Evaluation Of Tribological Characteristics Research Articles

Manufacturing of Poly-DL-Lactic Acid Nanosheets and Evaluation of Tribological Characteristics between Nanosheet Surfaces and Fingers

Attention is focused on ultra-thin polymer films (nanosheets) that have high flexibility and adhesiveness and their thickness can be controlled to several tens of nanometers. These nanosheets can be neatly attached to surfaces with complex irregularities without the use of adhesives. Therefore, the ratio of surface area to thickness is very large, and we believe that the relationship with friction is very significant in nanosheet technology for biomedical applications such as wearable devices and wound dressings. The purpose of this study is to investigate the contact mechanism of nanosheets with human fingertip skin in terms of friction coefficient by using the microgravure printing method, which enables thin film coating. From the results of film thickness measurements, it was found that nanosheets of any thickness can be fabricated by the microgravure printing method. The friction measurement results showed that the coefficient of friction of the nanosheets decreased except for vertical loads above Fz=2N. The coefficient of friction increased as the contact area increased. It was found to increase with increasing vertical load under the immersion in water conditions, and conversely, it decreased under the drying condition except for the high normal load of 2N. Furthermore, the coefficient of friction was found to increase with increasing nanosheet thickness. Observation of wear traces showed that when the vertical load was sufficiently high (Fz = 2 N), wear traces containing oily traces such as sebum and sweat appeared on the nanosheet surface. This is thought to function as a lubricant. Polymer nanosheets are a new material, and there have been few studies on friction with this material. Research on friction is very important because polymer nanosheets are expected to be applied to wound dressings and displays of electronic devices.

Evaluation of tribological characteristics of technical oils with fullerene compositions

The paper presents experimental studies of the tribological characteristics of liquid lubricants of various viscosity classes and various groups of operation when using fullerene compositions. Tribological characteristics were evaluated on a four-ball friction machine according to GOST 9490. The use of fullerene compositions in the form of a finely dispersed fullerene powder, pre-dispersed (dissolved) in vegetable high oleic oils, for example, rapeseed, with the subsequent addition of the resulting composition to technical oils of various viscosity classes and various groups of operation, leads to the following positive effect. The anti-wear properties of oils, which are assessed by the wear indicator, increase by 20,0…30,7 %, and the critical load on 18,8…25,0%. These indicators significantly exceed similar indicators when using fullerene fine powders without preliminary dispersion in vegetable oils, where the effect is on the border 11,1…15 %. Fullerene additives do not affect the extreme pressure properties of base oils, which are assessed by the scuffing load. This result makes it possible to state that the way to improve the tribological properties of lubricants by introducing a fine powder of fullerenes into base technical oils is ineffective. The experimental results obtained confirm the hypothesis about the possibility of the micelle formation mechanism in the lubricant under the action of the electrostatic field of the friction surface. The presence of a surfactant solvent (vegetable oil) allows you to "start" the micelle formation process at lower fullerene concentrations and to obtain the effect of increasing anti-wear properties.

Evaluation of tribological characteristics of liquid lubricants with fullerene additives

The paper presents experimental studies of the tribological characteristics of liquid lubricants of various viscosity classes and various groups of operation when using fullerene additives. Tribological characteristics were evaluated on a four-ball friction machine according to GOST 9490. Assessment was subject to: wear rate and critical load, which characterize the anti-wear properties of the lubricant, as well as welding load and bully index, which characterize an anti-bully properties of the material. It is shown that the improvement of the wear index for all oils begins with the concentration 0,2 % masses, fullerenes in the lubricant and does not exceed the values 11,1 … 15 %. At a fullerene concentration less than 0,2 % masses, no positive effect is observed. Positive effect 11,8 … 17,4 % characteristic of the indicator – critical load that characterizes the range of performance of anti-wear additives. At the same time, an increase in the critical load begins with concentration 0,1 % masses, fullerenes in a lubricant and manifests itself most effectively at a concentration 0,2 % masses. Changes in the magnitude of the welding load during the experiments were not recorded, this allows us to conclude, that the addition of a finely dispersed fullerene powder in a liquid lubricant does not improve anti-bully properties, but is only an anti-wear additive. It is shown that the way to improve the tribological properties of lubricants by introducing a finely dispersed powder of fullerenes in base technical oils is ineffective. It is necessary to develop other, more technological methods and methods for introducing fullerene additives into technical lubricants.

Evaluation of the performance of sealing rubbers operated in conditions of abrasive wear and low temperatures

The studied materials based on the new rubbers of unique frost resistance -propylene oxide rubber (Tg = -74 °C) and Hydrin T6000 epichlorohydrin rubber are recommended to be used as static and dynamic sealing parts for the equipment operated in the North. This was based on the full-scale tests in cold climates (Republic of Sakha (Yakutia)) and evaluation of tribological characteristics (coefficient of friction) at negative temperatures. The standard techniques were used in assessing of the changes of the physical and mechanical, relaxation, and low-temperature characteristics of model rubbers after aging. A special testing unit and a method for conducting the tests were developed to estimate the coefficient of friction at low temperatures.

S1104-2-2 生体適合性セラミックスの生理食塩水中におけるトライボロジー特性評価(トライボロジーの基礎と応用2)

S1104-2-2 生体適合性セラミックスの生理食塩水中におけるトライボロジー特性評価(トライボロジーの基礎と応用2)

J0402-1-6 マイクロ金型のトライボロジー特性評価(締結・接合部の力学・プロセスと信頼性評価(1))

J0402-1-6 マイクロ金型のトライボロジー特性評価(締結・接合部の力学・プロセスと信頼性評価(1))

Evaluation of Tribological Characteristics of Electric-Spark Coatings Prepared on Steel with Electrode Materials of the System TiN - Ni

The tribological and physicomechanical indices of electric-spark coatings of the system TiN - Ni are studied in relation to the phase and structural state of the electrode material. It is established that the optimum tribological properties are exhibited by TiN + (20–40)% Ni material due to forming a eutectic structure consisting of hard intermetallics and a ductile solid solution. It is shown that the ductile component (nickel) makes it possible to deform the coating material without embrittlement.

Adsorption control of synovia constituents on artificial joint materials by means of an electric field: evaluation of tribological characteristics.

The supplemental lubrication mechanism by means of an electric field was proposed to reduce friction and wear for the advanced joint prosthesis with the low elastic modulus bearing surface. The possibility of application of this mechanism to the prosthesis was investigated by the fundamental and experimental procedures in simplified sliding conditions. Conductive silicon rubber was used as the low elastic modulus surface. The counterfaces were a titanium alloy and a stainless steel. Protein (gamma-globulin) in lubricant appeared to cause the tribological characteristic to deteriorate in the mixed lubrication regime. High friction seemed to be brought about by the obstruction against the entraining of the fluid flow and the high shear stress due to the microbonding between the asperities of bearing surfaces, which were derived from the adsorbed protein on the hydrophobic surfaces. The repulsive force between the adsorbed film and the bearing materials by means of the d.c. electric field, and the continuous change in polarity on the surface by means of the a.c. electric field appeared to affect the adsorbed film adjacent to the bearing material, so that friction and wear were varied.