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Flow field distribution plays a vital role in electrochemical machining (ECM) because it can directly affect the machining stability and accuracy of ECM. In counter-rotating electrochemical machining (CRECM), the uniformity of the flow field is difficult to control due to the complicated and changeable flow channel shape. Through the simulation of the conventional lateral fluid flow pattern, it is found that the complexity of the flow channel with grid structures makes the flow field of machining area strongly disordered, which leads to the low velocity zones and dead zones. Based on the simulation results, a new electrolyte flow pattern with an auxiliary internal fluid is proposed, which can remarkably improve the uniformity of flow field by apply supplementary electrolyte to the machining area. Experimental results show that the new flow pattern effectively improves the machining stability of CRECM, and enhances the machining precision of grid structures, the sidewall taper angle is reduced from 29.3° to 7.7°.

Counter-rotating electrochemical machining (CRECM) is a novel electrochemical machining (ECM) method, which can be used to machine convex structures with complex shapes on the outer surface of casings. In this study, the evolution of the convex structure during CRECM is studied. The complex motion form of CRECM is replaced by an equivalent kinematic model, in which the movement of the cathode tool is realized by matrix equations. The trajectory of the cathode tool center satisfies the Archimedes spiral equation, and the feed depth in adjacent cycles is a constant. The simulation results show that the variations of five quality indexes for the convex structure: as machining time increases, the height increases linearly, and the width reduces linearly, the fillets at the top and root fit the rational function, and the inclination angle of the convex satisfies the exponential function. The current density distributions with different rotation angles is investigated. Owing to the differential distribution of current density on workpiece surface, the convex is manufactured with the cathode window transferring into and out of the processing area. Experimental results agree very well with the simulation, which indicates that the proposed model is effective for prediction the evolution of the convex structure in CRECM.

The role of Mo alloy element on the tribological behaviors of AT13/Mo coatings sliding against Si3N4 balls under boundary lubrication condition was investigated. The results revealed that the AT13 and AT13/Mo coatings were mainly composed of γ-Al2O3, α-Al2O3 and TixOy ceramic phases and both coatings underwent a transition from boundary lubrication to dry friction. Furthermore, the addition of Mo could greatly reduce friction. Moreover, the tribological properties of AT13/Mo coating under boundary lubrication condition were superior over those of pure AT13 coatings. According to XPS results, Mo has undergone a chemical reaction to generate a tribofilm covering the friction interface under boundary lubrication condition, and the film containing MoS2 and MoO2 can greatly enhance load-bearing capability and provide good boundary lubrication effect.

The effects of oxygen-enriched atmosphere on the morphological evolution of soot emitted from a methane co-flow laminar diffusion flame were studied using a 12-μm SiC fiber deposition sampling method combined with field emission scanning electron microscopy (FESEM) analysis. The temperature distribution and the soot morphological evolution along the flame radial and axial directions at different oxygen concentrations were systematically investigated. Results showed that the soot morphology was strongly dependent on its position and oxygen concentration in flames. At the same flame height, the soot morphology changed significantly when the oxygen concentration increased from 21% to 31%. The soot generation rate increased rapidly under the elevated oxidative condition, and the position of soot inception was closer to the burner nozzle. As the flame height and oxygen concentration increased, soot particles in the flame centerline were enlarged and evolved to fiber-like depositions. Furthermore, the large clusters of soot particles gradually evolved to even denser spongy and fibrous particles around the flame edges. In addition, unique sponge-like soot deposits were observed for the first time in methane flames.

The effect of oxygen concentrations on the formation and evolution of soot particles was investigated by analyzing soot morphology using SiC fiber deposition technique and thermophoretic sampling method in a co-flow diffusion ethylene flame. Soot particles were examined via transmission electron microscopy at different heights along the flame centerline. Results show that the flame temperature exhibits a bimodal distribution. As the flame height increases, the flame distribution gradually changes from bimodal to unimodal, and the increase in oxygen concentration not only causes the flame height to decrease, but also causes the bimodal distribution of the flame more pronounced. The morphological evolution of soot deposits are strongly dependent on the oxygen concentration, radial and axial position, and flame temperature. Soot deposits along the flame centerline begin to be oxidized into dense flocculent and fibrous mesh structures with the flame temperature increases. In front of the flame, the oxidation is enhanced with temperature rise at the same height, resulting in more dense morphology of the soot deposits and the decrease in primary particle size. The results of thermophoretic sampling show that soot growth undergoes various stages of nucleation, growth, coagulation, agglomeration and oxidation, and the average particle size distributions of soot increase first and then decrease. The increase in oxygen concentration leads to advances in all stages of soot formation, including surface growth, agglomeration and oxidation. Additionally, the flame temperatures increase sharply as the increase of flame heights, leading to the soot aggregates to be oxidized to loose chain-like agglomerates.

