Wear Area Research Articles

Mechanical Pressing of Coconut Oil and Evaluation of Its Lubricant Properties

Vegetable oils represent an important element in protecting a sustainable environment. The pursuit of environmentally friendly solutions and the ever-increasing costs of synthetic oil production are increasing the interest in natural vegetable oils. This paper presents and discusses the possibilities of using the oils obtained from coconuts (Cocos nucifera L.) harvested in Indonesia (North Sumatra region), with three maturity levels (green, yellow, and brown), as lubricants. The specific mechanical energy for linear pressing of the green, yellow, and brown types was 22.3, 20.7, and 18.5 J·goil−1, respectively. The water content of the oils obtained from the green, yellow, and brown types was 1786, 2033, and 1902 mg H2O·g−1, respectively. The mathematical models for linear pressing were established. The sizes of the wear area for the green, yellow, and brown types were 25.7, 24.4, and 34.3 mm2, respectively. The UV–visible spectral curves of the oils, in the range of 180–320 nm, were determined. The results of the lubrication properties of the Reichert test showed that better lubrication properties were exhibited by the green and yellow types, which are comparable to the lubricating properties of engine oils. The results from the SEM images also showed a better structure of the worn surface and fewer traces of abrasive wear.

Two-phase flow and wear of 90° bend pipes by normally distributed particles

Wear is a key cause of pipe failure in pipeline conveying systems. Solid-phase particles can lead to wall wear, which reduces the reliability of the conveying system. In this study, a numerical simulation of 1–3 mm particles with a normal distribution in a 90° bend section was performed based on a coupled computational method of computational fluid dynamics and discrete unit method. The results revealed that a protective layer of particles is formed near the outer wall of the bend, which reduces the direct collision of particles during the flow and protects the surface of the bend. Comparative analysis revealed that the maximum wear area of the bend is in the range 75°–90° in the middle of the bend section.

Research on Wear of Micro-Textured Tools in Turning GH4169 during Spray Cooling

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools.

Анализ архитектурно-планировочных решений поликлиник как инструмент управления при внедрении бережливого производства.

In the clinics of the Moscow region, within the framework of the project «A new model of a medical organization providing primary medical care», there is difficulty in achieving the target indicators of the project criteria. The analysis of the architectural and planning characteristics of polyclinics that affect the achievement of the criteria of this project was carried out. Purpose: analysis and evaluation of the architectural and planning capabilities of polyclinics in the Moscow region for the successful implementation of lean production technologies. Materials and methods: 224 polyclinics of the Moscow region were included in the project, statistical reporting forms were evaluated: Analysis of data from the federal register of medical organizations, forms of federal statistical observation No. 30, No. 47. shortage of polyclinic capacity), depreciation of polyclinic buildings. Research methods – analytical, observation, expert, mathematical, statistical. Results. In the clinics of the Moscow region, there is an imbalance between the attached population and the design capacity of the clinics. Also, a pronounced variability in the area of polyclinics in the Moscow region was revealed, 34% of polyclinics have a shortage of space. The physical deterioration of buildings leads to a limitation in their operation. Conclusions. Polyclinics of the Moscow region differ in variability in terms of capacity, shortage or redundancy of the area of polyclinics, wear and tear of the building, architectural and planning features of polyclinics. These criteria must be taken into account when choosing projects for the most effective achievement of results.

Study on pumping wear characteristics of concrete pipeline based on CFD-DEM coupling

Concrete pumping, integral to building construction, governs pipeline durability and overall construction efficiency. This study advances the traditional methods by employing the CFD-DEM coupling technique, a pioneering approach that integrates the irregular shape of coarse aggregates, capturing the intricacies of concrete pumping in pipelines. Beyond identifying primary wear areas and quantifying wear magnitudes, this research unveils a quadratic progression in average wear over time. The most pronounced wear appears in the pipeline’s bent sections. Notably, pumping speed, more influential than aggregate volume fraction, is pivotal to pipeline wear. Minimized speeds increase blockage risks, notably at elbows, while augmented speeds intensify wear. An optimal speed range between 2 and 3 m/s is deduced. Additionally, as the aggregate volume fraction surges, wear amplifies and blockages frequent. Hence, an aggregate volume fraction between 15 and 20% emerges as the recommendation.

