Dry Friction Characteristics Research Articles

Hysteretic Dynamic Modeling and Vibration Characteristics Analysis of Metal-Rubber Isolators

A novel hysteretic constitutive model (HCM) with four parameters was proposed to reproduce the nonlinear elasticity and dry friction characteristics of metal–rubber isolators (MRIs). The HCM accurately characterized the nonlinear hysteretic behavior due to its intrinsic relationship with the geometric properties of the hysteresis loop. A physics-based parameter estimation strategy was developed to provide reasonable initial iteration values. Three MRIs with different design stiffnesses were tested to investigate their hysteretic behavior under various excitation levels. The HCM accurately reproduced the entire experimental hysteresis loops using only a subset of the experimental data. This exhibited higher precision and scalability compared to the classical dynamic model. Friction damping forces were employed to distinguish the stick-slip states of the three MRIs. Additionally, the identified parameters were used to simulate the steady-state vibration response of a complex MRI system. The resulting frequency response functions (FRFs) agreed well with the experimental data. The proposed model can effectively capture the amplitude-dependent effects in MRI systems with various design stiffnesses, enabling more accurate predictions of vibration responses.

Hand operated tribometer versus twin disc dry friction characteristics measurements

Accurate friction-slip modelling is particularly important for locomotive traction and rail damage studies. This paper compares friction-slip measurement results from a hand operated (HO) tribometer and a twin disc tribomachine on AS60 rail. The results were used to calibrate traction coefficient-slip curves using the Modified Fastsim contact model. The differences between the two friction measuring instruments including scale, speed, and rail cleaning effect influenced the friction coefficient and slip value at which the friction peak occurred. The proposed equalisation technique was able to match the HO tribometer traction coefficient-slip curve with the tribomachine curve while preserving most of the Modified Fastsim contact parameters.

Thermo-mechanical coupling analysis of the end faces for a mechanical seal under dry friction

A three-dimensional rotating sliding contact model was developed to study transient dry friction characteristics of a mechanical seal based on a modified W-M fractal function. The mechanical action and thermal-mechanical coupling between asperities were simulated using the software ABAQUS. The effects of external load, rotating speed and roughness on contact characteristics of the friction pair (carbon graphite/tungsten carbide) were investigated. The stress on cross section of the rough entity was studied. The results show that circumferential normal stress of contact asperity changes in axial direction from compressive stress to tensile stress to compressive stress, and tensile stress may cause crack propagation in the carbon graphite ring. The roughness Ra has great influence on stress and temperature distribution of rough entity.

Morphological and tribological studies of thermal plasma jet deposited coatings used in cardan joints

All wheels drive (AWD) and railway vehicles require a longitudinal transmission. Double cardan joint is one of the most employed transmission, as it allows misalignments between the shafts. This transmission must support the maximum motor torque and high dynamic loads. In such situation, from tribological viewpoint, cardan joints are subjected to abrasive wear. To increase wear resistance of cardan joints, its rolling elements can be coated with ceramic or metal-ceramic coatings. This paper presents an experimental research on microstructure and dry friction characteristics of two steel samples obtained from cardan crosses (40Cr10 and RUL2), coated by two types of metallic powders (METCO32 and METCO72). Microstructural studies of both surface and cross –section of samples were performed using scanning electron microscopy (SEM). Dry tribological tests at constant speed and load were carried out on AMSLER machine. The micro-structural experiments revealed a structure with a relatively homogeneous character, partially melted particles and several microcracks being detected. Following the tribological tests, it was found that the METCO72 coating provides the lowest coefficient of friction, near values being obtained for both substrates of 40Cr10 and RUL2. The best combination is formed by 40Cr10 substrate and METCO72 coating.

Research of Electrolyte Plasma Treatment Impact on Wear Resistance and Roughness of 18HN3MA-SH Steel

This work provides the results of research of the wear resistance of the surface of samples of low carbon structural of 18HN3MA-SH steel, subjected to electrolytic-plasma treatment by nitriding and carbonitriding. The effect of the structure on the surface wear resistance of steel is shown. Changes in abrasive wear and dry friction characteristics were studied depending on temperature and processing time. The results of studies of tribological tests show that after electrolytic-plasma nitriding, the wear resistance of steel 18HN3MA-SH increases by 1.5–2 times compared with the initial state. The observed effects can be explained by the flowing surface modification - the formation of a modified surface layer with the formation of hardening phases. The nature of changes in the surface roughness Ra of steel samples after cementation, carbonitriding and nitriding was studied.

Preparation of Ni-P-diamond coatings with dry friction characteristics and abrasive wear resistance

The Ni-P-diamond composite coatings that contained diamond particles with various sizes in microns have been prepared by electroless plating. The effects of diamond particle size and heat-treatment on the microstructure, mechanical properties, dry friction behavior and abrasive wear performance of the Ni-P diamond composite coatings were investigated. It was discovered that a Ni-P diamond composite coating with the thickness of 30μm could be obtained. The diamond particles (2–9μm) could be homogeneously dispersed in the coatings with the volume fractions of 21%–25%. Subsequently to 400°C for 2h of heat treatment, the hardness of the Ni-P diamond coatings increased to approximately 1200HV. The friction coefficients of the Ni-P diamond composite coatings were stable in the range of 0.4–0.52, whereas the Ni-P coating coefficient increased with time and finally reached to beyond 0.50. The addition of diamond particles could improve the wear resistance significantly, whereas as the diamond particle sizes increased, the friction wear resistance and the abrasive wear resistance increased.

