Wear最新文献

Metal bond diamond tools are regularly used in the machining of various hard and brittle materials. The mechanical properties and wear resistance of the metal bond are very important for the tool's life and machining performance. Herein, a low-cost and highly wear resistant Fe₃Al bonded material for diamond tool was proposed. A novel two-step reactive sintering method, integrating short-term high-temperature reactive sintering and long-term low-temperature densification sintering, was proposed to prepare Fe₃Al bond diamond tools. The effect of sintering temperature on the microstructure and mechanical properties of the Fe₃Al bond was examined during one-step reactive sintering. The mechanical properties and tribological characteristics of the one-step and two-step reactive sintered Fe₃Al and commercial Fe alloy bond were compared. The machining performance of the two-step reactive sintered Fe₃Al bond diamond tool on sapphire was also examined and compared to that of a commercial Fe alloy bond diamond tool. The results showed that the relative density and mechanical properties of the Fe₃Al bonded material were enhanced by increasing the sintering temperature during one-step reactive sintering. Moreover, the sample sintered at 1150-850 °C exhibited better mechanical properties and wear resistance compared to the one-step reactive sintered Fe₃Al and commercial bond. The grinding ratio of the two-step reactive sintered Fe₃Al bond diamond tool was 157 % higher than that of the commercial Fe alloy bond diamond tool.

This study proposes a new slip-line field model to separately characterize the shearing-included cutting process and the pure-plough cutting process. The shear plane and dead metal zone in relation to the shearing effect are modelled by straight slip-lines, while the deformation area in relation to the ploughing effect is treated to have straight boundaries. The boundaries of the dead metal zone and ploughing area are determined by considering tool-workpiece frictional behaviours. The stresses acting on the boundaries of the ploughing area, dead metal zone and shear plane are separately modelled considering the thermal–mechanical coupling effect. Based on the minimum energy principle, the shear angle is originally modelled by following the dynamic requirement of chip flow to balance the forces acting on dead metal zone, shear plane and rake face. By iteratively solving the coupling effect among the temperature, stress and shear angle, the total cutting forces are acquired by integration operation through straight slip-lines. Experiment results and finite element simulations validate the proposed slip-line field model in predicting the shear angle and cutting forces for both micro and regular milling processes.

Widespread and popular use of ceramic products in various industry sectors necessitates the search for methods of their efficient processing. Lapping technology, which enables obtaining high dimensional and shape accuracy and high surface flatness, is one of the basic methods of finishing hard and brittle technical ceramics with a porous structure. This study analyzed the characteristics and wear value of an SLS-printed abrasive tool intended for single-sided lapping of Al₂O₃ technical ceramics. As earlier research demonstrated, introduction of a 3D printed lapping plate by selective laser sintering (SLS), leads to a significant development in the field of precision machining technology. This method showed not only efficient machining performance on oxide technical materials, but was also characterized by relatively low abrasive wear. Straightness errors were evaluated with the use of a least-squares method (LSQ) and minimum zone method based on control line rotation scheme (CLRS). The proposed model proved the experimental results by identifying a similar location of a higher contact density on the lapping tool, where this location is expected to be the one for bigger wear. Surface topography of the lapping tool depends on the tool wear intensity and as a consequence on its shape error. An SLS-printed lapping plate, by obtaining good technological effects, revealed its potential ability in machining hard and brittle technical ceramics.

Carbon nanotubes (CNTs), as water-based additives, are potential candidates for reducing friction and wear whereas the weak dispersion stability impedes their application in aqueous lubrication. Therefore, CNTs were functionally modified by 4-tert-butylcatechol (TBC) nucleophilic for synthesizing the ultra-dispersive TBC-CNTs. The particle sizes and dispersibility of TBC-CNTs in water were investigated. It was found that particle sizes of the most of CNTs were reduced after modification and 0.035 wt% TBC-CNTs remained uniformly dispersed in water for 2 months. The lubrication behavior of TBC-CNTs as water-based additives for ceramic/steel tribo-pairs was investigated by using a ball-on-disc apparatus. Notably, the optimum concentration of TBC-CNTs was determined 0.2 wt% that contributed to 30.6 % of friction reduction and 28.3 % of wear resistance, respectively, at 0.6 m/s and 8 N. The tiny structure of TBC-CNTs contributed to their entrance into the contact interface and playing lubricating roles. Furtherly, the increase of water film thickness within contacts and formation of lubrication film on rubbing surfaces caused by TBC-CNTs addition resulted in the friction and wear reduction.

This study aims to find out whether the working parts of ploughs of different manufacturers have different wear parameters. A comparative analysis of the resource of plough points and furrow coulter knives is performed (according to changes in mass, diagonal length of working parts, etc.). Reinforced plough points wore 2.5 times less by mass, and 4.53 times less diagonal shortening than non-reinforced plough points. Plough points strengthened with carbide plates suffered less wear and less shortening before being damaged by stones. As a whole, the abrasive wear of geometrically identical and close-in-composition parts is determined by the hardness of the steels from which the part is made, and the microstructure obtained during heat treatment. The performed numerical simulation of abrasive wear showed the results of plough point thickness variation close to field experiments. The obtained normal stress diagram explains the intensity of wear on the front edge of the plough point. The proposed soil bin improvement with a zone for smaller particles helps to avoid meshed geometry deformation.

