Determination Of Friction Coefficient Research Articles

A novel calculation expression for the experimental friction coefficient of the ball screw

The friction coefficient inevitably affects the friction force between balls and raceway thus might significantly change the performance of the ball screw. However, the traditional methods for determining friction coefficient are based on different empirical values which may lead to different results. To this end, this paper studies the variation law of the friction coefficient by considering different lubrication states between balls and raceway. An experiment is carried out, through which a Stribeck tribology-based expression of the friction coefficient is proposed. The given results provide two obvious stages of lubrication, and the turning point of the two stages represents the minimum value of the friction coefficient. Moreover, the rotational speed is the main factor that influences the value of the friction coefficient based on the calculation of the average central film thickness.

Dry friction under pressure variation of PACVD TiN surfaces on selected automotive sheet metals for the application in unlubricated metal forming

Forming without lubricants opens up ecologic and economic benefits for producing industries. In addition, dry friction allows better transmission of the process loads to the required forming force. Without any surface treatment, however, unlubricated contact leads to highly increased wear during forming. One way to describe friction in a way relevant for metal forming processes is the determination of Coulomb's friction coefficients over varying process parameters, which is usually measured on highly dedicated test facilities. Within the present study, kinetic and static friction coefficients have been examined by strip drawing on universal tensile testing machines. Contact pressure was varied from 1 to 100 MPa by deploying two different friction tools. Amongst the material specific coefficients and the resulting trends of friction vs. pressure, their comprehensive connectibility overarching the test assemblies was of key research interest. Plasma assisted chemical vapor deposition (PACVD) of titanium nitride (TiN) has been deployed to the friction jaws of the testing tools, after conventional surface treatments for sheet metal forming tools (i.e. Tenifer nitro-carburation, plasma nitration and PVD-AlTiN) have failed in preliminary dry friction experiments. With this coating technology, dry friction of different automotive-typical sheet metal materials was tested successfully even at elevated pressure. Proportionally increasing trends of kinetic and static friction over pressure were obtained, which are linked overarching the experimental setups by linear regression.

The friction of root crops on different surfaces in preparation for feeding animals

The purpose of the research was to determine the functional dependencies of the friction parameters of root crops on various surfaces for subsequent use in energy calculations of working bodies. The research methodology provided for the experimental determination of static and kinetic friction coefficients on various surfaces and subsequent statistical processing of experimental data to obtain a regression model of indicators from the pressure of compression. Based on the research, equations were obtained that characterize the friction processes of root crops on various surfaces (steel, rubber, painted steel), which will serve for their further use in the design of machines and energy calculation. The highest friction coefficient corresponds to a pressure of 4.0-5.0 kPa, regardless of the static or dynamic loading method. At motion speeds of surfaces up to 2.0…2.6 m/s, the released juice manages to squeeze out of the contact zone. This increases the friction coefficient. At speeds from 2.000…3.095 m/s, the resulting juice does not have time to leak out of the contact zone, and therefore works as a liquid lubrication. As the speed increases, the friction coefficient decreases.

Molybdenum strip test experiments and simulations at various temperatures to determine friction coefficients

The aim of the presented study was to perform the strip test of 0.5 mm thick molybdenum strip specimens by various simulated drawbead heights from 2 mm up to 6 mm and various temperatures from 20 °C up to 320 °C to obtain friction coefficients between the molybdenum strip and steel cylinders built-in the developed test device simulating the drawbead. The friction coefficients between the dry and lubricated molybdenum strip and the steel cylinders simulating the drawbeads were obtained by changing its value in the bilinear friction model and matching the holder drawing force and the drawbead restraint force curves achieved during the tests and the simulations. The increasing temperature of molybdenum strip led to reduced holder drawing force and drawbead restraint force and increased friction coefficient because of the decrease of molybdenum strip yield strength and the increase of surface contact between molybdenum sheet and the testing tool at elevated temperature.

