Variation Of Wear Rate Research Articles

Peridynamic modeling of rail wear during sliding contact considering thermal effects

Numerical simulations of rail wear during sliding contact pose significant challenges owing to the complex coupling between thermomechanical contact loads, material properties, and profile changes. This study proposes a modeling approach for rail wear during sliding contact, using nonlocal peridynamic (PD) thermomechanics and a bond damage criterion based on ratchet failure. To facilitate test verification, a two-dimensional PD model for twin-disc testing with elastoplastic materials was developed, and numerical simulations and corresponding twin-disc testing were performed during wheel idling under different loads, idling speeds, and idling times. The PD model accurately predicted rail wear under all operating conditions, exhibiting excellent agreement with the test results, and thus validating the proposed method and supporting the ratchet failure mechanism. Subsequently, thermomechanical modeling of sliding contacts with different creepages was performed. The PD model predicted continuous wear along the contact surface, with an increase in wear depth corresponding to higher creepage values. As the contact temperature increased with creepage, thermal stress and thermal softening caused slight and sharp increases in rail plastic strain, respectively. Therefore, thermal softening is the main factor responsible for the significant increase in wear rate with temperature. Finally, wear results of the PD model and classical Archard’s wear model were compared. The PD models can capture variations in wear rates that are difficult to address using the Archard model.

Study on the sliding wear map of cylinder liner − piston ring based on various operating parameters

The wear map can directly reflect the wear state and mechanism of the friction pair under different conditions and is widely used in wear prediction and fault diagnosis of steel materials. However, there are few reports on the wear map of the engine cylinder liner and its materials. In this study, the operating parameters were obtained through an engine bench test. The parameters near the cylinder liner's top dead center （TDC） were selected as wear test parameters. Thousands of hours of reciprocating lubrication wear tests were carried out on a multi-function wear tester. By analyzing the wear rate variation under different test parameters, the cylinder liner's wear state was divided into mild, medium, and severe wear. The morphology of the wear scar surface and cross-section of the cylinder liner was analyzed by scanning electron microscope (SEM) and then drawing the wear mechanism map. The results show that the primary wear mechanism under slight wear is spalling wear, accompanied by the plastic deformation phenomenon. Delamination wear is the primary mechanism in the medium wear state, accompanied by a small amount of massive spalling wear. The delamination wear is mainly caused by the crack generated by graphite in or below the deformation layer. The primary wear mechanism of the severe wear state is massive spalling. At this time, the graphite at the bottom of the deformation layer plays the role of primary cracks, which causes the plastic deformation layer to fall off.

Investigation of reciprocating wear characteristics of carbon steel at varying load, relative humidity, and operating temperature using ANN-NSGA methodology

Steel's friction and wear characteristics depend not only on the load applied and the nature of the contact surface but also on the environmental circumstances directly and indirectly. This research deals with an investigation of tribological behavior and the wear mechanism of low carbon steel and the effect of load (10 N–100 N), varying temperature (room temperature—200 °C), and relative humidity ranging between 30% and 70% under high-frequency reciprocating condition. Variation of wear rate and coefficient of friction with test parameters was evaluated by generating 3D surface and contour plots. Wear surface morphologies were also characterized. The synergistic effects of the parameters led to a very complex trend in the variation of wear rate and coefficient of friction. Due to the complexity of the problem, an artificial neural network was coupled with the genetic algorithm for the modeling and optimization of tribological characteristics. Simultaneous minimization of wear rate and coefficient of friction was obtained at 18.7349 N load, 199.99 °C temperature, and 49.8332% relative humidity. The worn surface comprised a low shear oxide film and pressed debris patches. The artificial neural network model was also obtained with a significantly high accuracy having an overall R-value close to 1 for both wear rate and coefficient of friction.

Experimentally verified prediction of friction coefficient and wear rate during running-in dry contact

When pristine solid surfaces experience sliding contact, the surface roughness undergoes various changes and deformations in a transient fashion giving rise to a nonlinear wear rate. During the first stage of the service life of the mechanical elements called running-in, this phenomenon occurs where many intertwined parameters interact in a complicated fashion. It is believed that the operating conditions of running-in largely impact the performance of a tribo-system. Thus, the ability to predict the variation of wear rate, friction coefficient, and surface asperities during running-in is important. To address this need, a model capable of predicting the variation of the aforementioned parameters is developed. To verify the predictions, the results are compared to pin-on-disk experiments. The comparison shows an acceptable agreement in the predicted and experimental data.

