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In industrial settings, the same friction pair can undergo both fretting and sliding wear depending on the working conditions. This study compares the fretting and sliding wear behaviors of TC4 against GCr15 at various temperatures. The results indicate that in fretting tests, the average friction coefficient decreases with increasing temperature, while in sliding tests, it shows the opposite trend. As the temperature rises, the material transfer is intensified, and a significant amount of Fe 2 O 3 oxide friction layer forms on the surface of TC4 alloy, providing protection to the worn surface and decreasing the wear rate. At 300 ℃, adhesive wear in fretting wear is more severe than sliding wear, with peeling being more pronounced around the wear scar of sliding wear. [ABSTRACT FROM AUTHOR]

This study aims to obtain key parameters such as the fretting wear coefficient and wear rate of M50 bearing steel through fretting wear experiments. By integrating the Umeshmotion subroutine, a validated 3D ball-plane energy dissipation fretting wear model was established. The research explores wear behavior and transition mechanisms under different normal loads and displacement amplitudes. Experimental and finite element analyses show that fretting wear rate is negatively correlated with normal load and positively correlated with displacement amplitude. These variables influence contact stress, shear stress, and slip distance, affecting wear morphology. Results indicate that increasing normal load transitions fretting wear from gross slip to partial slip, while increasing displacement amplitude shifts it from partial slip to gross slip. [ABSTRACT FROM AUTHOR]

Corrosion and fretting wear inevitably occur in wires, which are important parts of cables. To study the wear morphology and surface mechanical behavior of wires for different fretting and corrosion times, a numerical model of fretting wear of wire with different corrosion conditions is established using MATLAB and ABAQUS software's. Firstly, according to the surface roughness of wires under different corrosion times, the node coordinates in the numerical model are modified to simulate different rough surfaces. Secondly, the wear characteristics of wires under different fretting cycles are obtained by using a cycle jump concept and an ABAQUS user subroutine. Finally, the numerical model is validated using experimental data. The results show that when the corrosion time is 0 h, the wear area has a regular oval shape. The wear volumes of wires with corrosion times of 120 h and 480 h are the largest and the smallest, respectively. As wear volume increases, both residual surface contact pressure and stress decrease. When the corrosion time is 0 h and 120 h, the residual surface contact pressure is maximum and minimum, respectively. [ABSTRACT FROM AUTHOR]

In the aerospace industry, fretting and sliding wear are commonly encountered by components made from M50 bearing steel. This study aims to investigate the effect of temperature on the fretting and sliding wear behavior of M50 bearing steel. Research indicates that as the temperature rises from 25 ℃ to 350 ℃, the average friction coefficient decreases in fretting conditions and initially increases before decreasing in sliding conditions. At 350 °C, increased oxidation occurred, resulting in the formation of oxides mainly composed of Fe 2 O 3 and Fe 3 O 4 , with small amount of MoO 3 and Cr 2 O 3. The elevated temperature causes more oxide adhering to the surface and forming a protective oxide film, thus reducing the friction and wear. [ABSTRACT FROM AUTHOR]

Laser cladding technology was utilized to construct protective coatings on the surfaces of service materials and to study the mechanical and fretting wear properties of the coatings. The coating mainly consists of diffuse Cr 2 AlC phase, interdendritic Cr 7 C 3 phase and dendritic Cr-based solid solution. The hardness of the coating was enhanced to 690 HV, which is 3.1 times higher than the hardness of the substrate. The change in H3/Er2 values of the coating and the substrate were calculated by nanoindentation to be 0.04 and 0.024, respectively, and the anti-fretting wear properties of the coating was excellent. The statistical distribution of the Schmidt factor of the coatings is between 0.41 and 0.5, which indicates that the coatings have a high probability of initiating slip and high plastic deformation capacity. For those grains with large Schmidt factors, dislocations can be easily activated in response to applied stresses. Strength is the first element of wear resistance, and with sufficiently high strength, the plasticity enhancement can be very effective in improving the fretting damage resistance. After the fretting wear test in liquid LBE, the Cr-Al-C composite coating has a huge increase in wear resistance compared to the substrate. The wear resistance of the coating was 33 times that of the 316 stainless steel substrate at a test temperature of 450 °C [ABSTRACT FROM AUTHOR]

Micro-arc oxidation is an effective method to enhance surface wear resistance. This paper comparatively studies the fretting and sliding wear properties of micro-arc oxidation-treated 7075 aluminum alloy at different temperatures. Research indicates that both the untreated and MAO-coated samples exhibit peak friction coefficient values due to adhesion at elevated temperatures. At both room temperature and 150 °C, the fretting wear rate of the MAO-coated sample is lower than that of the sliding wear rate, which can be attributed to distinct surface damage mechanisms and third body behavior under different wear modes. Adhesive wear is more prominent in MAO-coated samples during high-temperature fretting compared to room temperature, while abrasive wear and spalling are more prevalent during high-temperature sliding. [ABSTRACT FROM AUTHOR]

In this study, the ambient temperature fretting wear behavior and the wear mechanisms of the Selective Laser Melting prepared IN738LC alloy with various micro-structures were systematically investigated under varying load conditions (35 N, 100 N). The results indicate that the running states of fretting gradually transitions from the gross slip regime (GSR) to the mixed slip regime (MSR) as the load increases. The HT-2 samples (Unimodal precipitation, hardness 512 HV) present more fine homogeneous and dense secondary γ′ phase compared with HT-1 (Bimodal precipitation, hardness 487 HV) and As-built (No precipitation, hardness 392 HV) counterpart, which result in excellent wear resistance. The main fretting wear mechanisms for all samples were oxidation wear, abrasive wear, fatigue wear. [ABSTRACT FROM AUTHOR]

