This paper presents comprehensive theoretical analyses and experimental investigations for evaluating the ultrasonic vibration-assisted turning (UVAT) of die steels with single-crystal diamond tools. The diamond tool wear was found to rely heavily on the feed rate and the cutting speed while being insensitive to the depth of cut and the tool relief angle under the cutting conditions used in the tests. The tool wear characteristics were further studied based on the observation of wear zone using Raman spectral analysis and energy-dispersive X-ray (EDX) analysis. The detection results of the tool worn topography, the phase transformation and the carbon diffusion of diamond crystals revealed that tool wear mainly occurred on the tool flank face due to the graphitization and the diffusion of the diamond tool. Analytical results of the function mechanisms of the ultrasonic turning indicated that the friction force between the tool flank face and the machined surface, which depended mainly on the ratio of the cutting speed and the vibration speed, could be effectively reduced in ultrasonic turning process. The analytical and experimental results indicated that compared with conventional turning (CT), the cutting performance, in terms of the tool life, was markedly improved by applying ultrasonic vibration to the cutting tool.

High precision and high efficiency in robotic grinding of aero-engine extremely thin blade edges is a challenging problem. In this article, a novel toolpath planning method is proposed based on the derived dwell time calculation model and the developed interpolation algorithm. The dwell time of each cutter contact point is solved based on the matrix method by consideration of the revised material removal model and machining allowance distribution. To optimize the previous interpolation algorithm based on geometric intersection, an arc length and Taylor binary expansion optimization are proposed to plan cutter contact points according to the dwell time and the curvature changes of blade edges. Subsequently, the tool orientation is corrected based on a double-vector controlling method to avoid the processing interference. Simulation results show that the proposed interpolation algorithm has improved the path coverage by 17.6%, and its computational efficiency is 34 times higher than that in previous algorithm. The comparative robotic grinding experiment results show that the proposed toolpath has improved the surface profile accuracy of blade edge to 0.042 mm, and its machining accuracy is 14.3–46.2% higher than that of other methods.

This work presents a series of experimental investigations and corresponding theoretical analyses to research on the effect of cryogenic minimum quantity lubrication (MQL) on machinability of diamond tool in ultraprecision turning of typical die steel. The tool wear and machined surface quality were determined as experimental indexes, which were measured using the scanning electron microscope and surface profiler, respectively. Besides, the maximum temperatures of diamond tool surfaces acquired by infrared thermal imager were used to indirectly evaluate the cutting process. The experimental results revealed that cryogenic MQL had obvious advantages in improving diamond tool durability and machined surface quality by comparison with flood cooling, cryogenic gas cooling, and MQL, and its essential function mechanisms were thoroughly understood. On the basis of this, carbon nanofluid was found to achieve optimal tool life in diamond turning compared with polyethylene glycol, castor oil, synthetic ester, and emulsified liquid. Ultimately, the combined machining method of ultrasonic vibration-assisted turning and cryogenic minimal quantity lubrication was proposed in this work. The results showed that this technique could observably improve the machinability of diamond tool and also provide a new direction for exploring a suitable processing method for ultraprecision machining of ferrous materials.

This study presents detailed experimental investigations on precision machining of the TiAl-based alloy with an abrasive belt flexible grinding method. Subsequently, the feasibility of this precision machining method is evaluated with respect to the material removal rate, abrasive wear, machined surface roughness, and residual stress. The material removal rate and surface roughness were determined as experimental indicators and were measured via a three-coordinate measuring instrument and surface profiler, respectively. Micro-morphologies of the machined surface and worn abrasive belt were investigated via a scanning electron microscope. The residual stress distributions in the machined surface layer were detected by using an X-ray diffractometer. The experimental results revealed that the aforementioned evaluation indicators satisfied the desired requirements, thereby indicating that the abrasive belt flexible grinding technique was suitable for precision machining of the TiAl-based alloy. Additionally, the optimal combinations of grinding parameters were determined to obtain desirable material removal rate and machined surface roughness. The basic wear processes and characteristics of the abrasive belt were thoroughly examined. The formation of desirable residual compressive stresses in the machined surface layer was mainly attributed to low frequency and small amplitude vibration knocking at the grinding interface.