Friction Zone Research Articles

Wear modes in testing the antifriction layer of babbitt B83

In this work, study of wear modes of antifriction layers of B83 babbitt during tribological tests was carried out. The assumed conditions for changing wear modes were determined during testing with a continuous increase in load by analyzing data of changes in the coefficient of friction and temperature near the contact zone. The data obtained made it possible to conduct experiments for a deeper study of the processes occurring in the friction zone. The results of friction experiments and studies by electron microscopy confirmed the correctness of the assumption about the conditions for change of wear modes. Changes in wear modes and wear mechanisms were judged by the behavior of the friction coefficient, the difference in friction surfaces, wear products, and wear intensity. The results obtained will make it possible to determine and recommend the modes of “wear-free” operation of the babbitt alloy.

Transition of interfacial friction regime and its influence on thermal responses in rotary friction welding of SUS304 stainless steel: A fully coupled transient thermomechanical analysis

Rotary friction welding (RFW) has proved to be a successful joining technology in advanced materials manufacturing. The highly transient thermal responses during friction heating, including heat generation and temperature distribution, are essential factors in the design and control of the RFW process. In this study, a 2D axisymmetric finite element (FE) model for the RFW process of SUS304 stainless steel is presented in order to investigate the transition of the interfacial friction regime and its influence on the transient thermal responses. By using the FE simulation, the in-process state variables, i.e., frictional stress and heat flux, and their spatial distribution at the welding interface are obtained. The FE simulation is validated by published experimental results. A new analytical model for the transient evolution of the friction regime is concluded from the FE simulation, which accurately predicts the shrinkage of the Coulomb friction zone while the Shear friction zone builds up from the workpiece periphery. Comprehensive analysis is conducted on the variation of interfacial heat flux, frictional stress and temperature resulted from the transition of friction regime. It is revealed that the transition of the interfacial friction regime from the Coulomb friction regime to the Shear friction regime is preferable for temperature homogenization at the welding interface.

ОПРЕДЕЛЕНИЕ ТРИБОЛОГИЧЕСКИХ ХАРАКТЕРИСТИК СПЛАВА АЛЮМИНИЙ-КРЕМНИЙ В ЗАВИСИМОСТИ ОТ СОСТАВА ДОБАВОК ДЛЯ ПОРШНЯ ДИЗЕЛЯ ТЕПЛОВОЗА

The study objective is to define the influence of various modifiers on the tribotechnical properties of an aluminum and silicon alloy. Determination of the most optimal additives in alloys that would reduce the friction factor and increase the unit load at which friction pairs set in comparison with the starting material, as well as determination of their wear resistance.
 Research methods are tests conducted for friction and wear of samples based on aluminum and silicon according to the following: plane (test sample) – the sleeve end (steel 40X), as well as conducting tests with the supply of free abrasive into the friction zone according to the following: flat sample - forming surface of a rubber disc.
 Research results and novelty: the influence of modifiers in the aluminum and silicon alloy composition on wear resistance and friction ratio at different loads and sliding speeds in a friction pair with steel are established.
 Conclusions: the regularities of changes in the friction ratio from pressure and speed, the load of seizure from the sliding speed are obtained. The wear resistance of samples with various inclusions is higher compared to the base material.

