Wear Particles Research Articles

Seasonal variations in concentrations of PM2.5 and tire wear particle of < 2.5 μm (TWP2.5) and polymeric components of PM2.5 at a bus stop

Air pollution is a global public health concern. Bus stops have heavy traffic and local emissions. PM2.5 was collected for 2 day at a bus stop each month for one year. Polymeric components in the PM2.5 samples were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Seasonal variations of the polymeric components, PM2.5 concentration, and concentration of tire wear particles <2.5 μm (TWP2.5) were investigated. Various polymeric components were found, including natural rubber (NR) and curing agents from TWPs, bitumen originating from asphalt pavement wear particles (APWPs), plant-related components (PRCs), and poly (ethylene-terephthalate) (PET) from PET fabric lint. The PM2.5 concentrations at the bus stop were 4–124% higher than those in the regional background, and the annual average PM2.5 concentration at the bus stop was more than 1.5 times higher than that in the regional background. Non-exhanst sources such as abrasion of tires, brakes, and asphalt pavements, vehicle exhaust emissions, and road dust resuspension accounted for the high PM2.5 concentrations. The PM2.5 concentrations during winter were higher than those in the other seasons. On average, the additional generation of PM2.5 at the bus stop was approximately 10 μg/m3, while that in the winter was approximately 18 μg/m3. The annual average TWP2.5 concentration at the bus stop was 1.28 μg/m3 (0.7–1.8 μg/m3), and the seasonal order was winter > fall > spring > summer. TWP2.5 is directly generated by the abrasion of tire tread through the friction with the road surface and also is produced from primary TRWPs by pressing and breaking them upon the contact with tires while driving vehicles. The annual average contribution of TWP2.5 to the PM2.5 concentration at the bus stop was 5.5% (1.6–14.0%).

Separation and quantification of tire and road wear particles in road dust samples: Bonded-sulfur as a novel marker

Tire road wear particles (TRWPs) are a large source of microplastics in the environment, while the quantification of TRWPs is still challenging due to the complex interferences and the uncertainties and inconsistencies among different methods. This study developed a TRWPs quantification method using optimized pretreatments and bonded-sulfur as marker. Road dust samples (n = 48) were collected, pretreatments including density separation, digestion and extraction were optimized to remove interferences of the bonded-sulfur (minerals, sulfur-containing proteins, hydrosoluble/hydrophobic sulfur-containing substances). Presence of TRWPs in the samples was confirmed by microscopy and scanning electron microscopyenergy dispersive spectrometry. Bonded-sulfur in the samples were quantified by inductively coupled plasmamass spectrometry (ICPMS). Additionally, bonded-sulfur in tire wear particles (TWPs) abraded from tires of top 10 best-selling brands were measured to calculate conversion factor (1.1 ×104 μg/g) for the quantification of TRWPs in real samples. TRWPs contents were 5.40 × 104 μg/g11.02 × 104 μg/g and 2.36 × 104 μg/g5.30 × 104 μg/g in samples from heavy and light traffic roads, respectively. The method provided better recoveries (88–107%, n = 18) and repeatability (RSD=2.0–7.9%, n = 3) compared to methods using rubber, benzothiazole and organic zinc as markers. Furthermore, stability of the bonded-sulfur was validated by Raman and ICPMS. Thus, this accurate and stable quantification method could promote research on TRWPs.

An Investigation into the Relative Efficacy of High-Velocity Air-Fuel-Sprayed Hydroxyapatite Implants Based on the Crystallinity Index, Residual Stress, Wear, and In-Flight Powder Particle Behavior.

