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Tool wear is a major cause of accelerated tool failure during the milling of aluminum alloy. The periodically cutting force directly affect the cutting heat and tool wear due to the intermittent cutting characteristics of the milling process. The focus of this paper is to analyze the influence of the variation of cutting force on tool wear behavior. The change law of cutting force by cutting parameters was analyzed firstly. Secondly, the variation of the wear land width (VB) of tool flank face by the milling length was analyzed. Thirdly, the wear morphology and the energy dispersive spectrometer (EDS) results of tool rake face and flank face in different cutting parameters were observed by tungsten filament scanning electron microscope. Finally, considering the cutting force effect, the tool wear mechanism during high-speed milling of Aluminum-Alloy Die Castings 12 (ADC12, 12 means aluminum number 12) was analyzed. The cutting force in tangential direction is predominant during high-speed milling aluminum alloy, which decreases gradually with the increase of cutting speed but increases gradually with the feed rising. The adhesion-oxidation wear was main wear mechanism of tool rake face during high-speed milling. While adhesive wear was the main wear mechanism of the tool flank face during high-speed milling. It is found that the formation of adhesive wear is the process from particle adhesion to melting until the formation of adhesive layer, which related to the change of cutting force. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the fatigue properties of C17200 alloy under the condition of quenching aging heat treatment at high temperatures, and to provide a design reference for its application in a certain temperature range. For this purpose, the tensile and rotary bending fatigue (RBF) tests were carried out at different temperatures (25 °C, 150 °C, 350 °C, and 450 °C). The tensile strength was obtained, and relationships between the applied bending stress levels and the number of fatigue fracture cycles were fitted to the stress-life (S-N) curves, and the related equations were determined. The fractured surfaces were observed and analyzed by a scanning electron microscopy (SEM). The results show that the RBF fatigue performance of C17200 alloy specimens is decreased with the increase in test temperature. When the temperature is below 350 °C, the performance degradation amplitudes of mechanical properties and RBF fatigue resistance are at a low level. However, compared to the RBF fatigue strength of 1 × 107 cycles at 25 °C, it is decreased by 38.4% when the temperature reaches 450 °C. It is found that the fatigue failure type of C17200 alloy belongs to surface defect initiation. Below 350 °C, the surface roughness of the fatigue fracture is higher, which is similar to the brittle fracture, so the boundary of the fracture regions is not obvious. At 450 °C, due to the further increase in temperature, oxidation occurs on the fracture surface, and the boundary of typical fatigue zone is obvious. [ABSTRACT FROM AUTHOR]

The interaction between adjacent asperities is a typical characteristic of the grinding process and plays an important role in the material removal mechanism. Therefore, in order to systematically investigate the formation mechanism of the subsurface damage, a precision grinding contact model between the diamond particle and optical glass with adjacent asperities is proposed in our research. The initiation and propagation mechanism of median/lateral cracks under residual stress, the propagation rules of the stress waves on the subsurface, and the interaction between the subsurface damage under stress superposition effect are fully investigated by a theoretical analysis and finite element simulation. The simulation results of the precision grinding model are verified by experiments, which show that the proposed numerical analysis model is reasonable and the finite element analysis process is feasible. [ABSTRACT FROM AUTHOR]

In this study, epoxy resin (EP) composites were prepared by using molybdenum disulfide (MoS2) and helical carbon nanotubes (H-CNTs) as the antifriction and reinforcing phases, respectively. The effects of MoS2 and H-CNTs on the friction coefficient, wear amount, hardness, and elastic modulus of the composites were investigated. The tribological properties of the composites were tested using the UMT-3MT friction testing machine, non-contact three-dimensional surface profilometers, and nanoindenters. The analytical results showed that the friction coefficient of the composites initially decreased and then increased with the increase in the MoS2 content. The friction coefficient was the smallest when the MoS2 content in the EP was 6%, and the wear amount increased gradually. With the increasing content of H-CNTs, the friction coefficient of the composite material did not change significantly, although the wear amount decreased gradually. When the MoS2 and H-CNTs contents were 6% and 4%, respectively, the composite exhibited the minimum friction coefficient and a small amount of wear. Moreover, the addition of H-CNTs significantly enhanced the hardness and elastic modulus of the composites, which could be applied as materials in high-temperature and high-pressure environments where lubricants and greases do not work. [ABSTRACT FROM AUTHOR]

The main focus of current research in polymeric matrix brake composites is on searching out a replacement for copper, which has been recently proved to be a hazard to human health and the environment. In this paper, rare earth lanthanum oxide was explored for the replacement of copper in composites. The mechanism of the role of lanthanum oxide in brake composites to replace copper was analyzed. Four series of polymeric matrix brake composites with various amounts of copper (15, 10, 5 and 0 wt %) and rare earth lanthanum oxide (0, 5, 10 and 15 wt %) were developed, in which the copper was gradually replaced by lanthanum oxide in the formula. These series were characterized in terms of physical, thermo-physical and mechanical properties. The results show that lanthanum oxide can be successfully used as a replacement for copper in brake composites. Brake composites with 15 wt % lanthanum oxide that are copper-free are considered optimal, where tribo-properties are considered best. Compared with the addition of copper in brake composites, lanthanum oxide is more conducive to the formation of compacted friction films and transfer films, which is beneficial to the tribological properties of the brake composites. The addition of La2O3 to the brake composites can cause the reaction between La2O3 and Al2O3 to form LaAlO3, and the reaction between Al2O3 and BaSO4 can produce Ba18Al12O36 and Al2SO4 during the friction and wear processes, which can effectively improve the tribological properties of the brake composites at elevated temperature. This research was contributive to the copper-free, metal-free and eco-friendly brake composites. [ABSTRACT FROM AUTHOR]

In this work, a new and effective treatment on bamboo fiber (BF) is presented, and its effect on the interfacial bonding properties of the BF/resin matrix was studied. The interfacial functionary mechanism of rare earth solution (RES) modification to improve the interfacial bonding properties between BF and the resin matrix was analyzed. The hardness and elastic modulus of the interfacial zone between BF and the resin matrix were measured using nanoindentation. Fourier-transform infrared spectroscopy (FT-IR) was used to analyze the change in the surface functional group of BF in the modification process. The surface chemical composition of BF before and after the modification was characterized by X-ray photoelectron spectroscopy (XPS). The results show that the RES modification significantly increases the hardness and elastic modulus of BF and its interfacial zone with the resin matrix. The hydroxyl concentration on the surface of RES-treated BF decreases, which reduces the hydrophilicity of BF. Rare earth ions react with oxygen in the hydroxyl group at the C2 position in the glucosylic ring of cellulose. The RES-modified BF bonds with the resin matrix to form a rare earth complex, which significantly enhances the interfacial adhesion between BF and the resin matrix. [ABSTRACT FROM AUTHOR]