Motion navigation for arc welding robots based on feature mapping in a simulation environment

The efficiency of the off-line programming for the arc welding robots depends on the complexity of the workpieces and the welding experience of the technician. When the workpieces or fixtures are redesigned or the robot workstation layout is changed, the result of prior off-line programming cannot be reused. With the thought of CAD/CAPP/CAM integration, this paper presents a feature mapping algorithm, which converts the design features of the workpieces to the machining features of the seams. Then a motion navigation method based on feature mapping in a simulation environment is proposed. This method comprises initial position guiding and seam tracking. For initial position guiding, a motion path with the least energy consumption is generated based on the weighted optimal control; then the path is revised for avoiding obstacles by setting the path tags dynamically. For seam tracking, the seam is dispersed into discrete welding points; then the welding gun moves through each point according to the welding sequence. The method is implemented in the development of an off-line programming simulation system. Industrial cases of the welding robot workcell layout for automobile door frames show the method can make the off-line programming much more effective.     

超厚板TC4钛合金电子束焊接接头应力腐蚀敏感性

针对100 mm超厚板TC4钛合金电子束焊接接头,采用慢应变速率拉伸方法评价接头在人造海水中的应力腐蚀敏感性,分析接头的显微组织和断口形貌,对接头的腐蚀机制进行研究. 结果表明,室温条件下应变速率为ε=1×10-6 s-1时,母材在海水中未表现出应力腐蚀敏感性;焊缝上部、中部和下部具有轻微应力腐蚀敏感性. 焊缝在海水中发生阳极溶解,产生氢吸附,导致裂纹的萌生. 同时氢扩散诱导α'相界及α'相内发生位错塞积,进而使裂纹在更低的应力水平下发生扩展.     

掩护攻击下从弹的导航与制导方法

针对全导式多弹头在确保射击精度与弹头密集分布条件下的作战需求,提出了一种数值导航计算和相对制导的方法。基于零视加速度理论,在自由段采用数值导航计算方法,有效地消除了惯性导航系统加速度计漂移误差对导航精度的影响,减小了弹头落点偏差。以摄动制导理论为基础,研究了从弹伴随主弹飞行的相对制导方法,设计了满足落点约束的姿态控制方程和制导关机方程,将从弹和主弹分离时刻的状态参数作为标准关机量,实时计算分离后从弹的关机量并与标准关机量进行对比,满足相对距离条件则实施关机。仿真表明:通过数值导航与相对制导方法能有效实现全导式多弹头的伴随飞行,并以较高精度命中目标,从弹掩护主弹攻击的效果较好。     

Research on droplet transfer in oscillating arc narrow gap GMA welding

In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc （ GMA ） welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The droplet transfer frequency in narrow gap groove is higher than that in bead-on-plate welding. Because of the change of arc location in narrow gap groove, the droplet transfer in oscillating arc narrow gap changes regularly. The droplet transfer frequency near groove sidewall is higher than that at the middle of narrow gap groove.     

一种用于5 V电源ESD防护的新型高维持电压MLSCR

针对5 V电源的静电放电(ESD)防护,提出一种利用PMOS管分流的新型优化横向可控硅(PMOS-MLSCR)。相比于传统MLSCR,PMOS-MLSCR具有更高的维持电压和相对较低的触发电压,有效避免了传统MLSCR面临的闩锁风险。基于0.18 μm BCD工艺,采用TCAD仿真模拟PMOS-MLSCR和传统MLSCR,并通过模拟TLP测试器件特性。仿真结果表明,PMOS-MLSCR的维持电压相对于传统MLSCR提升了3.64 V,触发电压降低了1.49 V,并且满足5 V电源ESD防护的设计窗口。     

Laccase‐catalyzed polymerization drying of Chinese lacquer sap with TiO2 nanoparticles

Nano‐TiO₂/lacquer hybrid coatings are prepared by the blend of nano‐TiO₂ and lacquer sap. Nano‐TiO₂ particles are involved in the laccase‐catalyzed polymerization process of urushiol, which improves the properties of lacquer film. With increasing nano‐TiO₂ from 0 to 5 wt %, the drying time of lacquer film to reach hardened dryness decreases from >12 h to 8 h 30 min under 30 °C and 80% relative humidity. Gel permeation chromatography analysis shows that the addition of nano‐TiO₂ accelerates the polymerization of urushiol. It is also related to the formation of Ti? O? C bonds due to the reaction between nano‐TiO₂ and the radicals produced by laccase‐catalyzed oxidation. The pencil hardness, flexibility, and adhesion of hybrid lacquer film can be improved and reach 4H, 1 mm, and grade 2, respectively. Its inhibition rate against Escherichia coli and Staphylococcus aureus increases from 22.6% and ?21.4% to 49.2% and 67.8%, respectively. Furthermore, nano‐TiO₂ hybrid lacquer films also possess higher thermo‐stability than the raw lacquer film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45865.     

煅烧干粒的制备与研究

本文介绍了玻化砖装饰的新动向－煅烧干粒装饰技术的实验室研究成果以及煅烧干粒的制备工艺,采用ＸＲＤ和ＤＴＡ－ＴＧ等测试手段,研究了煅烧干粒的组成和热行为。     

SFCC现场导热系数与温度场实测及预测方法研究

为确定钢纤维页岩陶粒混凝土（SFCC）现场实际的导热系数,与桥面板施工同步制作了不同钢纤维体积分数的SFCC试件,采用热板法进行测定,校核并扩展了导热系数预测公式,并且对高温沥青摊铺时SFCC桥面板的温度场进行了实测和数值模拟.结果表明：环境湿度为67%时,SFCC的实测导热系数为0.915~1.409 W/（m·K）,增加钢纤维体积分数可提高SFCC导热系数;考虑湿度和钢纤维影响后的扩展Maxwell公式预测值与实测值吻合良好;高温沥青摊铺时桥面板SFCC混凝土内的温度梯度可达20.5 ℃,超过规范日温差,采用数值模拟可有效计算桥面板温度场.     

北京市新建住宅配电设计原则

提供北京山区居民住宅用电负荷的设计计算标准。推荐了以“家用电器普及率”为基础的户用电负荷的计算方法。文中还介绍了北京地区目前正在实施的住宅配电系统（包括多层住宅及高层住宅系统）,以及用“需用系数曲线”进行设计计算的方法。此外,还介绍了居住小区的变压器容量及台数的选择原则。