Due to its resemblance to the bone, hydroxyapatite (HA) has been widely used for bioactive surface modification of orthopedic implants. However, it undergoes significant thermal decomposition and phase transformations at a high operating temperature, leading to premature implant failure. This investigation uses high-velocity air-fuel (HVAF) spray, an emerging low-temperature thermal spray technique, to deposit HA over the Ti-6Al-4V substrate. Coating characteristics, such as the crystallinity index and phase analysis, were measured using X-ray diffraction, Raman analysis, and Fourier transform infrared spectroscopy, residual stress using the sin2ψ method, and tribological performance by a fretting wear test. The coating retained an over 90% crystallinity index, a crystallite size of 41.04 nm, a compressive residual stress of -229 ± 34.5 MPa, and a wear rate of 1.532 × 10-3 mm3 N-1 m-1. Computational in-flight particle traits of HA particles (5 to 60 μm) were analyzed using computational fluid dynamics; it showed that 90% of particles were deposited at a 700 to 1000 m/s velocity and a 900 to 1450 K temperature with a 2.1 ms mean residence time. In-flight particle oxidation was minimized, and particle impact deformation was maximized, which caused severe plastic deformation, forming crystalline, compressive residual stressed coatings. The thermal decomposition model of low-temperature HVAF-sprayed HA particles helped to understand the implants' crystallinity index, residual stress, and tribological characteristics. Hence, this experimental and computational analysis shows that the HVAF process can be a promising candidate for biomedical applications for having strong and durable implants.

Robinia pseudoacacia L. (Black Locust) Leaflets as Biomonitors of Airborne Microplastics.

Here we investigate the suitability of Robinia pseudoacacia L. (black locust) leaflets as a novel biomonitor of airborne microplastics (MPs) including tyre wear particles (TWPs). Leaflets were collected from rural roadside locations (ROs, n = 5) and urban parks (UPs, n = 5) in Siena, Italy. MPs were removed by washing, identified by stereomicroscope, and analysed for polymer type by Fourier transform infrared spectroscopy. Daily MP deposition was estimated from leaf area. The mass magnetic susceptibility and the bioaccumulation of traffic-related potentially toxic elements (PTEs) were also analysed. The total number of MPs at ROs was significantly higher at 2962, dominated by TWPs, compared with 193 in UPs, where TWPs were not found. In contrast, total microfibres were significantly higher in UPs compared with ROs (185 vs. 86). Daily MP deposition was estimated to range from 4.2 to 5.1 MPs/m2/d across UPs and 29.9-457.6 MPs/m2/d across ROs. The polymer types at ROs were dominated by rubber (80%) from TWPs, followed by 15% polyamide (PA) and 5% polysulfone (PES), while in UPs the proportion of PES (44%) was higher than PA (22%) and polyacrylonitrile (11%). The mean mass magnetic susceptibility, a proxy of the bioaccumulation of traffic-related metallic particles, was higher at ROs (0.62 ± 0.01 10-8 m3/kg) than at UPs (-0.50 ± 0.03 10-8 m3/kg). The content of PTEs was similar across sites, except for significantly higher concentrations of Sb, a tracer of vehicle brake wear, at ROs (0.308 ± 0.008 µg/g) compared with UPs (0.054 ± 0.006 µg/g). Our results suggest that the waxy leaflets and easy determination of surface area make Robinia an effective biomonitor for airborne MPs including TWPs.

Sesamin inhibits RANKL-induced osteoclastogenesis and attenuates LPS-induced osteolysis via suppression of ERK and NF-κB signalling pathways.

Infection by bacterial products in the implant and endotoxin introduced by wear particles activate immune cells, enhance pro-inflammatory cytokines production, and ultimately promote osteoclast recruitment and activity. These factors are known to play an important role in osteolysis as well as potential targets for the treatment of osteolysis. Sesamin has been shown to have a variety of biological functions, such as inhibiting inflammation, anti-tumour and involvement in the regulation of fatty acid and cholesterol metabolism. However, the therapeutic effect of sesamin on osteolysis and its mechanism remain unclear. Present studies shown that in the condition of invitro, sesamin could inhibit osteoclastogenesis and bone resorption, as well as suppressing the expression of osteoclast-specific genes. Further studies on the mechanism suggest that the effect of sesamin on human osteoclasts was mediated by blocking the ERK and NF-κB signalling pathways. Besides, sesamin was found to be effective in treating LPS-induced osteolysis by decreasing the production of pro-inflammatory cytokines and inhibiting osteoclastogenesis invivo. Sesamin was non-toxic to heart, liver, kidney, lung and spleen. Therefore, sesamin is a promising phytochemical agent for the therapy of osteolysis-related diseases caused by inflammation and excessive osteoclast activation.

