Reciprocating Sliding Contact Research Articles

Nanoscale Reciprocating Sliding Contact Behaviors of an Isosceles Trapezoid Textured Surface in Space Environment

Background: In the space environment, microgravity and vacuum influence the mechanical behaviors of the devices. In the microgravity environment, the mechanical components vibrate with a small amplitude once there is a disturbance. The vibration can be seen as a reciprocating sliding contact with a small amplitude. In addition to the vibration, adhesion effects are predominant in a vacuum, which will induce a high friction force. Objective: To reduce the friction force, textured surfaces are widely used in mechanical engineering on the earth, and nanoscale textures are also verified to be used to improve the frictional behaviors of components in the size of nanometers. Methods: In this paper, the adhesion effects are considered by using molecular dynamics (MD) simulation, and the microgravity induced vibration is simplified as a reciprocating sliding contact. Coupling MD simulation and the finite element method which is a multiscale method are used to investigate the frictional properties of nanoscale reciprocating sliding contact between rigid multiasperity tips and an isosceles trapezoid textured surface. Results: Average friction forces for the different tips are presented, and the friction processes are analyzed. A stable friction process is discovered for a specific case, and the average friction force is kept at two stable values corresponding to two sliding directions. Conclusion: Compared with the total average friction forces of a smooth surface, the textured surface can reduce the friction forces greatly. This work could contribute to the textured surface design to improve frictional properties in the space environment.

Evaluation of friction behaviour on human finger skin considering precision grip task

Human hands perform daily different tasks and the fingers skin comes in contact with many surfaces and objects. Grip task of objects can be performed by using different combination of the fingers. Precision grip task is influenced by several factors which decide the grip force of the individuals performing the task. This study aims to evaluate in vivo the coefficient of friction (COF) between a steel cylinder and the skin of fingers’ phalanges from both hands for three healthy subjects. The experiments were realized in a reciprocating-sliding contact with normal loads of 1 N and 2 N and sliding speed of 1 mm/s. Also, indentation tests were realized in order to determine the skin deformation of the fingers phalanges under normal loads. The indentation results show that distal phalanges (fingertip) play a significant role in deciding the grip force. The friction tests reveal that the coefficient of friction varies between 0.3 and 1.1 along the fingers phalanges according to the age, gender and skin structure of the test subjects. The distal phalanges of index and middle fingers showed the highest value of the coefficient of friction in the case of the subjects that mainly use the right hand. These aspects can be considered in developing devices for grip and sensing tasks applications.

Tribolumen: A Tribometer for A Correlation Between AE Signals and Observation of Tribological Process in Real-Time—Application to A Dry Steel/Glass Reciprocating Sliding Contact

This paper deals with the development of an original apparatus called TRIBOLUMEN designed specifically for friction experiments on transparent materials. The friction measurement is synchronized with an acoustic emission (AE) sensor and the device is also equipped with a high-speed camera offering a direct view at the interface to gain a deeper understanding of tribological mechanisms. The TRIBOLUMEN device is in ball-on-flat contact configuration with a range of strokes from 5 to 500 µm and an oscillation frequency from 5 to 600 Hz. The experiments showed that this device has an adequate rigidity and can detect subtle friction modifications of the oscillating contacts. The observation of a steel-on-glass contact in real-time highlighted the initiation of Hertzian cracks followed by the formation of debris in the contact. Using the synchronous measurement, these mechanisms were clearly associated with different stages in the friction measurement and in the AE signals, which permitted to identify the AE signature of Hertzian cracks.