ТРИБОТЕХНИЧЕСКИЕ ПРОЦЕССЫ ПРИ ФРЕТТИНГ-ИЗНОСЕ

The work is devoted to obtaining and studying of tribotechnical characteristics during fretting wear of plastic metal films deposited on steel-45. The tribotechnical characteristics of the film coating (copper-containing film) deposited on the test surface of the specimens by the method of finishing antifriction nonabrasive treatment (FABO) have been studied. The analysis of the characteristics of these films in comparison with a deposited steel coating without a film is carried out. The antifriction characteristics of the brass film on the friction surface are investigated. The tribotechnical properties of friction surfaces during fretting wear are substantiated. As a result of the conducted research, the theory of abrasive wear was further developed. Recommendations on the choice of materials for obtaining coatings and films have been developed. New methods of preparing specimens for testing materials for wear resistance are proposed. As a result of the study, the distribution of oscillations dampening is obtained depending on the amplitude of the oscillations and the decrease in the molecular component of the friction coefficient. The ranges of values controlled in the experiment are substantiated, measuring devices for laboratory research are recommended. Optimal steel coatings have been selected. Based on the results of the research, three-factor graphs of the dependences of the coefficient of friction on the number of cycles and the amplitude of oscillations are constructed. It is established that over time, the alignment of the surfaces, the friction zone hardening, and the formation of wear particles occur. The process of wear occurs according to the scheme "hardening – lass of strength - destruction". It is proved that an increase in the load leads to an increase in the intensity of wear-and-tear. Simultaneously with an increases in the amplitude of the oscillations, the intensity of wear increases in accordance with the theory of limiting oxygen access to the contact zone during fretting. Theoretical foundations for the production of plastic metal films have been developed.

Estimation of tribotechnical parameters of composite polymer with metal filler

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 The use of composition material based on the polyamide (caprolon) Ertalon 4.6 as an anti-friction material in the sliding units in the aviation industry is considered. Low carbon electrotechnical sheet steel 21864 of different concentrations was used as filler of composite material. The article presents the thermal calculation of plain bearings with polymer insert in different operating modes. It is determined that the addition of a metal filler to polyamide causes a temperature decrease in the friction zone due to the effective heat exchange from the shaft to the bearing housing. The article conducts a study of tribo-technical properties of the proposed composite material on installation PT-4C under sliding conditions according to the scheme “cylinder-plane”, as well as modeling of the support unit in the software complex DS SolidWorks. It has been experimentally determined that the addition of finely dispersed steel filler enhances the antifriction properties of the Ertalon 4.6 polymer and extends the temperature range of the composite insert performance. Increasing the filler concentration to 20% results in a reduction of the friction coefficient by an average of 3.6 times and an increase in the temperature range of composite material use to 100 °C. The load-bearing capacity of the composite material bushing is increased to 25 MPa at a 20% filler concentration respectively.
 The practical significance of the work lies in the analysis of the antifriction properties of the polymer with metallic filler in comparison with the polymer without filler, which will prove the effectiveness of the use of such polymers in friction units instead of non-ferrous metals (bronze, babbitt).

Оценка надежности трибосистем на неустановившихся режимах работы

The issue of determining the wear rate in unsteady operating modes (during running-in period) and in stationary modes (after running-in is completed) during bench tests of vessel technical equipment is considered. The availability of such information will reduce the time for finishing prototypes. Moreover, it will help to identify ways to improve the reliability of technical equipment during operation. There have been carried out the experimental studies that showed the reliability of the kinetics of the surface destruction processes at the stage of tribosystems running-in. Experimental studies were carried out in two stages and determined the correlation between the rate of volumetric wear and acoustic emission parameters: the variance of signal amplitudes and the spectral power of radiation. The presented graphic dependences demonstrate that the spectral power has the optimal functional relationship with the friction parameters: friction torque and temperature. The analysis of the dependences obtained showed that the variance of the amplitudes and the spectral power of the acoustic emission signals reflects sufficiently complete the wear process. Thus, it is in a functional relationship with the rate of volumetric wear. It has been experimentally confirmed on various tribosystems that the spectral power of acoustic emission signals has a better correlation coefficient with the wear rate than variance. Therefore, it can serve as a parameter for estimating the wear rate in unsteady operating modes. A technique for evaluating the tribosystems wear rate during running-in is proposed. The technique is based on the recording of acoustic radiation from the friction zone. The spectral power of acoustic radiation correlates with the wear rate with a correlation coefficient R = 0.82.