This study explores the escalating significance of lightweight and biocompatible biomedical implants with a high strength-to-weight ratio, revolutionizing critical medical applications. Despite these merits, their widespread use is hampered by poor tribological performance. Investigating the impact of TiC nanoparticles, we synthesized Ti6Al4V (Ti64) powders with varying TiC content using spark plasma sintering. The resulting nanocomposites exhibited enhanced wear resistance attributed to heightened hardness and oxidation wear resistance. Notably, at 2.5 wt% TiC content, nanohardness reached 8.99 GPa, and specific wear rate significantly decreased to 4.2 × 10−9 mm3/N-m under constant loading (20 N, 1 Hz). This reveals substantial improvements compared to Ti64 monolithic alloys, emphasizing the potential for advancing implant materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the fretting wear mechanism of the directionally solidified superalloy (DZ125) surface created by wire electrical discharge machining (WEDM) are studied. Samples with varying surface characteristics are prepared by changing the number of wire cutting (NWC), ranging from one to five times (NWC-1 to NWC-5). Comparative analysis reveals that the NWC-3 exhibits the best surface characteristics. Subsequent fretting wear tests under different displacement amplitudes show increased dissipation energy with greater displacement. Compared with other samples, NWC-3 in the synergistic effect of surface roughness and hardness exhibits excellent fretting wear performance. In addition, the fretting mechanism transitions from mixed slip regime (MSR) to gross slip regime (GSR) as the displacement increases. The wear mechanism transitions from abrasive wear to oxidation wear and adhesive wear. [Display omitted] • The fretting friction behavior and wear mechanism of the surface created by WEDM are studied. • NWC-3 exhibits the lowest dissipation energy and excellent fretting wear performance under identical conditions. • The fretting mechanism of NWC-3 transitions from mixed slip regime to gross slip regime as the displacement increases. [ABSTRACT FROM AUTHOR]

Ti-6Al-4 V titanium alloy is used for low-pressure compressor blades of aero-engine due to its high specific strength, excellent corrosion resistance and high-temperature stability. Low-pressure compressor blades are subject to fretting wear in service, which may lead to fracture failure of the blades. The preparation of wear-resistant coatings is currently an effective solution in solving the problem of fretting wear on Ti-6Al-4 V titanium alloy. However, the fretting wear resistance and microstructure stability of the coating under variable cycle fretting conditions require more attention. In this work, the fretting wear performance and microstructure stability of the Ti-Al-C-N composite coating under variable cycle fretting conditions are investigated. The results show that the parameters of variable cycle operating conditions have a notable effect on the coefficient of friction (COF). The variable frequency and variable temperature working conditions result in the alteration of the fretting operation mechanism. Whereas the variable stroke amplitude and the variable load conditions do not cause changes in the fretting operation mechanism, and both are in the gross slip region (GSR). The lowest wear rate occurs under variable stroke amplitude conditions. The wear rate is the maximum under the variable cycle temperature condition. According to the dissipated energy calculation, the difference between the two different stroke amplitudes is the biggest among all the conditions. EBSD and TEM analyses show that the subsurface of variable stroke amplitude worn scar has a more uniform strain distribution, and reveals a unique subsurface structure with a transformation from crystalline to amorphous, which contributes to improving the wear resistance. This work provides insights into coating microstructure stability and wear mechanisms under variable cycle conditions. [ABSTRACT FROM AUTHOR]

Interproximal contact loss (ICL) between zirconia crown and adjacent natural teeth is a common complication that could lead food impaction and compromise the periodontal/peri-implant tissue health and patient's satisfaction. Both fretting and sliding wear mode can be found in the frictional pair between zirconia crown and interproximal enamel during mastication. In this study, fretting and sliding wear behavior of interproximal enamel against zirconia in artificial silva was investigated. The wear damage of the interproximal enamel in a sliding movement was higher than in a fretting movement. In fretting mode, the running condition fretting map (RCFM) composed of partial slip regime (PSR), gross slip regime (GSR), and mixed fretting regime (MFR) was constructed depending on different normal loads and displacement amplitudes. Intact surface was observed in the PSR. Plastic deformation at contact center and microcracks at contact margin were detected in the MSR. Severe wear damage occurred in the GSR, predominated by microfracture, brittle deformation. Macroparticles generation, fatigue delamination and abrasive wear prevailed in sliding mode. In contrast, enamel debris could be transferred on zirconia surface while the material loss of the antagonist zirconia was negligible in both fretting and sliding test. • The wear damage in a sliding mode is higher than in a fretting mode under the same normal load. • The RCFM of interproximal enamel includes three regimes: partial slip regime, mixed slip regime, and gross slip regime. • The interproximal enamel undergoes elastic, plastic and brittle deformation in the PSR, MSR and GSR, respectively. • Macroparticles generation and fatigue delamination dominated the wear mechanisms in a sliding movement. • The enamel debris was adhered on the contact surface of zirconia antagonist in the GSR and sliding movement without zirconia content loss. [ABSTRACT FROM AUTHOR]

Fretting wear is caused by a relative movement of the material surface on a small scale. Finding ways to reduce fretting wear is of great importance for extending equipment life and reducing maintenance costs. With the increase of load, the effecrt of fretting wear adhesion of surface treated material becomes more obvious. The materials treated with post-oxidation have stronger wear adhesion than those treated only with plasma nitriding, but the total wear volume is reduced. In this paper, the fretting wear of high strength steel alloy with different surface treatments is simulated by the finite element method. The coefficient of friction and wear volume can be obtained from the experimental results, and the wear coefficient is calculated using the wear energy model. The predicted two-dimensional wear profile curves (U-shape and W-shape wear profiles) under different wear conditions are compared with the experimental results. The W-shape wear profile is used to describe the adhesion state of the worn surface. In addition, the surface deformation and mechanical properties of U-shape and W-shape wear profiles are analysed. The simulation results show that double-sided wear and the addition of adhesive layer is important for the prediction of wear characteristics. [ABSTRACT FROM AUTHOR]