Plastics and the Environment

Plastics are persistent and pervasive throughout the environment and have now been reported from the deepest parts of the ocean to the tops of the highest and most remote mountains. There is a body of information on the sources, degradation, and transport of plastics as well as a variety of research investigating the ecotoxicological and wider ecological consequences of plastic ingestion and accumulation. Such knowledge has been obtained with developments in field and laboratory methods for plastic identification and then well-publicized in the media and wider public communications. However, although there has been a large focus on plastic pollution within the past decade, there is plenty that we do not yet know. Even within the past five years, sources of microplastics (1 μm–5 mm) to the environment have been confirmed that had not previously been considered, for example, road paints and tire wear particles. Initial research focused on plastic in the marine environment, but understanding on the accumulation and impacts in terrestrial and freshwater environments is growing. There is a substantial lack of basic science focused on the efficiency of solutions aimed at mitigating plastic pollution. This review highlights some recent (past five years) research on plastics in the environment, including investigations in accumulation, sources, distribution, impacts, solutions and provides directions for future work.

Toxic Tire Wear Compounds (6PPD-Q and 4-ADPA) Detected in Airborne Particulate Matter Along a Highway in Mississippi, USA.

Tire wear particles (TWPs) are a major category of microplastic pollution produced by friction between tires and road surfaces. This non-exhaust particulate matter (PM) containing leachable toxic compounds is transported through the air and with stormwater runoff, leading to environmental pollution and human health concerns. In the present study, we collected airborne PM at varying distances (5, 15 and 30m) along US Highway 278 in Oxford, Mississippi, USA, for ten consecutive days using Sigma-2 passive samplers. Particles (~ 1-80μm) were passively collected directly into small (60 mL) wide-mouth separatory funnels placed inside the samplers. Particles were subsequently subjected to solvent extraction, and extracts were analyzed for TWP compounds by high resolution orbitrap mass spectrometry. This pilot study was focused solely on qualitative analyses to determine whether TWP compounds were present in this fraction of airborne PM. The abundance of airborne TWPs increased with proximity to the road with deposition rates (TWPscm-2day-1) of 23, 47, and 63 at 30m, 15m, and 5m from the highway, respectively. Two common TWP compounds (6PPD-Q and 4-ADPA) were detected in all samples, except the field blank, at levels above their limits of detection, estimated at 2.90and 1.14 ng L-1, respectively. Overall, this work suggests airborne TWPs may be a potential inhalation hazard, particularly for individuals and wildlife who spend extended periods outdoors along busy roadways. Research on the bioavailability of TWP compounds from inhaled TWPs is needed to address exposure risk.

Shades of grey—tire characteristics and road surface influence tire and road wear particle (TRWP) abundance and physicochemical properties

There is mounting evidence that tire wear particles can harm natural systems, but worldwide trends in car weight and car usage, mean emissions are set to increase. To control tire wear emissions and help understand fate and transport, detailed characterisation of the particles, and the relationship between road surface properties and emission profiles is needed. This study deployed a suite of experiments utilising the advanced road simulator of the Swedish National Road and Transport Research Institute to compare seasonal tire types from three brands. An extraction method was developed for a coarse (&amp;gt;30 µm) fraction of tire and road wear particles (TRWP), and a comprehensive physicochemical characterisation scheme applied to both TRWP and tire-tread, including microscopy, energy-dispersive X-ray spectroscopy and pyrolysis-GC/MS. Road simulator dusts and hand-picked TRWP showed differences in shape, numbers, and mass between tire types and brands, and between asphalt and cement concrete road surfaces. Contrary to accepted perceptions, tactile analyses revealed that firm-elastic TRWP comprised only a minor proportion of TRWP. Fragile and chemically distinct tire-road-derived particles, termed here sub-elastic TRWP, comprised 39–100% of TRWP. This finding raises urgent questions about overall TRWP classification and identification features, resistance to weathering, and environmental fate. At the same time, differences in TRWP generation between tire formulations, and road surfaces, show potential for controlling emissions to reduce global impacts.