Rupture styles linked to recurrence patterns in seismic cycles with a compliant fault zone

Seismic cycles emerge in a broad range of rupture styles, from slow-slip events to pulse-like earthquake sequences. Meanwhile, large earthquakes in paleoseismic and instrumental catalogues exhibit various recurrence patterns going from periodic to chaotic cycles with characteristic or dissimilar ruptures. The potential connection between these observations is still poorly known. Here, we investigate the link between rupture styles and recurrence patterns in quasi-dynamic models of seismicity in two-dimensional faults embedded in a compliant zone, exploring a wide range of frictional and fault zone properties. The recurrence patterns evolve from purely periodic to multiple-periodic time- and slip-predictable cycles, to chaotic sequences of super-cycles with full and partial ruptures with an increasing number of aftershocks. This transition is accompanied by changes of rupture styles from crack-like to pulse-like ruptures. These behaviors can be obtained either by a more compliant fault zone or a reduced characteristic weakening distance of friction. The effects of the compliant zone and other physical characteristics can be conflated into a single non-dimensional number, such that seismic cycles with similar behaviors can be obtained with or without a compliant fault zone in quasi-dynamic simulations. The connection between recurrence patterns and rupture styles implies that the paleoseismic record can bring useful constraints to rupture characteristics and fault zone properties.

Affect and digital caregiving: challenging the performing arts canon with a ‘dig where you stand’ database

ABSTRACT This paper addresses the affective dimensions of caregiving in relation to materials outside the canon, influenced by Caswell and Cifor’s notion of radical empathy. The article employs the author’s positionality and lived experience, using specific examples to illustrate ‘zones of friction’ where the dominant discourse and its processes of canon formation show themselves, and how radical empathy can expose and destabilize the performing arts canon. The author begins to use these examples, and the feelings they evoke, as a waymarking tool for the application of methodologies such as ‘dig where you stand.’ This data collection methodology, by recording a wider and more inclusive range of participants as of equal value to performing arts work (in this case), brings Caswell and Cifor’s ‘caregiving’ to more stakeholders. The notion of ‘transforming affect into substantial data’ exemplifies the article’s engagement with the canon to articulate the potential for transformation.

Evaluation of tribological performance for laser textured surfaces with diverse wettabilities under water/oil lubrication environments

Friction and wear are considered as one of the major issues for engineering applications where surface interactions exist. Textured surface with modified surface functionalities as well as lubrication condition will greatly affect the tribological performance. In this work, laser-based surface treatment methods were developed to modify the physicochemical properties of the textured surfaces. The surface microstructure, contact angle, chemical composition and tribological performance under different lubrication conditions of the fabricate surfaces were evaluated and analyzed. The experimental results indicate that the surfaces fabricated by laser texturing combined with chemical immersion or long-time storage in air obtain distinct superhydrophobicity, and the superhydrophobic surfaces render significantly reduced friction coefficient in both starved-water or starved-oil environments. It is believed that the surface texture, wettability and chemistry have combined effects on the tribological performance, which can facilitate the formation of a relative thicker lubricant film on the friction zone, and thus the effective contact area between the friction ball and the surface is reduced. This work is expected to provide effective methods to design and fabricate textured surfaces with different surface properties aiming to enhance the tribological performance, thus benefiting various industrial sectors that have strong demand for anti-friction surface.

Do phospholipids affect the friction of articular cartilage on silicone rubber? (experimental study)

The results of model experiments showed that when surfaces of native articular cartilages interacted friction coefficient was within 0.02-0.07 (depending on the load quantity). When cartilagenous surfaces interacted with silicone rubber that index was 3 to 6 times higher. Putting of 3-6 mg/cm2 of egg or synthetic polymerized phosphatidylcholone on the surface of silicone rubber considerably decreased the friction coefficient at interaction of rubber with the cartilagenous surface while the administration of the same quantity of egg phosphatidylcholine in the form of 10% aqueous suspension into the friction zone gave no effect. The data obtained indicate that the of phospholipids for the improvement of tribological characteristics of joint implants is a prospective one.