In vitro tribological investigation and osseointegration assessment for metallic orthopedic bioimplant materials

Abstract This research study is aimed at finding a suitable uncoated metallic biomaterial based on its wear properties and osseointegration ability for orthopedic implants. In the present work, wear tests were carried out on uncoated metallic biomaterials such as Co-Cr-Mo, SS316L, Ti6Al4V and Titanium grade 2. The wear tests were performed to determine friction coefficient and wear loss in the presence of simulated body fluid having a common pH of 7.25 similar to human plasma. The wear resistance was found to be highest for Co-Cr-Mo material followed by SS316L, Ti6Al4V and Titanium grade 2 material. To grow an apatite layer, uncoated metallic substrates were immersed for two weeks in a simulated body fluid having ion concentration equivalent to human blood plasma. Adhesive bonding strength of the apatite layer formed on the different bioimplant substrates was evaluated under tensile stress. The worn metallic surfaces post wear tests and metallic substrates with apatite layer were analyzed using scanning electron micrographs. From the results it was found that uncoated Ti6Al4V material is more suitable for orthopedic implants as compared to other materials studied in this work.

The determination of friction coefficient in Nakazima test and its application in predicting FLCs with modified M-K model

In this work, the friction coefficient between the punch and the specimen during the Nakazima tests is determined by comparing the experimental and the numerical strain paths. Afterwards, the FLCs of the Al-Mg-Li alloy sheet are predicted with the modified M-K model, which considers the through-thickness normal stress and the friction through introducing the expressions of the normal stress and the friction stress into M-K model. Finally, the predicted FLCs of the sheet are compared with the forming limits determined by Nakazima tests.

Study of tribotechnical characteristics of 3D printed abs plastic samples

This work is devoted to research of tribotechnical characteristics of 3D printed samples from ABS plastic. The results of determination of friction coefficient and depth of counterbody introduction into the sample surface on Tribometer TRB-S-DE-0000 are presented. The article also presents the advantages of using 3D printing for repairing machine parts and describes the causes of gear failure.

Automated Determination of Friction Coefficient

Abstract The presented research is designed to meet a particular challenge facing the industry. Its aim is to automate the process of friction coefficient determination, using a method that enables quick and easy repeatability of measurements developed by S.C. Plasmaterm S.A in Târgu Mureş.

Electromagnetic Method for Determining the Internal Resistance of Conductive Materials

The electromagnetic method of vibration diagnostics of rod conductive parts is theoretically described. Natural frequencies of the transverse oscillations of the rod are determined for various boundary conditions. In theory, method of experimental determination of internal friction coefficient of electrically conductive materials is developed.

Tribological Characterization of Some Elastomers Used at Progressive Cavity and Piston Pumps

The progressive cavity pump (PCP) is a positive displacement pump, consisting of a polished helical-shaped rod (rotor) turning inside a helical elastomer (stator). PCP has many advantages, but the pump durability is manly limited by elastomer behavior. At piston pumps (PP) used for drilling mud piston has an elastomer sleeve that also limit the durability. Standards like ISO 15136.1 & 2 for pumps developed by manufactures and users’ committees provides requirements for design, quality design verification etc., but do not define specifically the elastomer for the stator or the metal used for the rotor. Each PCP and PP manufacturer used specific materials at pump construction. The aim of this study was to evaluate the tribological behavior of some elastomers such polybutadiene rubber (BR), polybutadiene acrylonitrile rubber (NBR), polybutadiene acrylonitrile carboxylate (XNBR) and polyamide (PA 6) in couples with hard chromium coated steel, nitride steel and cast iron. Were determined friction coefficients and wear on 2 types of friction couples (plane to plane and shoe to plane) on two tribometers and some mechanical proprieties (Young’s modulus, ultimate tensile strength, elongation, hardness).

