Total Wear Research Articles

Measuring total hip arthroplasty liner wear using the EOS Imaging System: experimental and clinical results.

The low-dose EOS Imaging System is an emerging tool for 3-dimensional measurements in orthopedics. The clinical feasibility for measuring total hip arthroplasty (THA) liner wear has not yet been investigated. We aimed to evaluate the feasibility of using EOS to measure THA liner wear by examining the experimental accuracy using a THA phantom and clinical precision of patients with THA, considering a clinically relevant precision at the 95% repeatability limit to be 0.2 mm. An experimental THA phantom with movable stem and a fixed cup with a plastic liner was constructed to simulate progressive 3D liner wear. Series of 11 pairs of radiographs with 50 μm femoral movement in between were obtained for each 3D axis in EOS. 30 patients with a THA were scanned twice using EOS to assess precision. Model-based radiostereometric analysis (RSA) was used for wear measurement. The mean difference (true minus simulated wear) with standard deviation (SD) and 95% limits of agreement for experimental THA wear were 0.005 (0.037) and [-0.069 to 0.079] mm for the vertical (y) axis. The mean (SD) and 95% repeatability limit for precision for clinical measurement were -0.029 (0.105) and 0.218 mm. Experimental THA liner wear using EOS was within clinically relevant tolerances and without bias. The clinical precision was just outside our defined clinically relevant precision. Compared with conventional RSA, EOS is less accurate and precise but may still be of value for certain clinical applications, provided larger sample size or longer follow-up are available.

Tribocorrosion of couplings in seawater environment: An investigation on the positive-negative role of synergy

Tribocorrosion is a recent paradigm of tribology defined as the combination of simultaneous mechanical and chemical wear of couplings. To date, this phenomenon is common in several engineering fields, such as the naval sector where marine equipment, offshore platforms and so on are clear examples. In this regard, the synergy between the mechanical and the chemical effects has a notable effect on the behavior of couplings in seawater environment. Nevertheless, the latter can act also as antagonistic factor. Hence, in this manuscript, an investigation was conducted on a tribosystem composed of an alumina sphere and a stainless-steel AISI 316 L flat, immersed in an artificial seawater solution of 3.8 % NaCl and a pH of 8.2. The analysis, carried out by a reciprocating tribometer equipped with a two/three-electrode potentiostat, was performed for different loads and frequency values, and their correlation with synergistic effects was investigated. The open-circuit potential, friction coefficient, tribocorrosive current and total wear were evaluated for different tribological conditions. It was found that the force and sliding velocity had a significant position in the synergistic response, passing from positive to negative mainly due to the protective action of oxide layer and lubrication behavior of corrosion products formed during the motion. Moreover, the current was modeled via two analytical laws discussed in literature, providing a good agreement with experimental data. Lastly, was provided the oxide thickness evolution formed on the samples surface and its relationship with total wear.

Effects of excitation parameters on fretting wear and corrosion of 316L stainless steel under random impact-sliding condition

In heat exchanger applications, the random vibration due to fluid excitation can cause mechanical wear between tubes and supports. In corrosive environments, the synergy between wear and corrosion can make wear more severe. Therefore, this paper focused on the effects of excitation amplitude and excitation force ratio (drag force/lift force) on fretting wear and corrosion of 316L stainless steel under random impact-sliding conditions. The results showed that as the excitation parameters increased, the friction coefficient and total wear amount would increase, the open circuit potential (OCP) decreased and the polarization curve self-corrosion potential shifted negatively. All synergistic coefficients in this paper were greater than 1, indicating that there was an obvious positive synergy between wear and corrosion. In the fretting wear and corrosion process, pure wear always played a dominant role. Under impact-sliding conditions, as the excitation force increased, the rate of wear-promoted corrosion increased from 3.0 × 10−7 to 2.0 × 10−6 g/h, an increase of 6.67 times. However, the rate of corrosion-promoted wear decreased from 1.1 × 10−6 to 2.0 × 10−7 g/h, a decrease of 5.5 times, showing a certain self-limiting property. The total synergy rose slowly with the increase of excitation parameters. The wear mechanism of materials under impact is characterized by adhesive wear, while under impact-sliding conditions, the wear mechanism involves abrasive wear and corrosion wear.

