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A combination of three methods, Griffith theory, work of interface separation, and first-principles tensile simulations, has been applied to uncover the Ti2AlC/TiAl interface's tensile properties and fracture mechanisms. The results show that the three methods give consistent fracture locations when considering the interface elastic energy for work of interface separation, i.e., C-hcp-hollow-BCA fractures inside the TiAl bulk, while Al-fcc-hollow-ACB, Ti(C)-hcp-hollow-ABC, and Ti(Al)-hcp-hollow-BAC all fracture at the interface; Ti(C)-hcp-hollow-ABC has a maximum critical strain (20 %) and the strongest ideal tensile strength (29.32 GPa), because it has a greater deformation energy at the inflection point and it doesn't fracture when Ti(Al)-hcp-hollow-BAC is fully fractured, and the PDOS shape of the interface's Ti atoms exhibits a higher degree of consistency during the tensile process, and the C atoms of the Ti2AlC-2 layer in the Ti(C)-hcp-hollow-ABC exert a strong influence on the Ti atoms at the interface; the fracture mechanism of the Ti2AlC/TiAl interface structure includes the formation of electron holes, the holes increasing, the formation of microcracks, microcracks increasing, the formation of electron depletion region due to a sharp increase in the bond length and the interlayer spacing, followed by a complete fracture.

A new type of multiphase nanoparticle-reinforced TiAl matrix composites ((Ti2AlC + Al2O3)p/TiAl composites) was successfully prepared by vacuum hot-pressing sintering using Ti powder and Al powder, which were ball-milled with different contents of stearic acid (CH3(CH2)16COOH). The component, microstructure, reaction mechanism, and mechanical properties were studied. The results indicated that the composites prepared by adding stearic acid as a process control agent during the ball-milling process not only contained γ-TiAl and α2-Ti3Al phases but also Ti2AlC and Al2O3 phases. The results of SEM and TEM showed that the composites were composed of equiaxed TiAl and Ti3Al grains, and the Ti2AlC and Al2O3 particles were mainly distributed along the TiAl grain boundary in chain form, which can effectively reduce the TiAl grain size. Through the room-temperature compression test, the maximum compression stress was significantly improved in those composites that added the stearic acid, due to the reinforcement particles. The maximum compression stress was 1590 MPa with a 24.3% fracture strain. In addition, the generated crack deflection and Ti2AlC and Al2O3 particles could also enhance the toughness of the TiAl alloy. (Ti2AlC + Al2O3)p/TiAl composites generated by adding stearic acid played a key role in improving the mechanical properties of the TiAl matrix.

Due to excellent power and energy density, low self-discharge and long life, lithium-ion battery plays an important role in many fields. Directed against the complexity of above noises and the strong sensitivity of the common Kalman filter algorithm to noises, the state of charge estimation of lithium-ion battery based on extended Kalman filter algorithm is investigated in this paper. Based on the second-order resistor-capacitance equivalent circuit model, the battery model parameters are identified using the MATLAB/Simulink software. A battery parameter test platform is built to test the charge-discharge efficiency, open-circuit voltage and state of charge relationship curve, internal resistance and capacitance of the individual battery are tested. The simulation and experimental results of terminal voltage for lithium-ion battery is compared to verify the effectiveness of this method. In addition, the general applicability of state of charge estimation algorithm for the battery pack is explored. The ampere-hour integral method combined with the battery modeling is used to estimate the state of charge of lithium-ion battery. The comparison of extended Kalman filter algorithm between experimental results and simulation estimated results is obtained to verify the accuracy. The extended Kalman filter algorithm proposed in this study not only establishes the theoretical basis for the condition monitoring but also provides the safe guarantee for the engineering application of lithium-ion battery.

