Sliding Contact Research Articles

電気しゅう動接点におけるライダ表面に設けた溝が通電および摩擦特性に及ぼす影響に関する実験的解析

電気しゅう動接点におけるライダ表面に設けた溝が通電および摩擦特性に及ぼす影響に関する実験的解析

Optimisation of Plasma Nitrocarburising for Reducing Wear in Dry Sliding Contacts

In this study, tool steel substrates were plasma-nitrocarburised at different processing parameters and afterwards tribologically tested under non-lubricated sliding conditions. It was observed that the micromechanical properties of the compound layer (thickness, hardness, roughness, surface topography) strongly affect the tribological behaviour of the nitrocarburised surface and can be tailored through the adjustment of the nitrocarburising parameters so that very favourable wear and friction behaviours can be achieved.

Erratum to: Analysis of Wear Particles Formed in Boundary-Lubricated Sliding Contacts

Erratum to: Analysis of Wear Particles Formed in Boundary-Lubricated Sliding Contacts

A New Tribological Approach for Lubricated Sliding Contact of Pitted Metallic Curvature Cup

ABSTRACTInterest in the development and application of plant-based lubricants for medical use is increasing. This study investigates palm oil lubricants as environmentally friendly and renewable resources to optimize the motion in an ergonomic simulated metal hip prosthesis with modification to the acetabular cup surface. Although metal hip replacements are extensively used, minimizing metal-on-metal friction and wear using safe lubricants requires further investigation. The main physical properties of palm kernel oil and palm fatty acid distillate are considered. The viscosity, wear scar, and coefficient of friction are compared to hyaluronic acid. A modified pin-on-disc tribometer simulates friction and wear on a 28-mm-diameter acetabular cup and microscopy image analysis is used to examine the wear scar. The physical properties of palm oil derivatives reduce friction and wear. In brief, the most significant results of this study include the effect of lubricant and number of pits on wear and friction coefficient. The contribution of this research work is to maintain stability and increase the lifetime of ergonomic metal hip implants.

On the Growth Rate of Tribomaterial in Bovine Serum Lubricated Sliding Contacts

Considering total hip arthroplasty, so-called tribolayers (aka tribomaterial), consist of carbonaceous material from the periprosthetic joint fluid or bovine serum mixed with nanometer size metal and oxide wear particles. Currently, its growth sequence and rate are unknown. Thus, smooth surfaces of low-Carbon (LC-) vs. high-Carbon (HC-)CoCrMo (Cobalt-Chromium-Molybdenum) alloys have been worn in a conforming contact under bovine serum lubrication by means of a pin-on-ball wear tester. These tests were interrupted at certain numbers of cycles in order to weigh the specimens, characterize the topography, and investigate the wear appearances. In addition, after cleaning in ethanol and anionic detergent, before-and-after comparison rendered the weight of the tribomaterial. This revealed that, during run-in, the specimens gained weight by generating tribomaterial. Afterwards the loss of material surpassed the generation of new tribomaterial and a steady weight-loss was measured. Topography measurements were used as input data for contact mechanics calculations. Apparently the incipient, locally high contact stresses accelerated tribochemical reactions. After run-in, the contact situation changes and leads to a much smaller generation rate. This paper provides information about the growth sequence and rate of such tribomaterial formation. It further highlights the significance of highly localized contact stress as an important factor for tribomaterial generation.

Modeling Sliding Contact Temperatures, Including Effects of Surface Roughness and Convection

The ability to predict contact surface temperatures in rolling/sliding contacting bodies is important if failure of tribological components is to be avoided. Many works on surface temperature analysis and prediction have been published over the past 75 years or so, but most of the analytical solutions that are readily available do not include such important factors as finite body geometry, surface roughness, or convective cooling. Approaches for addressing these deficiencies are presented in this paper. This paper builds on previous analytical work by the authors and others, and presents models that are based on experimental observations of contact temperatures and factors that affect them. It is shown that the total surface temperature rise above ambient temperature is the sum of nominal temperature rise and flash temperature rise. Models are developed for calculating nominal surface temperature rise for sliding bodies of finite size, including effects of both convection and conduction. Flash temperature models are developed for both single and multiple contacts, as would be found with rough surfaces. Methods are presented that are valid for a variety of geometries and kinematic operating conditions, and techniques are also presented for partitioning the frictional heat between the two contacting surfaces. Examples of the use of the methodology are presented, along with experimental verification of the predictions.