A predictive wear model in grinding using single-layer electroplated cBN tools

Wheel wear is a complex phenomenon significantly affecting grinding performance. While microscopic grit observation can detect various wear mechanisms, a predictive model is required to anticipate the total wear behavior under diverse grinding conditions. This study incorporates all wear mechanisms, including pullout, attrition, and fracture, into an analytical model aimed at determining improved grinding conditions. The grinding particles are approximated as standard constitutive geometries to model the wheel surface topography and the grit height reduction obtained from the wheel surface roughness is correlated with wear. The present model introduces an innovative approach to tracking and predicting wheel wear performance, eliminating the need for time-consuming grit micro-observation. Numerous grinding tests employing different tools were conducted, revealing strong agreement between the experimental results and the model predictions. The Application of this approach for predicting prolonged tool life is also demonstrated. Finally, the paper discusses how these findings contribute to a deeper understanding of the fundamental wear mechanisms in the grinding process.

METHODOLOGY AND EXAMPLE OF CALCULATING THE RATIONAL RESOURCE OF AXIAL-PISTON HYDRAULIC MACHINES OF MOBILE EQUIPMENT

The article analyzes approaches for creating models for optimizing the durability of mobile machine units. On the basis of the selected model, in which the target function is the total specific costs of purchasing the machine and the costs of maintaining its working condition, a method of calculating the rational resource of axial-plunger hydraulic machines has been developed for the condition when the resource of the hydraulic machine is limited by the resource of only its plunger pairs. The methodology, built on the basis of the chosen model for optimizing the durability of simple technical systems, takes into account the patterns of wear of plunger pairs under certain operating conditions, and also takes into account the proposed dependencies for calculating their total wear limit. The methodology consists of five consecutive operations, namely: determining the total marginal wear; obtaining experimental patterns of wear of plunger pairs over time in the form of regression equations; calculation of the number and periodicity of technical maintenance of the hydraulic machine for the inter-repair cycle; calculation of the rational resource of the hydraulic machine.The results of the comparative calculation of the rational resource of the adjustable axial-plunger pump 321.224 of the hydraulic system of the single-bucket excavator EO-3323 according to the developed method are also given.The total marginal wear of the pump was determined according to the criterion of reducing its efficiency, namely from the condition of a drop due to the wear of its volume coefficient of useful action by 30 %.To obtain the patterns of wear of the pump's plunger pairs, the results of previous operational tests of the pump were used for two variants of its lubrication: lubrication with ordinary hydraulic oil and lubrication with oil whose anti-wear properties are activated by an external electric field. Specific costs for the purchase of the pump, which are included in the durability optimization model in the form of depreciation deductions, were calculated for the inter-repair cycle. The specific costs of maintaining the working condition of the pump were equal to the costs of its maintenance, during which hydraulic oil and filters are replaced, that is, the pattern of wear of plunger pairs is returned to the starting point.

Can weekend catch-up sleep decrease the risk of cognitive dysfunction in older adults?

This study investigated whether weekend catch-up sleep was related to a decreased risk of cognitive dysfunction in older Taiwanese adults by using self-reported diaries and objective accelerometer measurements. This cross-sectional study enrolled participants who were aged ≥ 65 years and had the capability to walk independently from a medical center in Taipei City, Taiwan, between September 2020 and December 2022. Self-reported sleep diaries and tri-axial accelerometers were used to record and measure sleep-related data for 7 consecutive nights. Weekend catch-up sleep was defined as the mean of weekend sleep time minus the mean of weekdays sleep time. Mini-Mental State Examination (MMSE) was evaluated the risk of cognitive dysfunction. The association between weekend catch-up sleep and the MMSE score was examined using a binary logistic regression model. A total of 215 older adults (53.0% female; 80.5 ± 7.1 years old; 11.6% at risk of cognitive dysfunction) were included. In the adjusted model (adjusted for sex, education level, moderate-to-vigorous physical activity and total accelerometer wear time), both the self-reported sleep diaries (odds ratio [OR] = 0.26, 95% confidence interval [CI] = 0.09-0.69, P = 0.007) and the accelerometer data (OR = 0.27, 95% CI = 0.10-0.70, P = 0.007) indicated that weekend catch-up sleep could decrease the risk of cognitive dysfunction by 73-74%. The study findings suggest that there is an association between weekend catch-up sleep and lower risk for cognitive decline. The causal relationship between weekend catch-up sleep and cognitive function in older adults should be further investigated in a study with longitudinal design.