An analytical description of fretting wear is proposed wherein the volume of wear debris either removed from the sliding interface or retained within these areas, is represented as a fraction of the freshly-produced debris in each fretting pass. In the proposed model, the volumes respectively of removed debris and of retained debris are tallied over each pass of a fretting sequence to yield a closed analytical expression relating these volumes to the number of passes. The paper provides an example of the adaptation of the proposed model to experimental wear data on steel-steel fretting interfaces. [ABSTRACT FROM AUTHOR]

A hydroxyapatite (HAp)/copper (Cu) coating was deposited on a Ta substrate by plasma spraying to mitigate the fretting wear of bones. It was found that the HAp/Cu coating significantly reduced the fretting slip of Ta at the Ta-bone interface. The friction coefficient of the HAp/Cu coating-bone frictional pair (1.14) was much higher than that of the Ta-bone frictional pair (0.71). The HAp/Cu coating significantly mitigated the fretting wear of bones by forming a protective layer on the fretting interface and reduced the wear rate from 0.031 mm3/N·mm to 0.0029 mm3/N·mm. [Display omitted] [ABSTRACT FROM AUTHOR]

The current load is one of the most significant factors in the reliability of electrical contact under fretting conditions. In this paper, the fretting wear experiments are conducted for CuZn40 and AgCu10 alloys with varied current loads. The variations of electrical contact resistance (ECR), ECR endurance, temperature, and wear volume with the increasing current load of two alloy materials under fretting conditions are investigated, and the differences between their electrical contact behaviors are compared. The microstructures of the surface wear morphology are examined to reveal the mechanisms of fretting wear and electrical contact failure. In addition, the fretting wear volume evolution of both alloys under different fretting cycles is studied. The results show the current load impacts the wear morphology. The wear particles become smaller and the oxide layer becomes stable with the increase of current load. The effect of current load on ECR and temperature is more significant for CuZn40 alloy. The ECR endurance for both materials first increases and then decreases. This is attributed to two competitive mechanisms controlling the evolution of ECR endurance under varied current loads. [ABSTRACT FROM AUTHOR]

Splines are widely used in aeronautic applications; however, misaligned splines often suffer contact stress concentration and fretting wear fatigue failure. Crowned modification is a useful way to relieve contact stress concentration and mitigate fretting wear for misaligned splines, but it is unclear how this method works. In this study, contact stresses for involute splines are calculated using finite elements and correlated to first-hand experimental results on fretting wear obtained using a dedicated test rig. Both contact stress distribution prediction and fretting wear measurement indicate that the crowned magnitude of splines should be selected according to the operating angular misalignment. ● A dedicated test rig for spline fretting wear is constructed. ● First-hand experimental results on spline fretting wear are presented. ● Spline contact stress predictions are implemented using finite elements. ● Optimum crowned magnitude depends on operating angular misalignment.A positive correlation exists between spline fretting wear and contact stress. [ABSTRACT FROM AUTHOR]

Unlike many other surface treatment techniques, such as shot peening (SP), low plasticity burnishing (LPB), ultrasonic surface rolling process (USRP), ultrasonic nanocrystal surface modification (UNSM), laser shock peening (LSP) is a non-contact process. This means that LSP achieves surface modification without direct physical contact, thereby eliminating the risk of media contamination and undesired wear on the peening equipment. As a surface hardening technology, LSP tends to produce a hardened layer with a high gradient of residual stress (RS) in the near-surface, significantly enhancing wear resistance. The well-known wear theories applied for numerical prediction, whether Archard model or dissipated frictional-energy model, contain a multiplier for contact pressure and relative slip amplitude p · ds or shear stress and relative slip amplitude q · ds , respectively. These multipliers are sensitive to the mechanical properties near the surface. Additionally, the wear profile is governed not only by the wear effect but also by the deformation of materials. Therefore, to accurately evaluate the wear performance for surface-hardened materials, the influence of RS is hard to be overlooked. In this work, the finite element method (FEM) is utilised to construct a 3D numerical model, which ignores and considers RS, for both as-received and LSP-treated samples. Two distinct RS distributions induced by different scanning strategies (one- and five-time), are introduced in the finite element (FE) model. The numerical simulation results are then compared with the experimental data to verify the accuracy of the fretting wear model built in this study. On this basis, the impact of different RS distributions on fretting wear characteristics, including wear profile and volume, is extensively investigated. The findings reveal that higher amplitude RS can reduce the degree of fretting wear to a greater extent, highlighting the beneficial role of RS in enhancing wear resistance. Furthermore, the numerical models incorporating RS demonstrate superior predictive accuracy compared to those that omit RS. This naturally underscores the importance of integrating RS in numerical simulations of LSP and other surface-hardened materials. [ABSTRACT FROM AUTHOR]

The dovetail joint interfaces in aero-engine are susceptible to fretting wear, which can result in premature failure. Based on two-dimensional (2D) blade/disk contact finite element (FE) model and the energy model, an original substrate-debris-glaze conversion method is proposed and validated to predict the presence of a glaze layer at high temperatures in fretting wear. The present work investigates the effects of bottom angle, friction coefficient, centrifugal force and temperature on fretting wear of the dovetail joint. The results indicate that fretting wear predominantly occurs near the edges of the contact areas. Furthermore, the formation of glaze layer at high temperatures leads to a significant reduction in wear depth, ranging from 50% to 93%, compared to low temperatures without glaze layer. [ABSTRACT FROM AUTHOR]