Mitigating tire wear particles and tire additive chemicals in stormwater with permeable pavements

6PPD-quinone (6PPDQ) is a recently discovered chemical that is acutely toxic to coho salmon (Oncorhynchus kisutch) and can form via environmental exposure of 6PPD, a compound found extensively in tire wear particles (TWPs). TWPs deposited on roads are transported to aquatic ecosystems via stormwater, contributing to microplastic pollution and organic contaminant loads. However, little is known about the fate of TWPs and their leachable contaminants in these systems. We conducted three experiments at a high school in Tacoma, Washington, to quantify the treatment performance of permeable pavement (PP) formulations, a type of green stormwater infrastructure (GSI), for TWPs and ten tire-associated contaminants, including 6PPDQ. The PPs comprised concrete and asphalt, with and without cured carbon fibers, to improve the mechanical properties of PPs. Pavements were artificially dosed and had underdrains to capture effluent. Three experiments were conducted to evaluate PP mitigation of tire-associated pollution using cryomilled tire particles (cTPs). The 1st and 3rd experiments established a baseline for TWPs and contaminants and assessed the potential for continued pollutant release. During experiment 2, cTPs were applied to each pavement. Our results showed that the PPs attenuated >96 % of the deposited cTPs mass. An estimated 52–100 % of potentially leachable 6PPDQ was removed by the PP systems between the influent and effluent sampling stations. Background 6PPDQ concentrations in effluents ranged from 0 to 0.0029 μg/L. Effluent 6PPDQ concentrations were not explained by effluent TWP concentrations in experiments 1 or 2 but were significantly correlated in experiment 3, suggesting that leaching of 6PPDQ from TWPs retained in the pavement was minimal during a subsequent storm. Our results suggest that PPs may be an effective form of GSI for mitigating tire-associated stormwater pollution. The improved strength offered by cured carbon fiber-amended pavements extends PP deployment on high-traffic roadways where tire-associated pollution poses the greatest environmental risk.

Retention of microplastics and tyre wear particles in stormwater ponds

Stormwater runoff from urban areas contain a wide variety of pollutants which is typically managed using stormwater retention ponds. However, their performance with regards to emerging pollutants such as microplastics and tyre wear material remains unclear. In this study, samples of effluent water and sediments from four stormwater retention ponds were analysed for their content of microplastics and tyre wear material. Microplastics were analysed using state-of-the-art hyperspectral imaging technique while tyre wear material was analysed using pyrolysis-GC–MS. Microplastics were recovered in all samples and the mass balance revealed that on average 88% of small microplastics (<500 µm) were retain in the ponds while the removal efficiency for large microplastics (>500 µm) was 95%. Tyre wear material was identified in all sediment samples but found below the detection limit in three out of four effluent samples. On average 95% of the tyre wear material was removed by the retention ponds. The results from this study show that stormwater retention ponds are very effective in removing microplastics as well as tyre wear material from stormwater runoff.

Influence of Artificially Altered Engine Oil on Tribofilm Formation and Wear Behaviour of Grey Cast Cylinder Liners

This work investigates the influence of altered engine oil on the tribological performance, focusing in particular on wear and interconnected tribofilm formation. For this purpose, Zinc dialkyldithiophosphate (ZDDP) additivated engine oils of different degradation levels, produced in an artificial oil alteration process, were used in tribometer tests with a nitride steel piston ring against a grey cast iron cylinder liner model contact. Parameters were chosen to simulate the boundary and mixed lubrication regime typical for the top dead centre conditions of an internal combustion engine of a passenger car. Wear of the cylinder liner specimens was continuously monitored during the tribometer tests by the radio-isotope concentration (RIC) method, and tribofilms were posteriorly investigated by X-ray photoelectron spectroscopy (XPS). The results clearly show that the steady-state wear rates for experiments with altered lubricants were significantly lower than for the experiments with fresh lubricants. XPS analysis on the formed tribofilms revealed a decrease in sulphide and an increase in sulphate states for altered oils evaluated at 120 °C oil temperature, correlating with a decrease in steady-state wear rate. This finding emphasizes the role of sulphate species in the tribofilm formation process and its anti-wear capabilities, in contrast to the sulphide species and the (poly-)phosphate species, as outlined in most of the ZDDP literature. Moreover, the RIC signal that represents the amount of wear in the engine oil showed a decrease over time for specific altered lubricants and test conditions. These “negative” trends in the wear signal are remarkable and have been identified as an incorporation of wear particles from the lubricant into the tribofilm. This finding is supported by XPS results that detected an iron-oxide layer with a remarkably similar quantity within the tribofilm on the surface. Based on these findings, an assessment of the minimum film formation rate and particle incorporation rate was achieved, which is an important basis for adequate tribofilm formation and wear models.