Characteristics of tire-road wear particles (TRWPs) and road pavement wear particles (RPWPs) generated through a novel tire abrasion simulator based on real road pavement conditions

Microparticles such as tire-road wear particles (TRWPs) and road pavement wear particles (RPWPs) are generated by the friction between tire tread and road surface. TRWPs and RPWPs on roads are dispersed through traffic and transferred to rivers and seas via runoff to accumulate in sediments. However, research on the generation of both TRWP and RPWP has rarely been conducted. In this study, the generation of both TRWP and RPWP was investigated using a novel tire abrasion simulator equipped with paved road and bus tire, and their contributions to the generation of microparticles were examined. Two types of model paved roads, asphalt and concrete pavements (AP and CP, respectively), were applied. TRWPs generated from the simulator exhibited morphologies very similar to those on real roads. The abrasion rate for the CP was 2.8 times higher than that for the AP. The wear particle size distributions peaked at the size ranges of 63–106 μm and 212–500 μm for the AP and CP, respectively. Totals of 84 wt% and 89 wt% of the wear particles were distributed in size ranges of 38–212 μm for the AP and 106–1000 μm for the CP. The tire wear particle (TWP) contents in the total wear particles of 38–500 μm were 21.7 wt% and 30.0 wt% for the AP and CP, respectively, and decreased as the particle size decreased. The weight of RPWP was higher than that of TWP in TRWP. Contributions from road pavement to the generation of wear particles of 38–500 μm were 3.6 and 2.3 times higher than those from tire tread for the AP and CP, respectively, and the contribution increased as the wear particle size decreased.

Friction, wear, and anti-scuffing behaviors of zinc phosphate film on cylinder liners

Zinc phosphate chemical conversion coating possesses excellent tribological properties, which has attracted increasing attention. In this work, the friction, wear and anti-scuffing performance of zinc phosphate film applied on the cylinder liners were studied using a self-designed friction and wear experimental apparatus, which can sufficiently simulate the working conditions of the piston ring and cylinder in a real engine. The experimental results indicate that comparing with the uncoated cylinder liner, the friction force and total wear losses of friction pairs for the zinc phosphate coating are reduced by 8% and 27.5%, respectively, which is attributed to the formation of the protective film containing metal oxides and iron phosphate. In the scuffing test, uncoated cylinder liner exhibits better anti-scuffing performance because of the spalling of the cast iron graphite. On the contrary, the zinc phosphate coating particles remaining on the worn surface after oil-cut off are peeled off and acted as the abrasive at the contact interface, which accelerates the plastic deformation of friction pairs and the cast iron graphite is covered by the plastic flow of the material.

A within-subject examination of grandparents’ physical activity and sedentary behavior levels in the presence or absence of grandchild care provision

