The effect of fibrous fillers and metallic powders on the triboengineering characteristics of frictional composites based on the combined phenol-rubber binder

The findings of studies of the triboengineering characteristics of frictional composites based on the combined phenol-rubber binder filled with glass, basalt, carbon, and polyoxadiasol fibers and copper and iron powders are presented. The fibrous filler type and quality are found to influence the strength, friction, and wear characteristics of the composites. It is demonstrated that the composites filled with metallic powders have better thermal and physical characteristics.     

Influence of ethyl acetate and alkyl phosphate adsorption on the frictional properties of VC(100)

This report presents ultrahigh vacuum measurements of the frictional properties of the non-polar (100) surface of vanadium carbide (VC) as a function of the room temperature uptake and reaction of ethyl acetate, triethyl phosphate, and trimethyl phosphate. Atomic force microscopy, employing a silicon nitride probe tip, has been used to determine the changes in friction and interfacial adhesion as a function of adsorbate uptake. Changes in surface morphology have been monitored with scanning tunneling microscopy while the composition of the surface species formed through the reaction of these adsorbates with the VC surface has been determined by X-ray photoelectron spectroscopy. Adsorption and reaction of ethyl acetate leads to an increase in friction with little change in interfacial adhesion. The adsorption and reaction of triethyl phosphate and trimethyl phosphate have no influence on either the friction or adhesion properties of VC. The observed results are discussed in terms of the surface chemical composition, the extent of surface coverage, and the molecular details of the adsorbed species.     

The effect of annealing conditions on the adhesive properties of TiN coatings

The effect of low-temperature annealing on the adhesion strength and coefficient of friction of TiN coatings deposited on austenitic stainless steel by the vacuum-arc method is studied. The behavior of the coefficient of friction of titanium nitride upon annealing in air is discussed. It is shown that the adhesion strength of TiN coatings does not depend on annealing conditions.     

Influence of fibrous and disperse fillers on the frictional load in the polymer matrix

The influence of filler on the wear resistance of polymer composites is investigated. Three types of filler are considered: reinforcing fibers; short fibers; and disperse particles. Formulas for the proportion of the load on the polymer matrix permit optimization of the filler content in the composites, in the light of the frictional conditions.     

The effect of different nanoparticles and open time on bonding strength of poly (vinyl acetate) adhesive

Nanotechnology is one of the major technologies through in this century. Nano particles are an important part of this technology. Properties of many traditional materials can be changed by using the nanoparticles. Open time is one of key processing parameters for adhesive applications. Many adhesion failures are caused by exceeding of the open time. The main objective of this study is to improve the adhesion performance of PVAc adhesive by increasing open time through application of nanoparticles, specifically silicium dioxide (SiO₂) and titanium dioxide (TiO₂). For this reason, nano SiO₂ and nano TiO₂ were blended with PVAc at the open time 0, 5, 10 and 15 min. Effect of the nanoparticles and open time was determined by lap shear joint strength tests. Tests were carried out according to DIN EN 302-1. The results indicate that nanoparticles can considerably improve the bonding strength of PVAc at open-time of 5 and 10 min.     

The roughness effect on the frequency of frictional sound

Dry sliding of two bodies in contact generates a wide range of effects like friction, wear, heat and sound among others. The main interest of this study is in the frequency characteristics of the generated sound.In the past, frequency spectrum and sound pressure level with relation to surface topography (surface roughness in particular), have been studied mainly for concentrated contacts like stylus or hemispherical tip pin on a rough surface. Studies on flat–flat contacts were mainly focused on the topography of contacting surfaces and its relation to occurrence or non-occurrence of squeal (high pitch, high sound pressure level sound) in brake systems.The present study aims to clarify the effect of surface roughness on the frequency of non-squealing frictional sound generated in dry flat–flat sliding contact.Sound was generated by the dry contact in rubbing by hand of two rectangular cross-section stainless-steel plates having similar surface roughness. The roughness of the contacting surfaces varied in the range R_z=0.8–12.4 μm. The sound spectra had 5 peaks (P₁, P₂, P₃, P₄ and P₅) in order of increasing frequency and it was found that the peak frequency was shifted when the roughness of the rubbed surfaces changed. The first peak P₁ was most sensitive to change of surface roughness and it shifted from 3.0 to 4.5 kHz when the maximum surface roughness changed from R_z=10.9 to . When the surface was relatively rough, this peak was close to the first bending natural frequency of the plate at 2.377 kHz.     

The effect of hardness on the frictional behaviour of metals

It is shown experimentally that hard metals have lower frictional resistance than softer metals owing to stronger interatomic linking bonds. In hard metals the atomic bonds are strong and hence the resistance to adhesion is increased, providing low frictional characteristics. Surfaces hardened by heat treatment are also characterized by low friction. This is explained by metallurgical changes leading to changes in the structure by phase transformation, increase in the surface energy and the induction of internal (residual) stresses.     