Fabrication of CaSiO3 LTCC high aspect ratio microstructure by laser chemical assisted micro-milling

As a new generation of chip-packaging materials, CaSiO3 LTCC substrates have the characteristics of high frequency, low thermal expansion coefficient, and low dielectric loss. These materials are widely used in radar communication and other industries. However, in the condition of high heat density, it is difficult to adapt calcium silicate with a low thermal conductivity to the heat dissipation requirements. To improve the heat dissipation performance, high-aspect-ratio heat-dissipation microchannels must be prepared on the surface of the CaSiO3 LTCC substrate. In this study, a new nanosecond laser and chemical milling-assisted micro-milling (NLCAM) method is proposed. The processing mechanism of the nanosecond laser ablation of CaSiO3 is explored and the influence of the laser parameters on the depth of the etching groove, top width, and hardness of the residual modified layer are studied by establishing a laser energy superposition model and test method. The improvement of milling force and milling surface quality by laser is studied. The results demonstrate that the laser power has the most significant effect on the ablation depth and width of the top of the CaSiO3; the excess heat diffuses outside the laser irradiation area, increasing the width of the top of the CaSiO3 beyond the designed width. With an increase in the scanning speed and scanning distance, the ablation depth exhibited a decreasing trend, corresponding to the laser energy model. Nanosecond laser chemical milling (NLCM) can reduce the hardness of the material by 72.0–77.2%. The maximum reduction in the average axial milling force was 56.8%, and the fluctuation of milling force is reduced. Compared to pure micro milling, the tool wear area of NLCAM was reduced by 89.3% and the average roughness Sa of the bottom surface of the microgroove was reduced to 0.392 μm, which confirms the high-quality and efficient machining of the CaSiO3 LTCC substrate.

Assessing dynamic characteristics for friction draft gears with worn wedge shoes

A friction draft gear model was developed to assess the degraded dynamic characteristics of worn draft gears in the vehicle impact condition. It presents an approach to simulate multiple typical wear profiles of wedge shoes and reflect their effects on the draft gear performance. Based on the rated design indexes and existing overhaul regulations of MT-2 type friction draft gears in China, the safety wear limits for wedge shoes with different wear profiles were classified and assessed. The results indicate that wedge shoes with uniform or concave wear can significantly worsen draft gear performance, and the existing maintenance limit of 1 mm only applies to wedge shoes with uniform wear but not to the most common wedge shoes with concave wear. Also, for wedge shoes with concave wear, when the wear area covers 50%, 75%, and 100% of the total main friction surface, the corresponding safety wear limits are 0.5 mm, 0.8 mm, and 1.3 mm, respectively. Therefore, it is proposed to design multiple graded and dynamic maintenance limits to ensure the service safety of MT-2 type friction draft gears.

Applicability Verification of Restoration by Welding to Extend the Lifetime of Railway Wheel

Railway wheels, when subjected to wear beyond their designated usage standards due to the operation of railway vehicles, are traditionally managed through a turing maintenance method. This process involves turing the entire worn portion to secure the requisite cross-sectional shape. This approach often leads to disposal after just 2 to 3 turing maintenance cycles. Excessive turing, extending beyond the worn parts, can cause the wheels to fail to meet railway operating specifications. Discarded railway wheels, which contain a high carbon content essential for driving performance, are not repurposed but are instead entirely stockpiled. This research introduces a novel welding restoration technology for railway wheels, targeting the flange portion, a principal area of wear. Utilizing submerged arc welding techniques, this method enables the localized repair of worn parts, minimizing the turing thickness and thus extending the useful life fo railway wheel. To evaluate the on-site applicability and dependability of this welding restoration method, real rail vehicle driving tests were conducted using both conventionally turned and welding-restored railway wheels. Analysis of the wheel profiles substantiated that the welding restoration method delivers mechanical performance comparable to that achieved by traditional turning maintenance.