BackgroundThis study aimed to examine within-subject differences in levels of physical activity (PA) and sedentary behavior (SB) among Flemish grandparents aged 50 years and older during a day of providing versus not providing grandchild care. Additionally, grandparents’ PA and SB levels of the specific caregiving moment within the included care day were also compared with those of the corresponding specific time frame on the matching non-care day.MethodsData were obtained and pooled from three assessment time points of the Healthy Grandparenting Project. Objectively measured PA and SB levels were assessed through ActiGraphs wGT3x(+) worn during waking hours for seven consecutive days and expressed relative to the total wear time of the selected days or moments (i.e., percentage of time per day or per moment). Generalized linear mixed models were used to evaluate the within-subject differences in grandparents’ light intensity PA (LIPA), moderate-to-vigorous intensity PA (MVPA) and SB levels between a care and non-care day as well as between the care and non-care moment of those respective days.ResultsA total of 92 grandparents (64.6 ± 4.8 years, 67.4% women) were included in the analyses. During the care day and care moment, grandparents showed higher relative levels of LIPA (∆=4.0% and ∆=7.9%, respectively) and lower relative levels of SB (∆=3.7% and ∆=6.7%, respectively) as compared to their respective non-care day and non-care moment (all p < 0.001). While there was no significant difference in relative MVPA levels between a day of providing versus not providing grandchild care (∆=0.3%, p = 0.500), the grandparents showed significantly lower relative levels of MVPA during the specific care moment against the non-care moment (∆=1.3%, p = 0.029).ConclusionsThe higher percentage of time of LIPA and lower percentage of time spent on SB during a care day and care moment compared to a non-care day and non-care moment, highlight the positive impact of grandchild care provision on grandparents’ activity levels, potentially improving other health-related outcomes. Furthermore, grandparents seem to compensate for their lower MVPA levels during the actual care moment since no differences in MVPA levels were found at day level when compared to a day without grandchild care.Trial registrationclinicaltrials.gov, Identifier: NTC04307589. Registered March 2020.

Fretting wear behaviour of high strength alloy steel induced by plasma nitriding and post-oxidation

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.

Comparative studies on microstructural characteristics and wear behavior of high-speed and low-speed laser cladding graphene/CoCrFeMo0.5NiTi0.5 high-entropy alloy composite layers

To prevent the failure of curved parts due to wear under actual working conditions, a graphene/CoCrFeMo0.5NiTi0.5 high-entropy alloy composite coating was prepared on the surface of a curved part using both high-speed and low-speed laser cladding (LLC). The surface morphology, physical phases, elemental distribution, microstructure, microhardness, and wear behavior of this coating applied via high-speed and LLC were comparatively studied. The results showed that the maximum height difference on the surface of the high-speed laser cladding (HLC) layer was only 44.7 % of that of the LLC layer, and the surface powder was more completely melted. The average microhardness of the HLC layer was about 1.49 times higher than that of the LLC layer and showed a maximum hardness of 666.38 HV0.5, which was about 2.95 times higher than that of the substrate. The internal microstructure of the HLC layer was finer and the diffusion of Fe atoms from the substrate into the coating was significantly reduced. In all three wear environments, abrasive wear occurred in both the low-speed and HLC layers. The total wear rate of the LLC layer was 230.588 μm3 N−1 mm−1, which was about 3.06 times higher than that of the HLC layer (75.395 μm3 N−1 mm−1). The wear surfaces of both cladding layers were oxidized, and the wear rate increased with the oxygen content on the wear surfaces under the same wear conditions. Meanwhile, the oxygen content of the wear surfaces of both cladding layers in sodium chloride solution was significantly higher than that during dry wear.

Total Ankle Arthroplasty Polyethylene Wear Varies with Implant Type and Mode of Failure

