Laser Remelting Modification and Nondestructive Testing of Copper-Chromium Alloy Contact Surface

铜铬合金具有导电性好、导热性好、强度硬度高、抗腐蚀性强等特点，被广泛应用于电力及相关行业，例如高压电网、集成电路、电器元件等。随着高压电网的升级，传统方法制备的铜铬合金难以满足高电压、大电流下的电路开断要求，铜铬合金表层较大颗粒的铬被烧蚀击穿为主要失效原因。 激光表面改性技术可在材料表层实现快速熔凝以细化晶粒，大幅提升铜铬合金的电学及力学性能。目前的研究主要侧重于材料级的激光熔凝改性实验及基于有损检测的改性层性能研究，对于铜铬合金触头等结构件的表面熔凝改性工艺还不成熟。改性层的破坏性测试无法满足对结构件改性层的测试需求。缺乏有效的无损检测方法，难以在不破坏结构的情况下建立改性工艺和改性层性能之间的关联，成为制约铜铬合金激光熔凝改性技术在工业应用中的瓶颈问题。因此探索快速无损检测方法，建立激光工艺参数与改性层特征的关联，从而优化铜铬合金触头结构件表面改性工艺，是突破以上瓶颈问题的关键。本文结合高压输电行业对铜铬合金改性的重大需求和国内外研究现状，针对铜铬合金触头表面的激光熔凝技术，开展了以下研究工作。 1. 对激光表面改性试验平台进行部分升级改造。通过对设备调试升级实现了多个结构件并行改性，提升实验效率。建立了试样形貌实时采集系统，为后续无损检测研究提供实验基础。 2. 研究了改性层表面形貌与工艺参数的关系，探索表面形貌随激光能量输入的演化规律。依据不同的能量输入和改性后试样的表面形貌特征，对改性层进行分类，是通过无损检测建立改性层性能和工艺参数之间的关联的重要支撑。 3. 以表面形貌图像为基础提出了一种基于机器视觉的检测方法。采用一种改进的二值化方法从该背景图像中准确分割视觉显著区域，再基于几何矩提取具有空间变换不变性的连通域形状特征，最后结合支持向量机等分类算法检测试样的表面改性质量。 4. 基于以上研究工作，以无损检测结果为基础，对铜铬合金触头表面激光熔凝改性的工艺优化进行了探索性研究。</p

一种基于模糊语言TOPSIS的应急决策方法

在应急决策过程中,决策信息通常具有犹豫性、模糊性和非对称性,且决策者呈现出直观、快速的语言决策偏好。提出一种基于模糊语言TOPSIS的应急决策方法,使用犹豫模糊语言术语集和二元语义表达式对高度不确定环境下的语言进行处理,提高对犹豫模糊语言信息的提取能力,生成易于理解的语言评估结果,从而辅助决策者进行快速、准确的决策判断。案例证实该方法的可行性与有效性,为解决应急决策问题提供了一种新方法

基于机器视觉的激光表面改性质量快速检测

针对铜铬合金激光表面改性质量快速无损检测的需求,提出了一种基于机器视觉的检测算法。首先采集试样表面形貌图像,然后使用自适应二值化方法从背景图像中分割视觉显著区域,再基于几何矩提取具有空间变换不变性的连通域形状特征,最后依据激光能量输入定义4种基本改性状态并训练支持向量机,以检测改性质量。使用MATLAB语言实现上述算法,结果表明:本文算法在特征提取及模型训练阶段的耗时约为45 s,检测速度为5*10~6 pixel/s,检测准确率为97.0%。依据检测结果可进行相应的工艺参数优化。所提算法对光照等检测环境不敏感,可以实现激光表面改性质量的快速无损检测,且对工艺参数优化具有一定意义

Surface nanocrystallization of Cu-Cr alloy by a high power density continuous laser beam

A nanostructured surface layer of similar to 300 mu m thickness was fabricated on Cu-30Cr (wt%) hypereutectic alloy by a continuous laser beam with high power density (1.08 x 10(7) W/cm(2)). The average grain size of Cr-rich particles was refined to similar to 40 nm, and the solid solubility limit of Cr in Cu was extended to 1.96 at. %. Experimental results show that the dispersion of nano-sized Cr-rich spheroids in Cu-rich matrix was attributed to the Brownian motion of Cr-rich spheroids, and the high cooling rate (5.75 x 10(6) K/s) during liquid phase separation which inhibits the collisions between Cr-rich spheroids. (C) 2018 Published by Elsevier B.V

一种基于显微图像的激光栅线成形质量自动检测方法

本发明提供一种基于显微图像的激光栅线成形质量自动检测方法，包括：获取测量数据：进行激光栅线成形工艺试验，由三维形貌测量工具获取栅线表面高度数据并存储为数字量；提出测量指标：等效遮挡宽度、等效导电面积、无量纲的等效高宽比；编写计算机程序实现测量指标的自动测量。依据本发明可快速检测栅线成形质量是否合格或者符合预期，对工艺参数探索优化及激光栅线成形技术的工程应用均有较大意义

