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Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents. Traditionally, it is believed that both high strength and excellent ductility can reduce fretting wear damage. However, whether strength and ductility are contradictory or not and their appropriate matching strategy under the external applied normal stress (Fw) are still confusing problems. Here, by analyzing the subsurface-microstructure deformation mechanism of several samples containing various α precipitate features, for the first time, we design strategies to improve fretting damage resistance under different matching relation between Fw and the tensile strength of materials (Rm). It is found that when Fw is greater than Rm or Fw is nearly equivalent to Rm, the deformation mechanism mainly manifests as serious grain fragmentation of β and αGB constituents. Homogeneous deformation in large areas only reduces damage to a limited extent. It is crucial to improve the strength to resist cracking and wear, but it is of little significance to improve the ductility. However, when Fw is far less than Rm, coordinated deformation ability reflected by ductility plays a more important role. The deformation mechanism mainly manifests as localized deformation of β and αGB constituents (kinking induced by twinning and spheroidizing). A unique composite structure of nano-grained/lamellar layer and localized deformation transition layer reduces fretting damage by five times compared with a single nano-grained layer. Only when the strength is great enough, improving the plasticity can reduce wear. This study can provide a principle for designing fretting damage resistant alloys. [ABSTRACT FROM AUTHOR]

The influence of electric current pulses passing between parts during fretting wear of titanium alloys is examined. A description of the test bench and a description of the test methodology are given. [ABSTRACT FROM AUTHOR]

This study investigates the capability of WC/C coatings to protect bearing bores against fretting wear when there is a lack of lubrication, a typical failure mechanism in bearings subjected to vibrations. Linear pin-on-disc and rotary oscillating block-on-ring tribological tests were carried out reproducing fretting conditions to evaluate the tribological performance and fretting resistance of the developed WC/C coating in comparison with those of the two common coatings currently employed to prevent this type of bearing failure, i.e. thin-dense chrome and fluoropolymer coatings. The friction forces generated under fretting conditions were evaluated, and a deep surface analysis of the tribosystems was carried out through different microscopic techniques in order to identify the wear mechanisms prevailing in each coating. Results suggested that WC/C coatings could be promising candidates to mitigate fretting damage, as they combine a low friction coefficient with good wear resistance. Furthermore, WC/C coatings constitute a more sustainable solution compared to the currently employed PTFE and chrome-based coatings, paving the way to a greener society. [ABSTRACT FROM AUTHOR]

This study investigates the fretting wear resistance of Inconel 718 fabricated by laser-powder bed fusion (L-PBF) based additive manufacturing (AM) process. A set of the L-PBF processed coupons were subjected to homogenization followed by double aging heat treatment cycles to achieve hardness comparable to wrought material. Material characterization using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction techniques revealed a fine grained and textured microstructure in AM as-built samples. Point contact (ball-on-flat) fretting wear tests conducted under ambient conditions showed that AM as-built samples had the least wear resistance with a wear coefficient of 15.64 × 10−9 MPa−1 and a higher average coefficient of friction (COF) of 0.75. The wear resistance of the AM samples was found to be improved after heat treatment with the reduced wear coefficient of 10.35 × 10−9 MPa−1 and COF ranged between 0.60 and 0.70. The fretting loops, COF plots and SEM analysis on worn surfaces show that when the applied normal load is low (1N), the operating regime is gross slip regime and the corresponding wear damage is abrasion for all samples. When the load increases to high level (3N), a combined wear mechanism of delamination, adhesion and abrasive wear operating under partial slip regime is predominant with a considerable amount of subsurface cracking. The effect of heat treatment is seen as beneficial in terms of reduction in wear, COF and sub-surface crack which is attributed to improved hardness. [ABSTRACT FROM AUTHOR]

A systematic experimental investigation concerning the fretting-induced tribo-chemical state and its effect on the fretting wear behavior of titanium alloys under the vacuum atmospheres (4 × 10–3 Pa and 4 × 10–1 Pa) in different fretting regimes is reported. An in situ XPS analysis tester was developed to capture the real tribo-chemical state of worn surface for all test conditions. Results show that samples subjected to different vacuum atmospheres have varied tribo-chemical states depending on the fretting regime, which play significantly different roles in determining the associated damage mechanisms and the resulting fretting wear resistance. Under both vacuum atmospheres, in the partial slip regime (PSR) the worn scars were mainly covered by TiO2, showing comparable levels of very slight damage, while in the mixed fretting regime (MFR), the tribo-layer is still mainly consisted of TiO2, but with an evident peak of Ti metal for the high vacuum degree (4 × 10–3 Pa) in MFR, showing a mild damage. In contrast, in the gross slip regime (GSR), Ti metal was prone to be oxidized to Ti2O3 and TiO on the worn scar, especially for the low vacuum degree (4 × 10–1 Pa) having a highest content of Ti2O3. It might be inferred that the tribo-layer containing more Ti2O3 formed during fretting wear process is susceptible to be broken, hence showing a highest fretting wear volume in GSR for the low vacuum degree. The results suggest that for the vacuum environments, the Ti6Al4V may be more suitable to be used under the high vacuum atmosphere. [ABSTRACT FROM AUTHOR]

In order to systematically study the effect of different modulation periods on the friction and wear behavior of nickel-based single-crystal superalloy materials during micromotion wear, molecular dynamics methods were used to establish models of nickel-based single-crystal alloys with different modulation periods. The atomic displacement, wear marks, surface morphology, temperature, stress, dislocations, and dislocation density during the friction process were studied. The study found that as the modulation period decreases, the atomic displacements on the surface and subsurface of the workpiece increase, the wear track depth decreases, the debris is more prone to accumulate on both sides of the abrasive ball, the surface roughness of the wear track region increases. In contrast, the surface roughness of the unworked region decreases. The temperature of the workpiece increases, and the stress values of the system become higher. Moreover, the number of defects and dislocation density in the subsurface of the workpiece are higher. This article has important significance and reference value for determining the suitable working environment and accurately predicting the life of nickel-based single crystal superalloy materials. [ABSTRACT FROM AUTHOR]

