Study on the blackening phenomenon of leaded glass during microgroove molding using nickel phosphorous mold

Precision glass molding (PGM) is a recently developed method to fabricate glass microgroove components. Lead glass is commonly used as an optical material due to its high refractive index and low transition temperature. A nickel-phosphorous (Ni–P) plated mold is traditionally employed in the PGM process for microstructures optics. However, leaded glass is subject to color change and can blacken during the PGM process, reducing the light transmittance of microgrooves. In this paper, an equation for the redox reaction between Ni and Pb is proposed, which is based on the diffusion of inner Ni atoms to the surface of the mold and the standard electrode potential of the Pb ions in leaded glass. A viscoelastic constitutive model of the glass is established to simulate the compression stress distribution during molding. Finally, the effects of molding pressure, molding temperature, and mold material on glass blackening are studied. The results show that the blackening of leaded glass is caused by Pb enriching the surface. The rise in molding stress and temperature increases the deformation of Ni–P plating, which promotes the diffusion of Ni atoms. By adding a titanium incorporated diamond-like carbon (Ti-DLC) coating, the deformation of the Ni–P plating during molding is suppressed, and the diffusion of Ni atoms can be prevented. In this way, the blackening of leaded glass can be prevented.     

Suppression of forced vibration due to chip segmentation in ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V

Ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V is investigated in this research. Because products made of Ti–6Al–4V alloy are usually designed for possessing low-rigidity structures or good-quality cut surfaces, machining requirements such as low cutting forces and slow rate of tool wear need to be fulfilled for realization of their precision machining. Therefore, the ultrasonic elliptical vibration cutting is applied as a novel machining method for those products. Machinability of Ti–6Al–4V alloy by the ultrasonic elliptical vibration cutting with cemented carbide tools is examined to figure out suitable cutting conditions for precision machining of Ti–6Al–4V alloy. As experimental results, generated chips, cutting forces, and profiles of cut surfaces are indicated. A forced vibration problem occurred due to the segmented chip formation, which is also well-known in the ordinary non-vibration cutting. Therefore, characteristics of the forced vibration due to the chip segmentation are investigated in this research. Through the experiments, it is found that the frequency and magnitude of the forced vibration have relation with the average uncut chip thickness and cutting width. Especially, it is found that the averaging effect can suppress the forced vibration, i.e. the chip segmentation tends to occur randomly over the large cutting width, and hence the force fluctuations with random phases tend to cancel each other as the cutting width increases relatively against the average uncut chip thickness. Based on the investigations, a new practical strategy to suppress the forced vibration due to chip segmentation is proposed and verified. Using the proposed method significantly decreased cutting forces and good quality of surfaces are obtained when the forced vibration is suppressed compared to the ordinary non-vibration cutting results. Therefore, the results suggest that the precision machining can be realized without sacrificing the machining efficiency by increasing the width of cut and decreasing the average uncut chip thickness.     

高精度大跨距同轴孔的精密研磨加工

对高精度大跨距同轴孔的加工现状进行了分析,确认采用现有加工方法无法满足要求。在此基础上,提出针对高精度大跨距同轴孔采用精密研磨加工,并改进了研磨工具。介绍了高精度大跨距同轴孔精密研磨加工的注意事项。这一方法可应用于加工孔距1 m以内的高精度大跨距同轴孔,加工效果良好。     

Nanomechanical characterization of RB-SiC ceramics based on nanoindentation and modelling of the ground surface roughness

Reaction bonded silicon carbide (RB-SiC) ceramics are the primary structure and mold materials for the optical industry and mostly are machined by means of ultra-precision grinding to achieve a satisfactory surface quality. However, it is not easy to attain the theoretical prediction of surface quality, particularly surface roughness, because of different mechanical characterization of Si/SiC phases inside the RB-SiC ceramics. In this work, the nanoindentation tests were performed to investigate the nanomechanical characterization of individual phase inside the RB-SiC ceramics. On the basis of the nanoindentation results of RB-SiC, a theoretical model was established to predict surface roughness in the ultra-precision grinding process, which considered the different removal mechanisms of Si matrix and SiC particles. The comparison of the prediction results of existing and novel models and single-factor experimental results shows that the novel model was well consistent with the experiment.     