The study examines the fretting wear of the Laser Powder Bed Fusion (L-PBF) processed IN718 alloy under gas turbine-like conditions. It involves a large (>106) test cycle investigation at 550 °C and ∼800 N. The heat-treated L-PBF IN718 material exhibited higher hardness compared to heat-treated wrought IN718 due to the formation of finer precipitation of γ' and γ'' in the FCC nickel matrix. A custom wear test setup simulates the harsh industrial environment, revealing a two-fold lower wear coefficient in the L-PBF alloy due to improved hardness and a finer microstructure. The friction coefficient remains marginally different, with the L-PBF alloy showing lower values during the initial phase. The wear mechanisms are similar, but the wrought IN718 HT exhibits severe oxidation-assisted galling. • The study compares fretting wear in IN718 using traditional wrought and LPBF methods. • LPBF IN718 with two-step heat treatment outperforms wrought IN718 in wear resistance. • LPBF's finer grain structure boosts wear resistance vs. IN718 WT's coarser grains. • Wrought IN718 underwent faster wear due to localized stick-slip than LPBF IN718. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional (3D) continuum damage mechanics (CDM) finite element (FE) model was developed to investigate the effects of fretting wear on rolling contact fatigue (RCF) of bearing steels. In order to determine the fretting scar geometry, a 3D arbitrary Lagrangian-Eulerian (ALE) adaptive mesh (AM) FE model was developed to simulate fretting wear between two elastic bodies for different initially pristine fretting pressures (0.5, 0.75 and 1 GPa) and friction coefficients (0.15, 0.175 and 0.25) resulting in stick zone to contact width ratios, c/a = 0.35, 0.55 and 0.75. The resulting wear profiles were subjected to various initially pristine RCF pressures (1, 2.2 and 3.4 GPa). The pressure profiles for RCF were determined by moving the contact over the fretted wear profiles in 21 steps. These pressure profiles were then used in the CDM-FE model to predict the RCF life of fretted surfaces. The CDM-FE model uses Fatemi-Socie (FS) criteria for damage evolution and accounts for scatter in RCF life by implementing material topological variation through Voronoi tessellation. The results from CDM-FE RCF model indicate that fretting scar generated at 1 GPa with c/a = 0.35 has the most detrimental effect on RCF life at 1 GPa, reducing life by as much as 99.8% from pristine condition. However, it is to be noted that the remaining life expectancy at this RCF pressure (1 GPa) is significant and more than 17 billion cycles. As the RCF pressure increases (P RCF ≥ 2.2 GPa), the effect of fretting on RCF life decreases for all fretting pressures and c/a values, indicating that life is primarily governed by the RCF pressure. The results from CDM-FE model were also used to develop a life equation for evaluating the L 10 life of fretted M-50 bearing steel for the range of tested conditions. [ABSTRACT FROM AUTHOR]

The Zr-4 alloy tubes in nuclear fuel rods in pressurized water reactor (PWR) fuel assemblies were subjected to bi-directional composite fretting wear tests with different phase differences (0°, 90°, 180°, and 270°) at room temperatures and 300 °C by using a multi-modal fretting wear tester developed independently by the group. The experimental results show that the change in temperature as well as the change in phase difference has a significant effect on the fretting wear characteristics of Zr-4 alloy cladding tubes.The following conclusions were drawn: Among the bi-directional composite fretting tests with different phase differences, the most severe wear was observed for the bi-directional composite fretting test with a phase difference of φ = 90°. Bidirectional composite fretting wear tests at 300 °C show more intense wear and more severe damage compared to room temperature tests. At room temperature, the morphology of the abrasion mark region is characterized by zoning, and the wear mechanism is mainly dominated by adhesion wear, abrasive wear and delamination. [ABSTRACT FROM AUTHOR]

Fretting wear significantly affects the hysteresis behavior of the contact surface and leads to joint degradation due to material removal. Although numerous tests have been conducted to investigate fretting wear under constant normal force, the applied mechanical load on the contract surface more or less deviates from that in the operational condition. The normal force is typically time-varying due to the coupling of tangential and normal vibration, rather than remaining constant. The time-varying normal force can be regarded as the superposition of harmonics for steady-state vibration which is widely encountered in engineering. In this paper, we investigate how would the harmonic component of the normal force affect the evolution of interface morphology and contact parameters with fretting wear. To do that, we design a novel fretting wear test apparatus that generates the stable harmonic normal force. The normal force is controlled by a closed-loop control system, ensuring its consistency throughout the entire wear test. In addition, we develop various subsystems to realize different functions like support, constraint and measurement, enabling the acquisition of hysteresis loops under different normal forces. The critical performances of the test apparatus (e.g. force transfer, closed-loop control and repeatability) are also demonstrated. Results indicate that the harmonic normal force can significantly influence the hysteresis loop and the energy dissipation distribution on the contact surface. In comparison to the constant normal force, the worn surface has a higher degree of non-uniformity, characterized by alternating pits and prominences. Furthermore, the friction coefficient exhibits an outstanding upward trend after reaching a steady state, while the tangential contact stiffness continuously weakens as fretting wear progresses. These unique evolution characteristics could be attributed to the non-uniform energy dissipation caused by the harmonic normal force acting across the fretting space. This viewpoint can be partly validated through observing the interesting hysteresis loops, which are captured by the test apparatus. [Display omitted] • A novel apparatus is designed to perform fretting wear tests under harmonic normal force. • This apparatus can reproduce the interface load of tangential normal coupling vibration. • Under the harmonic normal force, the friction coefficient exhibits an upward trend. • The worn surface becomes rougher, characterized by alternating peeling pits and peaks. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of fretting wear on frictional contacts. A high frequency friction rig is used to measure the evolution of hysteresis loops, friction coefficient and tangential contact stiffness over time. This evolution of the contact parameters is linked to significant changes in natural frequencies and damping of the rig. Hysteresis loops are replicated by using a Bouc-Wen modified formulation, which includes wear to simulate the evolution of contact parameters and to model the evolving dynamic behaviour of the rig. A comparison of the measured and predicted dynamic behaviour demonstrates the feasibility of the proposed approach and highlights the need to consider wear to accurately capture the dynamic response of a system with frictional joints over its lifetime. • The impact of wear on the dynamics of structures has been experimentally quantified. • Wear leads to shifts in natural frequency and damping of structure vibration modes. • Wear needs to be included in models to capture the dynamics of jointed structures. • A Bouc-Wen formulation is presented to account for wear in dynamic simulations. [ABSTRACT FROM AUTHOR]

