内壁含螺旋槽的玻璃钢零件加工技术

电磁脉冲弹是一个新的武器研制方向,其中脉冲筒是电磁脉冲弹中的一个重要零件。由于脉冲筒内壁含有3段螺旋缠绕并露出内壁一半长的铜丝,而且3段铜丝的直径、缠绕螺距和缠绕圈数都是变化的;因此,存在一定的加工难度。本文详细描述了1个带3段螺旋槽的工装的设计和制造,并阐述了脉冲筒的加工工艺过程。     

Speciation studies of methyl butanoate ignition

The current work presents the results of an experimental study of the intermediates formed during ignition of methyl butanoate (C₅H₁₀O₂) and air mixtures. A rapid-sampling system and the University of Michigan rapid compression facility were used to acquire gas samples at conditions of P = 10.2 atm and T = 985 K using mixtures of χ_mb = 0.96%, χ_O2 = 20.79%, χ_N2 = 52.89%, and χ_Ar = 25.25% (mole fraction, percent basis); corresponding to ? = 0.30 and an inert gas to O₂ molar ratio of 3.76. The samples were analyzed using gas chromatography. Quantitative measurements of mole fraction time-histories of methane, ethane, propane, ethene, propene, and 1-butene are compared with model predictions based on a reaction mechanism developed in previous work. The methane and ethene time-histories are in excellent agreement (within ∼20%), while propene and ethane are underpredicted by the model. Sensitivity analysis shows ignition is controlled primarily by competition between H₂O₂ and HO₂ kinetics at these conditions. Reaction path analysis shows the methyl butanoate fuel consumption is dominated by H-atom abstraction by OH.     

Pyrolysis of wood at high temperature: The influence of experimental parameters on gaseous products

The pyrolysis of wood was carried out in an Entrained Flow Reactor at high temperature (650 to 950 °C) and under rapid heating conditions (> 10³ K s^− 1). The influence of the diameter and initial moisture of the particle, reactor temperature, residence time and the nature of the gaseous atmosphere on the composition of the gaseous products has been characterised. Particle size, between 80-125 and 160-200 μm, did not show any impact. Pyrolysis and tar cracking essentially happen in very short time period: less than 0.6 s; the products yields are only slightly modified after 0.6 s in the short residence times (several seconds) of our experiments. Higher temperatures improve hydrogen yield in the gaseous product while CO yield decreases. Under nitrogen atmosphere, after 2 s at 950 °C, 76% (daf) of the mass of wood is recovered as gases: CO, CO₂, H₂, CH₄, C₂H₂, C₂H₄ and H₂O. Tests performed under steam partial pressure showed that hydrogen production is slightly enhanced.     

Synthesis of carbon nanowalls by plasma-enhanced chemical vapor deposition in a CO/H2 microwave discharge system

Synthesis of carbon nanowalls was performed by a plasma-enhanced chemical vapor deposition in a CO/H₂ microwave discharge system. At the optimum CO/H₂ feed ratio of 46 sccm/4 sccm, the aligned carbon nanowalls with thickness of about several tens of nanometers were able to be synthesized. The extremely high growth rate of 1 μm min^− 1 was obtained in our system with a relatively low microwave discharge power of 60 W for a growth area of 1 cm². An optical emission spectroscopy was performed to clarify the characteristics of a CO/H₂ discharge system.     

A reduced chemical kinetic model for HCCI combustion of primary reference fuels in a rapid compression machine

A model for the Homogeneous Charge Compression Ignition (HCCI) of Primary Reference Fuels (PRFs) in a Rapid Compression Machine (RCM) has been developed. A reduced chemical kinetic model that included 32 species and 55 reactions was used and the affect of wall heat transfer on the temperature of the adiabatic core gas was taken into account by adding the displacement volume of the laminar boundary layer to the cylinder volume. A simple interaction between n-heptane and iso-octane was also included. The results showed the well-known two-stage ignition characteristics of heavy hydrocarbons, which involve low and high temperature cycles followed by a branched chain explosion. The first stage energy release decreases and the ignition delay increases nonlinearly with increasing octane number and decreasing the initial pressure. The energy release rate and total energy released were determined primarily by the rate of CO oxidation during the explosive phase following the ignition delay. The model reproduced the pressure curves obtained in the RCM experiments over a wide range of conditions remarkably well and was very sensitive to the fuel structure, the mixture composition and the initial temperature and pressure. Thus, the model can be easily adapted for predicting “knock” in spark-ignition engines and ignition-delays and burning rates in HCCI engines.     

基于Autoform的冲压件的数值模拟及模具设计

以冲压件为研究背景,论述了制件冲压成形有限元模拟的理论和主要步骤。采用Autoform软件对零件进行了冲压成形过程的有限元分析,完成了相关数值模拟,预测了板料成形过程中减薄等缺陷,同时根据模拟结果进行模具设计,证明了前期数值分析对模具设计周期及成形质量具有重要意义。     

3D打印：技术、材料、现状

3D打印技术以其独特的制造方式制作出了许多传统制造方式难以制作的产品,显示出广阔的发展前景,因此也引起政府和民众的极大关注。本文从3D打印技术、3D打印材料、国内外发展情况等几方面对3D打印做了一些介绍,同时对3D打印未来的发展趋势做了展望。     

一种基于C8051F021的温度场快速测控装置

为实现焊接阀体毒焊接过程中的温度控制，设计了基于C8051F021单片机的温度场快速测控装置。该装置以C8051F021单片机作为微控制器，采用热电偶作为温度传感器，通过多通道温度测量系统来测量整个焊接过程中阀体的温度变化情况。设计给出了相关的硬件和软件。通过调试运行，该装置性能可靠，具有通信、键盘显示、报警等功能。     

基于硅胶模技术的小批量塑料件快速制造

介绍了近年来不断被用于塑料工业的硅胶模真空注型快速制造技术。概述了硅胶模真空注型技术的特点、应用范围,介绍并分析了小批量塑料件的制造工艺方法。     

Fabrication of ZnO ring-like nanostructures at a moderate temperature via a thermal evaporation process

Applying melt-fluxing, how to predict the maximal recalescence temperature T_R upon rapid solidification of bulk undercooled Cu₇₀Ni₃₀ alloy has been investigated. Reproducible experimental results show that T_R decreases with the increase of the initial melting undercooling ΔT, and moreover, its value is much lower than that predicted by Level rule and Scheil equation, let alone the equilibrium liquidus temperature. Quantitative thermodynamic calculation, in combination with an analysis of solute distribution, demonstrates that, T_R is affected by the difference of Gibbs free energy between the residual liquid and solid after recalescence. Subjected to sufficiently high ΔT, T_R should be nearly equal to the thermodynamic T₀ point corresponding to the concentration of the residual melt after recalescence.