The thermoplastic polymer such as poly(methyl methacrylate) (PMMA), polyetheretherketone (PEEK), and polyimide (PI) is a kind of polymer material with properties of good mechanical strength. It has been widely used in the fields of aerospace, optical engineering, and microfluidics, etc. Thermoplastic polymers are considered to be one of the most promising engineering plastics in the future. Therefore, it is necessary to further study its mechanical properties and machinability, especially in ultra-precision machining. Furthermore, mechanical property and machinability were studied in this work. Through the dynamic mechanical analysis experiment, the elastic modulus and temperature effect of PMMA, PEEK, and PI are analyzed. In addition, the high-speed micromilling experiment is conducted to show that the surface roughness, burrs, and cutting chip characteristics in the high-speed micromilling process. In general, the surface quality of the brittle removal is generally better than that of the viscoelasticity state. The results show that PMMA, PEEK, and PI have good mechanical properties and machinability. Base on the results, the material will be in a viscoelastic state as the temperature increases. The surface quality of the brittle removal is generally better than the viscoelastic state.

Spin-coating is widely applied in the field of thin-film fabrication due to its simplicity and high film uniformity. To prepare thin films on rectangular substrates by spin-coating, the simulation and experimental methods were used to study the characteristics of the film thickness in this work. The two-phase flow simulations of spin-coating on a rectangular substrate and circular substrate were carried out with the volume of fluid (VOF) method. The simulation results showed that the airflow field and the substrate geometry had little effect on the evolution of spin-coated film thickness. However, in the experimental results, there was a significant difference in the thickness of the spin-coated film on the rectangular substrate and the circular substrate. According to further study, the solvent evaporation that was neglected in the simulation was the dominant factor of the differences. In addition, it was concluded that the non-uniform evaporation caused by the surface tension and edge accumulation in the later spin-coating stage was the main reason for the film accumulation of the windward area on the rectangular substrate. This work is useful to obtain a deeper understanding of the thin-film formation mechanism of spin-coating.

The lightweight design of the sandwich mirror, as a commonly used space primary mirror structure, is one of the key topics for the design of space-based optomechanical systems. Owing to the limitation of traditional manufacturing capabilities, the induced holes on the mirror back are usually of the open or half-open form, which compresses the optimization design space. With rapid development of additive manufacturing (AM) technologies, it is possible to fabricate a closed-back sandwich mirror with a complex internal structure to achieve outstanding performance. In this paper, a novel topology optimization model for a closed-back primary mirror of a large-aperture space telescope is proposed. First, extrusion constraints are considered in the optimization model to obtain the layout design of stiffening webs inside the mirror core. Then, a simply connected constraint, as one type of constraint in AM, is considered to avoid enclosed voids in the structures. Through solving the proposed model, a new c...

Subsurface damage (SSD) and grinding damage-induced stress (GDIS) are a focus of attention in the study of grinding mechanisms. Our previous study proposed a load identification method and analyzed the GDIS in a silicon wafer ground (Zhou et al., 2016, “A Load Identification Method for the GDIS Distribution in Silicon Wafers,” Int. J. Mach. Tools Manuf., 107, pp. 1–7.). In this paper, a more concise method for GDIS analysis is proposed. The new method is based on the curvature analysis of the chip deformation, and a deterministic solution of residual stress can be derived out. Relying on the new method, this study investigates the GDIS distribution feature in the silicon wafer ground by a #600 diamond wheel (average grit size 24 μm). The analysis results show that the two principal stresses in the damage layer are closer to each other than that ground by the #3000 diamond wheel (average grit size 4 μm), which indicates that the GDIS distribution feature in a ground silicon wafer is related to the depth of damage layer. Moreover, the GDIS distribution presents a correlation with crystalline orientation. To clarify these results, SSD is observed by transmission electron microscopy (TEM). It is found that the type of defects under the surface is more diversified and irregular than that observed in the silicon surface ground by the #3000 diamond wheel. Additionally, it is found that most cracks initiate and propagate along the slip plane due to the high shear stress and high dislocation density instead of the tensile stress which is recognized as the dominant factor of crack generation in a brittle materials grinding process.