Systematic experimental observations concerning the response of microstructural features on fretting wear of steel grades were conducted. Five steel grades with different typical microstructural features were selected. The effect of various microstructures on fretting wear behaviour and the resulting wear mechanism were evaluated. Results show that microstructural features play a significant effect on fretting wear resistance depending on the applied loads. The DP and Q&P steel having low hardness show comparable or even better fretting wear resistance than the FM steel of the highest hardness regardless of loads, which are all better than TWIP and IF steel. The result suggests that the combination of soft ferrite and hard martensite with/without retained austenite having low hardness displays superior fretting wear resistance. • The stabilized friction coefficient of DP, Q&P and FM steels is lower than that of IF and TWIP steels. • DP and Q&P steels with low hardness perform comparable or even better wear resistances than FM steel of highest hardness. • The order of wear resistance is DP/Q&P/FM, IF and TWIP steel for low load, but DP/Q&P/FM, TWIP and IF steel for high load. • An optimal microstructure may be the combination of soft ferrite and hard martensite with/without some retained austenite. [ABSTRACT FROM AUTHOR]

SAF 2507 super duplex stainless steel (SAF 2507 SDSS) is widely used in industrial fields while its fretting wear mechanism at high temperatures has not been well studied. In this paper, fretting behavior of SDSS in a wide temperature range from 25 °C to 800 °C at 20 N and 50 N has been studied. It is found that fretting wear behavior of SDSS is influenced by both temperature and load. Elevated temperature induces both surface softening and formation of oxide layer (Fe 3 O 4 and α-Fe 2 O 3). Compared with 20 N, oxide layer at higher load of 50 N is easier to transfer onto the counterpart surface under interrelated effects of heating temperature and applied load, finally leading to higher wear loss. Image 1 • The fretting wear behavior of SAF 2507 SDSS under different loads and temperatures were investigated. • The high temperature induces both surface softening and formation of the oxide layer. • At a high load of 50 N, the oxide layer is easier to transfer onto the counterpart surface under the interrelated effects of heating temperature and applied load. • At room temperature, the abnormal phenomenon of lower wear at high load occurs. [ABSTRACT FROM AUTHOR]

Abstract Fretting wear of cold-sprayed Cu MoS 2 and Cu MoS 2 WC composites rubbing against AISI 440C was studied under gross slip regime at a high normal force of 150 N. Third body rheology was expressed using tribological circuit according to morphology observations of the contact. WC particles boosted generation and ejection of large wear particles during running-in and early steady state yet promoted more stable and lower third body formation and ejection over subsequent test. This led to a considerably reduced wear rate (∼80 × 10−6 mm3/Nm) comparing to that of Cu MoS 2 (∼210 × 10−6 mm3/Nm) during steady state. The 12 wt% WC particles were able to prevent rapid detachment that was induced by MoS 2 , which was resulted from microwedging and pinning of the WC fragments. Highlights • Adding WC to Cu MoS 2 significantly improved its wear resistance at high normal load. • During running-in, WC helped to generate wear debris bed more rapidly. • During steady state, WC promoted more stable and low third body formation and ejection. • WC particles forced velocity accommodated within the top surface layer. [ABSTRACT FROM AUTHOR]

Abstract This study reports on fretting friction and wear behaviors of steel/copper test pairs lubricated in the nanodiamond-dispersed oil with a flat-on-flat configuration at 106 N. After 4 × 104 fretting cycles, results show that an addition of 0.2 wt% nanodiamonds in oil reduces the friction torque from 0.12 Nm of pure oil to 0.08 Nm. Particularly, the wear volume is decreased by an order of magnitude compared to that tested in pure oil. Microstructural analyses reveal that the substantial friction and wear reduction is attributed to collective effects including the formation of robust nanodiamond-strengthened tribofilms, wear-induced twin boundaries, and good mechanical bonding interface between tribofilms and the substrate. Highlights • Dispersing nanodiamonds (NDs) in oil dramatically reduced friction for fretting. • Wear volume was decreased by an order of magnitude after dispersing NDs in oil. • This can be attributed to formation of a robust nanodiamond-strengthened tribofilm. • Wear-induced TBs in the substrate also promoted to the high wear resistance. [ABSTRACT FROM AUTHOR]

In this study, a high-temperature fretting wear prediction model was established for metal rubber, which was then validated through experiments. Initially, a three-dimensional numerical model of metal rubber was reconstructed, and statistical distribution of contact points and types of curved wires inside the virtual component was achieved. Meanwhile, a high-temperature fretting wear evolution model for curved wires was constructed by introducing a temperature function f(T), considering material thermal expansion, softening, and oxidation. Subsequently, the model was incorporated into the macro model, establishing a cross-scale predictive model for wear from micro-coil elements to component wear. Experimental validation demonstrated good prediction performance of the model, with a maximum wear mass prediction error of 14.81% and prediction errors below 10% for 80,000 cycles. [ABSTRACT FROM AUTHOR]