Integrating metabolomics and high-throughput sequencing to investigate the effects of tire wear particles on mung bean plants and soil microbial communities

Tire wear particles (TWPs) generated by vehicle tires are ubiquitous in soil ecosystems, while their impact on soil biota remains poorly understood. In this study, we investigated the effects of TWPs (0.1%, 0.7%, and 1.5% of dry soil weight) on the growth and metabolism of mung bean (Vigna radiata) plants over 32 days in soil pots. We found that TWPs-treated soils had high levels of heavy metals and polycyclic aromatic hydrocarbons (PAHs). However, there was no significant impact of TWPs exposure on plant growth, suggesting that mung bean plants have a degree of tolerance to TWPs. Despite the lack of impact on plant growth, exposure to TWPs had significant effects on soil enzyme activities, with a decrease of over 50% in urease and dehydrogenase activity. Furthermore, TWPs exposure resulted in marked changes in the plant metabolite profile, including altered levels of sugars, carboxylic acids, and amino acids, indicating altered nitrogen and amino acid-related metabolic pathways. TWPs exposure also disrupted the rhizospheric and bulk soil microbiota, with a decrease in the abundance of bacterial (Blastococcus) and fungal (Chaetomium) genera involved in nitrogen cycles and suppressing plant diseases. In summary, our study provides new insights into the effects of TWPs on plants and soil, highlighting the potential ecological consequences of TWPs pollution in terrestrial ecosystems and underscoring the need for further research in this area.

Long-term sublethal exposure to polyethylene and tire wear particles: Effects on risk-taking behaviour in invasive and native fish

Anthropogenic polymeric particles pollute even the most remote ecosystems and may compromise organisms' behaviour and movement skills. It is expected that invasive species cope better with pollutants than native species (i.e., pollution resistance hypothesis). In this study, invasive gibel carp (Carassius gibelio) and native crucian carp (Carassius carassius) were used as model organisms. Specimens were fed daily with food pellets (1 % body weight) added with 0.1 % polyethylene (PE), tire wear particles (TWPs) and control. Their behavioural parameters were compared before and after 14 and 60 days of exposure. Additionally, we evaluated burst swimming capacity after 60 days of exposure to the treatments. The fishes exposed to the PE and TWPs treatments showed significant trends toward increased boldness scores and, in the PE treatment, higher utilization of the open field, and both behavioural changes are associated with higher risk-taking. Invasive gibel carp had substantially better swimming performance than crucian carp, but the expected trend in relation to the treatments was not found. Fish exposed to sublethal doses of PE and TWPs showed signs of behavioural changes after two months of exposure that may affect risk-taking behaviour, which might impact species interactions with predators.

Effect of femtosecond laser bionic texture on anti-wear properties of medical Ti-6Al-4 V

Ti-6Al-4 V (TC4) is used as a medical implant material. However, its wear resistance is poor, which is not conducive to the use of implants. In this study, three biomimetic textures were designed on the surface of materials by femtosecond pulsed laser processing technology. The wear resistance of the textured surface was studied by rotating dry friction. The results demonstrate that the textured surface effectively reduces and captures the generation of wear particles, leading to enhanced stability of TC4 during wear and reduced surface wear. Compared with the untextured surface, the wear of the textured surface is reduced by 73.68%. These results indicate that bionic texture can improve the wear resistance of TC4.