Experimental Wear Analysis of Nano-Sized Titania Particles as Additives in Automotive Lubricants

This study focuses on the wear effects of nano-sized titania as a potential engine lubricant additive. Titanium dioxide nanoparticles have promising wear-reducing properties and significant tribological potential. In this article, titania nanoparticles were homogenized in Group III automotive oil at five different concentrations (0.1; 0.2 … 0.5 wt%). The nanodoped oil samples were tested on a linear oscillating tribometer with oil circulation. Based on the tribological results, titania nanoparticles increased friction by 20–32% but can reduce the wear area by up to 32%. According to the confocal microscopic examination, wear volume can be reduced by up to 57% with titania nanoparticles. Titania nanoparticles improved the repeatability of tribological measurements. A scanning electron microscopy examination of the wear track revealed that the characteristic wear of the tribological system was abrasive, but a significant amount of adhesive wear was also observed. Energy dispersive X-ray spectroscopy analysis found that the nanoparticles fill the deeper trenches of the wear. The worn surface uniformly contains TiO2 particles and the quantified normalized titanium concentration was between 0.56 and 0.62%.

Frequency induced fretting corrosion mechanism evolution of Alloy 690 exposed to simulated secondary water

The effect of frequency (5–30 Hz) on the fretting corrosion behavior of Alloy 690 tube was investigated in simulated pressurized water reactor secondary water. The results show that the wear volume of the tube increases by ∼19 times with the frequency increases, and the wear mechanism changes from adhesive wear to delamination wear and abrasive wear. The increasing fretting frequency could affect the contact temperature and accelerates the change of contact stress, which cause a shift in the wear mechanism. Under the synergic effect of mechanical wear and corrosion, a gradient multi-layer structure is formed on the wear area, which is composed of the ultra-fine grain three-body layer, the tribologically transformed structure layer and matrix distributed from top to bottom. The three-body layer is mainly composed of Fe-rich spinel oxides and a small amount of Fe3O4 and Cr2O3, and its thickness increases with the increase of the fretting frequency.

Investigating the self-lubricating properties of novel TiSiVN coating during dry turning of Ti6Al4V alloy

The machining of titanium alloys like Ti6Al4V has been challenging owing to their low thermal conductivity, making them highly difficult-to-cut. Many techniques have been adopted to improve machinability of Ti6Al4V titanium alloy and the durability of the cutting tools during its machining. Thus, to improve their machinability, the current work investigates the applicability of TiSiVN self-lubricating coating deposited on Al2O3–SiC ceramic cutting tools during continuous turning of Ti6Al4V alloy under dry cutting environment. The TiSiVN coating accounted for lower surface roughness and cutting temperatures under all conditions. Due to the formation of V2O5 at high temperatures that were observed during oxidation and machining tests in EDS and Raman spectroscopy, the TiSiVN coating helped in reducing friction and, thus, retained the crater wear area. In contrast, the worn area on the crater surface reduced for uncoated and TiSiN coated cutting tools due to a significant increase in nose depth decrement with increasing cutting speed. Furthermore, increased nose depth decrement resulted in the drop of machining forces when using TiSiN coated and uncoated cutting tools. However, the coating delamination due to oxidation was apparent which reduced the effectiveness of lubricious phases present in the cutting zone for TiSiVN coated tool.

Tool wear area estimation through in-process edge force coefficient in trochoidal milling of Inconel 718

The rapid wear and premature failure of the cutting tool are prone to happen due to increased forces during machining difficult-to-cut materials such as Inconel 718. The application of alternative toolpath such as trochoidal milling has significantly improved tool life and reduced the overall cycle time of the process. The wear pattern of the tool has a direct impact on the cutting forces, which increases with tool deterioration. The cutting forces in milling are modeled through the mechanistic force model and can be designated through a set of force coefficients, i.e. cutting and edge representing the shearing and ploughing phenomenon of metal removal. It has been established in the literature that tool wear has a considerable effect on the value of edge force coefficients. This paper aims to determine the in-process edge force coefficients for the trochoidal toolpath and correlates them with the corresponding flank wear area. The proposed correlation will further assist in predicting the level of flank wear area based on the force values in trochoidal milling.