The formation of tribolayers may play significant influences on fretting wear. At elevated temperature, the adhesion among wear debris and the increased diffusion rate facilitate the formation of tribolayers. However, the intensification of oxidation at elevated temperature and the low diffusion rate in oxides may play an adverse role. The present study aims to investigate the role of temperature in tribolayers in fretting wear using a γ-TiAl alloy. Scanning electron microscope, energy dispersive spectrometer, Raman spectrometer, transmission electron microscope and nanoindentation were utilized to investigate the wear debris, tribolayers, and wear scars. The fretting tests showed that, compared with that at room temperature (RT) and 350 °C, significant reduction in wear rate and decrease in the fluctuation of friction coefficient occurred at 550 and 750 °C. It was further revealed that when temperature raised from room temperature (RT) to 750 °C, the oxidation of the wear debris increased slightly and the diffusion coefficients increased prominently, which facilities the formation of well tribo-sintered tribolayers. The well tribo-sintered tribolayers presented homogenous structure, nanocrystalline grains with excellent mechanical properties, and resulted in the improvement in the fretting wear resistance of the γ-TiAl alloy at 550 and 750 °C. [ABSTRACT FROM AUTHOR]

Fretting damage on contacting surfaces introduces major challenges in mechanical assemblies. Thermal sprayed hardmetal coatings are extensively used for surface modification in tribological applications under demanding conditions and may also be subjected to fretting-inducing loading. In the present work, the fretting behavior of High Velocity Oxy-Fuel (HVOF) and High Velocity Air–Fuel (HVAF) sprayed WC-10Co-4Cr coatings against quenched and tempered (QT) steel was studied by using a single bolt joint-type fretting experiment. This experimental approach was selected to obtain realistic data on the fretting fatigue performance of the contact pairs (both coating-to-steel and coating-to-coating). Experimental results were completed with continuum-scale linear elastic finite element method (FEM) calculations. [ABSTRACT FROM AUTHOR]

A method is proposed for protecting frictional pairs from fretting wear at high temperatures, without lubricant. In fretting wear of steel frictional pairs, the temperature has the main influence on the wear resistance. A system is developed for fretting wear tests with heating. This system is used to determine the wear resistance of steel samples in a frictional pair on fretting with heating to 200°C. [ABSTRACT FROM AUTHOR]

Compacted graphite cast iron is widely used in the field of diesel engines, and the fretting wear phenomenon of the joint surface will produce fatigue cracks, wear pits, etc., which will affect the life and reliability of the engine. The objective of this study is to investigate the effect of normal load and displacement amplitude on the fretting wear behaviors of compacted graphite cast iron. First, fretting wear behaviors of compacted graphite cast iron are revealed through the running condition fretting map. Under the condition of low normal load and large displacement amplitude, the gross slip region dominates, and the damage mechanism is mainly abrasive wear and plastic deformation. Under the condition of high normal load and small displacement amplitude, the partial slip region dominates, mainly adhesive wear, accompanied by oxidation wear and fatigue wear. Second, the study shows that the friction coefficient after stabilization decreases with the decrease of displacement amplitude and the increase of normal load, and the minimum value is 0.061. Third, the surface profile of wear scar and the wear rate is measured and calculated. Increasing the normal load can effectively reduce the wear rate to 1.88 × 10−3 mm3/N mm. Studying the fretting wear behaviors of compacted graphite cast iron has important theoretical significance for engine fatigue prevention. [ABSTRACT FROM AUTHOR]

Fretting wear phenomena arise when the tube collides with an intermediate support plate (ISP) under flow-induced vibrations and these vibrations can cause severe damage to the heat exchanger tubes. So, it is important to perform wear scar analysis of tubes to understand wear trends that lead to failure. This experimental study deals with scar analysis using a low-speed closed-loop water tunnel for an aluminium tube with a diameter of 12.7 mm. Three different ISP were used alternatively in the centre of the tube bundle. The tubes in the bundle are arranged parallelly in a triangular configuration with a Pitch-to-Diameter (P/D) ratio of 1.45. The experiments have been performed for each support plate thickness against six different time durations with an increment of half an hour and a cross-flow velocity of 0.5 m/s. The triaxial wireless accelerometer was used to measure the vibration response. The analysis revealed that the ISP tends to wear the circumferential length of the tube surface when they interacted for maximum time. When the thickness of the ISP increases, the film thickness between the tube and the baffle hole increases; resulting in a low amplitude of vibration because of the increased damping effect. Wear work rate and wear volume rate analysis indicated that the ISP of smaller thickness caused an earlier tube failure. [ABSTRACT FROM AUTHOR]

In this paper, the friction durability of an anodized aluminum alloy is investigated on relation to the effects of two elaboration parameters: the anodizing time (called the reaction time RT) and the applied current (J). For this purpose, the tribological behavior of the developed oxide layer is characterized using scratch and reciprocating cyclic friction tests under dry and severe conditions. Energy-dispersive x-ray spectroscopy, scanning electron microscopy and surface profilometry were used to correlate between the cyclic response and the worn surfaces and to highlight the impact of RT and J. The anodized layer exhibited an excellent wear resistance at 90 min RT, but its friction durability decreased at 30 min RT. The morphology of the anodized surface influenced the establishment and evolution of the friction-wear layer, which acted as a glass layer for 30 min RT/1A/dm2 (J) and an abrasive third body resource for 90 min RT/1A/dm2 (J) and for 30 min RT/2A/dm2 (J). The variation in the thickness, which affected by the change of the J and RT, has a strong influence on the adhesion strength of the oxide layer. The higher the oxide layer thickness is, the greater the adhesion strength. [ABSTRACT FROM AUTHOR]