α-Al2O3 nanoparticles can enter a micro-arc oxidation coating and participate in the coating-formation process through chemical reaction or physical–mechanical combination in the electrolyte. The prepared coating has high strength, good toughness and excellent wear and corrosion resistance. In this paper, 0, 1, 3 and 5 g/L of α-Al2O3 nanoparticles were added to a Na2SiO3-Na(PO4)6 electrolyte to study the effect on the microstructure and properties of a Ti6Al4V alloy micro-arc oxidation coating. The thickness, microscopic morphology, phase composition, roughness, microhardness, friction and wear properties and corrosion resistance were characterized using a thickness meter, scanning electron microscope, X-ray diffractometer, laser confocal microscope, microhardness tester and electrochemical workstation. The results show that surface quality, thickness, microhardness, friction and wear properties and corrosion resistance of the Ti6Al4V alloy micro-arc oxidation coating were improved by adding α-Al2O3 nanoparticles to the electrolyte. The nanoparticles enter the coatings by physical embedding and chemical reaction. The coatings’ phase composition mainly includes Rutile-TiO2, Anatase-TiO2, α-Al2O3, Al2TiO5 and amorphous phase SiO2. Due to the filling effect of α-Al2O3, the thickness and hardness of the micro-arc oxidation coating increase, and the surface micropore aperture size decreases. The roughness decreases with the increase of α-Al2O3 additive concentration, while the friction wear performance and corrosion resistance are improved.

Aiming at the attitude control problem of fixed wing UAV, this paper introduces S-plane control, which has good control effect in the field of underwater UAV, into the attitude control of UAV. At the same time, aiming at the problem that the coefficient setting of parameters in S-plane control completely depends on experience and cannot be adjusted adaptively, the radial basis function neural network (RBFNN) is introduced, and a neural network S-plane control model which can realize on-line adaptive adjustment of the coefficient of parameters in S-plane control is proposed. The simulation results based on the data of a certain UAV show that compared with the S-plane control, the proposed neural network S-plane control model has the characteristics of fast response speed, strong anti-interference ability, and strong robustness. In addition, it also has the function of adaptive adjustment, which shows good control performance.

A coupled finite-element genetic algorithm technique was used to optimize the arrangement order and layer thickness ratios of Ti-Al3Ti-Al laminated composites. Moreover, the damage evolution, energy conversion, and stress distribution of TC4-Al3Ti-Al laminated composites under impact were analyzed. The results showed that TC4-Al3Ti-Al laminated composites with a layer thickness ratio of 3:14:4 have optimum anti-penetration properties; the projectile kinetic energy is mainly converted into the internal energy of the bullet target system; during the penetration process of TC4-Al3Ti-Al targets, the TC4 layer is shear failure, the Al layer is a petal-like failure, the failure mode of Al3Ti layer is fragmentation; with the number of layer increases, the anti-penetration properties of TC4-Al3Ti-Al targets are gradually increasing. However, when the number of layers is more than 30 layers, the number of layers has little effect on the anti-penetration performance of these composites.

The high uniform magnetic field combined with pre-deformation and vacuum heat treatment processing is designed for improving the diffusion bonding properties of the 1420 Al-Li alloy. Serial magneto-thermal coupling treatment experiments of 1420 Al-Li alloy and the pure aluminium diffusion couple, together with the gallium interlayer, is carried out in a superconducting high magnetic field device. Various parameter combinations are used to produce different samples on which interface organization and connection performance are studied. Electron microscopic analysis reveals various interface topographies and fracture morphologies after shear strength tests. Influence of diffusion bonding temperature on element diffusion under a high uniform magnetic field is investigated. The diffusion activation energy of Mg element in pure aluminum under a 12 T magnetic field is calculated in this paper. It is found that the bonding quality and bonding performance of the interface are improved greatly after heat treatment with a strong magnetic field, and the bonding temperature is an important factor affecting the interface bonding and bonding strength. The diffusion coefficient of the Mg element in the 1420 Al-Li alloy to L2 pure aluminum increases with the increase of diffusion bonding temperature. Reducing the activation energy of elemental diffusion is beneficial to atomic diffusion.

