正弦函数基原子库微弱被动鱼声信号的稀疏检测

为实现海洋环境中微弱被动鱼声信号的检测,针对单频正弦信号稀疏分解用于微弱信号检测的局限性,采用正弦函数基拟合被动鱼声信号,构建不同幅值、频率和初相位的正弦波信号作为过完备原子库,通过稀疏分解,检测出淹没在强噪声环境中的微弱正弦信号的幅度、频率和初相位参数,从而恢复出待检测的被动鱼声信号。实验表明:该项技术在-40 d B条件下可以实现任意形式的鱼声信号检测。     

电磁铆接技术

作为一种新型铆接工艺,电磁铆接为钛合金和复合材料结构连接及大直径铆钉和难成形材料铆钉成形提供了一种先进的连接技术.从低电压铆接设备的发展和理论研究两方面对电磁铆接技术进行了分析,可知低电压电磁铆接设备的发展趋势为轻量化和装配系统的自动化,数值模拟和材料绝热剪切的变形机理是电磁铆接技术理论研究的重点.指出建立合适的分析模型将为电磁铆接的理论研究奠定基础,确定加载速率范围是控制电磁铆接中绝热剪切变形的关键.     

Microstructure and mechanical properties of Ti6Al4V powder compacts prepared by magnetic pulse compaction

Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.     

铜弹带磁脉冲焊接接头的力学性能

进行T2铜弹带与50#钢弹体磁脉冲焊接实验研究。结果表明:获得的冶金连接接头呈波状界面,波长和幅值分别约为60、30μm,没有泛铁现象发生;接头的轴向和环向压剪强度为91 MPa和132.37 MPa,显著高于铜环母材的初始屈服强度;接头扭转和密封性测试破坏均发生在较弱母材——T2铜环,对应最大承载能力分别为84.36 N·m和18 MPa。