Determining Friction Coefficient at Run-In Stage and Diagnosing the Point of Transition to Steady-State Phase Based on Acoustic Emission Signals

We study the joint dynamics of changes in the parameters of acoustic emission (AE) and in the friction coefficient during TRB friction machine testing of flat steel 12Kh2N4ASh specimens, including those with Ti + Al + N ion-plasma vacuum sputtering. The results of studying the shape of the curve of the reconstructed values of AE-event stream intensity in different parts of the experimental curves of the dependence of friction coefficient on test time are presented. A significant correlation was discovered between the friction coefficient and the reconstructed AE-event stream intensity. Methods are proposed for evaluating the friction coefficient and the time of the run-in stage end based on the reconstructed AE-event stream.

A 3D FEM-Based Numerical Analysis of the Sheet Metal Strip Flowing Through Drawbead Simulator

Drawbeads are elements of the stamping die and they are used to compensate material flow resistance around the perimeter of the drawpiece or to change the stress state in specific regions of the drawpiece. This paper presents the results of experimental and numerical analyses of tests of sheet metal flowing through a drawbead. The tests have been carried out using a special tribological simulator of the drawbead. Experimental tests to determine the coefficient of friction (COF) have been carried out for three widths of sheet metal strip and two drawbead heights. The three-dimensional (3D) elastic-plastic numerical computations were performed using the MSC. Marc program. Special attention was given to the effect of material flow through the drawbead on the distribution of the normal stress on the tool-sheet interface. The mesh sensitivity analysis based on the value of the drawing force of the specimen being pulled through the drawbead allowed an optimal mesh size to be determined. The errors between the numerically predicted values of the COF and the values experimentally determined ranged from about 0.95% to 7.1% in the cases analysed. In the case of a drawbead height of 12 mm, the numerical model overestimated the value of the COF for all specimen widths analysed. By contrast, in the case of a drawbead height of 18 mm, all experimentally determined friction coefficients are underestimated by Finite Element Method (FEM). This was explained by the different character of sheet deformation under friction and frictionless conditions. An increase in the drawbead height, with the same sheet width, increases the value of the COF.

Characterization on the yield stress and interfacial coefficient of friction of glasses from scratch tests

Based on dimensional analysis and finite element simulation, a new method is proposed to characterize the yield stress and interfacial coefficient of friction of materials by scratching with a Vickers indenter. Two simple equations are obtained: one is for determining the interfacial coefficient of friction between the scratched material and scratch tip via the ratio of tangential to normal force, and the other is for calculating the yield stress of scratched material with the groove width and normal force. In a case study, the method is applied to soda-lime and borosilicate glasses. It is shown that the measured results of yield stress and interfacial coefficient of friction between glasses and a diamond tip are consistent with that obtained by other methods, with a high accuracy. The quick and accurate determination of yield stress and interfacial friction coefficient provides important information for the design and processing of glass products.

Study of deformation and fracture of [formula omitted] ceramics by wedge splitting of a chevron-notched specimen

A method for determination of crack resistance of a material based on the test data of small-sized chevron-notched double cantilever beam specimens by wedge splitting is proposed. Specific fracture energy for small-sized chevron-notched double cantilever beam specimens is calculated using analytical expressions derived on the basis of the beam theory with a correction for elastic deformation of the ligament of a double cantilever beam specimen. A proper transition is performed from the pressing force on a wedge to the deflection force of cantilevers with account for the deformation of the ligament of a chevron-notched double cantilever beam specimen and the friction coefficient between the wedge and the specimen. An analytical formula that allows determination of friction coefficient during an experiment is worked out. New data have been obtained when testing ceramics based on ZrO2+3mol%Y2O3. The ceramics’ loading diagrams reveal an extensive inelastic stage of deformation that precedes specimen fracture. It is shown to be associated with the α-β polymorphic transformation in the chevron notch zone. The displacement contributed from inelastic deformation is ⩾21% at the moment of specimen fracture for tested specimens. The obtained evidence indicates the dislocation-free mechanism of inelastic behavior of ZrO2+3%Y2O3 ceramics. In chevron-notched specimens, the α-β transformation is performed under the action of stress concentration without a crack in the chevron notch zone. The paper points out the necessity to use the value of “nonelastic” displacement of chevron notch sides as an additional characteristic of crack resistance of a material when studying and modelling deformation and fracture of small-sized specimens.