A frictional cohesive zone model for characterizing transverse compression responses of unidirectional fiber-reinforced polymer composites

The Coulomb friction law is incorporated into the traction separation law, so a friction cohesive zone model (FCZM) combining sliding friction, interfacial debonding, and the coupling of the debonding and friction is developed. The proposed interface model is used to describe the interfacial mechanical responses of fiber/resin composite. To verify this model, the finite element model of microdroplet is built, then the calculated results of the finite element model are compared with the microdroplet test. To analyze the effect of interface friction on the macroscopic strength and stiffness of unidirectional composites, the FCZM is applied to representative volume element (RVE), and the mechanical behaviors of composites is simulated by finite element analysis of RVE, then the results are compared with the test in reference [1, 2]. It is found that the interfacial debonding is accelerated and the macroscopic strength is reduced due to the friction.

Tribological Properties of Coating Obtained by Magnetron Sputtering of the Composite Target Ni-Cr-B<sub>4</sub>C

The paper studies the tribological behavior of a Ni-B/Cr7C3 nanocomposite coating applied by magnetron sputtering on a Ni-Cr-B4C composite target. The composite target was obtained by detonation gas-thermal spraying of Ni-Cr-B4C powder composition. The study determined the hardness of the coating amounting to 7.8 GPa. The distribution of chemical elements in the contact zone of ball-coating friction by energy dispersive spectroscopy (EDS) was studied. The wear track width was 324 μm. Tribological wear tests and determination of adhesion/cohesion strength showed that Ni-B/Cr7C3 coatings have good wear resistance, and abrasive and adhesion wear mechanisms act simultaneously during wear. The resulting coatings can be used to protect critical parts and mechanisms susceptible to abrasive and adhesive wear.

ЗАКОНОМЕРНОСТИ ВЛИЯНИЯ ЭКСПЛУАТАЦИОННЫХ ПАРАМЕТРОВ ПОДШИПНИКОВ СКОЛЬЖЕНИЯ АВТОТРАНСПОРНЫХ МАШИН НА ТЕМПЕРАТУРУ В ЗОНЕ ТРЕНИЯ КАК ФАКТОР РЕСУРСА

The results of the study of the dependence of the temperature of the friction zone of two bodies (shaft and the inner sleeve) are presented from the operational parameters of the sliding bearing, such as pressure, slip speed and radial load in the resource aspect of the friction pair. On the basis of a multi-factor experiment, the regression of the friction process was obtained, which takes into account the influence of these parameters on the temperature in the contact zone, which makes it possible to determine the borders of the trouble-free operation of the friction of motor vehicles. Technological ways are proposed to solve the problematic performance of the friction pair on the temperature criterion without scoring.

On the Microstructure, Microhardnessand Wear Behavior of Gray Cast Iron Surface Layer after Laser Strengthening.

Cast iron is one of the most common structural materials and is widely used in mechanical engineering production. Taking into account its rather low mechanical properties, different technologies are currently used in industry, among other areas, for the mechanical and thermal strengtheningof the surface layer, as well as surface alloying of workpieces. The aim of this study was a comprehensive analysis of changes in the microstructure, microhardness of the surface layer and its wear resistance under lubrication friction conditions and changed surface energy density in order to ensure the effectiveness of laser strengthening of gray cast iron. In this research, the efficiency of gray cast iron GJL200 laser strengthening was described. The basic properties of the surface layer of gray cast iron under laser strengthening, including the microstructure, microhardness, tribological and wear behavior, were compared with the properties of cast iron in the initial state. It was found that laser strengthening under the right choice of the surface energy density ensured a five-to-tenfold increase in the wear resistance of gray cast iron in comparison with the initial state. This was due to forming unconventional pseudo-vermicular graphite shapes at the friction zone, as well as a spongy-capillary effect appearance. The appropriate selection of surface energy density values provided stable and low coefficients of friction and a very significant increase in the wear resistance compared with the values reached for a cast iron in the initial state. This fact is new and very important for the engineering practice. The values of the surface energy density can be easily controlled, which means that different parts can be operated efficiently after laser strengthening.