Non-kinematic calibration of a six-axis serial robot using planar constraints

This paper describes a non-kinematic calibration method developed to improve the accuracy of a six-axis serial robot, in a specific target workspace, using planar constraints. Simulation confirms that the stiffness of the robot, as well as its kinematic parameters, can be identified. An experimental validation shows that the robot's accuracy inside the target workspace is significantly enhanced by reducing the maximum distance errors from 1.321 mm to 0.274 mm. The experimental data are collected using a precision touch probe, which is mounted on the flange of a FANUC LR Mate 200iC industrial robot, and a high precision 9-in. granite cube. The calibration method makes use of a linear optimization model based on the closed-loop calibration approach using multi-planar constraints. A practical validation approach designed to reliably evaluate the robot's accuracy after calibration is also proposed.     

Exosomes: Key tools for cancer liquid biopsy

Precision medicine is based on the identification of biomarkers of tumor development and progression. Liquid biopsy is at the forefront of the ability to gather diagnostic and prognostic information on tumors, as it can be noninvasively performed prior or during treatment. Liquid biopsy mostly utilizes circulating tumor cells, or free DNA, but also exosomes. The latter are nanovesicles secreted by most cell types, found in any body fluid that deliver proteins, nucleic acids and lipids to nearby and distant cells with a unique homing ability. Exosomes function in signalling between the tumor microenvironment and the rest of the body, promoting metastasis, immune remodelling and drug resistance. Exosomes are emerging as a key tool in precision medicine for cancer liquid biopsy, as they efficiently preserve their biomarker cargo. Moreover, exosomes strongly resemble the parental cell, which can help in assessing the oxidative and metabolic state of the donor cell. In this respect, exosomes represent one of the most promising new tools to fight cancer. This review will discuss the clinical applications of profiling exosomal proteins and lipids by high-throughput proteomics and metabolomics, and nucleic acids by next generation sequencing, as well as how this may allow cancer diagnosis, therapy response monitoring and recurrence detection.     

轿车进气歧管成型工艺与成套注塑模具设计

以发动机进气歧管为例,在详细分析组成进气歧管的底壳和面盖结构、注塑成型材料及各塑件壁厚,运用MFI 2015分别对底壳和面盖最佳浇口位置进行了仿真分析。针对底壳和面盖质量不同、壁厚不同、成套生产而各个制品的壁厚必须均匀、有隔离凸台和众多加强筋等特点,确定本注塑模具采用三浇口+热流道+冷流道组成的混合式浇注系统方案;运用MFI对影响产品品质的充填时间、速度/压力切换时的压力、模流末端压力、流动前沿温度、锁模力、气穴、熔接线、缩痕等进行了详细分析与探讨;运用UG软件对模具型腔、型芯,底壳上方形管口A的成型,顶出与加强支承结构、模具整体等进行了分析设计。创造性地使用了由导柱导套+圆锥定位+方形块定位+楔紧镶块+厚薄调整垫组成的"五位一体"精度保证与保持系统,同时也使用了厚度调整垫,保证了型腔型芯的组合和开合模的精准。经生产证明:模具结构合理、动作可靠、产品成型完整、质量达到设计要求。     

压铸雷达用高精度波导管的研制

针对雷达用高精度波导管的特点,采用压铸和拼装工艺,生产出满足技术要求的波导管零件。通过分析波导管的工艺难点,开展了YL113合金的气体含量控制、压铸工艺优化以及配套工装装配工艺研究。结果表明,通过惰性气体精炼和真空除气处理,可有效降低合金熔体内氢含量,保证合金内部品质;通过浇道设计和压铸工艺优化,保证了喇叭、十字筋铸件的尺寸精度,且铸件屈服强度高于270MPa,伸长率高于2%;采用退火、自然时效处理以及装配工装,有效保证了波导管的装配尺寸精度,产品合格率达91%。     

Application of GMDH neural network technique to improve measuring precision of a simplified photon attenuation based two-phase flowmeter

Multiphase flowmeters have an important role to play in the industry and any attempts that lead to improvements in this field are of great interest. In the current study, group method of data handling (GMDH) technique was applied in order to increase measuring precision of a simple photon attenuation based two-phase flowmeter that has the ability to estimate the gas volumetric percentage in a two-phase flow without any dependency to flow regime pattern. The simple photon attenuation based system is comprised of a cobalt-60 radioisotope and only one 25.4 mm × 25.4 mm sodium iodide crystal detector. Four extracted features from recorded photon spectrum in sodium iodide crystal detector were used as the inputs of GMDH neural network. Equations related to the combination of the features and the error rate of each approximation is also reported in this paper. Applying the mentioned technique, the gas volumetric percentage in an oil-gas two phase flow was determined with the root mean square error of less than 2.71 without any dependency to the flow pattern. The obtained measuring precision in this study is at least 2.1 times better than reported in previous studies.