Introduction/Purpose: Polyethylene wear is a concern for failure of any joint replacement, including total ankle arthroplasty (TAA). Heterogeneity in bearing surface design among current TAA systems show no clear solution to the competing objectives of function (constraint and kinematics) and wear (contact stresses). Literature has begun to investigate polyethylene wear and damage; however, a comprehensive understanding of polyethylene wear patterns in vivo and location remains unknown. This study aims to quantify the type and severity of differing damage modes on the polyethylene insert from retrieved TAA prostheses following reoperation or revision. We hypothesized that polyethylene wear amount will be greater in TAAs that underwent revisions rather than reoperation, and that wear would vary between implants based on extent of constraint. Methods: This is a retrospective study of TAA patients (2007-2021) who underwent revision (removal of polyethylene and tibial and/or talar components) or reoperation (removal of polyethylene only) following primary TAA with a symmetric bicondylar (SB) implant with more constraint or an asymmetric bicondylar (AB) implant with less constraint. Demographics and surgical data were recorded. Retrieved polyethylene inserts were examined microscopically to characterize wear patterns according to a standardized protocol. Polyethylenes were divided into four regions on both the articular and backside surfaces: 1) lateral anterior, 2) lateral posterior, 3) medial anterior, and 4) medial posterior. Each region was graded by two independent raters on a scale of 0-3 based on severity for each of the following damage modes: 1) burnishing, 2) pitting, 3) scratching, 4) third body debris, 5) abrasion, 6) surface deformation, and 7) delamination. We assessed associations between polyethylene wear pattern and severity with implant type, revision, and reoperation. Results: 55 TAAs underwent revision (n=28) or reoperation (n=27). 30 (55%) ankles had primary TAA with AB implants (Salto Talaris) and 25 (45%) with SB implants (Inbone/Infinity) (Table 1). SB cohort had a shorter mean in-body duration (time from polyethylene implant to polyethylene explant) versus AB cohort (P=0.011). SB cohort had significantly greater overall polyethylene damage severity (P=0.007) and greater damage severity in all articular regions versus AB (P≤0.035 for all). Burnishing was significantly greater in SB versus AB (P &lt; 0.001). TAAs that underwent revision had significantly greater overall damage severity versus reoperation (P=0.005), with significantly greater damage severity on articular medial posterior (P=0.003), lateral anterior (P=0.001), and lateral posterior (P=0.004) regions. Scratching (P=0.005), pitting (P &lt; 0.001), and third body debris (P=0.036) were significantly greater in revision TAAs. Conclusion: While damage modes between SB and AB total ankle implants were similar, ankles with primary SB implants exhibited greater overall polyethylene damage severity in comparison to AB implants, despite being in-body for a shorter duration. In accordance with existing literature for total knee arthroplasty, this may suggest increased polyethylene damage severity with increased constraint. Irrespective of time in-body, failure for revision was associated with greater polyethylene damage than reoperation. This study provides the foundation for additional analyses to investigate radiographic alignment, mode of failure, and, ultimately, the association between polyethylene wear, peri-implant cysts and lucency, and TAA failure. Table 1 Patient demographics, revision, reoperation, and polyethylene in-body duration for the two patient cohorts: Patients with primary TAA with a symmetric bicondylar (SB) implant with more constraint and patients with primary TAA with an asymmetric bicondylar (AB) implant with less constraint. Values are expressed as means ± standard deviation for continuous variables, and frequencies with percentages for categorical variables. P-values reflect chi-square analyses and t tests between the two cohorts for categorical variables and continuous variables, respectively. SB cohort had significantly lower percentage of females, higher body weight, and shorter in-body duration. There was no significant difference in reoperations and revisions between the two groups.

Novel in-situ real-time line scan optical monitoring of wear and surface damage initiation in a laboratory twin disc test

A new optical monitoring system has been developed to photograph in-situ in real time the initiation of damage on the running surface of a rail steel twin-disc sample undergoing wear testing. The line-scan camera system has been demonstrated on the Sheffield University ROlling Sliding 2 (SUROS2) twin-disc machine. The results show the system can continuously track the development of wear flakes, with wear flake initiation and stabilisation of wear flake size observed without test interruption for the first time. Image analysis to quantify the total wear flake shadow pixel count showed a good correlation with the mass loss results, indicating the potential for the optical data to quantify rail steel wear without interruption to testing. Furthermore, in a water-lubricated test the new system enables observation of rolling contact fatigue (RCF) crack initiation through a water layer present on the specimens, without requiring test interruption. The improving knowledge of the wear and RCF performance of rail steels available from the new observation method can help improve understanding of steel performance and support to the selection of rail steel grades according to their performance.