一种双工位激光焊接机及带涂层薄板激光焊接方法

本发明提供一种双工位激光焊接机及带涂层薄板激光焊接方法，包括机床X轴组件、机床Y轴组件、机床Z轴组件、进料传送带、自动上料架、可移动式出料传送带、控制面板、焊接夹具；机床X轴组件为双导轨形式，固定在地面，在其上安装有机床Y轴组件，可沿X轴方向运动，机床Z轴组件安装在机床Y轴组件上；控制面板安装在机床Y轴组件端头；自动上料架设置在机床外侧，然后依次设置进料传送带，焊接夹具以及可移动式出料传送带，安装在地面上，可实现二维板材拼焊和三维结构件焊接的双工位加工。采用大圆轨迹和小圆轨迹的组合以及设定的工艺参数，实现带涂层板材的焊接。本发明能够降低设备购置成本、提高焊接的效率

一种激光焊接中抑制烟尘及飞溅装置

本实用新型提供一种激光焊接中抑制烟尘及飞溅装置,包括后压脚,前压脚,吹气板,集烟罩,烟尘净化机,竖向气帘,横向气帘和侧轴保护气嘴；焊接夹具中的前压脚、后压脚均为空腔结构,两端有堵头,吹气板和集烟罩分别安装在夹具的两侧,通过中心吹气+两侧吸气的方式提高焊接烟尘吸收效果,同时,通过侧轴保护气与横向、竖向气帘的组合,避免飞溅物向上运动。本实用新型从大幅面板材焊接时烟尘和飞溅物抑制的角度出发,对焊接设备进行一些优化工作来减少焊接加工对环境及设备的危害

一种可实现送丝异常检测的激光焊接装置

本实用新型提供一种可实现送丝异常检测的激光焊接装置,包括拉力弹簧,连接座,编码器、送丝嘴二号安装座,送丝嘴,接触开关,接触开关安装座,送丝嘴一号安装座,立杆,限位螺钉,横杆,立杆固定座,限位块,横杆固定座,弹簧固定座；通过拉力弹簧和限位螺钉的作用,使得送丝嘴呈现柔性连接,当送丝产生粘丝或者干涉时,送丝嘴和送丝嘴二号安装座运动,触发接触开关；当导丝管被挤压、弯折角度过大或者送丝嘴产生烧熔时,送丝阻力过大造成不正常的送丝状态,送丝速度被编码器检测到。本实用新型用来检测送丝不通畅、粘丝等送丝异常的情况,发生送丝异常时将信息反馈于焊接机控制系统,避免因送丝问题影响加工质量、损坏设备

Grain Refinement of Hypereutectic Immiscible Cu-50Cr Alloy during Rapid Melting and Solidification Induced by High Power Density Laser Beams

The microstructure of hypereutectic immiscible Cu-50Cr alloy (wt%) was effectively refined and homogenized by a high power density Nd:YAG continuous laser beam (power density 10(4)-10(5) MW/m(2)). The average grain size of Cr was effectively refined from similar to 100 mu m to similar to 1 mu m, and some of the Cr particles even decreased to a few hundred nanometers. The high cooling rate (7.29 x 10(6) K/s) effectively inhibited the coarsening effect on Cr particles during liquid phase separation (LPS). The spherical Cr particles were preferably dispersed in the melt layer, and the thickness of the layer was up to similar to 150 mu m. The refinement and dispersion of the Cr phase contributed to improving the interruption capability of the Cu-Cr contacts. Compared with the untreated samples, the arc duration and the withstanding voltage of the laser surface melting (LSM) treated contacts with refined microstructure increased to 21% and 33%, respectively. The results demonstrated that the LSM method was an effective approach to optimize the microstructure of Cu-Cr alloy, which made it a promising modification method for Cu-Cr vacuum contact applications

Effect of Surface-Active Element Oxygen on Heat and Mass Transfer in Laser Welding of Dissimilar Metals: Numerical and Experimental Study

The effects of the surface-active element oxygen on the laser welding of 304 stainless steel (304SS) and nickel were numerically and experimentally studied in pure argon and argon-oxygen mixed gas atmospheres containing 21% oxygen (AMO). In this study, the molten pool morphology, thermal behavior, solidification phenomenon, correlation between dilution and convection flow, and microhardness of welding joints were analyzed. As a result of oxygen effects, the molten pool was deeper, the maximum temperature was higher, and the maximum flow velocity was lower in the AMO. The cooling rate (GR) and combination parameter (G/R) were studied by the direct simulation of temperature gradient (G) and solidification growth rate (R). Combined with the solidification microstructure, it was found that oxygen had little effect on grain size. The major elements Fe, Cr, and Ni within the solidified molten pool in the AMO were uniformly diluted, while the distribution of the above elements was non-homogenous in pure argon. Stronger flow and multiple directions of convection inside the molten pool contributed to uniform dilution in the AMO. The distribution of microhardness was similar to the content of Cr, and the microhardness at the substrate interface of the joint was higher in the AMO than in pure argon. The preliminary conclusions of this study provide in-depth insights into the effects of surface-active element oxygen on heat and mass transfer in laser dissimilar welding