A microwave hybrid heating technique has been employed to develop NiCr-Mo-SiC composite cladding on titanium alloy (Grade-5/Ti-6Al-4 V/Titan-31). The developed claddings have been characterized for microstructural features, phase analysis, microhardness measurements, and 3D optical profile parameters by employing scanning electron microscopy, x-ray diffraction, Vickers microhardness tester, and 3D optical profilometer, respectively. Microwave clads have been subjected to linear reciprocator ball on plate wear test with static alumina indenter. Wear track parameters and friction coefficients have been studied. A dense microstructure with uniform distribution of hard phases and good metallurgical bonding with no visible pores and cracks has been obtained. Cladding exhibits nearly 2 times higher hardness than the base alloy. Coefficient of friction studies revealed that higher molybdenum content enhances internal lubricity. [ABSTRACT FROM AUTHOR]

Impact-sliding caused by random vibrations between tubes and supports can affect the operation of heat exchangers. In addition, a corrosive environment can cause damage, accelerating the synergism of corrosion and wear. Therefore, the focus of this work was the impact-sliding fretting tribocorrosion behavior of 316L heat exchanger tubes at different halide concentrations. A device system incorporating the in situ electrochemical measurements of impact-sliding fretting corrosion wear was constructed, and experiments on 316L heat exchanger tubes in sodium chloride (NaCl) solution with different concentrations (0.0, 0.1, 0.5, 1.0, 3.5, and 5.0 wt%) were carried out. The synergism between wear and corrosion was also calculated and analyzed. The wear and damage mechanisms were elucidated by correlating the corrosion-wear synergism, morphologies, and material loss rates. The results indicated that the stable wear stage occurred at approximately 9–12 h, after which the corrosion current increased with the expansion of the wear area. As the halide concentration increased, the scale of damage on the wear scars gradually decreased, changing from being dominated by cracks, delaminations, and grooves to being dominated by scratches, microgrooves, and holes. There was an obvious positive synergism between wear and corrosion. The material loss was dominated by pure mechanical wear and wear enhanced by corrosion, but corrosion enhanced by wear contributed more than tangential sliding fretting corrosion. The total mass loss increased gradually in the range of 0.0–0.5 wt% and decreased in the range of 0.5–5.0 wt%. Large-scale damage enhanced by corrosivity and small-scale damage reduced by lubricity dominated the material loss at low and high concentrations, respectively. [ABSTRACT FROM AUTHOR]

Coupling effects of fretting wear and cyclic stress could result in significant fatigue strength degradation, thus potentially causing unanticipated catastrophic fractures. The underlying mechanism of microstructural evolutions caused by fretting wear is ambiguous, which obstructs the understanding of fretting fatigue issues, and is unable to guarantee the reliability of structures for long-term operation. Here, fretting wear studies were performed to understand the microstructural evolution and oxidation behavior of an α/β titanium alloy up to 108 cycles. Contact surface degradation is mainly caused by surface oxidation and the generation of wear debris during fretting wear within the slip zone. The grain size in the topmost nanostructured layer could be refined to ∼40 nm. The grain refinement process involves the initial grain rotation, the formation of low angle grain boundary (LAGB; 2°–5°), the in-situ increments of the misorientation angle, and the final subdivision, which have been unraveled to feature the evolution in dislocation morphologies from slip lines to tangles and arrays. The formation of hetero microstructures regarding the nonequilibrium high angle grain boundary (HAGB) and dislocation arrays gives rise to more oxygen diffusion pathways in the topmost nanostructured layer, thus resulting in the formation of cracking interface to separate the oxidation zone and the adjoining nanostructured domain driven by tribological fatigue stress. Eventually, it facilitates surface degradation and the formation of catastrophic fractures. [ABSTRACT FROM AUTHOR]

This article investigates the influence of counterpart material on fretting wear of Polylactic Acid (PLA) plates printed by Fused Deposition Modeling (FDM). Fretting tests with three different spherical counterparts (high carbon chromium alloy steel, zirconium oxide, and silicon nitride) were conducted within a gross slip regime. PLA plates were printed with an infill density of 100% and then the surface of the plate was polished for obtaining an arithmetic average surface roughness of 0.1 µm. During a fretting wear test, the evolution of the kinetic friction coefficient was determined. It was identified that the evolutions for high carbon chromium alloy steel (AISI 52100) and zirconium oxide (ZrO2) counterparts increased and then became steady. Meanwhile, the evolution for silicon nitride (Si3N4) remained stable by 2000 fretting cycles. The kinetic friction coefficient for Si3N4 was lower than those found for ZrO2 and AISI52100 counterparts. After 2000 cycles, worn surface profiles were measured and then wear volumes were calculated. The wear volume of PLA against Si3N4 was found to be lower than those against other two counterparts. It was identified that the wear rate of PLA increased with increased the hardness of the counterpart. Obtained results provide useful information on the design of tribo-components subjected to fretting wear. [ABSTRACT FROM AUTHOR]

In pressurized water reactor (PWR), fretting wear is one of the main causes of fuel assembly failure. Moreover, the operation condition of cladding is complex and harsh. A unique fretting damage test equipment was developed and tested to simulate the fretting damage evolution process of cladding in the PWR environment. It can simulate the fretting wear experiment of PWR under different temperatures (maximum temperature is 350 ℃), displacement amplitude, vibration frequency, and normal force. The fretting wear behavior of Zr-4 alloy under different temperature environments was tested. In addition, the evolution of wear scar morphology, profile, and wear volume was studied using an optical microscope (OM), scanning electron microscopy (SEM), and a 3D white light interferometer. Results show that higher water temperature evidently decreased the cladding wear volume, the wear mechanism of Zr-4 cladding changed from abrasive wear to adhesive wear and the formation of an oxide layer on the wear scar reduced the wear volume and maximum wear depth. [ABSTRACT FROM AUTHOR]