Feasibility, functionality, and user experience with wearable technologies for acute exacerbation monitoring in patients with severe COPD

Background: The increasing interest in remote patient monitoring technologies in patients with chronic obstructive pulmonary disease (COPD) requires a phased and stepwise investigative approach, which includes high-risk clinical subgroups who stand to benefit most from such innovations.Methods: Patients aged &amp;gt; 40 with spirometry-confirmed COPD presenting with a current acute exacerbation (ECOPD) were recruited from a tertiary centre Day Hospital in this prespecified feasibility study. Heart rate, respiratory rate, oxygen saturation, skin temperature, and daily activity and overnight sleep quality parameters were collected remotely by a wearable biometric wristband and ring for 21 consecutive days. “Total ambulatory wear time” and “percent of useable data” for eligible vital sign parameters were calculated. Correlation and agreement between cardiorespiratory vital sign data were performed using Spearman’s correlation rho and the Bland-Altman test, respectively. User experience was measured with end-of-study System Usability Scale (SUS) questionnaires.Results: Nine participants (mean age 66.8 ± 8.4 years, 22% female, mean FEV1 1.4L (34.1% predicted), with “severe” (56%) or “very severe” (44%) COPD) experiencing a current ECOPD were included. Wear time was 94% (wristband) and 88.2% (ring) of the total ambulatory study period. Wristband-obtained data (every 1 min, artefact-free) revealed 99.2% and 98.6% of all heart rate and temperature data, respectively, was useable, whereas only 17.6% of all respiratory rate data was useable. Ring-obtained data (every 5 min, “average” and “good” quality) revealed 84.5% of all heart rate data was useable. Cross-sectional analyses with nurse-obtained vital signs revealed correlation coefficients of 0.56 (p = 0.11) and 0.81 (p = 0.0086) for wristband-obtained and ring-obtained heart rate, respectively, and only 0.15 (p = 0.74) for wristband-obtained respiratory rate, without evidence of systematic/proportional bias. Longitudinal heart rate and respiratory rate inter-device analyses demonstrated correlations of 0.86 (p &amp;lt; 0.001) and 0.65 (p &amp;lt; 0.001), respectively. Finally, end-of-study SUS scores were 86.4/100 (wristband) and 89.2/100 (ring).Conclusion: Older adults with severe/very severe COPD experiencing a current ECOPD were capable of autonomous physiological data collection/upload/transmission from their home environment over several weeks using sophisticated wearable biometric technology, with favourable user experiences. Cross-sectional and longitudinal comparative results call into question the paradigm of single sets of infrequent/interval vital sign checks as the current “gold-standard” in frontline clinical practice.

Прогнозирование и оценка триботехнической эффективности азотированного слоя деталей машин

Following the laws of tribology and tribotechnics, also the results of experimental studies of reality of structure and properties change in the zone of contact tribodeformation of structural steels and alloys of different structural classes subjected to nitriding, an approach to forecasting and comprehensive assessment of the tribotechnical efficiency of nitriding of structural materials and products made of them has been developed. Analysis of the patterns of changes in the structure of the diffusion zone of nitriding steels: abnormal, martensitic and austenic, and relative wear resistance tests, taking into account their composition and technological parameters of the treatment process, showed that maximum wear resistance was provided by a nitration coating containing hardening dispersed particles of incoherent nitrides, ensuring a lower liability to brittle behavior of the nitration case due to low level of matrix level microdeformation. At the same time, preliminary types of treatment (thermal treating and deformation processing) of nitriding steels contribute to structural and phase state of the surface layer, which has added tribological performance. For nitrided ferroalloys with different matrix lattices, the most significant characteristics of the structural state and properties of the surface layers affecting the level of surface fracture under friction have been found empirically: the particle size of nitrides of alloying elements, the distance between them, the density of their distribution, the matrix lattice microdeformation, the values of X-ray lines intrinsic broadening for structural components of the material in the friction deformation zone, the hardness of the nitration case and its changes under friction. These experimental results are taken as a principle of the proposed method for forecasting and assessment of metal tribotechnical efficiency. This principle of method is based on a tribological criterion containing micro- and macroscopic characteristics of the material in the zone of contact deformation under friction, the choice of fabricating methods for the product takes place to ensure an acceptable level of wear intensity. Then, by measurement, using surface large deformation method, the ability of the nitration case formed as a result of treatment according to the selected treatment schedule to perceive surface nondestructive plastic deformation is evaluated. It affords a basis for the selected nitriding treatment schedule. The completion of the assessment is the determination of the values of the maximum operability of the nitriding material under conditions of friction and wear (alarm pressure when a tribocouple operates steadily; critical pressure when it is inoperable, but its operation is possible with short-term overloads; the average total wear intensity of the couple combined). The totality of the identified parameters allows recommending the material, its working and predicting operating modes and durability of tribounit.