PC/ABS is a polymer blend widely used due to its nearly additive combination of the best properties of its components. However, there is almost no literature available regarding its failure behavior while under compression loading. This work presents sphere-to-flat experimental analyses of four PC/ABS weight ratio compositions: 100:0, 80:20, 65:35 and 0:100. Specimens are tested for indentation, creep and axial–torsional fretting wear at severe loads. Moreover, the contribution of each one of these three failure phenomena is determined and discussed. Creep has a major effect in most materials, while fretting wear is particularly critical to the 100:0 and 80:20. The 65:35 blend exhibited the best results in all test conditions, making it a good candidate for various industrial applications. [Display omitted] • A novel method for the study of coatings under severe compression loads is presented. • Indentation, creep and axial–torsional fretting wear tests of PC/ABS are carried-out. • Damage mark's morphology, depth and volume are reported and extensively discussed. • Creep is the major source of damage at most test conditions. • Results show the excellent performance of the 65:35 PC/ABS blend. [ABSTRACT FROM AUTHOR]

Fretting tests on four commercial greases were run on a ball-on-disc machine at 25, 7, − 20, − 40 °C. Post-test wear was measured on the ball and the chemical composition of lubricant films in the wear scar analysed by FTIR (RA-IRS), Raman and SEM-EDS. At 25 and 7 °C the greases had similar friction and wear properties. At − 20 and − 40 °C the highest base-oil viscosity grease gave an inferior friction and wear performance. RA-IRS analysis showed thickener remaining in the wear scar for most test conditions. The highest wear was linked to the absence of thickener in the scar. Better wear and friction performance at low temperatures was associated with thickener present in the lubricated contact and lowest base-oil viscosity. [ABSTRACT FROM AUTHOR]

For understanding the long term fretting mechanism, the effect of normal force on the fretting wear behavior of 690 TT heat transfer tube against 304 stainless steel (SS) ball in simulated secondary water with 10 6 total fretting cycles was studied. The changes of the friction coefficients can be divided into five stages: small and slowly increase stage, sharply increase to a peak point, dramatically decrease to a steady value, steady stage, and continuously increase stage. And the friction coefficient decreases with the increase of the normal force. The morphologies of the worn scars under different normal forces are quite different. A stratified layer structure is formed on the 690 TT surface during the fretting wear process when the normal force is 60N. [ABSTRACT FROM AUTHOR]

Fretting wear in the displacement- and load-controlled settings is considered. The axisymmetric wear contact problem with stick and slip zones is studied under the assumption that the contacting bodies are elastically similar and their stress-strain states can be modeled by half-space approximations. It is shown that in the presence of a stick zone, the worn shape of profiles in contact tends to some limiting shape which is determined solely by the solution of a certain frictionless normal contact problem. In the both cases, it has been proved that the value of the limiting stick-zone radius corresponds to that of the initial stick zone, and the limiting shape of profiles is obtained in a closed form involving one quadrature. The novelty of this work is in study of the limiting shapes in load controlled fretting wear situations. [ABSTRACT FROM AUTHOR]

The present research describes a study to explore the possibility to improve the wear resistance by healing microcracks that initiated under fretting wear. To this aim Ti 3 SiC 2 coatings prepared at different plasma powers (33 and 34 kW) were investigated comparatively under fretting. The results showed that the amount of Ti 3 SiC 2 phases was higher at the lower plasma power, leading to a major difference on fretting wear properties. Coatings with a higher content of Ti 3 SiC 2 phases exhibited a remarkable decrease in the friction coefficient and an enhancement in the wear resistance. The enhanced wear resistance was mainly attributed to the healed cracks by selective oxidation of Ti 3 SiC 2 . The reduced friction coefficient was strongly related to the formation of tribo-induced oxides. [ABSTRACT FROM AUTHOR]

The subsurface damage mechanisms of Inconel 690 induced by fretting wear in pure water were investigated. The results showed that the major damage mechanism were oxidation, deformation, fatigue and delamination cracks in worn subsurface. Due to the low oxygen concentration in pure water, preferential oxidation of Cr occurred and plugged into tribologically transformed structure (TTS) at the interface of wear debris layer (WDL)/TTS, which produced complex structures of Cr-rich oxide zone surrounded by Ni-rich zone in TTS. Continued oxidation led to spread of Cr-rich oxide zone, accompanying with formation of WDL consisting of nano-sized oxides and Ni-based grains, however such a spread was limited by the TTS/general deformed layer (GDL) interface, and did not extend to GDL. [ABSTRACT FROM AUTHOR]

Fretting wear behavior of CuNiAl against 42CrMo4 was investigated under different lubrication conditions with the flat on flat contact configuration. In oil, filtered water and artificial seawater, it was under a mixture of liquid lubrication and third body solid lubrication, so the friction torque was lower than that under dry fretting. Wear was the slightest in oil and the most serious under dry fretting. The corrosion products under seawater lubrication presented a friction and wear reducing effect. The wear mechanisms depended on the lubrications. In oil, they were dominated by abrasive wear and plastic deformation; under the two water lubrications, they were mainly cracks, delamination and abrasion; under dry fretting, they were mainly abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation into the effects of contact conformity, contact pressure and displacement amplitude on gross-slip fretting behaviour for grease-lubricated cylinder-on-flat contacts in the context of flexible marine riser pressure armour wire, and compares behaviour with that observed in unlubricated conditions. Characterisation of friction and wear is critical to fretting fatigue life prediction in flexible risers since friction directly controls trailing-edge fretting stresses and hence fatigue crack initiation, on the one hand, and on the other hand, directly affects wear via relative tangential slip (displacement). Wear can have a beneficial or detrimental effect on fatigue crack initiation and propagation, depending on relative slip and slip regime. For the grease-lubricated conditions, the behaviour is determined by whether grease can be retained in the contact (as opposed to being extruded out). Retention (or replenishment) of grease in the contact results in low rates of wear and low coefficients of friction; these conditions are favoured by fretting displacements above a critical value, by low contact conformity, and by low applied loads. [ABSTRACT FROM AUTHOR]

