激光熔覆钴基合金涂层的组织结构

利用5kWCO2连续激光器在16Mn钢表面进行激光熔覆钴基合金涂层，研究了激光覆合金涂层的显微组织形貌，相结构以及显微硬度。激光熔覆涂层可分为三个区域：熔化区（合金层）结合区及基材热影响区。合金涂层由γ-Co枝晶及其间的共晶组织组成，合金涂层的主要组成相为γ-Co和（Cr,Fe)7^C3。     

Laser cladding of copper with molybdenum for wear resistance enhancement in electrical contacts

Laser cladding of Mo on Cu has been attempted with the aim of enhancing the wear resistance and hence increasing the service life of electrical contacts made of Cu. In order to overcome the difficulties arising from the large difference in thermal properties and the low mutual solubility between Cu and Mo, Ni was introduced as an intermediate layer between Mo and Cu. The Ni and Mo layers were laser clad one after the other to form a sandwich layer of Mo/Ni/Cu. Excellent bonding between the clad layer and the Cu substrate was ensured by strong metallurgical bonding. The hardness of the surface of the clad layer is seven times higher than that of the Cu substrate. Pin-on-disc wear tests consistently showed that the abrasive wear resistance of the clad layer was also improved by a factor of seven as compared with untreated Cu substrate. The specific electrical contact resistance of the clad surface was about 5.6 × 10⁻⁷ Ω cm².     

激光扫描技术在靶场测试中的应用研究

为了解决光电类仪器在武器射击准确度和射击密集度的测试中遇到天空背景亮度不够,或弹丸口径小,弹道偏高而无法测试的问题,利用旋转棱镜使激光束在空中扫描,照亮弹丸表面,从而大大降低对光电传感器灵敏度的要求,使得该项测试工作不受天空背景条件的影响,并提高测试精度.     

电场的增强作用对介质膜光栅损伤形貌的影响

研究了电场在介质膜光栅结构中的增强效应对其抗激光损伤阈值的影响.使用傅里叶模式方法计算了电场在介质膜光栅浮雕结构内的分布.数值分析表明：电场在介质膜光栅中增强的最大值为入射光的2倍,其最大的位置出现在相对于入射光对面的光栅槽侧壁。实验测试介质膜光栅样品在1 064 nm和12 ns, 51.2°和TE偏振光入射时,其抗激光损伤阈值为6.61 J/cm2.对损伤形貌进行扫描电镜精确分析,发现介质膜光栅的初始损伤产生于电场在介质膜光栅内增强最大的位置处.     

激光功率和能量计量技术的现状与展望

功率和能量是激光器的两个基本参数,激光功率和能量测量一直是激光参数计量中最基础的测量工作.总结了美国标准技术研究院(NIST)、英国国家物理实验室(NPL)以及中国国家计量院(NIM)在激光功率能量计量方面的技术现状,重点介绍了国防科工委光学计量一级站激光功率能量计量方面已具备的条件,详细说明了所采用的测量原理以及所达到的测量范围和测量不确定度等技术指标.提出了激光功率和能量计量的发展趋势和发展方向.     

Pulsed Nd:YAG laser welding of AISI 304 to AISI 420 stainless steels

The technique to weld AISI 304 stainless steel to AISI 420 stainless steel with a pulsed Nd:YAG laser has been investigated. The main objective of this study was to determine the influence of the laser beam position, with respect to the joint, on weld characteristics. Specimens were welded with the laser beam incident on the joint and moved 0.1 and 0.2 mm on either side of the joint. The joints were examined in an optical microscope for cracks, pores and to determine the weld geometry. The microstructure of the weld and the heat affected zones were observed in a scanning electron microscope. An energy dispersive spectrometer, coupled to the scanning electron microscope, was used to determine variations in (weight %) the main chemical elements across the fillet weld. Vickers microhardness testing and tensile testing were carried out to determine the mechanical properties of the weld. The results of the various tests and examinations enabled definition of the best position for the incident laser beam with respect to the joint, for welding together the two stainless steels.     

中值滤波在激光雷达点云数据预处理中的应用

为了研究3维激光雷达测量系统采集到的点云数据如何进行去噪处理,根据灰度图像中对灰度值进行滤波去噪的概念,采用改进的2维中值滤波方法对点云数据中的噪声点加以处理。基于激光雷达点云数据数据量庞大且存在噪声点特点,重点分析了改进2维中值滤波算法和点云数据信噪分离方法,并通过实验验证,得到了速度对比数据和滤波效果图。结果表明,利用改进后的2维中值滤波方法,速度明显得到改进,对激光雷达点云数据的滤波效果良好。     

基于全卷积神经网络的焊缝特征提取

基于深层卷积神经网络的特征学习能力,提出了一种基于全卷积神经网络的焊缝特征提取方法。该方法利用全卷积神经网络将包含焊缝特征信息的像素预测出来,通过融合低层与高层特征信息来补充焊缝边缘的特征信息。研究结果表明:所提方法能在强烈弧光和烟尘干扰下准确地提取出焊缝位置,具有抗干扰能力强、识别准确的优点。     

激光驾束制导仪性能测试系统研究

为试验测试需要,文中提出了一套激光驾束制导仪性能测试系统方案,并对方案各组成部分分别进行了论述。该测试方案可以检测激光架束制导仪的指令特性曲线、激光光斑照度分布、瞄准通道与信息通道光轴平行性误差及制导仪变焦工作时间等。通过分析及部分样机实验,认为该可以满足测试要求。     

Synthesis of cation-exchanged laponite suspensions by laser ablation of microsized-metal particles in liquid

Laser ablation in the liquid technique has been used to synthesize cation-exchanged laponite suspensions. In summary, laser ablation of the microsize-metal powder (Co, Al, and Cu) dispersed in an aqueous solution containing deionized water laponite crystals was carried out using laser beam generated by a single-mode, Q-switched Nd-Yag laser operating at 532 nm with a pulse duration of 5.5 ns and 10 Hz repetition rate. Laser fluence was 0.265 J/cm² for all tests. For all samples, the mass fraction of laponite was 1%. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Al) were ablated in it for about 1 h, even with a small amount of the metal (0.025% and 0.050%) were generated, the suspension became highly viscous and behaved as a shear-thinning and thixotropic material. That is, the suspension gelled strongly when it was allowed to rest. The gels, however, could easily be reverted to a low viscosity liquid with simple shaking. Information from TEM and XRD analysis indicated that such a sol-gel transformation might be due to the charge exchange between the cationic species produced during the laser ablation and the sodium ions in the interlayers of the clay sheets.