Modelling of Unidirectional Reciprocating Sliding Contacts of Nanoscale Textured Surfaces Considering the Impact Effects in Microgravity Environment

In space environment, the adhesion effects can cause a high adhesion component of a friction force, and the impact effects caused by the microgravity can induce a high ploughing component, so the friction force is higher than the ground environment. Nanoscale textures affect the adhesion behaviors by reducing contact areas, and they also vary the shear strength of the interface, which are beneficial to the friction reduction. Considering the impact effects, the motion of a clearance joint is simplified as a unidirectional reciprocating sliding contact, and a multiscale model is employed to investigate the friction and wear characteristics between a rigid cylindrical tip and nanoscale textured surfaces. The effects of texture shapes on running-in stages, average friction forces and wear characteristics are investigated. The results show that the isosceles trapezoid textured surface (surface II) and the surface with right-angled trapezoid textures on the right side (surface III) can come to steady states for different sliding modes. Surface II presents the lowest total average friction force to show its potential to reduce friction forces. The worn atoms are the least for surface III, and surface III can be used to improve the wear behaviors. The impact effects make that the unidirectional reciprocating sliding contacts show higher total average friction forces than reciprocating sliding contacts. This work could contribute to designing textured surfaces, reducing friction and wear in unidirectional reciprocating sliding contacts under impact effects in microgravity environment, and help to prolong the life of components in the spacecraft.

Vibration Induced Reciprocating Sliding Contacts between Nanoscale Multi-Asperity Tips and a Textured Surface

Microgravity and vacuum are two main environments in outer space. In the microgravity environment, vibration is a typical phenomenon, and it will induce a reciprocating sliding contact between a journal and a bearing in a clearance joint. In vacuum environment, the adhesion effects are severe, and the friction forces are much higher than the ground environment. Nanoscale textures can reduce the contact area and trap the wear particles, which are beneficial to the friction reduction. Most of the current studies focus on the single-pass sliding contact. Actually, considering the roughness of the contact surfaces, a multi-asperity tip should be more reasonable. In this paper, vibration induced reciprocating sliding contacts between nanoscale multi-asperity tips and a textured surface are investigated using a multiscale method, and the material is FCC copper. Six rigid tips are modelled with different cylindrical asperities and slid on the textured surface. Corresponding to the tips, the average friction forces are compared, and the effects of the tip radii are analyzed. The total average friction forces of the textured surface are compared with the case of a smooth surface, and the mechanism of the friction reduction is discussed. The results showed that the total average friction forces decrease as the increase of the asperity radii, and the textured surface can reduce friction forces effectively compared with the smooth surface. This work could contribute to reducing friction by designing the tip and the textured surface in vibration induced reciprocating sliding contacts under microgravity, which will be beneficial to prolong the life of components on the spacecraft.

Microstructure and Wear Behaviors of Plasma-Sprayed FeCrNiMoCBSi Coating with Nano-Grain Dispersed Amorphous Phase in Reciprocating Sliding Contact

A novel FeCrNiMoCBSi amorphous/nanocrystalline coating was fabricated using a plasma spraying process. The coating was dense with a low porosity of approximately 0.99%. The coating consisted of a 67.8 vol% amorphous phase coupled with many nanocrystalline grains that were approximately 5 nm in diameter. The mechanical properties of the as-sprayed coating were determined by nanoindentation measurement, and the tribological behaviors were systematically investigated in a reciprocating sliding contact. The results show that FeCrNiMoCBSi coatings possess superior wear resistance compared to other typically similar Fe-based amorphous coatings. The tribological behaviors evolve with the combination of normal load and sliding velocity. Herein, the dominant wear mechanisms are delamination wear and oxidation wear. With an increase in normal load and sliding velocity, the abrasive wear is gradually weakened, the formation of oxide films on the worn surfaces is facilitated, and wear debris is ground to powder. The oxide films suffer from fatigue wear with induced cracks undergoing reciprocating sliding effects.