Wear and corrosion behaviour study of LM0 alloy

The current work investigates the wear and corrosion behaviour of plasma melting and sand casting LM0 alloy. LM0 alloy was prepared by both plasma melting and sand casting techniques. A comparative study of optical, hardness, density, corrosion, and wear of plasma melting and sand casting alloy samples was carried out. For the corrosion behaviour study, alloy samples are held on Seawater for 2-weeks, and weight loss/gain and corrosion rate in each week was calculated.Pin-on-disc wear testing machine conducted dry sliding wear tests at applied load 10–20 N, with varying sliding velocity 0.94-1.88 m/s for 5 min. Mass loss and wear rate variation with the normal load and sliding velocity were studied in the experiment. It is noticed that finer microstructure in plasma melting and coarse microstructure in sand casting samples were obtained from optical image analysis. Higher hardness and lower density of sand casting sample than plasma melting alloy sample. But sand-casting sample shows higher wear resistance and lower corrosion resistance than the plasma melting sample. The worn surfaces and surface corrosion products morphology was analyzed by SEM analysis to examine the wear and corrosion mechanism. The abrasive wear and pitting corrosion phenomena get from the experimental study.

Masking Effect of LPSO Structure Phase on Wear Transition in Mg97Zn1Y2 Alloy

Room- and elevated-temperature wear tests were conducted using a pin-on-disk testing machine to study wear behavior of Mg97Zn1Y2 alloy and role of long-period-stacking-ordered (LPSO) structure phase in mild–severe wear transition (SWT). Variation of wear rate exhibited a three-stage characteristic with load at various test temperatures, i.e., a gradual increasing stage, a slightly higher plateau stage, and a rapid rising stage. The wear mechanisms in the three stages were identified using scanning electron microscope (SEM), from which the first stage was confirmed as mild wear, and the other two stages were verified as severe wear. The interdendritic LPSO structure phase was elongated into strips along the sliding direction with Mg matrix deformation in the subsurface, plate-like LPSO structure phase precipitated at elevated temperatures of 150 and 200 °C. The fiber enhancement effect and precipitation effect of LPSO structure phase resulted in a little difference in wear rate between the first and second stages, i.e., a masking effect on SWT. Microstructure and microhardness were examined in the subsurfaces, from which the mechanism for SWT was confirmed to be dynamic recrystallization (DRX) softening. There is an apparently linear correlation between the critical load for SWT and test temperature, indicating that SWT is governed by a common critical DRX temperature.

Effects of natural shoe wear on traction performance: a longitudinal study

Footwear outsole design is an important factor for shoe-floor friction and for preventing slipping. Shoes with small, uniformly-separated tread blocks (often included on slip-resistant shoes) have decreased slip risk due to their increased friction and better under-shoe fluid drainage. However, these traction performance metrics (friction and fluid drainage) diminish with wear. This study quantifies shoe traction performance in response to natural wear and compares the relationship between common wear metrics: time, distance walked, and worn region size (WRS). Participants wore two pairs of shoes in the workplace for up to 11 months and the distance walked was tracked with a pedometer. After each month of wear, traction performance and WRS of each shoe were measured. Traction performance was quantified by the under-shoe available coefficient of friction and fluid force during a simulated slip test. Increased wear (months worn, distance walked, and WRS) was associated with decreased traction performance. A WRS of 800 mm2 was associated with reductions in friction of 16–38% and increases in fluid force by 286–528%. Three and six months of wear were associated with WRS values of 251 mm2 and 462 mm2 and distances of 203 km and 519 km, respectively. A walking distance of 500 km was associated with a WRS of 406 mm2. This study showed that all of these wear metrics are good indicators of shoe traction performance loss. Thus, the most practical metric in a particular application can be selected. We argue that WRS may be the best indicator due to variations in wear rate from the user and environment. Therefore, tracking footwear usage and monitoring outsole wear can aid in shoe replacement recommendations to reduce slips and falls.

Characterization of mechanical and wear properties of ABS/SiO2 nanoparticles

Objective: In this present work, the SiO2 nanoparticles as filler materials and ABS as a matrix material taken for the injection molding process to prepare the specimens, after that, to study the enhancement of mechanical properties and wear performance of composite materials. Method/Findings: SiO2 nano particles are added to Acrylonitrile Butadiene styrene(ABS) polymer composites at various weight fractions. It is also found that tensile strength, hardness, and wear properties improved in reinforcement. A pin-on-disc type friction and wear monitor (ASTM G99) was employed to evaluate wear behavior of ABS/SiO2 polymer composites. In this experimental study, the input process parameters such as load, sliding distance, and speed are considered and optimized for the composite materials’ properties. Tensile tests and wear tests were conducted to examine, and the properties of the material were studied. Morphology of the fractured material was studied using SEM analysis. The wear debris observed to explore the flacks and groves of the content during wear test for this study Orthogonal array (L9) and control parameters. Applications/Improvements : The significant contributions of this work are the decrease of ultimate strength with increasing content of SiO2 in the composites, and the sliding speed conversed to 45.51% of the wear rate variation. Mechanical and wear properties of ABS/SiO2 nanoparticles polymer composites were studied further. Keywords: ABS; SiO2 Nanoparticles; tensile; hardness; wear; SEM

