The dynamic responses of milling system change the ideal trajectories of cutting teeth and therefore plays a critical role in determining the machining accuracy. The amplitude of cutting vibrations could reach tens of or even hundreds of micrometers in low-stiffness cutting conditions, for example, when milling thin-walled parts and/or using slender tools. Usually, moderate cutting parameters are utilized to avoid excessive cutting loads, strong milling chatter or large dynamic deflections, which however, significantly lowers the productivity. In spite of decades of study, it is still a challenge to accurately model, efficiently analyze, reliably monitor and precisely control the dynamic milling process in low-stiffness cutting conditions. In this paper, the recent advances and research challenges on dynamics modeling and response analysis are briefly reviewed.
Titanium alloy material has excellent properties such as low density, high strength, good oxidation resistance, creep resistance, etc. It has a broad application prospect in various fields. However, these characteristics also make it dif-ficult to process. Grinding is an essential method for high efficiency and precision machining of titanium alloy, ob-taining good machining precision and surface quality. The removal mechanism of titanium alloy is helpful to im-prove the surface quality of titanium alloy grinding. The recent research results in this field are reviewed. Firstly, the grinding technology types of titanium alloy were summarized, and the machining characteristics were systematically analyzed from two aspects of abrasive wear and material removal behavior of titanium alloy. Finally, the development trend of titanium alloy grinding technology in the prospect.
Abstract: Severe stress concentration and bad sealing performance are encountered in a non-metallic engineering part during an interference fit assembly process. Both numerical calculation and experimental test are employed to analyze the causes resulting in the assembly failure. Based on the finite element method (FEM), commercial computational software, ANSYS, is first used to simulate the whole assembly process with different boundary conditions. By comparing simulation results of the assembly process with various boundary conditions, it is found that deformation energy and friction force contribute differently to the reaction force at varying assembly depths. In virtue of these simulation results, an improved engineering part is designed and fabricated. Experimental test results show that stress concentration and sealing performance problems are basically solved compared to those in the original model. Moreover, reaction forces calculated from numerical simulation and measured from experimental tests agree reasonably with each other during the interference fit progress. This work is beneficial to the understanding of the interference fit process in engineering application and the avoiding of part failure resulting from inappropriate design.
Abstract: Superhydrophobic surfaces have special restrictions and manipulation capabilities on liquids, and have great potential applications in fields of biological analysis. However, the preparation of bio-friendly superhydrophobic surfaces by high efficiency methods remains a challenge. In this work, a new one-step preparation method to fabricate bio-friendly superhydrophobic surface based on atmospheric pressure cold plasma is proposed. Using argon as the working gas and HMDSN as the monomer, the superhydrophobic surface can be prepared in one step by APCP whether on the surface of conductive metal, the surface of a flexible paper, or the surface of hard and brittle glass. The plasma characteristics, surface wettability, surface morphology, chemical composition, adhesion performance and bounce phenomenon have been systematically studied, which proves the excellent performance of the prepared superhydrophobic surface. Finally, the bio-friendly properties were verified by the cultivation of Hela cell, Escherichia coli, the seeds of bacopa monnieri and clover on the prepared superhydrophobic surface. This work shows great potential in applications for biological system cultivation and analysis.
Abstract: Minimally invasive surgery(MIS)has the advantages of less trauma and quick recovery, so it is favored by patients. However, there are more requirements for surgeons' skill and experience in MIS. Combining robot-assisted tech-nology with MIS can improve the quality of surgery and shorten the learning time for surgeons. Besides, with the help of robot-assisted technology, remote surgery can be achieved. Because of small incisions in MIS, the manipu-lator must pass through a fixed point during movement, which is the key point to develop the MIS robot and an obvious feature of the MIS robots. The ways whose classification is made into mechanisms with redundant degrees of freedom (DOF) and constrained by mechanisms to meet the requirement are summarized, and the principles, advantages, and drawbacks of each method are analyzed in this article. Based on summarizing the research results and analyzing the key technologies, the insight into future work is proposed.