The SOC estimation of UAV lithium batteries plays a crucial role in the mission planning and safe flight of UAVs. Aiming at existing UAV lithium battery SOC estimation problems, such as low estimation accuracy and poor real-time performance, a real-time online estimation scheme for UAV lithium battery SOC is proposed. A model-based approach is adopted to establish an SOC estimation model on the basis of the Thevenin equivalent circuit model, and a UAV lithium battery online monitoring device is developed to monitor the current and voltage of the UAV lithium battery in real time and import the data into the SOC estimation model in real time for calculation. Using the developed online monitoring device, the current and voltage of the lithium UAV battery are monitored in real time, and the data are imported into the SOC estimation model in real time for calculation, realizing the real-time online estimation of the SOC of the lithium UAV battery. The experimental results show that the program can realize the real-time online estimation of UAV lithium battery SOC, and the estimation error is less than 3%, which meets the requirements of online estimation accuracy of the UAV lithium battery SOC.

Titanium alloys are difficult to machine and have poor tribological properties. Nanoparticles have good cooling and lubricating properties, which can be used in metal cutting fluid. The lubrication characteristics of the two-dimensional materials Ti₃C₂T_X MXene and graphene oxide in water-based fluid for titanium alloys were comparatively investigated in this paper. Graphene oxide had smaller friction coefficients and wear volume than Ti₃C₂T_X MXene nanofluid. As to the mechanism, MXene easily formed TiO₂ for the tribo-chemical reaction, which accelerated wear. Moreover, GO nanofluid can form a more uniform and stable friction layer between the frictional interface, which reduces the friction coefficient and decreases the adhesive wear. The effects of different surfactants on the lubricating properties of MXene were further investigated. It was found that the cationic surfactant Hexadecyl trimethyl ammonium chloride (1631) had the lowest friction coefficient and anti-wear properties for the strong electrostatic attraction with MXene nanoparticles. The results of this study indicate that 2D nanoparticles, especially graphene oxide, could improve the lubricating properties of titanium alloys. It provides insight into the application of water-based nanofluids for difficult-to-machine materials to enhance surface quality and cutting efficiency. The developed nanofluid, which can lubricate titanium alloys, effectively has very broad applications in prospect.

During the machining of nickel-based superalloys using coated tools, a significant amount of cutting heat is generated. This study employs ABAQUS finite element analysis software to establish two-dimensional orthogonal cutting simulation models for three types of coated tools: single-layer AlTiN, double-layer AlTiN/AlCrN, and AlCrN/AlTiN. The research focuses on simulating the cutting temperature and cutting stress of carbide tools with these three different coating types and thicknesses when machining nickel-based superalloy GH4169. The simulation results indicate that the double-layer AlCrN/AlTiN-coated tool exhibits lower maximum cutting temperature and cutting stress on the tool rake face and tool substrate during the cutting process. Compared to the other two coated tools, the cutting temperature and cutting stress on the rake face are reduced by up to 13.2% and 13.3%, respectively. When the AlCrN/AlTiN coating thickness is 2.5 μm with a ratio of 1.5:1, the maximum cutting temperature and cutting stress are minimized. During the cutting process with coated tools, the cutting speed, coating type, and coating thickness significantly influence the maximum cutting temperature and cutting stress. Therefore, investigating the effects of cutting speed, coating type, and coating thickness on carbide-coated tools can reduce tool wear, extend tool life, and thereby improve machining efficiency.

In order to explore the effect of modulation period on the structure and properties of TiSiN/NiTiAlCoCrN nanomultilayer films, the films were deposited on 304 stainless steel via a magnetron sputtering system. The structure and element distribution of the films were observed via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The cavitation erosion of the films was investigated using an ultrasonic vibration cavitation machine. The results show that the TiSiN/NiTiAlCoCrN nanomultilayer film exhibits a face-centered cubic (FCC) structure and preferred orientation on the (200) crystal plane. TiSiN/NiTiAlCoCrN nanomultilayer films grow in the form of columnar crystals, which grow perpendicularly to the direction of the substrate. With increasing modulation periods, the hardness, elastic modulus, and adhesive force firstly increase and then decrease. When the modulation period is 11 nm, the TiSiN/NiTiAlCoCrN nanomultilayer film has the biggest hardness of (14.649 ± 0.591) GPa, elastic modulus of (249.065 ± 10.485) GPa, and adhesive force of 11.3 N. With increasing modulation periods, the mass loss firstly decreases and then increases. When the modulation period is 11 nm, the mass loss is the minimum of 0.6 mg. There are two reasons for improving the cavitation erosion resistance of the films. The TiSiN/NiTiAlCoCrN nanomultilayer film has the highest hardness, and the interfaces of the nanomultilayer film can hinder the generation and expansion of cavitation pits.

The impact of modulation periods on the microstructure, as well as the tribological and mechanical characteristics of the AlCrTiVNbN/TiSiN nano multilayer films, was investigated. The films were prepared with modulation periods ranging from 4 nm to 7 nm, and their properties were explored using X-ray diffraction (XRD), scanning electron microscope (SEM), nanoindentation, and a tribological tester. All nano multilayer films revealed a face-centered cubic (FCC) structure with a preferred planar direction of (200). As the modulation period increased, the XRD peak moved to higher angles, and the interplanar distance decreased. Also, the mechanical properties deteriorated, and the COF rose monotonically as a result. The nano multilayer film with a modulation period equal to 4 nm exhibited a smooth surface with minimal small particles, the highest hardness of 15.51 ± 0.16 GPa and elastic modulus of 182.89 ± 2.38 GPa, the highest values for the ratios of H/E and H³/E², the lowest average friction coefficient of 0.73, and a wear rate equal to (8.2 9 ± 0.18) × 10⁻⁸ mm³·N⁻¹·m⁻¹. The improvement in the properties of the film was ascribed to the coherent growth and alternating stress field between the AlCrTiVNbN and TiSiN layers.

In order to investigate the effect of Co contents on the structure and cavitation erosion property, NiTiAlCrCo_xN films were prepared by the magnetron sputtering system. The X-ray diffractometer (XRD), the scanning electron microscope (SEM) and the energy dispersive spectrometer (EDS) were used to characterize the structure and morphology of the films. The nanoindenter and the scratch tester were used to analyze the mechanical properties of the films. Cavitation erosion experiments were carried out by the ultrasonic vibration cavitation machine. The results show that NiTiAlCrCo_xN films with different Co contents have a simple face-centered cubic (FCC) structure and show a preferred orientation on the (200) crystal plane. The diffraction angle on the (200) crystal plane decreases and the interplanar spacing increases with the increase in Co content in NiTiAlCrCo_xN films. NiTiAlCrCo_xN films exhibit a typical columnar crystalline structure. With the increase in Co content, the nanohardness of the films increases and the elastic modulus of the films decreases, while the mass loss of cavitation erosion monotonously increases except for the film with a 1.2 Co molar ratio. The NiTiAlCrCo_1.4N film has a minimum hardness of 13.264 GPa, a maximum elastic modulus of 253.22 GPa and a minimum mass loss of 0.72 mg in the cavitation erosion experiment. The NiTiAlCrCo_1.4N film exhibits the best cavitation corrosion resistance because the addition of the Co element enhances the solid solution strengthening effect and the NiTiAlCrCo_x1.4N film with the biggest elastic modulus has better elasticity to reduce the micro jet impact.