Diamond tools play a critical role in ultra-precision machining due to their excellent physical and mechanical material properties, such as that cutting edge can be sharpened to nanoscale accuracy. However, abrasive chemical reactions between diamond and non-diamond-machinable metal elements, including Fe, Cr, Ti, Ni, etc, can cause excessive tool wear in diamond cutting of such metals and most of their alloys. This paper reviews the latest achievements in the chemical wear and wear suppression methods for diamond tools in cutting of ferrous metals. The focus will be on the wear mechanism of diamond tools, and the typical wear reduction methods for diamond cutting of ferrous metals, including ultrasonic vibration cutting, cryogenic cutting, surface nitridation and plasma assisted cutting, etc. Relevant commercially available devices are introduced as well. Furthermore, future research trends in diamond tool wear suppression are discussed and examined.

Silicon carbide (SiC) is a promising semiconductor material for making high-performance power electronics with higher withstand voltage and lower loss. The development of cost-effective machining technology for fabricating SiC wafers requires a complete understanding of the deformation and removal mechanism. In this study, molecular dynamics (MD) simulations were carried out to investigate the origins of the differences in elastic–plastic deformation characteristics of the SiC polytypes, including 3C-SiC, 4H-SiC and 6H-SiC, during nanoindentation. The atomic structures, pair correlation function and dislocation distribution during nanoindentation were extracted and analyzed. The main factors that cause elastic–plastic deformation have been revealed. The simulation results show that the deformation mechanisms of SiC polytypes are all dominated by amorphous phase transformation and dislocation behaviors. Most of the amorphous atoms recovered after completed unload. Dislocation analysis shows that the dislocations of 3C-SiC are mainly perfect dislocations during loading, while the perfect dislocations in 4H-SiC and 6H-SiC are relatively few. In addition, 4H-SiC also formed two types of stacking faults.

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...

A ultrasonic elliptical vibration cutting (UEVC) technique, as an advanced cutting method, has been successfully applied to machine difficult-to-cut materials for the last decade. In this study, the mechanism of the elliptical vibration locus caused by the “asymmetric structure” on the horn was analyzed theoretically first, and the corresponding relationship between the degree of asymmetry and the elliptical vibration locus was determined based on the finite element method (FEM). Then, an efficient single-excitation UEVC device with “asymmetric structure” was developed and optimized. The resonant frequency of the device was 40.8 kHz, and the amplitude reached 14 µm, which effectively broke the limitation of cutting speed in UEVC. Finally, the UEVC device’s performance was tested, and the advantages in improving the tungsten alloy surface quality and reducing diamond cutting tool wear validated the technical capability and principle of the proposed device.