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Gear involute artifact (GIA) is an indispensable tool in the detection of high-precision gears. In this paper, a new method of horizontal electrode wire electrochemical contour evolution machining (HE-WECEM) was proposed to machine GIA. Compared with traditional circular interpolation for machining involute, HE-WECEM simulates the evolving process of involute to greatly improve the machining accuracy. Firstly, the machining mechanism of GIA by HE-WECEM was studied through mathematical models and electric field simulations. Secondly, reciprocating feed and two-way flushing fluid system was used, and its effectiveness in updating the electrolyte in the machining slit was analyzed through a flow-field simulation. And then, comparative experiment was designed to further validate the effectiveness of the flushing fluid system. The results indicate that the flushing system can effectively improve the stability of HE-WECEM. Finally, single-factor experiments were designed to investigate the effects of electrical parameters on machining. Based on the single-factor experiments, the Box–Behnken experiment was conducted on the electrical parameters. The response surface methodology (RSM) was used to analyze the composite effects of electrical parameters and obtain the optimal combination of machining parameters. A GIA blank with base circle radius of 50 mm was fabricated on an 8-mm-thick GCr15 workpiece, and the maximum deviation of tooth profile can reach 17.18 μm. The average surface roughness Sa reaches 1.435 μm. It is proved that HE-WECEM is a reliable method for machining GIA blank. [ABSTRACT FROM AUTHOR]

In order to further reduce the machining errors of microstraight thin walls caused by the elastic deformation in micromilling process, the deformation mechanism has been studied, and a compensation method is proposed to reduce the machining errors. Firstly, conventional micromilling experiments have been conducted. It shows that large dimensional errors exist in finished thin walls. Second, a mathematical model is established to calculate the thin wall deformation based on Rayleigh–Ritz theory. The deformation values are determined by calculating the selected discrete measurement points. Based on the deformation of measurement points, the thin wall deformation of any position can be calculated by numerical method. Finally, the thin wall dimensional errors are reduced by compensating the deformation according to the analysis based on the introduced mathematical model. The high machining quality of the thin wall is realized. The experimental results show that the dimensional errors of the thin wall have been significantly reduced after the deformation compensation. The average relative dimensional errors have been reduced from 6.86 to 1.11 ~ 2.69%. Also, the fabricated thin walls keep good shape accuracy. The experimental results show that the introduced device and the compensation method can effectively improve micromilling quality of thin walls. [ABSTRACT FROM AUTHOR]

In order to further improve the dimensional accuracy of micromilled thin walls with high aspect ratios, the machining process should be actively controlled. A device for active cutting force measurement and cutting parameter compensation is developed to realize the real-time measurement of radial cutting forces and compensation of radial cutting parameters in thin wall cutting process. Firstly, a mathematical model is established to calculate the deformation and cutting force of thin walls based on the cantilever beam deformation theory. The thin wall deformation in the cutting process is estimated by measuring the cutting force. Then, the obtained incremental thin wall deformation is to be compared with the compensation threshold, which is set at 0.5 μm. If the value of the incremental deformation is less than 0.5 μm, compensation will not be processed. Otherwise, the incremental deformation is used as the compensation value for iterative compensation, until the incremental deformation of the thin wall is less than 0.5 μm. At last, a contrast experiment is carried out. The experimental results show that the introduced device and compensation method are feasible. Machining quality of the thin wall has been obviously improved in dimension precision after the cutting parameter compensations. [ABSTRACT FROM AUTHOR]

The neutral curve of a flexspline (FS) is usually represented by the function curve of cam-shape curve in the traditional harmonic drive (HD) model. This representation may induce tooth tip interference and excessive deformation. In this study, a novel mathematical model of the FS deformation is established to accurately depict the neutral curve. Then, a tooth profile design method is proposed based on this model, which can obtain an exact conjugate tooth profile when giving an initial tooth profile. In addition, another design method that does not demand the initial tooth profile is proposed for simplicity of design. The HD designed by this method has a larger number of meshing teeth and a larger depth of engagement compared to traditional HDs. Moreover, a meshing model of a tooth pair is employed to verify the feasibility of the two design methods. Next, one of them is used to investigate the effect of the wave generator shape on the engagement of a couple tooth profiles, and the results show that the wave generator shapes with different parallel distances have no effect on the continuous engagement. Furthermore, an instantaneous transmission ratio calculation method of a tooth pair is developed for future calculations of the instantaneous transmission ratio between the input and output shafts of the HD. The calculation results manifest that the instantaneous transmission ratio of the tooth pair belongs to a variable transmission ratio. [ABSTRACT FROM AUTHOR]

Concrete is often used in building, bridges, dams, roads and other infrastructures. However, the porosities and natural hydrophilicity of concrete often induce the damage of the concrete architecture or other disasters. Endowing the concrete with superhydrophobicity can effectively improve the antifreeze–thaw, anti-corrosion and anti-icing properties and expand the application prospect of concrete in the modern construction industry. Despite all this, the compressive strength of superhydrophobic concrete is not high enough, limiting its application. Here, we maintained superhydrophobic concrete for 28 days and improved the compressive strength for 3.5 times from 10 MPa to 34.48 MPa. The main mechanism is that calcium silicate hydrate structures grow with the increase in maintenance time and make the inside microstructures connected more closely. In addition, XPS spectra were also collected to investigate the chemical compositions of the superhydrophobic concrete. A series of tests were carried out on superhydrophobic concrete and indicated that the superhydrophobic concrete after maintenance had high surface robustness, anti-corrosion property and high anti-icing and deicing capacity, showing the application value. [ABSTRACT FROM AUTHOR]