The effect of strain-hardening on frictional behavior in tip test

In previous investigation of the tip test using aluminum alloy AL6061-O, it was found that the distance of radial tip from the external side surface of the workpiece deformed has a linear relationship with the maximum forming load measured at a certain punch stroke. In this study, further experiments with aluminum alloys AL2024-O, AL5083-O, AL6061-O, AL7075-O, annealed carbon steel AISI 1010 and pure copper C12100 were carried out to investigate the effect of material properties on frictional behavior by the tip test for the materials commonly used in bulk metal forming. To characterize the relationships among radial tip distance, maximum forming load and shear friction factor, finite element analyses were employed. It was observed that the linear relationships among these three were maintained for the various tested materials. Also, it was found that the friction condition at the punch was always higher than that at the lower die interface such that the ratio of shear friction factors at the die and punch interfaces should be less than one. By examining the material properties currently tested, it was determined that this ratio could be estimated from a logarithmic equation from the value of strain-hardening exponent, depending on the material used.     

The effects of methane-debris molecules on the frictional properties of diamond

Molecular dynamics simulations have been used to examine the friction between two surfaces placed in sliding contact. These simulations show that the presence of methane-debris molecules squeezed between two hydrogen-terminated diamond (111) surfaces significantly reduces the friction compared to the same two surfaces in the absence of debris. These findings are in agreement with macroscopic experiments that have examined the friction of diamond on diamond in the presence of debris. In addition, the friction coefficients are significantly lower compared to the same system with methyl groups chemisorbed to one of the diamond surfaces.     

The effect of different ratios of nano‐sized hydroxyapatite fillers on the micro‐tensile bond strength of an adhesive resin

The purpose of this study was to evaluate the micro‐tensile bond strength (μTBS) of dentin bonding agents containing different ratios of nano‐sized hydroxyapatite fillers (HA). X‐ray diffraction analysis was used for characterization, and scanning electron microscope (SEM) analysis was used to determine the HA particle size after that HA were mixed a bonding agents without filler. Dentin bonding agents were divided into four groups according to addition of different ratios of nano‐sized hydroxyapatite fillers as 2% HA, 5% HA, 7% HA, and no‐filler control group. The teeth (n = 32) were sectioned with a low‐speed diamond blade under water cooling to expose the mid‐coronal dentin. Following the bonding application, restorations were applied incrementally. Each tooth was cut on the x and y axis, and each specimen was fixed to a testing device and stressed until failure occurred. The debonded specimens were examined under 250× magnification without a coating layer at 2.00 kV using a SEM to determine failure patterns. μTBS data were analyzed using a anova and Tukey's post hoc test. The failure mode data were analyzed using the Chi‐Square test. The maximum mean value of μTBS was in the 7% HA group, while the minimum mean value of μTBS was observed in the control group. 7% HA group was statistically significant and higher than other groups while there were no significant differences between the control, 2% HA, and 5% HA groups. According to SEM analysis, fracture analysis revealed that the mixed fracture type was seen more often than the other fracture types. The particle size and amount of HA fillers added to the adhesive resin seem to affect the success of the bond strength to the dentin. Adding different ratio nano‐sized HA fillers to the adhesive resin contributed positively to the immediate μTBS values in the dentin.     

涂层刀具摩擦磨损特性的研究进展

总结了涂层摩擦学研究进展,对常见涂层摩擦磨损特性的研究现状进行了介绍,分析了各种涂层在摩擦过程中的磨损破损机制,并简要介绍了应用于摩擦学领域涂层的发展趋势.     

Surface topography and properties of frictional contacts

The influence of surface topography on contacting solids is considered. The rough surface model is suggested and is used for the calculation of some tribological contact characteristics. A rough surface is modelled by a set of asperities of regular shape (wedge, cone, cylindrical, spherical segment), of differing height. A simple height distribution function and asperity shape function are used. These functions may be integrated analytically in further calculations.The surface model is used for calculation of one of the main contact parameters - real contact pressure (or real contact area) and other principal contact parameters, such as deformation, number of contact spots, average spot area, average distance between contact spots and intercontact gap.It is shown how the above parameters may be used for the calculation of such operational contact characteristics as friction coefficient, wear rate and electrical and thermal resistance.     

Investigation of adhesive and frictional behavior of GeSbTe films with AFM/FFM

Frictional force microscope (FFM) was used to investigate the nanoscale frictional behavior of GeSbTe films deposited by magnetron sputtering. The effects of relative humidity, scanning velocity and surface roughness on friction were taken into account. Besides, the frictional behavior of GeSbTe films with different compositions was analyzed. Experimental results show that the coefficient of friction of GeSbTe films is almost independent of scanning velocity, while the frictional force decreases with increasing velocity. Both the relationship of friction vs. normal load and that of friction vs. RMS keep relatively linear, and the coefficient of friction increases with the increase in RMS. The influence of humidity on adhesion between the tip and the GeSb₂Te₄ film is more significant than that between the tip and the Ge₂Sb₂Te₅ film.     