In order to resolve the external disturbances and model parameters uncertainty during the unmanned aerial vehicles flight process, in this paper, we designed the H∞/S-plane controller for longitudinal control of unmanned aerial vehicles (UAVs). The S-plane control model with strong nonlinearity was used as the outer loop controller and the robust Hoc control algorithm with strong robustness was used as the inner loop controller. The effectiveness of the H∞/S-plane controller in the longitudinal control of unmanned aerial vehicles without external interference, with external interference and parameter perturbation, was simulated by a certain UAVs nominal model. The results showed that compared with H∞/PD controller and PID controller, H∞/S-plane controller has faster response speed and stronger anti-interference ability. So H∞/S-plane controller is more suitable for the longitudinal control of unmanned aerial vehicles than H∞/PD controller and PID controller.

NiCo(OH)4-NiO composite electrode materials were prepared using hydrothermal deposition and electrophoretic deposition. NiCo(OH)4 is spherical and flowerlike, composed of nanosheets, and NiO is deposited on the surface of NiCo(OH)4 in the form of nanorods. NiCo(OH)4 has a large specific surface area and can provide more active sites. Synergistic action with NiO deposits on the surface can provide a higher specific capacitance. In order to study the influence of hydrothermal reaction temperature on the properties of NiCo(OH)4, the prepared materials of NiCo(OH)4-NiO, the hydrothermal reaction temperatures of 70 °C, 90 °C, 100 °C, and 110 °C were used for comparison. The results showed that the NiCo(OH)4-NiO-90 specific capacitance of the prepared electrode material at its maximum when the hydrothermal reaction temperature is 90 °C. The specific capacitance of the NiCo(OH)4-NiO-90 reaches 2129 F g−1 at the current density of 1 A g−1 and remains 84% after 1000 charge–discharge cycles.

The ductile Al in the Ti-Al Laminated Composites has a significant influence on their microstructure, distribution of internal stress, mechanical properties, failure modes and so on. This paper is mainly focused on the effects of the ductile Al on the ballistic limit velocity, the penetration process, the crack propagation, and the energy change of the Ti-Al3Ti targets by using finite element analysis. Results indicated that compared with the Ti-Al3Ti targets without the ductile Al, the ballistic limit velocity of the targets containing 30% Al increased from 465 m/s to 498 m/s. During the penetration process of the Ti-Al3Ti targets, the ductile Al reduced the impact force of the projectile and prolonged the duration of friction and shear between the projectile and the targets. The ductile Al changed the 45° ceramic cone failure of Al3Ti layers into the delaminated failure. Meanwhile, the ductile Al made the total energy of the Ti-Al3Ti targets increase.

In order to further improve the mechanical properties of Ti-Al 3 Ti laminated composites, the endothermic semisolid reaction was used to fabricate Ti-Al 3 Ti-Al laminated composites, and the quasi-static compressive test, dynamic compressive test, and the ballistic penetration test were conducted on these composites. The results showed that the compressive strength and failure strain of Ti-Al 3 Ti-Al laminated composites prepared at 660°C are 1432 MPa and 35%, respectively. The dynamic response of these composites has obvious strain rate effect, and the crack grows in the shape of “Z.” The V 50 of Ti-Al 3 Ti-Al targets is 509 m s −1 . To sum up, Ti-Al 3 Ti-Al laminated composites have better mechanical properties and anti-penetration properties compared to Ti-Al 3 Ti laminated composites.

To determine the ballistic limit velocity of titanium–titanium tri-aluminide (Ti/Al 3 Ti)-laminated composites under the action of tungsten alloy spherical fragments, a type of 12.7 mm ballistic gun loading system was used to test the tungsten alloy spherical fragments vertically impacting the Ti/Al 3 Ti-laminated composite targets with different thickness. The relationship between the ballistic limit velocity and the target area density of the Ti/Al 3 Ti-laminated composite was obtained. As the area density increased, the ballistic limit velocity and the ballistic energy absorbed by the target plate also enhanced. Based on the dimensional analysis and similarity theory, a simulation law of tungsten alloy spherical fragments penetrating Ti/Al 3 Ti-laminated composite targets with different thickness was studied and an empirical formula for the ballistic limit velocity was obtained. The research results had an important application value for the optimal design of the light armor protection structure.