Fretting in the partial-slip and gross-slip regimes under a constant normal load is considered. The tangential force—displacement relations for the forward and backward motions are described based the generalized Cattaneo—Mindlin theory of tangential contact and Masing's hypothesis on modelling the force—displacement hysteretic loop. Besides the critical force and displacement parameters (characterizing the triggering of sliding), the model includes one dimensionless fitting parameter that tunes the tangential contact stiffness of the friction—contact interface. Explicit expressions are derived for the main tribological parameters of the fretting loop, including the slip index and the signal index. The presented phenomenological modelling approach has been applied to the analysis of two sets of experimental data taken from the literature. It has been shown that the experimentally observed simple relation of a rational type between the slip index and the slip ratio corresponds to the gross-slip asymptotics of the corresponding model-based predicted relation. The known quantitative criteria for the transition from the partial slip regime to the gross slip regime are expressed in terms of the stiffness parameter, and a novel geometric transition criterion is formulated. [ABSTRACT FROM AUTHOR]

Aluminium and its alloys have a wide range of applications, especially in the automotive sector. Typically, aluminum alloys are utilized in pistons and cylinders of automotive engines. Hence, repeated sliding with low amplitude (fretting) under adverse thermal and mechanical loading conditions dominates the wear of components. In this present work, the effect of solutionizing time on the fretting wear behaviour of Al-Si-Mg-Ni hypoeutectic alloy against alumina ball is investigated under varying normal loads of 5, 10, and 15 N. The fretting wear characteristics in terms of friction coefficient, wear volume and wear scar analyses with the aid of scanning electron microscope and optical profilometry have been systematically conducted. Results showed that with varying solutionizing time, a considerable change in the microstructural aspects of Al-Si-Mg-Ni alloy in the form of Al3Ni and Si precipitation is observed. Moreover, a refinement in the grains is also noticed as the solutionizing time increased from 2 to 10 h. The improved wear resistance is corroborated by the increased hardness arising from the improved intragranular precipitation of Al3Ni and Si. In addition, a reduction in the steady-state coefficient of friction with an increase in the normal load and a concomitant decrease in the wear scar size is also reported. This friction coefficient reduction could be ascribed to the presence of a tribolayer generated between the contacting surfaces for which the formation and coverage are escalated with increasing normal loads. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNT) are of great interest to the research community due to their outstanding mechanical, transport, and optical properties. These nanoparticles have also shown exceptional lubricating capabilities, which coupled with their electrical conductivity show promising results as solid lubricants in electrical contacts. In this study, three different CNT coatings were deposited over copper platelets via electrophoretic deposition and subsequently tribo-electrically characterized including electrical contact resistance evolution during fretting wear, wear protection, chemical analysis of fretting marks, as well as influence of CNT coating thickness, duration and normal load applied during fretting, and atmospheric humidity. Thicker CNT coatings show improved wear protection while retaining similar electrical behavior as uncoated copper, or even improving its electrical contact resistance. Moreover, the compaction of the porous CNT coating is crucial for optimal electrical performance at low humidity. For longer fretting tests (150,000 and 500,000 cycles), the coatings are displaced thus affecting the wear protection offered. However, the coatings stabilize and reduce ECR compared to uncoated samples. Furthermore, thicker CNT coatings can bear higher loads during fretting due to the increased lubricant reservoir, with carbonaceous tribofilm remaining at the contacting interface after 5,000 fretting cycles regardless of normal load. [ABSTRACT FROM AUTHOR]

In the present work, aluminum matrix composite is manufactured layer by layer using ZrO2 as reinforcement through friction stir surface additive manufacturing process. Four holes in AA6063-T4 Al alloy consumable rod (matrix) are filled with ZrO2 reinforcement prior to additive manufacturing. Each layer is deposited at rod plunging speed of 60 mm/min, tool rotational speed of 1500 rpm, and substrate traverse speed of 200 mm/min. Two composites each possessing different percentage of ZrO2 (8% and 12%) revealed finer grains and homogenous distribution of reinforced particles. Composite with 12% ZrO2 showed maximum improvement in microhardness and ultimate tensile strength of 46% and 53%, respectively, than as-deposited rod. Wear resistance of composites was found to improve significantly compared to as-received rod irrespective of the applied normal load. The newly identified solid-state process would be useful over melting-based approaches for fabricating Al-based composites. [ABSTRACT FROM AUTHOR]

The body of an automobile must be lightweight and crash-worthy. The use of advanced high-strength steel reduces the manufacturing cost for automobile body and improves energy absorption during an impact. However, increasing the strength of the steel sheet results in a variety of issues related to tool wear due to a higher forming pressure in the sheets than that in the conventional low-strength steel sheets. Therefore, systematic wear experimentation and evaluation procedure are required to quantify the extent of tool wear during the press forming process. This study aims to develop a methodology for quantifying the wear of a sheet metal forming tool using experimental databases. A progressive die set is designed to conduct the wear test systematically, saving both time and money. The testing machine is capable of testing four different types of punches simultaneously under a variety of tooling and process parameters, such as different tool materials, punch shapes, and coating conditions. The wear depth, roughness, and surface imaging of the tool are all used to establish quantitative evaluation methods for tool wear in the sheet metal forming process. Consequently, we found that punches with small radius of curvature wear rapidly, while tools and coatings with a high hardness have high resistance against wearing. Additionally, by referring to the measured wear database, it is confirmed that analyzing the reasonable tool wear characteristics is appropriate. The proposed testing method can be used to obtain reliable results for quantitatively and qualitatively evaluating the wear lifetime of various tool materials. [ABSTRACT FROM AUTHOR]

