Effect of adding Nb foil on joint properties of laser fusion welding for TC4 titanium and 7075 aluminum alloy

It is difficult to gain effective Ti-Al fusion welding joints due to their differences in thermal properties and the appearance of brittle Ti-Al Intermetallic Compounds (IMCs). The experiments of laser fusion welding for TC4 titanium and 7075 aluminum alloy were carried out, temperature field and ductility/brittleness, as well as chemical potential of elements, were calculated, and the effect of adding Nb foil on mechanical properties of the weld was also investigated. The results suggested that Nb atoms tend to diffuse toward Al side, which is conducive to the participation of Nb in the metallurgical reaction and contributes to forming the Ti-Nb-Al IMC layer at the interface. As the thickness of Nb foil increases, the tensile-shear force of joint climbs first but then declines, and reaches the highest value of 1663 N with 0.10 mm-thickness Nb foil, representing 58.38% enhancement compared with the non-added one. Adding Nb foil slows down the heat transfer as a blocker, and thus both the melting amount of Al and the mixing area of Ti and Al decrease. In addition, Nb alloying reduces the brittleness of the Ti-Al compound. Hence, the joint properties of titanium/aluminum are improved with the addition of Nb foil.     

Integration of nanoindentation and finite element method for interpretable tensile properties:A cross-scale calculation method of uneven joints

Nanoindentation testing and its Reverse Analysis Method(RAM) show great potential in understanding the tensile properties of metallic alloys with various microstructures. Nevertheless,the tensile properties of heterogeneous materials such as nickel-based superalloy welded joints have not been well interpreted by combining the microstructures and nanoindentation results, due to their diverse and complex microscopic zones, which throws shade on the properties of separated zones in the material. He...     

胶接修复对碳纤维复合材料层合板挠度的影响

为了研究胶接修复对碳纤维复合材料层合板弯曲挠度的影响，试验设置了阶梯搭接和斜面搭接两种搭接方式，通过三点弯曲实验和数字图像相关技术（DIC）来研究胶接接头的弯曲变形情况。结果表明，在相同搭接长度下，阶梯搭接试件的失效载荷和弯曲强度均低于斜面搭接试件；试件的弯曲挠度与强度和搭接长度有关，搭接长度越长，弯曲强度越高，而弯曲挠度越小。由此表明，搭接长度越长，胶接层合板的强度越高，但不利于层合板的柔性变形。     

基于PROFIBUS总线的控制器智能从站设计

针对控制器智能化、网络化的发展趋势,为了使具有RS485/RS232接口的控制器方便地接入PROFIBUS现场总线网络,基于C8051F020单片机,研制了以西门子公司的协议芯片SPC3为基础的PROFIBUS-DP从站。首先介绍了PROFIBUS通信的基本原理,然后详细论述了硬件的几个组成部分的功能,对软件的整体结构及部分模块进行了论述,同时还给出了抗干扰的几种措施,最后给出了实验结果。实验结果表明设备间通信正常,可以应用于设备数据采集、执行和控制等,实现RS485/RS232设备与PROFIBUS现场总线的无缝互联。     

高密度内埋空空导弹战斗部优化设计

空空导弹破片战斗部对空中运动目标的单发杀伤概率模型存在不足,精确计算其单发杀伤概率,并对导弹战斗部主要参数进行优化设计,对战斗部的总体设计和提高战斗部效能具有重要意义。在分析战斗机要害部位特性的基础上,根据战斗部对运动目标的杀伤机理,分别建立单枚破片对目标的击穿模型、引燃模型和冲击波杀伤模型;基于所建立的战斗部条件杀伤概率模型,采用多指标单目标粒子群优化算法对战斗部的装填系数、破片数量、单枚破片质量、破片静态飞散角和破片静态飞散方向角五个主要参数进行优化设计。结果表明:优化不仅改善了高密度内埋空空导弹单发杀伤效能,而且减小了战斗部的质量。研究结果可为新型战斗部设计提供参考。