Theoretical and Experimental Modelling of the Combined Dry Friction Effects

AbstractIt is presented phenomenological models of the sliding and spinning dry friction for the circle contact spots. These dry friction models permits to take into account both the dynamics coupling of the components defining force state and the more realistic representations about dry friction characteristics and the normal contact stresses distributions in the case of combined kinematics. Introduced models are based on the replacing of the exact integral models by the appropriate Pade expansions or Zhuravlev approximations. These dry friction models enable to describe adequately the relationship between force and kinematical characteristics over the entire range of angular and linear velocities. The approximate models preserve all analytical properties of the exact integrals models as functions of the kinematics parameters. Their coefficients are numbers that can be identified from experiments. Consequently, the models based on Pade or Zhuravlev approximations may be considered as phenomenological models of combined dry friction.

Dry friction characteristics of Ti-6Al-4V alloy under high sliding velocity

Tribological behaviours of Ti-6Al-4V alloy pins sliding against GCr15 steel discs over a range of contact pressures (0.33–1.33 MPa) and sliding velocities (30–70 m/s) were investigated using a pin-on-disc tribometer under unlubricated conditions. The wear mechanisms and the wear transition were analyzed based on examinations of worn surfaces using SEM, EDS and XRD. When the velocity increases, the friction coefficient and the wear rate of the Ti-6Al-4V alloy show typical transition features, namely, the critical values of sliding velocities for 0.33 and 0.67 MPa are 60 and 40 m/s, respectively. The experimental results reveal that the tribological behaviours of Ti-6Al-4V alloys are controlled by the thermal-mechanical effects, which connects with the friction heat and hard particles of the pairs. A tribolayer containing mainly Ti oxides and V oxides is formed on the worn surface of Ti-6Al-4V alloy.

Chaos caused by non-reversible dry friction

In this short communication we investigate how the non-reversible dry friction characteristics will alter the non-linear responses of a simple mechanical oscillator. The presented approach is based on a certain mathematical description of the experimentally determined non-reversible dry friction characteristics, which causes chaotic and irregular motion of the studied system. A novelty of our idea is an introduction of the relative acceleration in description of the dry friction model.

On the Calculation of Stationary Solutions of Multi-Dimensional Fokker–Planck Equations by Orthogonal Functions

In this paper, nonlinear stochastic systems are investigatedvia associated Fokker–Planck equations. Their stationary solutions arecalculated by expansions into orthogonal functions, e.g. especiallyadjusted polynomials and Fourier series. The weighting functions of thenew polynomials are obtained by the application of the stochasticaveraging method. The proposed analysis is demonstrated with severalexamples. The first one is a two-dimensional problem of nonlinearoscillators driven by white noise. The second one describes two-massoscillators with independent coloured noise excitations leading tosix-dimensional probability density functions. The next example ispresenting a system driven by both harmonic and stochastic excitationleading to three-dimensional probability density functions. Finally,oscillators with dry friction characteristics are examined.

Non-reversible dry friction oscillator: Design and measurements

A Coulomb oscillator with a variable normal force has been designed and manufactured to carry out a wide range of experimental dynamic analysis, especially the study of the non-reversibility of dry friction characteristics. The design choice was based on the criteria of accuracy of the mathematical model and flexibility in terms of parameter changes such as the natural frequency of the system, coefficient of friction and normal force. The system consists of a block mass attached to two coil springs and a dry frictional damper in which the friction force is varied by a pneumatic actuator. This allows a constant pressure between sliding surfaces to be maintained. The experimental set-up, the calibration procedure for the clamping device and typical results are presented. Experimental non-reversible dry friction characteristics are discussed.

A study of the dry friction characteristics of some cermets at high sliding speeds : M. E. Belitskii and B. I. Kostetskii, Soviet Mater. Sci., 2 (1) (1966) 51–53; 4 figs., 1 refs. (Translation by Faraday Press, New York of Fiz.-Khim. Mekhan. Mater., 2 (1) (1966) 67–71.)

A study of the dry friction characteristics of some cermets at high sliding speeds : M. E. Belitskii and B. I. Kostetskii, Soviet Mater. Sci., 2 (1) (1966) 51–53; 4 figs., 1 refs. (Translation by Faraday Press, New York of Fiz.-Khim. Mekhan. Mater., 2 (1) (1966) 67–71.)

A study of the dry friction characteristics of some cermets at high sliding speeds

Satisfactory performance of rotary seal materials demands not only a relatively low hardness and high resistance to heat, but also good antifriction properties; the latter are required to ensure that the blade tips and rotary seal rings can readily cut into the inserts at high sliding speeds without seizing.