With the increasing demand for lightweight and high-strength materials, aluminium alloy composites have shown promising properties for structural applications. This work investigates the fabrication of AA6063/Si3N4 nanocomposites through the friction stir processing (FSP) route. The study evaluates the effect of the volume fraction of Si3N4 on the mechanical properties, fretting wear, and corrosion behaviour of the aluminium composite. The microstructure, distribution of the reinforcement, and phase changes were characterized using field emission scanning electron microscopy images and X-ray diffraction. The results indicate that the FSP route is an effective method for producing AA6063/Si3N4 nanocomposites which exhibit improved mechanical properties and wear resistance compared to the base material. Additionally, the corrosion resistance of the composite was found to be enhanced to that of the base material. In comparison with the base material, a significant improvement of 81% in hardness and 47.2% in tensile strength was observed in the 10% Si3N4 AMC. These findings demonstrate the potential for using FSP to produce high-performance nanocomposites for various industrial applications. [ABSTRACT FROM AUTHOR]

In the present study, Cr3C2-25wt%NiCr, CoCrWC (Stellite-6) and CoCrWC (FSX 414) coatings were deposited by the high-velocity oxy-fuel process on Hastelloy X substrates. The microstructure of the coatings was characterized using field emission scanning electron microscopy. X-ray diffraction was employed to identify the phase composition of the coatings. Tensile bond strength, elastic modulus and Vickers microhardness of the coatings were measured. A self-mated fretting wear test was also carried out on the coatings at room temperature and 550 °C. The results showed that some carbide dissolution occurred during the formation of Cr3C2-NiCr coating, although the coating displayed the highest bonding strength, Vickers microhardness and elastic modulus. The Stellite-6 coating showed a significant amount of unmelted particles and the most surface roughness. Oxide stringers were the main microstructural defect of the FSX 414 coating. The Stellite-6 and Cr3C2-NiCr coating had the best fretting wear resistance at the temperature of 25 and 550 °C, respectively. The wear mechanisms of the hardfacing coatings were discussed in detail. [ABSTRACT FROM AUTHOR]

A hi-rail device is a vehicle designed to travel both on roads and on rails. In this case, a truck was modified to accept the wheels for rail locomotion. The rear wheel/axle set was attached to the truck frame. Both the front and rear wheel/axle sets were raised by means of a hydraulic cylinder driven off the PTO of the truck. The wheel/axle set was rigidly fixed into an up or down position by the use of locking pins. It was assumed by the manufacturer that there would be no load on the cylinder once the wheel/axle set was in its locked position. However, as the cylinder pivoted about its mounting trunnion and extended during its motion, it interfered with a frame member. This caused both a bending load and a rotational movement. These effects caused a combination of fretting, galling, and fatigue to the internal thread structure of the clevis. As a result of these deleterious effects, failure of the thread structure of the clevis occurred. The failure occurred where the cylinder rod screws into the clevis. The rod was manufactured from 1045 steel. [ABSTRACT FROM AUTHOR]

In the present work, the atomic-scale study of grain boundary evolution in the abrasive wear of an Al–Li alloy was conducted. The results showed that abrasive wear was one of the main wear mechanisms of the Al–Li alloy during the fretting tests. After heat treatment, the grains were refined, which led to an increase in grain boundaries. According to the molecular dynamics simulations, the increase in grain boundaries could impede abrasive wear. The migration of grain boundaries was observed during the abrasive wear. Compared with the abrasive particle sliding inside a grain, the abrasive particle sliding across grain boundaries led to more grain boundary migration. The mechanism of grain boundary migration was revealed, which was related to the formation and movement of steps between grain boundaries and grains. The movement of the Shockley partial dislocation 1/6 < 112 > resulted in the occurrence of atomic rearrangement which led to the formation and movement of steps. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) was carried out in AA6063 alloy using the tools with different pin eccentricities (0 and 0.6 mm) under different cooling rates. Results showed that the FSP using a tool with 0.6 mm pin eccentricity enhances the hardness, tensile strength, fretting wear resistance, and corrosion resistance of AA6063 alloy. Moreover, a high cooling rate using a water circulating copper block further enhances the hardness, tensile strength, fretting wear resistance, and corrosion resistance of AA6063 alloy. Pin eccentricity and increasing cooling rate reduce the peak temperature during FSP, thereby preventing grain coarsening, resulting in fine grain structure, enhancing the hardness, tensile strength, fretting wear resistance, and corrosion resistance. The XRD pattern reveals no phase changes due to FSP, but peak broadening occurred in FSP specimens. [ABSTRACT FROM AUTHOR]

The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism. The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage. Based on the two basic principles of surface strengthening and friction reduction, a substrate (AISI 4135 steel) surface was treated by laser quenching (LQ), plasma nitriding (PN), and bonded MoS2 coating. Systematic fretting wear tests were conducted, and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated. The results indicate that the wear resistances of the LQ- and PN-treated surfaces were significantly improved, and their main wear mechanisms were abrasive wear, delamination, and oxidation wear. The MoS2 coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property, but it incurs the highest wear rate and failure in the form of plastic deformation. Furthermore, the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface, consequently resulting in a significant reduction in wear. An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation, which provides a reference for the anti-fretting protection of related mechanical components. [ABSTRACT FROM AUTHOR]