The effect of different thermal treatment on the physical properties of PGA/PCL copolymer suture material

Samples of polyglycolic acid PGA/polycaprolactone PCL copolymer absorbable suture materials, which is called Poliglecaprone PGC copolymer suture, were thermally treated by two different processes. The first method is the direct heat exposure, from 20 to 38 °C, in the surrounding medium. Which is an environmental study. The other method is the annealing process at temperatures ranged from 65, 80, 100, 120, and 140 °C, for two different duration periods 60 and 120 min. This is an extensive technical study. The refractive indices of thermally treated PGA/PCL copolymer sutures were measured using multiple‐beam Fizeau fringes. The birefringence profiles across the suture cross‐sections were studied for different annealing conditions. The effect of heat on the polarizabilty per unit volume, dielectric properties, and suture diameter were investigated. The activation energy for the heating processes was calculated using Arrhenius equation. Microinterferograms are given for illustration.     

Effect of mechanical properties on frictional behaviour of metals

The coefficient of friction was experimentally determined for some common metals and is correlated with their mechanical properties. Strong metals are shown to give a lower coefficient of friction and are characterised by high hardness, low shear to hardness ratio and low surface energy to hardness ratio     

Modelling of frictional and adhesive contacts at silicon/polymer interface for nanotechnological applications

Abstract

The minimisation of friction and adhesion during sliding contacts is crucial for the industrial fabrication of many micro/nanodevices (e.g. MEMS/NEMS), as well as in nanotechnological processes, e.g. in nanoimprint lithography where a silicon mould is used to fabricate polymeric nanostructures by imprinting. We have conducted intensive research on the contact between the mould and PMMA polymeric resist film via advanced modelling and computer simulations. The properties of the contacting surfaces have been identified with the atomic force microscope and nanoindentation, as well as wettability tester applied for the identification of the surface free energy. A model of contact has been elaborated and adequate original software was used to calculate the frictional and adhesive forces in particular at the silicon mould/polymeric resist interface.     

The effect of frictional force amplitude on the degradation of SiC abrasive papers

The degradation of 600 and 100 grade SiC abrasive papers by unidirectional and reciprocating frictional contact was studied. The mechanism of deterioration is basically different for each grit size. Detachment of grits from the resin base and the volume of metal removed depend on the type of friction. The rate of detachment of blunt grits is higher for reciprocating frictional contact than for unidirectional frictional contact. This can be explained in terms of the fatigue strength of the cementing resin base under completely reversed stress and pulsating stress caused by the rubbing action.     

Deformation by scratches and frictional properties of MgO crystals

The subsurface structure of MgO crystals frictionally damaged on their (001) faces by scratching with a diamond stylus in the 〈100〉 direction was investigated using a scanning electron microscope in both the cathodoluminescence and the secondary electron modes. The friction is independent of the load below a critical value, and above this value it depends on the load W according to μ ∝ Wⁿ where μ is the coefficient of friction.The subsurface beneath the sliding contact consists of four characteristic material zones: zone I is severely deformed with a high defect density which causes quenching of the luminescence; zone II is a plastically deformed intermediate zone showing enhanced luminescence; zone III is a slipped zone which on etching shows a dislocation pit pattern; zone IV consists of non-deformed crystalline material. The normalized depth $\text{d}\text{a}$, where d is the depth of each deformed zone and a is the track half-width, is independent of the load.The frictional behaviour was examined by using empirical relations for the damage to estimate the plastic work done during the scratching process.     

The effect of applied voltage on the frictional behaviour of carbon black filled elastomers

This paper presents the results of an experimental test programme undertaken to investigate the effects of d.c. applied potential on the frictional behaviour of carbon black loaded rubbers sliding on aluminium. Within a defined black content, elastomers exhibit a markedly increased apparent frictional coefficient with voltage application. An applied field causes a capacitive effect to operate within the asperity contact areas, thereby producing an electrostatic attractive force to supplement the normal load. This force is the subject of this paper, evaluated and reported for a range of experimental sliding conditions.     

The microtextured plastic moldings to control human tactile sense: The texture effect enhancement due to apical shape and material frictional properties

The purpose of this study is to develop a plastic molding with a distinguishing tactile character for various industrial applications. In the present paper, we investigated the effects of the apical shape of the texture and the frictional properties of the plastic material on the tactile sense of the textured plastic molding in order to enhance the texture effect. Based on the analyses conducted, it was found that both the apical shape and the material frictional properties affect the particular tactual sensation of the plastic molding. The “Uneven” and similar trend sensations, which are mainly dominated by the fluctuation of friction, were dependent on the apical shape due to the sticking characteristics of the fingerprint. The strength of these sensations was caused by the sharper apical shape. The “Sticky” sensation was dominated by the complex effect of the fluctuation of friction and the frictional properties of the plastic material. The larger texture effect elicited for “Slick” sensations was obtained at round and sharp textures with a pitch of 120 μm. The enhanced texture effect of material frictional properties was observed at the apical shapes with large contact area, and it was obtained at the round texture. However, flat texture elicited a similar sensation to that elicited by the nontextured surface as a result of the small texture effect and large contact area. These results indicate that control of the apical shape and material frictional properties is effective in enhancing the texture effect of the plastic molding surface.