Effect of crystal size on the tribological properties of lithium disilicate glass-ceramics sliding against alumina and tungsten carbide spheres

PurposeLithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of natural teeth. This study aims to investigate the tribological features of LS2 GC with crystalline volume fraction of 64% and different crystal sizes from 8 µm to 34 µm for different counterparts.Design/methodology/approachThe tribological behavior was investigated using a pin-on-disc tribometer with alumina and tungsten carbide (WC) spheres, applied load of 5 N and sliding speed of 5 cm/s at normal conditions. The coefficient of friction was measured continuously up to 10,000 sliding cycles. The specific wear rate was calculated from tribological and profile measurements. The wear mechanism was investigated by surface morphology analysis.FindingsThe coefficient of friction during running-in varied from 0.8 to 1.0 for the alumina counterpart, because of severe wear. Afterwards, it reduced and reached a stationary regime, characterized by a mild wear regime and the formation of a tribolayer formed by the debris. For the WC counterpart, the coefficient of friction curves increased initially with sliding cycles up to a stationary regime. The samples tested against WC presented the lowest specific wear rate (k), and no variation of wear rate with crystal size was observed. For samples tested against the alumina, crystallization and crystal size increased the wear resistance.Originality/valueThis study evaluated the effect of different counterfaces on the tribological properties of the LS2 GC, an important glass-ceramic base for many dental prosthetics and dental restorations, discussing results in light of the contact mechanics. Different specific wear rates, wear regimes and dependence on the glass-ceramic microstructure were observed depending on the counterpart.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0352/

Evaluation on tribological characteristics of (TiC+TiB)/Ti–6Al–4V composite in the range from 25 °C to 600 °C

The tribological characteristics of 6%(TiC + TiB)/Ti–6Al–4V composite against Cr12MoV steel were systematically investigated using a pin-on-disc wear machine in a static temperature range of 25–600 °C. At 25 °C, the wear rate variation was proportional to the load and inverse to sliding speed. Meanwhile, the wear mechanism underwent a transition from delamination and slight oxidative wear at 0.11 m/s to delamination and abrasive wear at 0.22 m/s and then became mainly oxidation wear at 0.33 m/s. At elevated temperatures, the critical temperatures can be found, 300 °C under 300 N and 400 °C under 100 N, respectively. Above critical temperatures, the effect of load on the wear rate was weakened due to the appearance of massive tribo-layers, and the specific wear rates were reduced by roughly an order of magnitude compared with room temperature, furthermore, the coefficients of friction still remained high value without heat attenuation, the main mechanism was mild oxidation wear. The composite exhibited excellent wear resistance due to high strength and the formation of dense and continuous tribo-layer with tribo-oxides, particularly the presence of Fe2O3.

Dry sliding wear performance and behaviour of powder bed fusion processed Ti–6Al–4V alloy

Ti–6Al–4V alloy is the most commonly used alloy in powder bed fusion (PBF) additive manufacturing processes for a wide range of applications. Thus, properties such as tribological performance are important to be known. In this study, dry linear reciprocating (sliding) wear tests have been conducted to evaluate how wear rate (WR) of the alloy samples processed differently (by laser PBF, electron beam PBF and processed conventionally) may differ. Wear experiments have been conducted with a wide range of test conditions using WC-Co as counter material. Results have shown the expected increase in WR as load (FN) increases, but the dependence of WR on frequency (f) has been found very weak. The major finding of this study is that WR is not affected by the alloy processed in different manufacturing routes having different microstructures and hardness values. It will be shown that despite the little variation in WR under a same wear test condition for the three different samples, their deformation behaviours leading to fracture and thus wear loss differ significantly. It will be reasoned that WR does not only depend on strength and thus hardness, but also ductility of the alloy.