Both wear and fatigue occur in fretting condition, and they interact with one another during the whole process. Fretting fatigue is commonly analysed without considering the effect of wear in partial slip regime, although wear affects the lifetime of crack initiation. This paper investigates, for the first time, the effect of wear debris on fretting fatigue crack initiation. To investigate the effect of debris, first fretting wear characteristics in partial slip regime are analysed for loading conditions. Then, the effect of wear on fretting fatigue crack initiation is investigated using Ruiz parameters and critical plane methods without considering the debris effect. Through the results, we can see that loading conditions affect the wear profiles in different ways. Moreover, wear has a significant effect on the fatigue in partial slip regime without considering debris especially on the crack initiation location. Finally, considering wear debris in the analysis, its effect on critical plane parameters is investigated. It is found that by considering the wear debris effect, the fretting fatigue crack initiation location is shifted towards the trailing edge. The predictions of both crack initiation location and lifetime show a good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In the present study, the effect of thermal oxidation (TO) treatment duration on the fretting wear behavior of Ti6Al4V alloy in Ringer's solution was investigated. The treatment was carried out on Ti6Al4V coupons at 650 °C for different treatment durations of 16 h, 24 h, and 48 h in air. Fretting wear tests were carried out in Ringer's solution on TO-treated and untreated coupons using a ball-on-flat contact configuration with the following test parameters: displacement amplitude of 50 ± 5 μm, a normal load of 0.98 N, frequency of 5 Hz, counter body of alumina ball of 10 mm diameter. TiO2 layer formed due to TO treatment has been found to influence friction coefficient and the fretting wear resistance. TO treatment for 48 h resulted in about 80% reduction in wear rate compared to that of the untreated coupons. [ABSTRACT FROM AUTHOR]

In this paper, the fretting wear and fretting corrosion behaviour of the AA6063 alloys and hybrid AA6063 matrix composite (HAMCs) was studied. The optical microscope and secondary electron microscope were used to characterize the microstructural features of the HAMCs. The composites were subjected to a dry fretting wear test under three different applied loads (5 N, 10 N, and 15 N). In comparison with the base material, the HAMCs demonstrated a significant increase (3.7 times) in specific wear resistance. The dissipation energy was reduced in HAMCs (15.9 × 10−3 J) as compared to the base material (24.2 × 10−3 J). The coefficient of friction and open-circuit potential decreased in the fretting regime in fretting corrosion as compared to dry fretting wear. The HAMCs exhibited higher fretting corrosion resistance as compared to base materials. The predominant wear mechanism of the fretting corrosion was abrasion, cracks, delamination, and corrosion. [ABSTRACT FROM AUTHOR]

Fretting wear caused by flow-induced vibration (FIV) is a leading cause of fuel failure in light water nuclear reactors. This study describes a numerical methodology, validated with dedicated experiments, for predicting flow-induced vibrations in cantilever rods exposed to axial water flow, a paradigmatic configuration informative for fuel rods in water-cooled nuclear reactor cores. Utilising strong two-way fluid–structure interaction (FSI) simulations with an efficient computational approach, the study focuses on two key aspects of self-excited FIV: the dominant vibration frequency and the amplitude of the vibration. Correctly reproducing the former depends on optimising the solid domain and FSI coupling, while the latter hinges on the fluid solver’s ability to accurately replicate unsteady flow behaviour, especially in areas of flow separation. Two unsteady Reynolds averaged Navier–Stokes turbulence models, both being high-Reynolds number versions, and several discretisation schemes for the convection transport are evaluated for their capacity to reproduce the correct unsteady flow behaviour. When the axial flow is directed from the free end to the fixed end of the rod, both the Eddy viscosity model k-ω\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\omega $$\end{document} SST and the Reynolds stress model by Launder, Reece, and Rodi reliably predicted the frequency and amplitude of vibrations for a Reynolds number range between 16.4k and 61.7k. When the flow direction is reversed, while vibration frequencies were accurately modelled, replicating precise unsteady flow behaviour proved more challenging. The study underscores the importance of properly resolving the flow in areas of flow separation to achieve accurate simulation of unsteady flow behaviour. [ABSTRACT FROM AUTHOR]

The paper presents the tasks and study technique dedicated to fretting wear of air foil bearings of cryogenic turbomachines under internal and external vibrations as well as fretting wear test unit for air foil bearings. [ABSTRACT FROM AUTHOR]

This paper examines the effect of dispersant and anti-wear additives on fretting wear in lubricated bearing steel contacts. Reciprocating sliding ball-on-flat fretting tests with a stroke length of 50 μm have been carried out on steel-to-steel contacts in both dry and lubricated conditions. Wear and friction coefficient have been measured, and surface characterisation has been carried out using optical techniques to investigate fretting wear. The presence of base oil reduces fretting wear markedly compared to dry conditions, but fretting damage is still observed at low reciprocation frequencies. As frequency is increased, there is a transition from oxidative to adhesive/scuffing damage. The anti-wear additive ZDDP is effective in forming a tribofilm on the surfaces and reducing visible oxidation and wear. A succinimide dispersant also reduces the accumulation of solid debris but does not alleviate wear damage. The combination of both ZDDP anti-wear additive and dispersant in base oil appears to provide significant protection against fretting wear. [ABSTRACT FROM AUTHOR]

The effect of microstructure on fretting wear behavior of Inconel 625 alloy was studied after different thermal deformation conditions (strain rate and temperature). The results show that grain size and microhardness have a significant influence on the fretting wear. As thermal deformation temperature increases and strain rate decreases, grain size increases and microhardness decreases. The oxide formed on the surface of Inconel 625 helps to reduce wear, but oxidative wear is the main wear mechanism. In the thermal deformation temperature range of 900–1000 °C and strain rate of 0.1–1 s−1, grain size is less than 4.5 μm, and the hardness is greater than 252.9 HV. Under these conditions, the coefficient of friction is the highest and the wear volume is the lowest. This paper proposes to improve the fretting wear resistance of the workpiece by adjusting the strain rate and temperature during the thermal deformation process. [ABSTRACT FROM AUTHOR]

