UHTC-based matrix as protection for Cf/C composites: Original manufacturing,microstructural characterisation and oxidation behaviour at temperature above 2000 °C

In space propulsion applications, the development of new ceramic matrix composites with improved resistance to oxidation and ablation at high temperature is needed and ultra-high temperature ceramics-based ones appear the most suitable. Combination of both powder impregnation (ZrB₂, C) and liquid silicon infiltration enabled manufacturing of UHTC based matrices in C_f/C preforms with less than 10 vol% open porosity and various proportions and homogeneous distribution of C, ZrB₂, SiC and Si. Oxidation behaviour was evaluated on composite structures using an oxyacetylene torch at temperatures higher than 2000 °C. Chemical analyses and microstructural observations before and after oxidation testing evidenced the protection ability of ZrB₂-SiC-Si matrices thanks to the formation of multi-oxide scales which resisted even tested durations of 6 min and pointed the unharmful presence of residual 12 vol% silicon on the composite for use at high temperature under high gas flows.     

北京2022年冬奥会和冬残奥会火炬传递机器人

面向北京冬奥会对机器人跨域火炬传递的需求,研发水陆两栖机器人、水下变结构机器人、空中飞行机器人、地面机器人、冰雪面六足机器人和助力外骨骼机器人等6型面向火炬接力的系列机器人,利用这些机器人可在地面、空中和水下完成火炬传递。最终,根据北京2022年冬奥会火炬接力路线方案的调整,将水陆两栖机器人、水下变结构机器人和水下特种火炬应用于北京2022年冬奥会火炬传递活动中,实现了奥运史上首次机器人与机器人之间的水下火炬传递;助力外骨骼机器人应用于北京2022年冬残奥会火炬传递活动中,残疾人代表使用下肢助力外骨骼进行了火种汇集,两位残疾人火炬手分别借助上肢和下肢助力外骨骼机器人一起进行了火炬传递,传递出“科技改变生活”的理念,体现出“技术温暖人心”的精神。     

醋酸装置火炬头的低噪无烟化改造

分析了醋酸厂低压甲醇羰基化生产醋酸装置火炬头运行噪音过高的原因,认为运行噪音过高主要是由于助燃蒸汽喷射噪音所引起;比较了几种降低噪音方法的可行性;改造采用火炬头中下部的蒸汽引射空气喷嘴注入方式的方法代替火炬头顶部简单的蒸汽喷射,并加设高效盆式消声器.改造后距火炬中心80 m处的噪音强度从原来的105dB(A)降低至79 dB(A),取得了良好的效果.     

Design and characteristics of a new type laminar plasma torch for materials processing

Laminar plasma jet(LPJ) generated by laminar plasma torch(LPT) has a favorable temperature and velocity distribution. Thus, it is superior to the turbulent plasma jet in material processing.However, most of the reported LPTs usually operate at a relatively low output power with a relatively low arc voltage and thermal efficiency, which limits its capabilities. In this context, this paper attempts to design a new type of high-power LPT with a relatively low arc current and a high thermal efficiency. In the first section, the design principle of the main components is studied and discussed in detail, and a new high-power LPT is proposed. Then, the experimental characteristics of the proposed high-power LPT are examined. Experimental results reveal the following characteristics of the proposed LPT.(1) The max jet length of the proposed LPT reaches at 540 mm.(2) Its mean arc voltage is higher than 290 V when the LPT works with arc currents lower than 200 A, leading to an output power greater than 50 kW.(3) The mean thermal efficiency is higher than 50%. Lastly, the proposed LPT has been applied to spheroidize the aluminum oxide powers. The experiment results for the production of spherical powders show that the proposed LPT has a good characteristic for material processing.     

Knowledge-based CNC torch path generation for laser cutting of planar shapes

In this paper, we propose a knowledge-based method for generating a CNC torch path for laser cutting of the outlines of planar shapes. The proposed method consists of two main phases: laser cutting knowledge construction and CNC torch path generation using the knowledge. In the first phase, laser cutting experiments are conducted on various operating parameters, and then empirical data are stored and analyzed to make up the knowledge of laser cutting. With this knowledge, we can inquire what a kerf width is for specific operating parameters. In the second phase, using the knowledge of laser cutting, the CNC torch path is generated for cutting the outlines of the given planar shapes. This phase is basically based on the offset generation of each outline by a sequence of arc splines, where the offset distance is the same as the half of the kerf width determined from the constructed knowledge. The proposed method based on laser cutting knowledge makes full use of arc interpolators in CNC torch path generation. The method can efficiently reduce the number of path segments while keeping the torch path within the desired accuracy.     

Treatment of Bone Waste Using Thermal Plasma Technology

Daily meat consumption produces a lot of bone waste, and dumped bone waste without treatment would result in environmental hazards. Conventional treatment methods of waste bones have some disadvantages. Herein, an investigation of bone waste treated using thermal plasma technology is presented. A high-temperature plasma torch operated at 25.2 kW was used to treat bone waste for seven minutes. The bone waste was finally changed into vitric matter and lost 2/3 of its weight after the treatment. The process was highly efficient, economical, convenient, and fuel-free. This method could be used as an alternative for disposal of bone waste, small infectious animals, hazardous hospital waste, etc.     

分层实体制造激光头切割路径的建模与优化

分层实体制造(LOM)技术中分层制造时间是由该层的切割速度与切割路径确定的，当切割工艺参数(如：切割功率、切割速度)确定之后，每一层制造的时间是由该层切割(扫描)路径确定的。因此优化切割(扫描)路径对提高成型效率有重要意义，而分层实体制造技术中激光切割路径优化的实质是空行程路径的优化。建立了切割路径空行程路径优化的数学模型。由于求解该模型的复杂性，采用了分级规划的两个分步算法：首先用改进的最近邻域算法求解轮廓边界线上的切割起点，然后当切割点确定后把路径优化问题归结为旅行售货员问题(TSP)，采用了高效的智能仿生算法一蚁群系统算法来求解。运行结果表明，该算法显著缩短了分层制造中的空行程，提高了快速原型制造的效率。     

等离子-MIG焊接设备的设计与研制

为解决厚壁铝及铝合金构件的焊接效率低的实际问题，提出了等离子-MIG双电弧高效焊接新方法.该方法是采用双电源和双电弧共枪体等技术，完成等离子-MIG焊接设备的研制.所研制的设备以PLC为主控单元, 设计了焊接参数专家库管理系统,同时，还采用了有限元模拟技术研究了该设备的核心组件——等离子-MIG枪体内部的水流场和温度场,为枪体的设计和结构优化提供了重要的参考数据, 该焊接方法已应用于三峡电站大型开关断路器的制造工程中.     

基于金属熔流的未爆弹药销毁技术研究进展

结合未爆弹销毁作业的特点,分析常用销毁方法的适用范围,将烟火切割技术应用于弹药销毁作业,介绍了一种引燃非引爆的销毁方法。概述了金属熔流销毁技术的原理,梳理了燃烧剂配方和燃烧炬结构的研究现状,分析了燃烧剂体系配比,添加剂成分和燃烧炬结构对金属熔流的作业时间、熔穿金属效率、效果的影响。对比文献资料,采用火箭发动机型燃烧炬和利用高热剂、合金剂、稀释剂和造气剂优化燃烧剂,更有利于未爆弹药的销毁。并为下一步深入研究基于金属熔流的弹药销毁技术提供参考。     

氧—乙炔火焰钎焊在LF21铝合金上的应用

从铝钎焊机及具体工艺操作方面进行阐述，解决了LF21防锈铝用氧－乙烯火焰作为热源进行钎焊的工艺问题。