Laser cladding (LC) is a promising technique to overlay a protective coating on grey cast iron (GCI) brake discs to enhance the wear and corrosion resistance. This study utilized a pin-on-disc tribometer in an aerosol chamber to investigate the tribology and airborne particle emissions from tungsten carbides (WC) reinforced coating overlayed onto GCI substrate through laser cladding. Uncoated GCI brake discs served as reference material, while low-metallic (LM) and non-asbestos organic (NAO) brake pads were used as counterparts. The results indicate that LC coating exhibited slightly higher coefficient of friction and significantly lower wear than uncoated GCI discs. Abrasive wear is the dominant wear mechanism for both uncoated GCI brake discs and LC coatings. LC coatings substantially decreased the particle mass concentrations. All three friction pairs displayed a mass weighted size distribution with a major peak around 2–3 μm. The number size distribution was dominated by a mode below 1 μm. Emissions by number were generally low. Meanwhile, all three friction pairs emitted sheared off and agglomerated particles, with iron being the dominant element. Tungsten was identified in the particles emitted from LC coatings, indicating that the hard coating has a potential to wear off and become airborne particles.

This study explores the friction and wear performance of brake materials for new energy micro logistics vans under different ambient temperature (3 °C, 23 °C, 43 °C) and humidity conditions (35 %, 65 %, 95 %) using pin-disc experimental device. The findings reveal that at 3 °C, the friction coefficient exhibits extreme sensitivity to changes in humidity, with a significant reduction as humidity increases. Simultaneously, the increase of humidity leads to the transition from adhesive wear to abrasive wear and fatigue wear. At room temperature (23 °C) and 43 °C, humidity has minimal impact on the friction coefficient; however, higher humidity promotes oxidation film formation on the friction surface leading to dominant oxidation wear. Notably, in low-humidity environments, temperatures at 3 °C and 43 °C cause severe brake pad wear. The severity is greater at 43 °C because the resin-based components within the brake pad material decompose at elevated temperatures. Under such circumstances, appropriately increased humidity helps mitigate brake pad wear rates. However, too much humidity can increase fatigue wear of brake pad materials.

This study focuses on the evolution of fluting damage in bearing outer races. Fluting damage first occurred at the loading position and then extended along outer races. This non-uniform distribution of fluting damage is related to the non-uniform load inside bearing. It is speculated that the alteration of bright and dark areas in fluting is related to the periodic destruction and reconstruction of lubricating film. The phase transition from α′-Fe to α-Fe is observed beneath erosion surface. At microscale, non-uniform damage of the fluting appears as the dark area exhibiting more severe erosion, lower oxidation, greater roughness, deeper depth, and lower hardness. The results can provide deeper understanding of the failure process and damage mechanism of bearings in electric fields.

The tribology behavior of the brake interface is a vital aspect since it determines the service life and operation safety of the train. To be more understanding about this, a fully coupled thermo-mechanical-wear finite element algorithm is proposed to study the evolution of temperature, wear and mechanical contact at the interface of high-speed train brake systems, and the correctness of which is experimentally validated. In this approach, contact stress is extracted to calculate the interfacial heat flux for the subsequent thermomechanical coupling analysis. Meanwhile, based on the Achard wear model, the interfacial wear degradation under thermal conditions is simulated through ABAQUS subroutine UMESHMOTION with the help of arbitrary Lagrangian–Eulerian (ALE) remeshing technique. Using the proposed method, the dynamic interaction between temperature, wear and contact stress is investigated, and the coupling mechanism between these factors is revealed. The results indicate that the temperature magnitude will be overestimated without considering the wear effect. In reverse, the thermal expansion has a significant influence on the wear and contact behavior. The interfacial contact behavior is jointly influenced by surface wear and thermal effects. Therefore, it is impossible to accurately predict the tribology behavior of the brake interface without a comprehensive consideration of these factors.

Large-displacement high-intensity sanding hydraulic fracturing operations often cause casing perforation erosion and thus temporary plugging failures, exacerbate the unevenness of fracture initiation and expansion, and induce casing damage. In order to clarify the dynamic evolution of perforation erosion and predict perforation diameter, the effects of different types of proppants, the viscosity of sand-carrying liquids, and large sand-passing quantities on perforation erosion rate were experimentally explored in the study. The evolution of perforation erosion and the particle size distribution of quartz sand and ceramsite were analyzed in the experiment and a prediction model for perforation erosion under various fracturing parameters was established. Compared to ceramsite, quartz sand had the more significant effect on perforation erosion and the more serious particle abrasion and fragmentation under the same sand-passing quantity. Increasing the viscosity of the sand-carrying liquid slowed down perforation erosion and made the edge of perforation entrance more uniform. As the sand-passing quantity through the perforation increased, perforation erosion in the initial stage was concentrated at the perforation edge. Then, the inner wall of the perforation was also eroded, but the average erosion rate was reduced. A prediction model of perforation erosion considering multiple fracturing parameters was established based on the principle of fluid similarity. The errors between predicted values and downhole eagle-eye observation values were less than 15 %. The model provides an important basis for the optimization of fracturing parameters and downhole casing strength design.