Co-Cr-Mo alloy is an excellent wear-resistant material which is widely used in many industrial fields. Due to external vibrations, fretting wear often occurs at the interfaces of well-matched connectors and induces surface wear, resulting in an accumulation of wear debris on the contact surfaces. This leads to a damage at the interface and the deterioration of matching contact pairs. Excellent wear and corrosion resistance are essential requirements for ideal industrial materials to resist the increasingly harsh working conditions of Co-Cr-Mo alloy, such as elevated temperatures. In this study, the fretting wear resistance of a Co-Cr-Mo alloy was investigated for different test parameters (temperatures, normal loads and displacements) with friction equipment. The fretting wear degree of the alloy was slight at 25 °C, and the wear mechanism at 25 °C was mainly abrasive wear. The analyses showed that elevated temperatures accelerated oxidative adhesion wear due to the formation of an oxide layer inside the interfaces and led to severe adhesive wear. [ABSTRACT FROM AUTHOR]

Fretting wear among steel wires is one of the important factors for the wire rope fracture. The influence of the wire diameter and crossing angle on the fretting fatigue behaviors of steel wires under tensile-torsional coupling force was explored in the present study. The test principles and analysis methods were introduced. Result shows that the variation laws of the coefficient of friction (CoF) between steel wires with increasing crossing angle under different wire diameter contacts are the same. For the same crossing angle, the CoF under different test conditions increases in the following sequence: both with the diameter of 0.8 mm < both with different diameters < both with the diameter of 1.0 mm. According to the hysteresis loops of the frictional force versus displacement amplitude, the contact area between steel wires with larger crossing angle is easier to enter into partial slip state. Moreover, as the crossing angle increases, the relative amount between steel wires increases in the relatively stable phase, and the wear is more drastic. The main wear mechanisms of steel wires with different wire diameters are fatigue wear and adhesive wear, and the worn surface of steel wires shows more obvious abrasive wear with decreasing crossing angle. [ABSTRACT FROM AUTHOR]

The effect of annealing and SiC additions on the process of wear of electrolytic nickel-phosphorus (NiP) coatings under different friction conditions (sliding, fretting and fretting-corrosion) is studied. It is shown that the sliding friction causes much lower wear than the fretting wear and the fretting corrosion. The lowest wear under the friction conditions considered is exhibited by the heat treated NiP coating without SiC additions. [ABSTRACT FROM AUTHOR]

A two-parametric geometry optimization problem for a symmetrical punch with compound curvature in frictionless contact with and an elastic half-plane is considered. An almost constant pressure distribution is sought for by means of least-square method. Another sub-optimal solution, which equalizes the three local maximum peaks (one at the center, and two at either side of the contact interval), is constructed using an asymptotic modeling approach and compared with the exact solution known in the literature. [ABSTRACT FROM AUTHOR]

Fretting wear is a common cause of failure of an electrical contact (EC). In this study, we analyzed in detail the failure of EC induced especially by sliding using the representative electrical terminals. Furthermore, combining the friction energy dissipation theory, we proposed a prediction model to evaluate the electrical connector endurance (ECE) based on the contact stress and geometrical changes during the wear process obtained from a numerical model. The study helps establish that the friction energy dissipation theory is a powerful tool to analyze a contact failure due to wear. The proposed model proves to be effective in predicting the ECE for all considered cases such as micro-slip amplitude, contact force, overturning angle, superficial layer thickness, and friction/wear coefficients. [ABSTRACT FROM AUTHOR]

Fretting wear characteristics of Inconel X-750 were investigated under the dry test condition. Ball-on-flat contact configuration was subjected to the oscillatory movement at different sliding amplitudes through the different time duration and normal loading. Fretting tests were carried out according to the American Society for Testing and Materials standards (ASTM D6425) by the high frequency linear-oscillation wear test rig SRV 4 at room temperature with ∼60 % relative humidity. Worn surface morphologies in the case of stick, partial slip and gross slip regimes were examined by 3D optical profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The aim of this research is to study the tribological characteristics of the Ni-based Inconel X-750 superalloy, which is widely used in the air lubricated gas foil bearing applications where contacting surfaces are subjected to fretting motion. It is found that the displacement amplitude and normal load had strong effect on the fretting mode and damage mechanism. Wear mechanisms were associated with the plastically sheared asperities and crack nucleation and propagation during the stick and partial slip regimes, respectively. As the displacement increased, the wear modes were switched to adhesion, abrasion, debris oxidation, delamination and plastic deformation during the gross slip condition. Fretting time dependence was critical in the higher displacement amplitudes where the wear volume loss progressed significantly. However, test duration was less consistent in the stick and partial slip regimes where the wear properties remains unchanged over time. [ABSTRACT FROM AUTHOR]

The effect of fretting on fatigue performance of different microstructures for titanium alloy was studied using a high-frequency push-pull fatigue testing machine. Both plain and fretting fatigue curves were obtained for comparative analysis of the fretting effect on fatigue performance of the different titanium alloy. The result shows that the strength, plain fatigue of Ti6Al4V titanium is lower than those of Ti1023 titanium. But the fretting fatigue of Ti6Al4V titanium is higher under each contact stress. The fatigue source depth of Ti1023 alloy is greater than Ti6Al4V alloy. Hardening of Ti1023 alloy is more serious after fretting. The wear mechanism of two titanium alloys is different, Ti1023 titanium alloy is more sensitive to fretting wear. [ABSTRACT FROM AUTHOR]

This paper deals with elastic and elastic-plastic fretting problems. The wear gap is taken into account along with the initial contact distance to obtain the Signorini conditions. Both the Signorini conditions and the Coulomb friction laws are written in a compact form. Within the bipotential framework, an augmented Lagrangian method is applied to calculate the contact forces. The Archard wear law is then used to calculate the wear gap at the contact surface. The local fretting problems are solved via the Uzawa algorithm. Numerical examples are performed to show the efficiency and accuracy of the proposed approach. The influence of plasticity has been discussed. [ABSTRACT FROM AUTHOR]