Study of the Tribological Properties of Modified Potassium Titanate Whisker-Reinforced Resin-Based Friction Composites

The surface modifications of reinforcing components have significant influence on the tribological performance of resin-based friction composites. In this work, 3-aminopropyltriethoxysilane coupling agent (KH550) and octadecyltrichlorosilane (OTS) were used to modify nanosized potassium titanate whiskers (PTW). Subsequently, the modified potassium titanate whiskers were used as reinforcing components in phenolic resin-based friction composites. The tribological behavior and wear mechanism of the composites were studied. The results show that the surface free energy of 5% OTS-modified potassium titanate whiskers is the closest to that of the resin matrix, which is 26.4 mJ/m2. Moreover, the OTS-modified PTW-reinforced composites possess a more stable friction coefficient and a lower wear rate at high temperature. The OTS-modified PTW-reinforced composite (O-C) has a 19% lower total wear rate than the unmodified PTW-reinforced composite (P-C). That is mainly because the modified potassium titanate whisker is more evenly distributed in the resin matrix and tightly bonded to the resin. Results demonstrate that OTS-modified PTW-reinforced composites displayed preferable tribological performance. This article provides a new method for PTW modifications in improving the tribological performance of the resin-based friction composites.

Experimental study of the effect of contact line profiles on the wear mechanism of a skateboard

Using an experimental approach, the researchers investigated the wear of a skateboard according to different profile contact lines. A high-speed current-carrying test machine was used to simulate underground railway operational conditions and obtain parameters such as the coefficient of friction, arc discharge energy, temperature increase, current-carrying efficiency, and offline rate of friction pairs comprising a skateboard and contact lines with varying profiles. The researchers analysed the impact of experimental parameters on skateboard wear matched with the different contact lines, as well as the wear mechanism of the skateboard. The experimental results revealed the following order for the total skateboard wear when matched with different contact lines: oblique contact line > pitted contact line > normal contact line. For the total skateboard wear with oblique contact line, the electrical wear of the skateboard predominantly contributed to the overall wear. Across all experiments, the total skateboard wear when matched with the oblique and pitted contact lines reached 10.291 g and 5.537 g, respectively, which was approximately 3.232 and 1.739 times the wear observed when matched with the normal contact line (3.184 g). With other experimental parameters held constant, the skateboard wear was directly proportional to current and sliding velocity, but inversely proportional to the normal load. The effect of sliding velocity on skateboard wear, arc energy, offline rate, etc., was less significant than the impact of current and normal load, especially at low speeds.

МОРФОЛОГИЧЕСКИЕ И ТРИБОЛОГИЧЕСКИЕ СВОЙСТВА МЕХАНОАКТИВИРОВАННОГО MOS2, ИСПОЛЬЗУЕМОГО В КАЧЕСТВЕ ПРИСАДКИ ДЛЯ МОТОРНОГО МАСЛА