The effects of sliding amplitude and normal load on the fretting wear behavior of alloy 690 tube exposed to an environment simulating the secondary side water chemistry of nuclear power plant are studied and the fretting wear process is discussed. The results indicate that with the increase of sliding amplitude and normal load, the wear volume of the alloy 690 tube is increasing, however, the wear coefficient firstly decreases then becomes relatively constant. This is because that the wear mode of the materials is changed from abrasive wear to delamination wear with the increase of sliding amplitude and normal load. The synergic effects of corrosion and mechanical wear on fretting wear behavior of the alloy 690 tube are also discussed and a model is proposed to qualitatively reveal the fretting wear process of the alloy 690 tube. [ABSTRACT FROM AUTHOR]

Fretting experiments of Alloy 690TT tubes against 405 stainless steel (405 SS) plates were carried out to evaluate the influence of temperature on fretting performance of Alloy 690TT tubes in air. The results indicated that an adhesive and smooth protective third body layer was generated on Alloy 690TT tubes above a certain temperature, between 150 ℃ and 200 ℃ for given conditions. The protective layer was a mixture of oxides and transferred 405 SS, which was directly associated with fretting conditions. Thus, a wear transition map of Alloy 690TT was established. Besides, the results of this work also revealed that the plastic deformation of 285 ℃ was slighter than that of 150 ℃. • An adhesive and smooth protective third body layer was generated on Alloy 690TT tubes above a certain temperature. • A wear transition map of Alloy 690TT was established and discussed. • The frictional-induced temperature has a significantly influence on the formation of protective layer. [ABSTRACT FROM AUTHOR]

Multi-strand, copper conductors in submarine power cables (SPCs) for offshore wind are susceptible to fretting wear and fatigue, due to multiplicity and complexity of contacts, subjected to potentially severe dynamic loading. This paper presents (i) a global-local methodology for coupled hydro-aero-elastic dynamic loading of a representative SPC for identification of local inter-wire fretting-related conditions, (ii) fretting wear characterisation of copper conductor material, and (iii) local fretting multiaxial wear-fatigue finite element models for fretting fatigue life assessment of SPC copper conductor contacts. Predicted fretting fatigue lives are shown to be consistent with previously published bending fatigue test data on SPC copper conductors. Fretting fatigue life is shown to be significantly affected by aero-hydrodynamic loading, wear, slip regime and wire diameter. [ABSTRACT FROM AUTHOR]

The molecular dynamics method was used to simulate the micro-motion friction process of nickel-based single-crystal alloy. With the repeated friction processes increases, the peak friction force gradually increases, the friction coefficient changes more drastically, the transmission of atomic displacement gradually changes from having discontinuity to having continuity, the increment of abrasion depth gradually decreases, the dislocation entanglement is more likely to appear near the two-phase interface, and the friction hardening effect is weakened when the position of the grinding ball is closer to the two-phase interface. The transfer of temperature is relatively linear, which is different from the effect of the amorphous interface layer. Under constant load, the faster the friction speed, the smaller the wear of the workpiece. [ABSTRACT FROM AUTHOR]

Loosening tests of bolted joints are carried out under various preloads and excitation amplitudes. Three coatings are utilized to treat bolts, and their effects on the anti-loosening performance are studied. For the MoS 2 coated bolt, a reasonable preload is calculated, and its anti-loosening performance is also examined. It is found that the anti-loosening performance of MoS 2 coating on bolt is better than that of the other two coatings. Under the same equivalent stress as that of the uncoated bolt at the thread root, both the preload and the anti-loosening performance of the MoS 2 coated bolt are significantly greater. Additionally, a FE model is created to simulate the bolted joint, and very good agreement is found between numerical and experimental results. [ABSTRACT FROM AUTHOR]

We present fretting wear analysis of a dry Ti-6Al-4V cylinder/plane contact, investigating sliding frequency, contact size, and cyclic normal force effects. The investigation showed that easy contact oxygenation promoted by low contact pressure, low frequency, small contact size and varying normal force favored a U-shape fretting scar morphology and high abrasive wear rates. By contrast, increasing contact pressure, frequency and contact size by reducing the contact oxygenation in the center of the contact promoted adhesive metal/metal interactions, transfers and TTS structures. This induced a W-shape fretting scar and lower wear rates. XPS analyses confirmed this description, highlighting Ti-nitriding processes in the under-oxygenated Ti transfers. A friction energy power density approach is introduced to predict wear rate and the U-to-W shape transition. [ABSTRACT FROM AUTHOR]

A finite-element-based wear modelling methodology and a computational device for decoupling wear effects is presented in this study. The decoupling of wear effects facilitates the capture of plasticity accumulation on a particular wear-scarring profile after a specific number of cycles. It was determined that significant plasticity accumulation due to plastic shakedown was predicted in a partial-slip case, while a saturation of plastic deformation was predicted in a gross-sliding case. It was also predicted that a significant amount of plasticity does not meaningfully contribute to the stress and strain range observed in the contact region. It was assumed that plasticity accumulation contributes towards wear of the material and feeds the stress changes, which indirectly affects fatigue life. [ABSTRACT FROM AUTHOR]