In this study, the interactions of magnesium (Mg) atom and Mg(001) surface with different metal-atom-doped graphene were investigated using a density functional theory (DFT) method. For the interactions of magnesium with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene, it was found that the magnesium atoms were physisorbed into the hollow sites of the intrinsic graphene with only the smallest interaction energy (approximately −1.900 eV). However, the magnesium atoms tended to be chemisorbed on the doped graphene, which exhibited larger interaction energies and charge transfers. Additionally, the Zn-doped graphene displayed the largest interaction energy with the Mg atom (approximately −3.833 eV). For the interactions of Mg(001) with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene (intrinsic and doped graphene/Mg interface), doped atoms interacted with a Mg layer to make graphene wrinkle, resulting in a higher specific surface area and better stability. Mg–C chemical bonds were formed at the Al-, Zn-, and Zr-doped interface, and Mg–Mn chemical bonds were formed at the Mn-doped interface. This study provided the fundamental research for future research into doped atoms on graphene reinforced magnesium matrix composites.

The two-sheet hollow structure of the 1420 Al-Li alloy was prepared by the method of superplastic forming and diffusion bonding. The interface combination status of the diffusion bonding region and the microstructure of the superplastic forming region were observed by an optical microscope. The thickness distribution of the superplastic forming region was measured by an ultrasonic thickness meter machine, the defect detection was tested by X-ray nondestructive inspection, and the failure modes of the samples were analyzed. The results showed that the two-sheet hollow structure of the 1420 Al-Li alloy was prepared successfully, the structure was integrated, and there were no shape defects such as pit, wrinkle, and collapse. The structure shape was almost attached to the die completely, and the thickness was almost uniform distribution. The no deforming area of the two-sheet hollow structure of the 1420 Al-Li alloy was a long strip, rolled microstructure, while the grains near the round corner area were equiaxed states resulting from dynamic recrystallization. The improper control of the superplastic gas pressure in the forming process would lead to the tearing or the die-attaching failure for the two-sheet hollow structure of the 1420 Al-Li alloy.

The Ti–Al3Ti–Al laminated composites with different Al contents were prepared by vacuum hot pressing sintering technology. The effects of Al content on the dynamic mechanical properties of the composites were studied using the combination of Split Hopkinson Pressure Bar experiment and finite element analysis. The results showed that different Al content changes the fracture mode of the composites. The laminated composites without Al have higher brittleness and lower fracture strain. The Ti–Al3Ti–Al laminated composites containing 10–15%Al have better dynamic mechanical properties than those without Al, but the subsequent increase of Al content is not conducive to the improvement of strength. However, when the Al content in the specimen reaches 30%, the dynamic mechanical properties of the composites decrease, multi-crack phenomenon and relatively large strain occur, and the Al extruded from the layers fills the crack.

For improving the mechanical properties of Ti-Al3Ti metal-intermetallic laminated (MIL), it is of vital importance for reducing tensile thermal stresses of this composites. In this work, finite element analysis was used to study the distribution and various reducing methods of thermal stresses in Ti-Al3Ti MIL composites, such as changing the layer thickness ratios, the layer numbers, remaining the residual Al, etc. The results showed that the tensile thermal stresses in outer Al3Ti layer is the highest, and the outer Al3Ti layer is the most likely fail. When the layer numbers are larger than 47, the tensile thermal stresses in outer Al3Ti layer are almost minimal and keep constant. When the thickness ratios are larger than 5, the tensile thermal stresses in Al3Ti layer decrease only a little. With the introduction of residual Al, the thermal stresses in Al3Ti layers switch from tension to compression state. Keywords: Laminated composites, Thermal stresses, Ti

To solve the nonlinear Bayesian estimation problem in underwater terrain-aided navigation, a terrain-aided navigation method based on improved Gaussian sum particle filter is proposed. This method approximates the Bayesian function using multiple Gaussian components, and the components can be obtained by radial basis function neural network. This method has no resampling process, the particle depletion of particle filtering is eliminated in principle. The simulation shows that the proposed method has good matching performance, which is suitable for autonomous underwater vehicle navigation.