Subsurface Dynamic Deformation and Nano-structural Evolution in 40Cr Steel Under Dry Sliding Wear

Dry sliding tribological properties of normalized 40Cr steel pins against quenched and tempered GCr15 discs were investigated under various sliding distances through disc-on-pin contact configuration. Microstructural feature evolution and strain-hardening behavior of worn subsurface in 40Cr pins were systematically analyzed using scanning electron microscopy and transmission electron microscopy. It is found that based on the variation of wear rate, three stages can be divided throughout the friction process: initial wear, slow wear and stable wear. The corresponding microstructures beneath contact surface are subjected to significant strain-hardening effect and structural rearrangement. Nano-grains of 40–100 nm are produced in the topmost subsurface layer and the nanocrystallization mechanism during friction process is further elucidated. Pronounced vortex structures are generated in the localized subsurface zones due to high strain localization and shear instability. With the prolongation of sliding distances, vortex structures suffer dynamic embrittlement and exfoliation from the wear surface as a result of periodically excessive hardening effect, leading to the high wear rate in stable wear stage.

Lubrication Oil Anti-Wear Property Degradation Modeling and Remaining Useful Life Estimation of the System Under Multiple Changes Operating Environment

Anti-wear property (AWP) is one of the critical characteristics that define the lubrication performance of the lubrication oil. The AWP deterioration is characterized by the wear rate variation and is often related to the operating environment. Since a low AWP can lead to system failure, proactive means to predict the remaining useful life (RUL) considering the environmental factors is an important practical relevance. This paper presents a stochastic model to determine the oil AWP deterioration in order to predict the RUL of the related system. The model assumes that the operating environment behaves as a continuous-time Markov chain (CTMC). A Bayesian methodology using three sources of information (online degradation information, observed degradation, and environmental data) is applied to update dynamically the RUL. In order to demonstrate the applicability of the proposed model, a case of study is presented. Furthermore, to show the accuracy and effectiveness of the proposed approach, a comparative study is conducted with a previously developed model, which does not consider the operating environment.

Effect of Experimental Parameters on Wear Response of Thermally Sprayed Carbide Based Coatings

Friction and abrasive wear response of WC-12 Co and Cr3C2-25 NiCr coatings was studied. Abrasive wear experiments were conducted with SiC abrasive particles with varying load and sliding speeds. The results were analyzed using SEM, XRD and XPS observations of worn surfaces, wear debris and worn out abrasive paper. Friction coefficient diminished with rise in sliding speed and increased for increase in load while wear rates decreased for increasing sliding speed for both coatings. WC-12 Co coating had better wear resistance than Cr3C2-25 NiCr coating while Cr3C2-25 NiCr coating displayed lower friction coefficient. The variation in wear rate and friction response of coatings was due to combined effects of adhesion, abrasion and tribo oxidation effects. The composition of tribo films was strongly influenced by load and sliding velocity and altered friction and wear response of the coatings.

Frictional wear performance under oil-lubricated conditions and wear resistance mechanism of high-velocity arc-sprayed FeNiCrAl coating

To expand the application of Fe-Al intermetallic compounds in abrasion-resistant coatings and improve the room-temperature brittleness of Fe-Al alloys, FeNiCrAl cored wires based on an Fe-Al alloy for high-velocity arc spraying were manufactured in this study. To further study the friction and wear characteristics of the resulting high-velocity arc-sprayed FeNiCrAl coating, a 3Cr13 coating was selected as a comparison material. Friction tests at various loads (20 N, 50 N, and100 N) were conducted using a UMT-3 multifunctional friction and wear tester under oil-lubricated conditions, and an X-ray diffractometer, a hardness tester, a laser scanning microscope, and a scanning electron microscope (SEM) combined with energy-dispersive spectroscopy (EDS) were used to analyze the friction coefficient variations, phase compositions, Vickers hardness, microstructures, and friction surface morphologies of the two coatings. The results indicate that the friction coefficient of the FeNiCrAl coating is less than that of the 3Cr13 coating under the same conditions. The wear rate variation of the FeNiCrAl coating is smaller than that of 3Cr13 as the load increases. The FeNiCrAl coating mainly exhibits plowing wear at low loads; as the load increases, the pressure on the plowing regions extrudes the material and generates slight peeling wear. The FeNiCrAl coating has superior abrasion performance because dense iron oxide, along with both Fe3Al and Al2O3 oxide films, forms on the friction surface. Furthermore, the FeNiCrAl coating has superior hardness, covers the friction surface, and improves the coating abrasion performance.