Analysis of Wear Particles Formed in Boundary-Lubricated Sliding Contacts

The wear process in a sliding contact results in generation of wear debris, which affects the system life. The impact depends on the wear particle properties, such as size, shape and number. In this paper, the wear particles formed during a cylinder-on-disk wear test were examined. PAO additive-free oil, steel–brass and steel–steel contact pairs were employed. A particle isolation procedure was applied, and SEM/EDS analysis was used to validate it. DLS measurements indicated the wear particles radius to be in the range from 230 to 260 nm for both materials under applied nominal pressures from 87 to 175 MPa. AFM data revealed the wear particles size to be in the range from 133 to 175 nm. A slight increase in particles size with load was observed by AFM for both materials and confirmed by DLS for steel samples. AFM measurements were taken to determine thickness, length and width distributions of the wear particles. The number of wear particles per sliding distance and per unit load was estimated to be in the range from 150 to 750particlesmmN for steel and approximately 1600–1900 particlesmmN for brass.

Triboplasma Generation and Triboluminescence in the Inside and the Front Outside of the Sliding Contact

Previously, high-intensity triboplasma was discovered in the rear outside gap of the sliding contact by measuring the triboluminescence. However, we have almost no information on the triboplasma generation inside of the sliding contact. This is because the intensity of the photon emission from the inside of the sliding contact is too weak to be detected compared to that from the high-intensity rear outside plasma. On the other hand, plasma generated at the front outside of the contact was also difficult to observe since the intensity was also so weak. In the present article, the author investigated the triboplasma generation at the inside, front outside and very vicinity of the sliding contact together with the rear outside of the sliding contact by measuring the two-dimensional images and intensities of the UV, visible and IR photons emitted from the sliding contact while sliding a diamond pin with a 4-mm tip radius on a sapphire disk in dry sliding in dry air under a normal force of 2 N and a sliding velocity of 34 cm/s. The results showed that extremely weak triboplasma is generated even in the small asperity gap of the sliding contact, that the sliding contact is surrounded by weak circular plasma and that weak plasma is generated further in the front of the sliding contact. Namely, four kinds of triboplasma were observed inside and outside of the sliding contact including the previously reported rear outside high-intensity plasma, (1) weak front outside plasma, (2) weaker circular outside plasma surrounding the contact, (3) weakest inside plasma and (4) high-intensity plasma, visible at the rear outside of the contact. Based on the experimental results, a new model of triboelectromagnetic phenomena has been proposed.

The Effect of Pits on the Curvature Cup: For Reducing Friction in Soft on Hard Sliding Contact

The purpose of this feasibility study is to elucidate the effect of surface modification on the curvature cup made of Acrylonitrile Butadiene Styrene (ABS) against metal ball bearing was investigated. In the tribology soft on hard (SoH), the pits embedded on the curvature cup have shown potential for reducing friction in curvature structure. A modified four ball machine as a hard-on-soft screening machine has been used to evaluate the friction on the curvature cup sample with an inner diameter of 12.8 mm. This study revealed that the treated curvature cup with pit in lubricated of palm oil optimizes the rate of frictional and allows for a stable of soft on hard sliding contact.

潤滑すべり条件下における金属及び樹脂材料の焼付き挙動

潤滑すべり条件下における金属及び樹脂材料の焼付き挙動

307 ゴムブロックと正弦波路面との滑り接触(機素潤滑設計II)

307 ゴムブロックと正弦波路面との滑り接触(機素潤滑設計II)

Wear Prediction Model for Composite Bearing Balls under Pure Sliding Contact Condition

Wear Prediction Model for Composite Bearing Balls under Pure Sliding Contact Condition

A Viscoelastic Sliding Contact Problem with Normal Compliance, Unilateral Constraint and Memory Term