Point-Based Visual Status Evaluation of Worn Pavement Markings Based on a Feature-Binary-PointNet Network and Shape Descriptors Using LiDAR Point Clouds: A Case Study of an Expressway

Inspecting the visual wear status of pavement markings is important to guide the maintenance plans of roads and ensure traffic safety. This study proposes a point-based visual status evaluation system for pavement markings using light detection and ranging (LiDAR) technology. The system includes a feature-binary-PointNet (FBP) network to accurately extract pavement markings from raw point clouds. Furthermore, multi-shape descriptors are constructed to efficiently identify different types of pavement markings, and a four-level wear-grading system is established based on two indices (point-based visual wear area and wear area proportion) of each pavement marking. The proposed method was tested using the mobile laser scanning technique considering a case study of an expressway. The proposed FBP network performed better than the existing state-of-the-art networks in extracting the pavement markings, with accuracy, recall, precision, and mean intersection over union scores of 97.04, 84.42, 91.11, and 79.36%, respectively. The main types of expressway markings were rapidly identified, and maintenance advice was provided based on the two computed indices and the wear grade of each marking. The study findings can guide managing agencies in allocating the maintenance budget for fixing highly defective road sections.

Flow characteristics of moist-mixed materials for shotcrete: From experiment to CFD-DEM simulation

Moist-mixed materials for shotcrete is an effective way to solve the volume control of shotcrete equipment in small and medium cross-section tunnels. The material of moist-mixed materials for shotcrete is characterized by cross-scale particle composition, and the problems of difficult dust control and short conveying distance remain unsolved. The pneumatic conveying simulation of the moist-mixed materials for shotcrete is studied using the CFD-DEM method. At the same time, a pipeline test system is designed, and the effectiveness of the CFD-DEM coupling model is verified by comparing the pressure drop and flow pattern with the field experiment. The model is used to study the pressure drop characteristics under different tilt angles, lifting angles, bend diameter ratio, and bend angle, involving three aspects: pressure drop in acceleration section (PDAS), unit pressure drop in stable section (PDSS), and energy loss caused by the elbow (ELE). The pressure drop model of pneumatic conveying of moist-mixed materials for shotcrete is established, and the relationship between the PDAS, PDSS, and ELE is obtained. The relationship between the Froude number and solid-gas ratio is clarified, and the calculation formula of maximum feed rate or minimum air flow rate is deduced. The velocity and spatial position distribution of particles at different tilt and lifting angles are revealed, and the elbow's main wear areas and wear rates at different bend angles and bend diameter ratios are obtained. The fundamental research has realized the unification of experiments and numerical simulation. The pressure drop law brought can guide further research on long-distance pneumatic conveying of moist-mixed materials for shotcrete.

Numerical Simulation and Experimental Study on Sediment Wear of Fixed Guide Vanes of Hydraulic Turbines in Muddy River Based on Discrete Phase Model

The erosion of the fixed guide vane of a hydraulic turbine by sandy water is influenced not only by flow velocity and mud concentration but also by the direction and speed of the sandy water over the surface. This study aims to investigate the erosive effect of sediment-laden water on a specific type of hydraulic turbine’s fixed guide vane, validate the efficacy of the discrete phase model (DPM) in simulating wear on the fixed guide vane, and identify the critical areas of wear on its surface. To achieve these objectives, the wear model and DPM model are employed to conduct numerical simulations on the fixed guide vane. Additionally, samples of sand are collected from the power station site, and laboratory tests are conducted on the hydraulic turbine’s flow passage components using actual sediment concentration and sand-to-water ratio to determine the sediment wear conditions. The numerical simulation results of the guide vane’s surface wear rate are compared with the experimental data to verify the wear condition of the fixed guide vane under its rated working condition. These findings serve as a reference for the later-stage design of erosion-resistant solid guide vanes for hydraulic turbines.