The issues of improving the operational parameters of internal combustion engines are given a lot of attention, and in this regard, the direction related to improving the quality of engine oil with the help of dispersed additives is of great importance. In the article morphological and tribological properties of mechanically activated MoS2 used as an additive for semi-synthetic engine oil are considered. The obtained materials were investigated by the method of electron (scanning) microscopy, and the distribution of MoS2 particles as an additive in motor oils was analyzed, as well as IR spectroscopy of the material before and after mechanoactivation was carried out. Comprehensive comparative studies of tribological parameters (friction machine MI-1M) (running-in time, running-in wear, friction coefficient ratio, established friction coefficient and total wear) of motor oil with and without MoS2 additive were carried out. The mass concentration of MoS2 in the engine oil (Mannol Semi-synthetic Classic 10W-40), varied from 0.03 to 0.07 with a step of 0.02 wt.%. It was found that the addition of MoS2 to the engine oil reduces wear from 5.7 to 4.1 microns, with a decrease in the steady-state coefficient of friction from 0.115 to 0.08, which follows from the decrease in the steady-state coefficient of friction from 0.115 to 0.08. The time during which the working-in process increases from 1.57 to 2 h, which also reflects the reduction of friction when using engine oil with MoS2 additive. At the same time during operation the concentration of MoS2 additive in engine oil decreases, which leads to deterioration of properties. So, reduction of concentration from 0.07 to 0.03 (change by 57%) increases wear from 7.7 to 7.90 microns, which is 2.5%, and when reducing the concentration from 0.07 to 0.05, the increase in wear is 1.2%. Thus, considering the factors related to filtration, accumulation effect and the values of the studied typological parameters, a MoS2 concentration in the range of 0.03 to 0.07 wt.% is optimal.

Investigating the impact of heat treatment on the tribological behaviour of AZ80 magnesium alloy at high temperatures

The purpose of this research is to investigate the effect of heat treatment on the high-temperature wear characteristics of stir-cast AZ80 magnesium alloy. Dry sliding wear tests were performed on as-cast, T4, and T6 AZ80 using ASTM G99 - 17 at 25 °C, 150 °C, and 250 °C with a constant normal load of 10 N, a sliding speed of 1 m/s, and a sliding distance of 1000 m. Microstructures were analyzed with a Field-Emission Scanning Electron Microscope (FESEM) and an Electron Microprobe Analyzer (EMPA). X-ray diffraction (XRD) was used to examine the phases before and after the wear tests. In addition to α-Mg, the intermetallic phases Mg17Al12 and Mg2Al3 are also identified in AZ80. Compared to as-cast AZ80, T6 heat-treated alloy shows a maximum grain size of 72.64 ± 25 μm, with grain coarsening of 38.83 %. All test specimens, including T6 AZ80, exhibit indication of the Al-rich zone in the EPMA analysis, while T6 AZ80 shows evidence of the Mn-rich zone. Except for T4 AZ80 at 250 °C and T6 AZ80 at 150 °C and 250 °C, where the alloy experiences adhesive wear and oxidation, the abrasive wear and oxidation are common mechanisms observed in all test settings. At 150 °C, adhesive wear is responsible for 9.5 mg of the total wear in T6 AZ80. The alloy's wear behaviour is unaffected by presence of Zn. Intermetallic oxides (MgAl2O4) play a vital role in deciding the wear characteristics of the alloy.

Wear characteristics of the pipeline transporting cemented paste backfill containing coarse aggregate

Cemented paste backfill (CPB) offers unique advantages for managing tailings and underground mining voids, sometimes incorporating coarse aggregate. The pipeline is crucial for transporting CPB that contains coarse aggregate (CPBC), and excessive wear can compromise safety and continuity of transportation. However, the wear characteristics of the pipeline that transports CPBC are not well understood. In this study, wear tests were conducted using a novel self-designed instrument to investigate the impact of CPBC mass fraction (76–84%), flow velocity (1.0–2.5 m/s), coarse aggregate content (0–35%), and coarse aggregate particle size (1.05–7.34 mm). The results indicate that the wear rate increases in a power-law manner with both flow velocity and the size of coarse aggregate particles. The wear rate exhibits a non-monotonic trend with increasing CPBC concentration, initially rising, then declining before sharply increasing. With an increase in coarse aggregate content, the wear rate initially decreases slowly and then increases rapidly. The inflection point in the wear rate is associated with the interconversion between abrasion and erosion, which is governed by the yield stress of CPBC. Given the same material composition and wear type, and minimal variation in aggregate particle size, a higher yield stress of CPBC results in a higher wear rate. Abrasion and erosion dominate the total wear, contributing an average of 71.3%. The findings facilitate the selection of CPBC recipes and pipe materials to mitigate excessive pipe wear, while also providing significant potential for predicting pipe wear based on yield stress of paste.