We consider a mathematical model which describes the equilibrium of a viscoelastic body in frictional contact with a moving foundation. The contact is modeled with a multivalued normal compliance condition with unilateral constraint and memory term, associated to a sliding version of Coulomb’s law of dry friction. We present a description of the model, list the assumption on the data and derive a variational formulation of the problem, which is in a form of a system coupling a nonlinear equation for the stress field with a variational inequality for the displacement field. Then we prove an existence and uniqueness result, Theorem 4.1. The proof is based on a recent result on history-dependent quasivariational inequalities proved in Sofonea and Xiao (Appl Anal. doi:10.1080/00036811.2015.1093623, 2015). We proceed with a convergence result in the study of the contact problem, Theorem 5.1. It states the continuous dependence of the solution with respect to the relaxation tensor, the surface memory function and the applied forces.

Computational Fluid Dynamics Analysis of a Machine Hammer Peened Surface Structure for Lubricated Sliding Contacts

Machine hammer peening (MHP) is an incremental surface finishing process. It enables both surface smoothing and texturing. Compared to well-established surface texturing processes, MHP has the advantage of simultaneous induction of strain hardening and compressive residual stresses. Both texturing and surface layer modification are very beneficial in case of mixed-boundary lubrication. MHP has been only recently developed. Therefore, the influence of surface textures manufactured by MHP on tribological interactions is unknown and lacks fundamental investigations. In this work, hydrodynamics of MHP textures is investigated by means of a three-dimensional (3D) computational fluid dynamics (CFD) analysis. The analyzed MHP textures have already been experimentally used to reduce friction in strip drawing tests. Using CFD analysis, an optimal arrangement of multiple elliptically shaped surface structures for maximizing the fluid pressure and the load-bearing capacity is determined. Furthermore, a correlation between the determined process parameters and the lubrication properties is presented. Because of significantly high hydrostatic pressures, cavitation is neglected in this work. Additionally, the effect of structure pileups is neglected in this study. Within the range of parameters investigated, it was found that an arrangement of surface textures by MHP should be transversally overlapping and clearly separated longitudinally. High structure depths, lubricant viscosities, and sliding velocities further improve the load-bearing capacity as well as small fluid-film thicknesses.

Wear at high sliding speeds and high contact pressures

Metal on metal wear at high sliding speeds and high contact pressures results in the melting of one or both of the sliding solid bodies due to heat generated at the contact interface. Understanding the influence of sliding speeds and contact pressures on normalized wear rates is important in developing predictive models for designing more efficient and effective engineering system components. Typical engineering applications subjected to extreme sliding conditions include ultrahigh speed machining, rocket sleds, large caliber cannon, and electromagnetic launchers. Sliding speeds on the order of 1000m/s and contact pressures in excess of 100MPa are common in these applications and difficult to replicate in a laboratory environment. A unique electromagnetic tribometer based on a minor caliber electromagnetic launcher has been designed and implemented to characterize wear deposition of a 6061-T6 aluminum pin (slider) on a UNS C11000-H2 copper flat (guider) at sliding speeds from 0 to 1200m/s and contact pressures from 100 to 225MPa. Optical microscopy and 3D profilometry were used to investigate and quantify slider wear. Three distinct wear regions were observed. Test results provided evidence that the aluminum slider contact interface was molten and experimental wear data showed a dependence on both pressure and velocity. Comparisons between melt lubrication theory and experimental data provide insight into the nature of the contact interface under the sliding conditions tested.

Lubrication Characteristics of Electric Sliding Contacts Consisting of Rotating Circular Grooved Disk and Stationary Rider With Spherical Surface Under Lubricated Condition