Process Relationship in High-Stress Friction Coupled with Complex Shaped Counterbody and Friction Stir Welding Al-Mg-Sc-Zr Alloy

Model research tests of plastic deformation, fragmentation and flow of aluminum alloy material of Al-Mg-Sc-Zr system under high loaded friction in pair with a steel counterbody of a complex shape and comparison of the obtained result with the structure formed by friction stir welding have been carried out. The conducted studies show that the structure formed by extrusion of the material from the friction zone and its compaction in the channel of the counterbody is, in general, close in structure to the structure formed by friction stir welding of similar material. The distinguishing features of the structure formed in the model experiments on friction include the introduction into the stirring zone of material with deformed large-crystal structure, increased grain size of the stirring zone, the presence of defects and differences in the geometry of the stirring zone.

A Simulation and Experimental Study on Identification of an Electromechanical System

The current applications in electromechanical energy conversion demand highly accurate speed and position control. For this purpose, a better understanding of the motion characteristics and dynamic behavior of electromechanical systems including nonlinear effects is needed. In this paper, a suitable model of Permanent Magnet Direct Current (PMDC) motor rotating in two directions is developed for identification purposes. Model is parameterized and identified via simulation and using real experimental data. Linear and nonlinear models for the system are built for identification, and the effective nonlinearities in the system, which are Coulomb friction and dead zone, are integrated into the nonlinear model. A Weiner- Hammerstein nonlinear system description is used for identification of the model. MATLAB is selected as the investigating tool, and a simulation model is used to observe the error between the simulated and estimated outputs. Identification of the linear and nonlinear system models using experimental data is performed using the least squares (LS) and recursive least squares (RLS) methods. Performance of the model and identification method with the real time experiments are presented numerically and graphically, revealing the advantages of the proposed nonlinear identification approach.

РЕАЛИЗАЦИЯ МЕХАНИЗМА ИЗБИРАТЕЛЬНОГО ПЕРЕНОСА В ПОДВИЖНЫХ СОПРЯЖЕНИЯХ СИЛОВЫХ ПЕРЕДАЧ ПРИ ЭКСПЛУАТАЦИИ СЕЛЬСКОХОЗЯЙСТВЕННЫХ МАШИН

Searching for new effective ways of increasing the wear resistance of power transmissions and improving their durability, the authors propose a device for enriching the lubrication system of power transmissions with copper-alloying elements. The tribochemical processes have been studied and the components of the lubricating composition have been selected to provide for the self-organized selective transfer in the “steel-steel” friction couples accompanied by the formation of a servovit film. The authors developed a utility model for enriching the lubricating system oil with copper-alloying elements for power transmission. For testing the effectiveness of the proposed additive and the method of forming the servovit film during operation, a roller test bench was used. It provided for synchronous measurement of the wear rate and the friction force moment during the whole experiment without disconnecting the friction zone. The friction zone (test contact) was formed by the cyclic surfaces of a roller with a diameter of 70.0 ± 0.1 mm made of steel 45 (HRs 50) and a homogenized pad with a radius of 35.0 ± 0.1 mm and dimensions (plan view) of 2.01 mm (along the sliding line) and 7.27 mm (across the sliding line). The friction area was 0.1461 cm2. A set of normal forces: 730; 925; and 1130 N – was experimentally determined to ensure that there was no seizure. The shaft speed of 100 min-1 (a linear velocity of 0.37 m) was experimentally chosen under the condition of guaranteed absence of the hydrodynamic lubrication mode. The presented method of cladding additive production is easily implemented in the transmission units and also prevents the sedimentary instability of the lubricating composition. The device for enriching the lubricating system oil with copper alloying elements in the process of operation provides for a stable and self-organized mode of selective transfer. The results of tribological studies have shown the high efficiency of the cladding additive – the wear rate in the range of the normal force of 720 to 1130 N has reduced in 2.8…7 times.

