method. The effects of the entrainment velocity and the applied load as well as the slide-roll ratio on the film were chiefly discussed. Meanwhile, the comparison of films between smooth and dented surfaces was conducted under simple sliding conditions.

Under pure sliding conditions, the minimum film thickness presents itself near the marginal bump at lower entrainment velocity. The inlet dimple before the marginal bump is subjected to the operating conditions. Under pure rolling conditions, the shape of the dent is almost unchanged when it is passing through the contact region at lower entrainment velocity. The dent depth hardly depends on the applied load under static conditions. However, larger load enhances the inlet dimple and the elastic deformation of the dent with the marginal bump under pure sliding conditions.

This work is helpful to understanding the effect of the marginal bump before the single dent on point contact EHL films.

The purpose of this paper is to study the behavior of a single ridge passing through elastohydrodynamic lubrication of point contacts problem for different ridge shapes and sizes, including flat-top, triangular and cosine wave pattern to get an optimal ridge profile.

The time-dependent Reynolds’ equation is solved using Newton–Raphson technique. Several shapes of surface feature are simulated and the film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds’ equation and film thickness equation, including elastic deformation. Film thickness and pressure distribution are chosen to be the criteria in the comparisons.

The geometrical characteristics of the ridge play an important role in the formation of lubricant film thickness profile and the pressure distribution through the contact zone. To minimize wear, friction and fatigue life, an optimal ridge profile should have smooth shape with small ridge size. Obtained results are compared with other published numerical results and show a good agreement.

The study evaluates the performance of different surface features of a single ridge with different shapes and sizes passing through elastohydrodynamic of point contact problem in relation to film thickness and pressure profile.

The purpose of this paper is to study the elastohydrodynamic lubrication point contact problem with bio-based oil as lubricants for an isothermal case. The simulation of the problem is analyzed on smooth and rough asperity.

The modified Reynolds equation is discretized using finite difference and multigrid method with full approximation scheme (FAS), applied for its solution with varying load and speed.

This paper traces out the comparison of minimum and central film thickness with the standard formulation of Hamrock and Dowson. The effect of longitudinal roughness on surfaces is investigated by means of numerical simulations.

The results obtained are comparable with the standard results, and are shown by graphs and tables. Bio-based products bring out an alternative source of lubricant to reduce energy crises.