Measurement of Friction Coefficient between Glass and Rubik's Beam on the Sloping Field using Rubik Lubricant

This research is based on a rubik game involving the coefficient of friction. Rubik when difficult to rotate then the coefficient of friction is large. Rubik has several lubricants including Maru Lube, Ellips, and Kit Shampoo. This study aims to determine friction coefficient between the inclined plane of glass and rubik beams with lubricating. The beam is launched on an inclined plane and measured travel time. The results of the measurement of the coefficient of friction of the three lubricants namely Maru Lube lubricant has a coefficient of friction value of 0.4586, Ellips lubricant of 0.4375, and shampoo Kit lubricant of 0.4630. Based on these data it can be concluded that Ellips lubricant is the most slippery and more effective lubricant to use.

Determination of The Rotational Friction Coefficients of Solid Cylinder with Various Inclined Plane Angle

The layer texture differences of an object have an influence on the friction force caused by both planes. This research aims to determine the static and kinetic friction coefficient on several solid cylinder materials. The benefits of this research can be used to develop experimental learning activities on friction coefficient. This research used experimental method. The research was carried out by rolling samples at various inclined plane angles and measuring the traveled distance traveled in one rotation (D). The results showed that the static and kinetic friction coefficients between aluminum cylinder and glass were 0.146 and 0.097, iron cylinder and glass were 0.136 and 0.096, glass cylinder and brass were 0.132 and 0.094, nylon cylinder and glass were 0.101 and 0.090, and stainsless cylinder and glass were 0.122 and 0.094, respectively.Perbedaan tekstur lapisan sebuah benda mempunyai pengaruh pada gaya gesek yang ditimbulkan oleh kedua bidang. Penelitian ini bertujuan untuk menentukan nilai koefisien gesek statis dan koefisien gesek kinetik pada beberapa bahan silinder pejal. Manfaat yang dapat diambil dari hasil penelitian ini adalah dapat digunakan sebagai mengembangkan kegiatan pembelajaran praktikum koefisien gesekan benda. Penelitian ini menggunakan metode eksperimen. Penelitian dilaksanakan dengan menggelindingkan sampel pada berbagai sudut kemiringan dan mengukur jarak tempuh untuk satu kali putaran (D). Hasil penelitian menunjukkan bahwa nilai koefisien gesek statis dan koefisien gesek kinetik secara berurutan untuk silinder aluminium dengan kaca sebesar 0,146 dan 0,097, untuk silinder besi dengan kaca sebesar 0,136 dan 0,096, untuk silinder kuningan dengan kaca 0,132 dan 0,094, untuk silinder nylon dengan kaca sebesar 0,101 dan 0,090, dan untuk stainsless dengan kaca sebesar 0,122 dan 0,094.

Effect of topography parameter, load, and surface roughness on friction coefficient in mixed lubrication regime

AbstractSurface topography parameters significantly control physical processes which have asperity‐to‐asperity contacts in tribological components undergoing friction and wear. In this study, the effect of correlation length, maximum contact load, and surface roughness on friction coefficient and load distribution is studied. The load‐sharing concept is employed to determine friction coefficient and load distribution in the mixed‐lubrication regime. Results clearly demonstrate the effect of correlation length on friction coefficient and load distribution. It is found that the lower value of the coefficient of friction may be achieved even at low velocity for the smooth surface as compared with rough surfaces having higher surface roughness. For a particular value of velocity, the coefficient of friction decreases with an increase in maximum contact load. This work will help in predicting the coefficient of friction in the mixed‐lubrication regime for the engineering surfaces produced by processes like grinding, which is the result of an abrasive action.