Study on the Wear Resistance of Ni-Co-ZrO2 Composite Coatings with Different ZrO2 Nanoparticle Concentrations Prepared Using Electrodeposition on the Micro-Surface of Spindle Hook Teeth

To improve the wear resistance of the surface of the cotton picker spindle, a Ni-Co-ZrO2 composite coating with different ZrO2 nanoparticle concentrations was prepared using electrodeposition technology on the micro surface of spindle hook teeth, and the morphologies of the surface and cross-section, element contents, grain sizes, microhardness and friction coefficients of the Ni-Co-ZrO2 composite coating were obtained; a simulated wear test was conducted based on the independently developed spindle hook tooth wear device, and the morphologies and elemental distributions of the composite coating before and after wear were obtained; the effects of different ZrO2 nanoparticle concentrations (0, 2, 4, 6, 8 g/L) on the morphology, element content, grain size, microhardness, friction coefficient and wear resistance of the coating were discussed. The test results indicated that compared with Ni-Co coatings, Ni-Co-ZrO2 composite coatings featured a more compact coating structure, a greater coating thickness, and a smaller grain size. The presence of ZrO2 nanoparticles led to further improvement of the coating’s microhardness, friction coefficient and wear resistance. When the mass concentration of ZrO2 nanoparticles reached 4 g/L, the microhardness of Ni-Co-ZrO2 composite coating reached the maximum value, 545.4 Hv0.1, and the friction coefficient decreased to 0.06. At the same time, in the simulated wear test, the composite coating with this concentration had the smallest wear area and the highest wear resistance.

Wear resistance of CAD/CAM one-piece screw-retained hybrid-abutment-crowns made from different restorative materials.

The aim of this study was to measure the wear progress of three high performance polymers (HPP) materials as well as that of zirconia after artificial aging (simulated 2.5- and 5-year of clinical service with thermo-mechanical loading) and compare it with the well-documented wear of lithium disilicate. Forty implants were used to restore a maxillary first premolar, where the abutment and the crown were manufactured as hybrid-abutment-crown and connected to the implant using a titanium insert. The implants were randomly divided, according to the restorative materials used, into five groups: 3Y-TZP zirconia (Z), lithium disilicate (L), ceramic-reinforced polyetheretherketon (P), nano-hybrid composite resin (C) and polymer-infiltrated ceramic-network (E). All hybrid-abutment-crowns were produced using CAD/CAM technology. A design of a maxillary first premolar was created with an angle of 120° between the buccal and palatal cusps, which were designed as planes. The restorations were adhesively luted onto the titanium inserts, according to the manufacturers' recommendations for each material individually, by means of dual-curing luting resin with the exception of group P, where the blocks were pre-fitted (heat-pressed) with an integrated titanium insert. The suprastructures were assembled onto the implants through titanium screws. The screw channels were sealed with Teflon tape and composite resin filling material that was polished to high-gloss. All specimens underwent 1 200 000 thermo-dynamic loading cycles with 49 N in a dual-axis chewing simulator. Elastomeric impressions were made for all specimens after 600 000 and after 1 200 000 cycles. The corresponding impressions were imaged using a laser scanning microscope and then 3D-analyzed using the software (Geomagic Wrap) to measure the volume loss of the wear area for all specimens. Statistical analysis was performed using Wilcoxon-Test regarding the two different time measurements for each material. For the analysis of the material variable, Kruskal-Wallis test was conducted followed by Mann-Whitney test. Group Z showed statistically the lowest volume loss compared to the other test materials, both after 600 000 and 1 200 000 cycles of artificial aging, with a median value of 0.002 mm3 volume loss after 1 200 000 cycles. In contrast, group E showed the highest volume loss with median values of 0.18 and 0.3 mm3 after 600 000 and 1 200 000 cycles, respectively. Artificial aging had significantly negative effect on the volume loss for all test materials. In addition, the choice of material had statistical influence on the outcome. Monolithic zirconia ceramic demonstrated lower wear than that reported for enamel after simulated 5-year of clinical service, whereas all other test materials showed higher volume loss after artificial aging.

