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This paper aims to investigate how ball milling (BM) and load influence transfer film on counterbody and the correlation between transfer film and tribological properties of copper-based composites.

The copper-based mixed powders preprocessed by BM for different times were used to manufacture sintered materials. Specimens were tested by a custom pin-on-flat linear reciprocating tribometer and characterized prior and after tests by optical microscope, scanning electron microscope and energy-dispersive spectroscopy. Image J® and Taylor-hobson-6 surface roughness meter were used to quantify the coverage and thickness of the transfer film.

Main results show that an appropriate amount of BM time and applied load can contribute to the formation of the transfer film on counterbody and effectively improve the tribological properties of the copper-based material. The transfer film coverage is linearly related to the friction coefficient, thickness of transfer film and wear volume. As the transfer film coverage increases, the coefficient of friction decreases. As the thickness of the transfer film increases, the amount of wear increases.

This work intends to control and optimize the formation of transfer film, thereby helping improve the tribological properties of materials and providing a reference to guide the preparation of Cu-based composites with excellent tribological properties.

The purpose of this paper is to investigate surroundings for transfer film formation and removal, the effect of the transfer film formation on friction coefficients, the effect of four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃ and Fe₃O₄, on transfer film formation and the effect of lubricating component MoS₂ on transfer film formation and friction coefficients.

Two different MoS₂ contents of 5.5 and 8.5 per cent were added to friction materials with no MoS₂ content, which have four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃, Fe₃O₄. Friction tests composed of three different stages were conducted for those materials, and the friction surfaces of the counterpart disks were examined by scanning electron microscopy (SEM) to access the formation of transfer film at each stage.

For the transfer film formation, high temperature was a prerequisite, but the magnitude of deceleration rate was not important. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Friction coefficients of materials which contain lubricating component MoS₂ were higher than those which contain no MoS₂ for most friction materials. The effect of the lubricating component MoS₂ was to suppress the formation of transfer film, thus resulting in increase in friction coefficients.

The transfer film was rather thin, with thickness of 1-2 µm for most friction materials. That hindered the examination of mechanical properties of the transfer film, such as hardness.

This research explained the surroundings for transfer film formation, and its effect on friction coefficients. The research suggests to suppress the formation of transfer film to make friction materials with high friction coefficient, and the lubricating component MoS₂ can be used for the purpose.

Development of high-friction-brake materials conventionally depends on the use of strong abrasive components, which may induce attacking of counterpart disks. The enhancement of friction coefficients with addition of MoS₂ content is expected to open a new prospect in development of high-performance friction materials, which can be applicable to brake pads for racing cars.

The study is in pursuit of the transfer film formation in successive friction stages, which revealed the conditions for transfer film generation and removal. Specimen preparation for SEM observation of cross section of friction surface was painstaking to not damage the developed friction surface. The study revealed the effect of different abrasive components on transfer film formation and the effect of lubrication contents of MoS₂ on transfer film formation and friction coefficients.

The purpose of this paper is to investigate the distribution and surface characteristic of transfer film of polyamide composites filled with ZnOw during traction rolling.

In this paper, the traction rolling tribological behavior of polyamide composites filled with ZnOw was studied with a twin-disc traction rolling tester. The topography of transfer film was observed with a three dimensional profiler. Meantime the thickness of transfer film was measured. The chemistry elements of transfer film were analyzed with EDS and XRD.

The results indicated that transfer film of composites patchily covered on the surface of counter disc, the amount of which increased with increasing cycles. The coverage and thickness of pure PA film increased against rolling cycles. However, the thickness of 15 wt.% ZnOw/PA film remained at 6 μm as the coverage rose against rolling cycles. Fe element was found in pure PA transfer film, which existed in Fe0 and FeO for chemical reaction between Fe and atmospheric oxygen. Transfer film of 15 wt.% ZnOw/PA composites included a little Zn and Fe element. Fe element existed as Fe0. Zn element existed as ZnO.

This paper presented the distribution and surface characteristic of transfer film during traction rolling.

The purpose of this paper is to investigate the film cooling effectiveness and heat transfer coefficient in a flat plate with two rows of rectangular injection holes.

Experimental and numerical investigation of film cooling effectiveness in a flat plate with two rows which are rectangular injection holes. The liquid crystal technique has been used for measuring the heat transfer coefficients on the mixture region. Three injection holes in model are in a single row. The holes are rectangular cross section and they are 9 × 6.5 mm. The injection holes are inclined at 30° along the mainstream direction. The blowing ratios are from 0.5 to 2.0. The experiments and their computational models are established to investigate its effects at the 330 and 340 and 350 K injection temperatures and the different blowing ratios.

The results show that the film cooling effectiveness and heat transfer coefficient of a given flat plate surface, both along the mainstream and lateral direction, depend on the optimum selection of parameters. In this study, the highest effectiveness is determined at a blowing ratio of 0.5. Further increasing the ratio results in reverse effect on the film cooling effectiveness.

It is the fist time the film cooling effectiveness is compared at the rectangular injection holes with two rows as experimental and numerical.