The characteristics of soot in the diffusion flames of methane and ethylene under different oxygen concentrations and the influence of mixing methane in ethylene on soot generation were investigated using thermophoretic sampling and subsequent transmission electron microscopy image analysis. The process of soot particle nucleation, surface growth, coagulation, agglomeration and oxidation along the flame axis was analyzed. The variation of soot particle size distribution and aggregate characteristics at different heights along the centerline of the flame at different oxygen concentrations and methane doping ratios were obtained. Results show that the various stages of soot generation in methane flame obviously lags behind the ethylene flame at different oxygen concentrations, and increasing the oxygen concentration makes the various stages of soot formation in the flame advance. A 10% methane doping can promote soot generation at low flame locations. Increasing the doping amount to 30%, the generation of soot can be promoted at high flame locations. The synergistic effect of soot formation in fuel combustion occurs in the above two cases. However, the synergistic effect of the fuel will disappear under high blending ratio conditions. The effect of methane-ethylene at high blend ratios is more like a neutralization effect.

To solve the problem of insufficient protective performance of the existing body armor, an impact-resistant shear stiffening gel (SSG) with excellent flexibility and formability was innovatively used as buffer plate for body armor, and then combined with ultra-high molecular weight polyethylene (UHMWPE) ballistic panel to form a UHMWPE/SSG composite body armor. Based on the ballistic impact experiment and numerical simulation, the effect of buffer plate on the protective performance, and the dynamic behavior and protective mechanism of UHMWPE/SSG were analyzed systematically. The results indicated that the flexible SSG buffer plate could quickly stiffen under ballistic impact, thereby producing the strong “Jamming” effect to resist impact deformation and absorb impact energy. Moreover, the “Jamming” effect enhanced with the increase of impact load, and showed a distribution mode that weakened from the ballistic impact area to the periphery. Compared with traditional buffer materials, more impact energy was dispersed and absorbed by SSG, but less impact energy was transmitted to the human body. Therefore, the impact strength of UHMWPE/SSG on the human body and backface signature of human body were also significantly reduced (up to 50%), which showed that the composite body armor with SSG buffer material exhibited superior protective performance.

Electrochemical machining (ECM) is a cost-effective method for the machining of difficult-to-cut Inconel 718 superalloy. However, the machining accuracy of ECM is still limited by the poor localization effect due to the existence of stray corrosion. In this paper, a mixed solution of neutral NaNO3 and alkaline NaOH is used to improve the localization effect during ECM of Inconel 718. The potentiodynamic polarization curves and current efficiencies for metal dissolution are measured, and the micro morphologies are examined. The results show that the use of an alkaline solution can promote the formation of a compact passive film on the surface of Inconel 718. ECM tests with cylindrical electrodes are specially designed to verify the effect of alkaline solution on the localization of anodic dissolution. The experimental results indicated that the stray corrosion of the non-machined surface of Inconel 718 alloy can be effectively eliminated by using a mixed solution of NaNO3 and NaOH. The surface roughness of the non-machined area can be noticeably improved.

Counter-rotating electrochemical machining (CRECM) holds the unique advantages to machine thin-walled revolving parts, especially for thin-walled engine cases. The electric field intensity distribution on the revolving anode surface is non-uniform, which is difficult to calculate accurately. In this work, a novel equivalent model for analytic solution of the electric field in CRECM is proposed based on complex variable function, and anode material dissolution model is established for CRECM. The variations of the material removal rate (MRR) and interelectrode gap (IEG) at different machining parameters have been fully investigated. The results indicate the MRR can reach a relative equilibrium state after a transition stage. The relative equilibrium MRR is higher than the feed rate, leading to a linear increase in the IEG. Moreover, machining parameters are optimized numerically to shorten the time reaching the relative equilibrium state. Experiments are conducted to verify the theoretical results. The experimental results fit well with the theoretical values. It means that the proposed model is effective for the prediction of the material dissolution process in CRECM.