The study focuses on understanding how to govern the fretting wear behaviors under dry lubricated contact to find out the keys to develop new coatings for rubber seal applications. Fretting wear behaviors of acrylonitrile-butadiene rubber (NBR) against steel substrate, diamond-like carbon, and graphene coatings were comparatively investigated under dry conditions. Dynamic analyses were performed in combination with examinations through scanning electron microscopy (SEM), 3D surface profilometry, and X-ray photoelectron spectroscopy (XPS). Experimental results show that, there was significant difference between the fretting running regime for graphene coating and the fretting running regimes for diamond-like carbon (DLC) coating and steel substrate; the mixed fretting regime (MFR) disappeared and the boundary between the partial slip regime (PSR) and the slip regime (SR) shifted to the direction of smaller amplitude displacement in running condition fretting map (RCFM). Moreover, it had excellent anti-friction and wear-resistant performances under fretting condition. However, the fretting running behaviors of the DLC coating are similar to those of the steel substrate, so the DLC coating could not migrate the fretting running regimes effectively. The damage on all the tribopairs in partial slip regime was very slight and the adhesion was the main damage mechanism for the DLC coating and the steel substrate in the MFR and SR. The sticky layers on the worn surface played an important role. For the graphene coating, no obvious damage could be observed on the tribopairs. Therefore, the graphene coating exhibited widely potential applications for alleviating fretting wear. [ABSTRACT FROM AUTHOR]

Abrasive water jet (AWJ) milling has speedily developed in popularity due to its adaptability and fast production of blind features like channels, pockets etc. But the surface property of AWJ-milled samples was found to be poor, restricting the process of being commercially used widely. In this work, a two-step methodology has been tried to modify the surface properties of Ti6Al4V substrate, which includes fast fabrication of miniaturised channel using AWJ technique followed by electrophoretic deposition (EPD) of hydroxyapatite-carbon nanotube (HAp-CNT) coating. The fretting wear test divulges the enhanced wear resistance of synergistically textured Ti6Al4V substrate with EPD HAp-CNT, due to its lower coefficient of friction (0.22 ± 0.0) and wear depth (− 18.1636 μm) when compared with that of textured Ti6Al4V (0.27 ± 0.005 and − 18.8221 μm, respectively). The coefficient of friction and wear depth were observed to be highest for bare Ti6Al4V sample (0.41 ± 0.007 and − 27.4985 μm, respectively). The observed increment in wear resistance is due to the textured channels trapping the wear debris and a decrease in the real contact area due to the coating of HAp-CNT. Thus, fabrication of micro-channels by AWJ combined with HAp-CNT coating may provide potential self-lubrication and enhance damage tolerance of Ti6Al4V alloy for biomedical and manufacturing applications. [ABSTRACT FROM AUTHOR]

Roughness parameters convey important information about the tribological properties of a material subjected to fretting conditions. They significantly affect the fretting life of the material. An experimental study has been conducted to characterize the variations in roughness parameters with respect to fretting wear and clearance in aero-engine spline couplings which are prone to angular misalignment. A dedicated test bench has been used to test spline couplings made of nitrogen hardened 42CrMo4 with crowned teeth. Tests were performed on samples of identical geometry and material under varying conditions of torque and misalignment angle between the hub and shaft of the coupling. Percentage differences in roughness parameters before and after the test have been characterized which showed symmetric variations, but interestingly mirrored in amplitudes for applied torques and misalignment angles. Even non linear variations behaved similarly for the most of the parameters. Both clearance and fretting wear were found to be in a direct relation with torque and misalignment angle. The parameters, namely peak count and mean height of the peaks have been found to be the most characteristic representation of fretting damage. [ABSTRACT FROM AUTHOR]

Heat exchanger tubes are supported at intermediate points by support plates. Flow-induced vibration of tube can cause it to impact or rub against a support plate or against adjacent tubes and can result in tube fretting wear. Fretting wear damage assessment procedure has been presented. This procedure is implemented by studying classical heat exchanger cases of premature failures. The authors expect this study to be useful for estimating the fretting wear damage of heat exchanger tubes. The study shows that based on fretting wear volume rate the life of heat exchanger tube can be predicted. [ABSTRACT FROM AUTHOR]

We consider fretting wear in an adhesive contact due to tangential oscillations of small amplitude. While both wear in non-adhesive contacts and adhesive contacts without wear have been studied in detail, there still have been no attempts to combine both approaches. In the present paper, we study the problem of wear in adhesive contacts under the simplified assumption, that the adhesive (attractive) stress is constant up to some critical distance h and vanishes beyond this range (Dugdale approximation). In this approximation, the normal adhesive contact problem can be solved to a great extent analytically. In a series of previous works, it was shown that the worn shape due to fretting wear tends to some limiting shape which is determined solely by the solution of the normal contact problem. In the present paper, we exploit these ideas to derive the limiting shape of the worn body in an adhesive contact. [ABSTRACT FROM AUTHOR]

Very high cycle bending fatigue behaviors of FV520B steel under fretting wear were studied by the ultrasonic fatigue technique. The specimen system for ultrasonic bending testing was designed and the stress distribution of fatigue specimen was obtained by finite element method. The microstructure of FV520B steel was characterized by means of optical microscope, transmission electron microscope, and energy-dispersive spectroscope. The P–S–N curve was drawn based on fatigue data. The micromorphology characteristics of fretting wear surface and fracture surface for fatigue specimen were observed. The results indicate that the microstructure of FV520B steel is mainly composed of lath martensite, ferrite, and precipitation particles, with some randomly distributed internal inclusions. The P–S–N curve shows that there exists no “conventional fatigue limit” and the fatigue life decreases continuously with the increase of applied stress Smax. Most of fatigue cracks are observed on fractography and initiate from the overlap region of fretting wear zone and stress concentration zone. The fracture failure for tested specimen is ascribed to fretting wear and bending vibration fatigue. [ABSTRACT FROM PUBLISHER]

Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear. [ABSTRACT FROM AUTHOR]