Mechanism of Electrochemically Assisted Friction and Wear Behavior of GaN in KMnO4 Slurry

Electrochemically assisted friction and wear behavior of gallium nitride (GaN) in a KMnO4 slurry was investigated to optimize the composition of the chemical mechanical polishing (CMP) slurry, and the material removal effect of GaN was visually evaluated by using the coefficient of friction (COF) curve and wear area. The results showed that the surface oxidation of GaN was effectively enhanced by KMnO4 and electrochemical assistance. The average COF and wear area of GaN increased with stronger oxidation of the environmental media, which improved the removal of the GaN surface material. Under acidic conditions, the oxidation of KMnO4 for GaN surface was significantly stronger than that under neutral and alkaline conditions, and the GaN surface was effectively oxidized and corroded when the initial mass fraction of KMnO4 was 5 wt%. When the chemical and mechanical actions reached a synergistic effect, the oxide layer generated on the GaN surface was immediately removed by the Si3N4 ball and SiO2 abrasive, which led to a large increase in material removal rate (MMR); the COF curve tended to stabilize, and the average COF increased. The experimental results of the electrochemically assisted CMP of GaN were consistent with the friction and wear test results.

Elucidating friction properties and strengthening mechanisms of Ni-based surfacing layer containing 9R phase

This study analyzed the strengthening mechanisms and friction properties of Inconel 625 surfacing layers fabricated by plasma transfer arc surfacing (PTA-surfacing) in ball-on-disc friction tests at room temperature and 650 °C. Results showed that Inconel 625 exhibited poor tribological performance at room temperature, but excellent at 650 °C. The average Vickers hardness of the high-temperature wear area (1.6826 ± 0.4059 GPa) was higher than that of the room temperature wear area (1.3900 ± 0.1875 GPa). The coefficient of friction for Inconel 625 decreased from 0.5362 at room temperature to 0.2846 at 650 °C. The wear rates of Inconel 625 at 650 °C and room temperature were 1.2063 × 10−5 mm3/N·m and 20.9740 × 10−5 mm3/N·m, respectively. The wear mechanisms at 650 °C were mainly abrasive, adhesion, oxidation wear, and some degree of delamination wear. The microstructural characterizations revealed that the wear subsurface at 650 °C comprised polycrystalline-mixed oxide layers (Ni(Cr,Fe)2O4, (Cr,Fe)2O3, and NiO), gradient grain refinement, nanoscale precipitations (M23C6, M6C, and laves), 9R structural phases, I-type twinning, and high-density dislocations, which synergistically enhance the outstanding high-temperature friction properties and strength.

Effect of the addition of coated SiO2 nanoparticles on the tribological behavior of a low-viscosity polyalphaolefin base oil

This work reports tribological properties of PAO6 containing SiO2 nanoparticles modified with stearic-acid (SiO2-SA) as additives at concentrations (0.05, 0.10, 0.20, 0.30) wt% and the same concentration of SA as a dispersant. Tribological experiments were performed at 120 °C in pure sliding and rolling-sliding conditions (5% slide-to-roll ratio). All nanolubricants have better anti-friction capabilities than PAO6. The optimum concentration for friction reduction was 0.30 wt% for both tribological conditions. The best anti-wear results for the specimens tested in pure sliding conditions were achieved with PAO6 + 0.20 wt% SiO2-SA with reductions of 55%, 86% and 92%, in wear track width, wear track depth and wear area, respectively. Tribological mechanisms of the nanoparticles have been analyzed through roughness measurements, concluding that polishing, tribofilm and adsorption of the additives occur.