Вплив мастильних матеріалів на довговічність трибоспряжень

The aim of the research is to determine the influence of motor oils on operating modes, durability of tribocouples and substantiation of expediency of use of motor oils of corresponding brands. A study of the tribological properties of motor oils from different manufacturers. Characteristic features of friction moment change during lubrication with ZIC and Xado oils have been studied. During friction in the ZIC oil environment, significant oppositely directed changes in the moment of friction (oscillation) were recorded, which indicates an unstable friction mode. At the beginning of the experiment, a gradual increase in the friction moment when lubricating tribocouples with Xado oil was recorded. Studies of the dynamics of temperature in the friction zone depending on the lubricating medium are performed. It was found that the maximum temperature in the friction zone was when using Xado and ZIC engine oil - 90.0 ºC and 84.5 ºC, respectively. The value of wear intensity of steel-steel tripods depending on the engine oil of different manufacturers is determined. An analysis of micrographs of surfaces before and after the experiment was performed. It is established that the amount of damage to the surface friction as a whole without drastic changes. Unidirectional light lines are the places of direct contact between two friction bodies. After the experiment with lubrication with Xado engine oil on the friction surface of the pad recorded minor accumulations in the grooves and on their peripheries. It was found that the moment of friction when using the selected motor oils for the selected modes of friction of the tribocouples differs slightly, 1.13 N ∙ m and 1.15 N ∙ m, respectively, for ZIC X5 and Xado. At the same time, it should be noted that when lubricating with Xado engine oil, a higher constancy of the friction moment was recorded, compared to working in ZIC oil environment. It is established that the dynamics of temperature rise is gradual. The intensity of linear wear when using Xado oil is 17.7% lower compared to lubrication with ZIC oil. Thus, it can be concluded that the use of Xado motor oil can increase the durability of tribocouples.

МИТАЦИОННОЕ МОДЕЛИРОВАНИЕ ТЕМПЕРАТУРНОГО РЕЖИМА ПОДШИПНИКОВЫХ УЗЛОВ, ПРИСПОСОБЛЕННЫХ К ТЕРМОНАГРУЖЕННОСТИ

Modern transport and technological machines operate under the seasonality conditions of agricultural operations and significant energy loads. Universal joints of unequal velocity, being part of mechanical power transmissions, work under adverse conditions and limit equipment reliability. It was established that the temperature mode of the bearing assemblies of the universal joints affects the wear rate of their working surfaces. When the temperature in the friction zone increases due to mechanical operation and heating from the environment and adjacent heat sources, boundary friction and temperature conditions exceeding the level of material self-tempering occur. As a result of research, the universal joints (RU199508) were designed to ensure the intensification of cooling its bearing units directly in the maximum heat generation zone during the universal joint operation. Numerical simulation was performed according to the thechinque of calculating radiators for a universal joint with a cross K 040 GOST 13758-89 on needle bearings No. 804704 K5. The results showed the size of the outer surface area that is sufficient for its cooling. When the maximum values of the fracture angle of the universal joint, torque, angular velocity, and efficiency of 0.99 are combined, its bearing units are effectively cooled. It has been found that if the efficiency of the bearing assemblies is less than 0.952, their surface is no longer sufficient to provide efficient cooling and maintain thermal balance conditions in the friction zone. The use of the radiator can increase the heat transfer area by 19%. The radiator ribs fixed on the side surfaces of the yoke eyes with a thickness of 2 mm and a distance of 4 mm and a total area of 166.1 cm2 will ensure the operability of the bearing units. It will remain satisfactory even if their efficiency decreases to 0.943 as a result of mechanical wear.

Effect of cryogenic friction conditions on surface quality

This paper presents an experimental investigation on the tribological behavior of titanium alloys under cryogenic lubrication. The main goal of the study is to reproduce of thermomechanical loading encountered during a cryogenic machining operation. A tribological characterization was performed on a designed tribology system that allows contact between parts and wear tests under different controlled environments (hot temperature, lubrication, cryogenic, humidity, ...). The experimental bench has been equipped with the cryogenic fluid routing in the friction zone. A detailed analysis of the surfaces damage of the samples was then carried out to highlight the effects of the loading conditions on the surface integrity. The friction coefficient and wear volume are deeply analyzed to identify physical phenomena governing dry and cryogenic contacts.