Electric sliding contacts are widely used in various electrical components such as for home appliances and automobiles. The purpose of the present study is to improve the performance characteristics of the electric sliding contacts operating under the lubricated condition by the combination of circular grooved disk and rider with a spherical surface. The experimental and theoretical analyses have been carried out to investigate the effect of cross-sectional area of circular grooves provided in the rotating disk surface on the frictional characteristics and the electrical conductivity. The experimental analysis is conducted with a pin-on-disk friction tester to measure the frictional force and the contact voltage between the sliding contacts under the lubricated condition. The oil-film force and the frictional force between the rider and disk are also calculated with the Reynolds equation and they are found to be closely corresponding to the experimental results. The results obtained in the present study show that increasing the cross-sectional area of the circular grooves on the disk extends the operation condition yielding the metal contact to a higher value of the bearing characteristic number S, which is defined by ηU0L0λ/W (η is the lubricant oil viscosity, U0 is the sliding velocity, L0 is the rider arc length in the sliding direction at the middle of radial width, W is the applied load, and λ is the aspect ratio of rider), and also decreases the frictional force at the maximum value of S at which the rider could contact with the disk surface. These are expected since upstream lubricant oil dragged into the contact region tends to easily leak out along the circular grooves, yielding a lower oil-film force between the rider and disk and enhancing the metal contact.

The Simulation Model of a Sliding Contact

This paper deals with the brush slip ring contact modeling. Approaches the sliding contact problem with the synergy theory. The contact layer is considered using mechanical, electrical and thermal properties. The simulation model includes algorithms of: - generation of microscale contact surface, - approachment of two surfaces, - fritting and breakdown effects of oxide layer, - extracting clusters of conducting area, - calculating constriction resistance using fractal dimensionality, - generation of heat caused by electrical current and mechanical friction, - calculation of integral characteristics. The program implementing the model may be used to optimize the contact materials before time-consuming and expensive tests. Finally discusses the implemented model and its results, problems of verification and validation.

Tribological Performance and Coating Characteristics of Sputter-Deposited Ti-Doped MoS2 in Rolling and Sliding Contact

In this work, the tribological behavior of Ti-containing MoS2 film is studied under sliding and rolling contacts. Ti-MoS2 films deposited on AISI 52100 and M50 specimens contain ∼16 at% Ti are slightly substoichiometric in sulfur and have an amorphous structure. Experiments show that the friction and wear performance of Ti-MoS2 films is influenced by humidity and temperature.For the first time, the rolling contact performance of Ti-MoS2 films was evaluated using a thrust bearing tribometer and ball-on-rod tribometers at ∼1 GPa Hertzian contact stress. Rolling contact measurements performed in humid air indicate that the useful life of Ti-MoS2 as a solid lubricant depends upon the amount of coating material retained in the contacts. Results of the rolling contact experiments performed in a vacuum indicate that Ti-MoS2 film on balls may function extremely well as a solid lubricant for ball bearings operating in vacuum.

Investigation on the Effect of Linear Kinematic Hardening Model on Plasticity Prediction of Reciprocating Sliding Contact

This paper discusses a finite element analysis of cylinder on flat contact configuration subjected to constant normal load and reciprocating tangential displacement with linear kinematic hardening models based on bi-modal Ti-6Al-4V cyclic stress-strain curves. The predicted evolution of plastic deformation such as the equivalent plastic strain, tangential plastic strain and shear plastic strain distributions on the contact region has been studied along with its respective predicted stress distributions. The effect of applied forward and backward sliding displacement movements on predicted stress and strain distributions have also been looked at. It is found that the stress distributions predicted for kinematic hardening model is similar for forward and backward movements while the predicted plastic strain distribution is increasing with reciprocating sliding movement. The predicted value keep increasing when it moves forward, backward and finally moves forward again. This is due to large strain effect of the model and its dependant on the displacement movement amount.

Characterisation of Ti-6Al-4V Reciprocating Sliding Wear Test Behaviour

Sliding contact will experience wear in majority of mechanical components during their service life where it reduces the performance of the components. The capability to predict the evolution of reciprocating wear scars, such as the scar’s width and depth, would be a valuable tool when designing mechanical components. Wear scar mechanism behaviour is characterised during stabilized cycle reciprocating sliding wear test of Ti-6Al-4V investigated using pin-on-flat arrangement under variable duration of sliding. The test samples were analyzed using profilometer test, optical microscopy test, Scanning Electron Microscopy (SEM) test, Energy Depressive X-ray (EDX) test and Vickers Hardness (HV) test. Stabilised high number of cycles shows low wear rate and initiation period of low cycles produced higher wear rate.