Effects of surface chemical groups and environmental media on tribochemical running-in behaviors of silicon surface

Abstract In order to offer insight into the removal of outmost silicon atoms, the various tribochemical running-in processes at the Si/SiO2 interfaces were investigated. The running-in of Si–SiOx surface in humid air exhibited a transition from protrusion to groove. By contrast, the initial wear of Si–H surface began with a nearly wearless state in air and revealed apparent material removal after only one sliding cycle in water. The variations in wear rate and friction force suggested the changes of interfacial dangling bonds and energy dissipation. Not only the removal of native oxide layer but also the condensation of interfacial water molecules and the change of surface chemical groups were proposed to interpret the tribochemical running-in mechanisms of silicon surface.

Characterization of Al-Al2Cu functionally graded material produced by using horizontal centrifugal casting

Purpose The purpose of this paper is to investigate the characterizations of high energy thick-walled functionally graded (FG) cylinder containing Al-26%Cu fabricated by horizontal centrifugal casting technique. Design/methodology/approach Field emission scanning electron microscopy in conjunction with image analyser software and energy dispersion spectroscopy is applied to measure the variations of constituent phase’s content and elemental ratios along the radial direction, respectively. Distributions of the FG properties are measured through hardness, CTE, E and σy along the radial direction to investigate the mechanical and physical properties corresponding to the variations in microstructure. In addition, the variations of wear rate along the thickness are evaluated through a series of dry sliding wear tests using the pin-on-disk wear machine. Moreover, scanning electron microscopy is employed to characterize the worn-out surfaces and morphology of wear debris in order to clarify the dominant operative wear mechanism. Findings Results showed that Al2Cu content gradually decreases from the inner wall containing 33.3 vol.% to outer wall containing 26.4 vol.% in the FG cylindrical shell. The elastic modulus and yield strength measured through compression tests reveal that these mechanical properties are limited up to certain value of Al2Cu. The obtained optimum value of Al2Cu content for studied Al-Al2Cu FG is almost 31 vol.%. Originality/value The obtained optimum value of Al2Cu content for studied Al-Al2Cu FG was almost 31 vol.%.

A mechanistic understanding of the wear coefficient: From single to multiple asperities contact

Sliding contact between solids leads to material detaching from their surfaces in the form of debris particles, a process known as wear. According to the well-known Archard wear model, the wear volume (i.e. the volume of detached particles) is proportional to the load and the sliding distance, while being inversely proportional to the hardness. The influence of other parameters are empirically merged into a factor, referred to as wear coefficient, which does not stem from any theoretical development, thus limiting the predictive capacity of the model. Based on a recent understanding of a critical length-scale controlling wear particle formation, we present two novel derivations of the wear coefficient: one based on Archard’s interpretation of the wear coefficient as the probability of wear particle detachment and one that follows naturally from the up-scaling of asperity-level physics into a generic multi-asperity wear model. As a result, the variation of wear rate and wear coefficient are discussed in terms of the properties of the interface, surface roughness parameters and applied load for various rough contact situations. Both new wear interpretations are evaluated analytically and numerically, and recover some key features of wear observed in experiments. This work shines new light on the understanding of wear, potentially opening a pathway for calculating the wear coefficient from first principles.

Comparison of wear methods at nanoscale: line scanning and area scanning

Two wear methods, line scanning and area scanning, were investigated to clarify their effect on wear experimental results at nanoscale. Wear tests of pure copper against diamond tip in vacuum and silicon against SiO2 tip in water were performed using atomic force microscopy. Results show that two scanning methods can result in marked differences in experimental results for either pure mechanical wear or tribochemical wear. The variation in wear rate with sliding cycle indicates that the nanowear of material surface is a dynamic evolution process, which highly depends on the scanning methods. Line scanning is usually a simple and efficient wear method that can markedly change the interfacial contact profile and even induce a regional “work hardening” on the contact interface. By tuning the scan overlap rate, area scanning can reduce the influence of thermal drift of instrument and local defects of samples, as well as better present wear behaviors of material surface in initial wear stage. This study not only elucidates the importance of choosing wear methods as well as scan parameters in nanotribological investigations, but also provides an in-depth understanding of nanowear behaviors of material surfaces.

Dry slipping steel–steel contact at high current density

The behavior of steel 3 in dry slipping under the action of high-density electric current is studied. In these conditions, the surface layer undergoes plastic deformation; its temperature rises; and new phases and structural defects are formed. That gives rise to a layer of secondary structures. The basic factor disintegrating the surface layer is the contact current density. The mean contact temperature and layer thickness of the secondary structures increase with increase in current density. The variation in wear rate and electrical conductivity with change in contact temperature is studied. The wear rate depends linearly on the contact temperature in normal wear. Catastrophic wear appears as sharp increase in the wear rate and simultaneous decrease in the contact electrical conductivity at 500—600°C. The thickness of the layer of secondary structures is 50 μm in these frictional conditions.