The influence of grain size on degradation of electrical contacts during fretting wear was investigated. Copper polycrystals with grain sizes of 2–162 µm were used to examine friction, wear, and electrical contact resistance. The results showed that the electrical contact failure was caused by the compact oxide layer produced at the contact junction. Copper specimens with smaller grains had a longer lifecycle because of grain-size strengthening. However, this strengthening effect was limited to a critical grain size and, with further increase in grain size, plastic deformation underneath the contact surface played a major role in delaying the contact failure caused by oxide formation on the fretting surface. [ABSTRACT FROM AUTHOR]

Fretting occurs when two loaded contacting surfaces are exposed to oscillatory relative movement of small amplitude. Depending on conditions such as surface finishing, coefficient of friction, normal load and slip amplitude, fretting may reduce the service life of a component by fretting wear. The effect of surface roughness on the fretting wear profile is still uncertain and may be significant. However, most of the finite element (FE) models that are used to predict fretting wear do not take it into consideration. In this paper, we propose a multiscale procedure to study roughness effect on fretting wear using FE models. In order to do that, we treat the problem in two scales: a) micro scale to analyse the effect of roughness on the contact pressure for frictionless conditions, and b) macro scale to estimate the wear profile evolution for a cylinder on plane contact configuration. [ABSTRACT FROM AUTHOR]

Fretting can lead to surface wear and/or crack nucleation depending on the sliding condition and contact geometry. To formalize this aspect, Ti-6Al-4V cylinder/plane and punch/plane contacts were investigated. The experimental crack nucleation domains in partial and gross slip conditions were established and simulated combining SWT cumulative damage analysis with FEM surface wear simulations. Good correlations were achieved if the experimental boundary conditions including system tangential accommodation and micro-rotations measured using DIC analysis, were considered. Fretting maps were simulated by predicting partial slip and gross slip displacement amplitudes above which cracks were respectively nucleated and removed by surface wear. Finally, it was shown that whatever the contact geometry, the gross slip cracking domain was inversely proportional to the surface wear rate. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental and computational methodology for fretting wear-fatigue prediction of pressure armour wire in flexible marine risers. Fretting wear, friction and fatigue parameters of pressure armour material have been characterised experimentally. A combined fretting wear-fatigue finite element model has been developed using an adaptive meshing technique and the effect of bending-induced tangential slip has been characterised. It has been shown that a surface damage parameter combined with a multiaxial fatigue parameter can accurately predict the beneficial effect of fretting wear on fatigue predictions. This provides a computationally efficient design tool for fretting in the pressure armour layer of flexible marine risers. [ABSTRACT FROM AUTHOR]

Fretting wear is a material damage in contact surfaces due to micro relative displacement between two bodies. It causes some unexpected results, such as loosening of fasteners or sticking in components supposed to move relative to each other. Since this micro motion of fretting wear is difficult to measure in experiments, finite element method (FEM) is widely used for investigating the evolution of contact variables and wear scars during fretting wear process. In most FEM simulations of fretting wear, coefficient of friction (CoF) is assumed to be constant in order to simplify the models. As measured in experiments, however, the evolution of CoF has a relation with the wear number of cycles, especially during the running-in stage. In this research, the effects of variable CoF are considered in both gross sliding and partial slip conditions of fretting wear. The wear scar and wear volume predicted by FEM models for constant and variable CoF cases are calculated. Results indicate that, in gross sliding condition, whether or not using a variable CoF has little effect on wear volume at the end of the steady state stage of fretting wear cycles. However, when considering partial slip or running-in stage of gross sliding conditions, FE models with variable CoF achieve predictions that are closer to experimental results. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the impact fretting wear behavior of thin-walled tubes under different support interfaces with a novel impact wear testing rig. A tube/cylindrical contact model was used, and V-shaped fixtures with varied angles were applied. The 304 stainless steel tubes with varied lengths and a GCr15 bearing steel roller were used as the test materials. The interface deformation, impact energy absorption, and damage behavior were investigated in terms of the influence of the support angle, tube length, and the initial impact energy. After the test, the wear mechanism of the tube was investigated. The results showed that under the same lengths, when the support angle increased, the deformation displacement increased, but the contact peak force, energy absorption, and the area of worn scars decreased. The increasing length increased the contact force, energy absorption ratio, and serious damage but reduced the deformation. The increasing kinetic energy of the initial impact will decrease the energy absorption ratio. Contact fatigue spalling and oxidation are the wear mechanisms of the impact fretting wear of 304 stainless steel. [ABSTRACT FROM AUTHOR]

Fretting maps of Zr alloy tube under grid-to-rod configuration in high temperature pressurised water were established. Running condition fretting map shows three fretting regimes, namely, partial slip regime, mixed fretting regime and gross slip regime. According to material response fretting map, the wear mechanism under partial slip regime is adhesive wear with the character of delamination of local regions, both adhesive wear and cracking are found for mixed fretting regime, while abrasive wear and severe delamination for gross slip regime. Compared with the results at room temperature, the mixed fretting regime range increases obviously at high temperature, while friction coefficient at high temperature is lower. In addition, fretting wear behaviour of Zr alloy tube under different fretting regimes is discussed. [Display omitted] • RCFM and MRFM of Zr alloy cladding tube in HTP water was established. • Compared with RT condition, the range of MFR increases obviously in HTP water. • The main wear mechanism under PSR and MFR is adhesive wear. • The main wear mechanisms under GSR are abrasive wear and delamination. [ABSTRACT FROM AUTHOR]