A METHOD FOR THE DETERMINATION OF THE KINETIC FRICTION COEFFICIENT IN FRICTION PAIRS BASED ON DIRECT ACCELERATION MEASUREMENT OF AN OBJECT ON AN INCLINED PLANE

The paper presents and experimentally verifies a method for the determination of the kinetic friction coefficient of friction pairs. The method involves a direct acceleration measurement of an object sliding down an inclined plane and the determination of the momentary friction force based on acceleration. The laboratory test rig was presented and the theoretical foundations of the method were discussed in detail. The laboratory experiments were conducted for the following material pairs: steel-cast iron, steel-bronze, and for various inclined plane angles. The experiments results were presented, acceleration vs. time curves were plotted, and friction coefficients were determined. These values were compared to the values known from literature [L. 1–3]. The uncertainly analysis of kinetic friction coefficient determination was conducted. The method effectiveness and accuracy was verified, noting the sources of possible measurement errors and the ways to eliminate them.

Mathematical modelling of an experimental‐analytical method for friction coefficient determination in deep drawing

AbstractThe main aim of this paper is to determine the friction coefficient μ and maximum drawing force in deep drawing process of aluminum alloy EN AW 1050 utilizing strip drawing method. Influence and interaction between lubrication condition, blank holder force and strip surface roughness on maximum drawing force and friction coefficient are investigated. Response surface methodology and D‐Optimal design are utilized in order to create an experimental plan. According to the design, 23 strip drawings experiments are performed and statistical analysis was done. The regression and variance analysis results with 18 significant mathematical models which are derived in order to describe influence of mentioned parameters on friction coefficient and maximum drawing force. Results are discussed according to previous research. Finally, the optimization of processing parameters is performed aiming for lower friction coefficient and maximal drawing force.

ANALYTICAL DETERMINATION OF THE REDUCED ROTATIONAL RESISTANCE COEFFICIENT OF THE CONSTRUCTION MACHINE SLEWING GEAR

Purpose. Designing new models of construction machines is closely related to the development of slewing gear, and that, in turn, has a drive whose power and dimensions depend on the rotational resistance and the reduced friction coefficient in the units. The absence of analytical dependencies for determining the reduced coefficient of friction for the rotation of construction machines, first, restricts the designer's ability to select materials, and secondly, does not allow the adoption of optimal design solutions. Therefore, the purpose of the article is to find analytical solutions to determine the rotational resistance in the slewing gear of construction machines, which allows projecting more advanced gears and machines in general. Existing techniques are based on empirical dependencies and experimental coefficients that reduce the accuracy of calculations, increase the size and cost of work. It is proposed to improve the accuracy and simplify the process of determining the rotational resistance and the magnitude of the reduced rotational resistance coefficient of the building tower cranes. Methodology. The set objectives can be achieved by means of analytical dependencies for determination of rolling friction coefficients over linear and point contacts. This will enables to find the more accurate value of the resistance coefficient, and the constructor during the calculations to take targeted measures to reduce it, using the mechanical constants of materials of the units and their geometric parameters. The calculation is based on Hertz contact deformation theory and the body point plane motion theory. Findings. The obtained dependencies will allow analytically to find the resistance of rolling resistance of rollers in construction machines with fixed and rotating pillars, with circular rotary devices, as well as in ball and roller slewing rings. The calculated values of the rotational resistance coefficients for some types of mechanisms give similar values with those recommended, while for others they significantly differ and require their refinement in reference values. Originality of the work consists in the use of analytical dependences for determining the reduced coefficient of the rotational resistance over linear and point contacts using Hertz contact deformation theory and Tabor partial analytic dependencies theory. Practical value. The obtained dependencies will allow to design new types of slewing gear units of the construction machines and to reveal the additional rotational resistances.