Wear mechanisms of aluminum 5083/6061/7075 with and without T6 treatment

The application of hardened aluminum alloys on the drive elements must be safe and reliable, T6 treatment is often used to improve their mechanical properties and dimensional stability. However, the impact of T6 treatment on operating life is not easy to evaluate. Hence, the effects of T6 treatment on the wear of aluminum 5083/6061/7075 were studied by a steel ball on disk tester. The results showed that T6 treatment tended to reduce the values of the friction coefficient about 9%. Moreover, T6 treatment had no significant effect on the frequency of the change of the friction coefficient of 5083 and 6061, but significantly affected that of 7075. T6 treatment can also reduce the size of wear particles about 16%. Based on the results, the wear mechanisms of aluminum 5083/6061/7075 with and without T6 treatment are described in this paper.

Effect of bioturbation of the mitten crab on distribution of tire wear particles and their combined effect on sediment ecosystem

Tire wear particles (TWPs) are a major source of environmental microplastic pollution which gradually settle and accumulate in sediments after entering the aquatic environment, which can affect the behaviors of benthic organisms. Bioturbation of benthic species could affect the fate, impacts and potential risks of TWPs by altering the properties and structure of sediments. Therefore, in this study, the effect of TWPs on the burrowing activity of Chinese mitten crab (Eriocheir sinensis) was investigated. In addition, the effects of crab bioturbation on the distribution of TWPs and their additives were studied. The combined effects of TWPs and crab bioturbation on the microbial communities in the sediments were also explored. The results of this study showed that both TWPs and the leachate significantly inhibited the burrowing activity of crabs. TWPs in the surface layer of sediments were re-distributed by crab bioturbation and enriched mainly in the sediments near the burrow walls. Meanwhile, the heavy metals (i.e., Zn, Ca, Mg, Ba and Al) used as additives during the tire production in the burrow walls significantly increased as the accumulation of TWPs near burrow walls. In this study, TWP exposure decreased the bacterial diversity and abundance, as well as the functional genes related to carbon and nitrogen cycling process, but crab bioturbation increased them in the sediments of burrow walls by constructing a unique habitat. However, after TWPs entering into burrows, they were significantly decreased in the sediments near the burrow walls like the effects of TWPs, suggesting the negative effects of TWPs could play a dominant role in this combined system. Overall, this study is important for evaluating the distribution and effects of TWP pollution in the sediment ecosystem under biological factors such as bioturbation.

What is hiding below the surface – MPs including TWP in an urban lake

Inland lakes play an important role as habitats for local species and are often essential drinking water reservoirs. However, there is limited information about the presence of microplastics (MPs) in these water bodies. Thirteen sediment samples were collected across a Danish urban lake to map MPs, including tyre wear particles (TWP). The lower size detection limit was 10 µm. MPs were quantified as counts, size, and polymer type by Fourier-transform infrared microspectroscopy (µFTIR) and mass estimated from the 2D projections of the MPs. As TWP cannot be determined by µFTIR, counts and sizes could not be quantified by this technique. Instead, TWP mass was determined by pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The average MP abundance was 279 mg kg−1 (µFTIR), of which 19 mg kg−1 (Py-GC/MS) were TWP. For MPs other than tyre wear, the average MP count concentration was 11,312 counts kg−1. Urban runoff from combined sewer overflows and separate stormwater outlets combined with outflow from a wastewater treatment plant were potential point sources. The spatial variation was substantial, with concentrations varying several orders of magnitude. There was no pattern in concentration across the lake, and the distribution of high and low values seemed random. This indicates that large sampling campaigns encompassing the entire lake are key to an accurate quantification. No preferential spatial trend in polymer characteristics was identified. For MPs other than TWP, the size of buoyant and non-buoyant polymers showed no significant difference across the lake, suggesting that the same processes brought them to the sediment, regardless of their density. Moreover, MP abundance was not correlated to sediment properties, further indicating a random occurrence of MPs in the lake sediments. These findings shed light on the occurrence and distribution of MPs, including TWP, in an inland lake, improving the basis for making mitigation decisions.