A three‐dimensional numerical analysis was carried out to study in detail the combined heat and mass transfer processes between a moist air flow and a cooled surface when film condensation occurs. A cross‐flow was considered between the air flow and the film flow. A turbulent flow was modelled using the Wilcox k−ω turbulence model. The shape of the interface between the air and the film was treated as a moving boundary, and it was calculated with the assumptions that the interface ways remain an interface, the stress at the interface is continuous and that there is no slip at the interface. Numerical results were obtained by solving simultaneous coupled equations of the air, film and solid. The results show that the condensate film flow has a significant effect on the extended surface temperature distribution and consequently on its efficiency. It is shown that the simultaneous influence of gravity and the air flow on the condensate film results in an asymmetric velocity profile in the film as well as in the asymmetric shape of the film.

To develop a reliable methodology and procedure of simulating the jet‐in‐crossflow using the current turbulence models and numerically investigate the cooling performance of a new scheme for the engines of next generation.

A new advanced film cooling scheme is proposed based on the literature survey and a systematic methodology developed to successfully predict the right level of heat transfer in the CFD simulation of film cooling.

The proposed cooling scheme gives considerable lower heat transfer coefficient at the centerline in the near hole region than the traditional cylindrical hole, especially at a high blowing ratio when traditional cylindrical hole undergoes liftoff.

The number of cooling holes in the computational domain is limited by the speed of the computers used.

The new methodology can be used to numerically test new cooling schemes in the design of turbine blades and to provide useful information/data under actual working conditions to design engineers.

This paper provides some useful information on the simulation of film cooling in terms of the performance of different turbulence models and wall treatments and also sends some valuable messages regarding the design of cooling scheme of turbine blades to the technical community.

This paper aims to simulate the effect of counterface roughness on the friction transfer and wear of the polymer material sliding against steel.

The dynamic process of friction transfer and wear of polytetrafluoroethylene (PTFE) sliding against steel 45 was simulated by the software of particle flow code in two dimensions and a discrete element method. The effect of the counterface roughness was considered in the simulation. The definitions of the transferred particle and worn particle were given.

The simulation results showed that a transferred particle layer was formed on the surface of steel 45 during friction. The wear rate of PTFE can be effectively reduced by the formation of the transferred particle layer. The formation and stability of this particle layer is certainly affected by the counterface roughness (Rz). In this paper, the transferred particle numbers increased with Rz increase. And so did the worn particle numbers. However, there was little effect of Rz on the wear rate of PTFE.

The dynamic process of the friction transfer and wear of the PTFE/ steel 45 friction pair was reproduced at the micro-level. Then, the transfer and wear were quantitatively exhibited. The relations between the transfer or wear and counterface roughness was simulated and discussed. It will be meaningful for the optimization and effective control of friction and wear of polymer/metal sliding system.

This study aims to form composite solid lubricant coatings on the surface of bearing steel, which can significantly improve the tribological properties of thrust cylindrical roller bearings (TCRBs). Phosphating films possess microscopic porosity that typically needs to be sealed with oil, grease or wax. Due to its unique crystal structure, the phosphating film itself also exhibits a certain degree of lubricity. In this study, solid lubricants are used to fill the pores of the phosphating film. By combining the phosphating film with solid lubricants, lubrication and wear reduction can be achieved.

In this study, the surfaces of the shaft washer (WS) and seat washer (GS) were treated with zinc-phosphating. Subsequently, a solid lubricant solution (polytetrafluoroethylene [PTFE], MoS₂ and graphite) was sprayed onto the phosphated samples at concentrations of 1 , 2  and 3 g/L. The porous and adsorptive nature of the phosphating film was used to embed the solid lubricant particles into the film, thus forming a composite lubrication layer containing solid lubricants on the surface of the bearing steel.

The addition of solid lubricant materials has shown significant potential in reducing wear losses compared with phosphated samples without such additives. Increasing the amount of solid lubricant added can facilitate the formation of a transfer film, which further enhances the protective properties. However, it is important to note that excessive amounts of solid lubricant material can contribute to seizure, leading to increased wear losses of the cage and a higher average coefficient of friction (ACOF).By spraying a PTFE solution with a concentration of 2 g/L, the lowest ACOF and cage wear loss were achieved, resulting in reductions of 60.5% for the ACOF and 89.4% for the cage wear loss. Similarly, when spraying a graphite solution with a concentration of 3 g/L, the lowest wear losses for GS and WS were observed, with reductions of 51.7% for GS wear loss and 38.9% for WS wear loss.

The combination of the phosphating film and solid lubricants aims to achieve lubrication and wear reduction, providing a new approach to wear-resistant technology for TCRBs.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0231/

The purpose of this paper is to reveal the mechanism of effect of surface groove on speed‐regulating start.

This paper investigates numerically and analytically the torque transfer and load capacity of oil film between separator and friction disc with grooves commonly used at present by solving simultaneous equations: modified Reynolds, energy, and temperature‐viscosity equations.

The results show friction discs with wider and deeper groove are not suitable for speed‐regulating start. To improve performance of speed‐regulating start, distribution and size of surface groove should be designed to obtain ascending trend of oil film load capacity during startup process.

This paper reveals the mechanism of effect of surface groove on speed‐regulating start and facilitates the conceptual design of speed‐regulating start control system.

Moving images represent a category of material which has historically received short shrift in most libraries and archives. Film, video, and now digital images form a significant part of many library and archival collections, however, and can be found in many formats and genres. Despite the ubiquity of such media in cultural institutions, the majority of libraries and archives owning collections of moving images have neglected these holdings—with the specific exception of those few archives devoted primarily to the care and preservation of moving images.