Synergistic wear-corrosion analysis and modelling of nanocomposite coatings

Abstract This paper presents analysis and modelling of synergistic wear-corrosion performance of Nickel-Graphene (Ni/GPL) nanocomposite coating and compares it with un-coated steel 1020 under reciprocating-sliding contact. A novel synergistic wear-corrosion prediction model incorporating Archard description with nano-mechanics and electrochemistry was developed for Ni/GPL and steel 1020. The model is equally applicable to any kind of nanocomposite coating and bulk material like metals. For various nanocomposite coatings; their respective mechanical parameters should be used as inputs such as poisons ratio (v), Elastic Modulus (E), Hardness (H), Coefficient of Thermal Elastic mismatch (CTE) and intrinsic grain size (Do). The synergistic wear-corrosion effects were significantly-prominent in steel compared to Ni/GPL especially under contaminated lubricating oil conditions. This behaviour of Ni/GPL attributes to compact, refined grain structure leading to minimal grain pull-out during wear cycles which was also assured by less severe micro-ploughing in Ni/GPL compared to severe micro-cutting in steel. The predictions and experimental results were in good-agreement. Modelling of synergistic effects of wear-corrosion applied to nano-composite coatings have never been presented prior to this research. The significance of this work in terms of precision based wear-corrosion synergistic analysis, modelling and predictive techniques is evident from various industrial applications. This work will bring impacts for both in-situ and remote sensor based condition monitoring techniques to automotive, locomotive, aerospace, precision manufacturing and wind turbine industries.

Investigation of Friction and Surface Damage of Bearing Steel in Cyclic Reciprocating Sliding Contact by Making Use of Fatigue Testing Machine

Investigation of Friction and Surface Damage of Bearing Steel in Cyclic Reciprocating Sliding Contact by Making Use of Fatigue Testing Machine

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.

Friction and Wear of Hemiarthroplasty Biomaterials in Reciprocating Sliding Contact With Articular Cartilage

Friction and wear of four common orthopaedic biomaterials, alumina (Al2O3), cobalt-chromium (CoCr), stainless steel (SS), and crosslinked ultra-high-molecular-weight polyethylene (UHMWPE), sliding against bovine articular cartilage explants were investigated by reciprocating sliding, nanoscale friction and roughness measurements, protein wear assays, and histology. Under the experimental conditions of the present study, CoCr yielded the largest increase in cartilage friction coefficient, largest amount of protein loss, and greatest change in nanoscale friction after sliding against cartilage. UHMWPE showed the lowest cartilage friction coefficient, least amount of protein loss, and insignificant changes in nanoscale friction after sliding. Although the results are specific to the testing protocol and surface roughness of the examined biomaterials, they indicate that CoCr tends to accelerate wear of cartilage, whereas the UHMWPE shows the best performance against cartilage. This study also shows that the surface characteristics of all biomaterials must be further improved to achieve the low friction coefficient of the cartilage/cartilage interface.

Tribological Characteristics of WC-Ni and WC-Co Cemented Carbide in Dry Reciprocating Sliding Contact

Four WC-based cemented carbides produced by liquid phase sintering with different binder composition and similar carbide grain size were tested in order to evaluate their dry reciprocating sliding friction and wear behavior against WC-6 wt.%Co cemented carbide. The pin-on-flat wear experiments were executed on a Plint TE77 tribometer using normal contact loads of 15 N up to 35 N and a sliding velocity of 0.3 m/s. Analysis of the wear tracks revealed several wear mechanisms; i.e., polishing of WC grains, abrasion, adhesion, formation of wear debris layer, and removal of the surface binder from between the WC grains. Higher contact load increased the wear volume and slightly decreased the friction coefficient. The hardness as well as the type and the amount of binder phase were found to affect the wear resistance significantly. One WC-Ni alloy exhibited superior tribological characteristics compared to the other grades.

Wear in Ceramic/Ceramic and Ceramic/Metal Reciprocating Sliding Contact. Part 1

This paper is the first of a series of two devoted to an investigation of wear mechanisms in ceramic/ceramic and ceramic/metal sliding contact tribological systems at high temperatures and exhaust gas environment. The first part presents results of the experiments carried out at room temperature and air environment. Scanning electron microscope, optical microscope and X-ray dispersion analysis were used for an identification of wear mechanisms. Surface geometry and morphology, friction coefficients and wear were determined as functions of sliding distance, nominal contact pressure, sliding velocity and mechanical properties of specimens (hardness and fracture toughness). The wear mechanism of ceramics rubbed against ceramics may be attributed to intensive plastic deformation of surfaces resulting in low cycle fatigue. The wear mechanism of ceramics rubbed against metals was polishing and surface fracture, while that of metals was adhesive transfer of material on to ceramic surfaces. Wear rates and friction coefficients were independent of mechanical properties of metallic samples.