Ensemble Deep Learning for Wear Particle Image Analysis

This technical note focuses on the application of deep learning techniques in the area of lubrication technology and tribology. This paper introduces a novel approach by employing deep learning methodologies to extract features from scanning electron microscopy (SEM) images, which depict wear particles obtained through the extraction and filtration of lubricating oil from a 4-stroke petrol internal combustion engine following varied travel distances. Specifically, this work postulates that the amalgamation of ensemble deep learning, involving the combination of multiple deep learning models, leads to greater accuracy compared to individually trained techniques. To substantiate this hypothesis, a fusion of deep learning methods is implemented, featuring deep convolutional neural network (CNN) architectures including Xception, Inception V3, and MobileNet V2. Through individualized training of each model, accuracies reached 85.93% for MobileNet V2 and 93.75% for Inception V3 and Xception. The major finding of this study is the hybrid ensemble deep learning model, which displayed a superior accuracy of 98.75%. This outcome not only surpasses the performance of the singularly trained models, but also substantiates the viability of the proposed hypothesis. This technical note highlights the effectiveness of utilizing ensemble deep learning methods for extracting wear particle features from SEM images. The demonstrated achievements of the hybrid model strongly support its adoption to improve predictive analytics and gain insights into intricate wear mechanisms across various engineering applications.

Material Removal Mechanism and Force Modeling in Ultrasonic Vibration-Assisted Micro-Grinding Biological Bone

Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottleneck of mechanical stress-induced crack damage. In response to this challenge, the ultrasound-assisted biological bone micro-grinding novel process with a spherical grinding head has been proposed by researchers. Force modeling is a prerequisite for process parameter determination in orthopedic surgery, and the difficulty in establishing and accurately predicting bone micro-grinding force prediction models is due to the geometric distribution of abrasive grains and the dynamic changes in geometry and kinematics during the cutting process. In addressing these critical needs and technical problems, the shape and protrusion heights of the wear particle of the spherical grinding head were first studied, and the gradual rule of the contact arc length under the action of high-speed rotating ultrasonic vibration was proposed. Second, the mathematical model of the maximum thickness of undeformed chips under ultrasonic vibration of the spherical grinding head was established. Results showed that ultrasonic vibration can reduce the maximum thickness of undeformed chips and increase the range of ductile and bone meal removals, revealing the mechanism of reducing grinding force. Further, the dynamic grinding behavior of different layers of abrasive particles under different instantaneous interaction states was studied. Finally, a prediction model of micro-grinding force was established in accordance with the relationship between grinding force and cutting depth, revealing the mechanism of micro-grinding force transfer under ultrasonic vibration. The theoretical model’s average deviations are 10.37% in x-axis direction, 6.85% in y-axis direction, and 7.81% in z-axis direction compared with the experimental results. This study provides theoretical guidance and technical support for clinical bone micro-grinding.

Byakangelicol suppresses TiPs-stimulated osteoclastogenesis and bone destruction via COX-2/NF-κB signaling pathway.

Aseptic loosening (AL) is considered a significant cause of prosthesis revision after arthroplasty and a crucial factor in the longevity of an artificial joint prosthesis. The development of AL is primarily attributed to a series of biological reactions, such as peri-prosthetic osteolysis (PPO) induced by wear particles around the prosthesis. Chronic inflammation of the peri-prosthetic border tissue and hyperactivation of osteoclasts are key factors in this process, which are induced by metallic wear particles like Ti particles (TiPs). In our in vitro study, we observed that TiPs significantly enhanced the expression of inflammation-related genes, including COX-2, IL-1β and IL-6. Through screening a traditional Chinese medicine database, we identified byakangelicol, a traditional Chinese medicine molecule that targets COX-2. Our results demonstrated that byakangelicol effectively inhibited TiPs-stimulated osteoclast activation. Mechanistically, we found that byakangelicol suppressed the expression of COX-2 and related pro-inflammatory factors by modulating macrophage polarization status and NF-κB signaling pathway. The in vivo results also demonstrated that byakangelicol effectively inhibited the expression of inflammation-related factors, thereby significantly alleviating TiPs-induced cranial osteolysis. These findings suggested that byakangelicol could potentially be a promising therapeutic approach for preventing PPO.