基于区域生长算法激光深熔焊监测图像处理研究

根据同轴监测系统采集到的熔池和小孔的同轴视觉传感原始图像特点,分析了数字图像处理的方法并提出相应图像处理的流程。通过监测沿垂直速度方向熔池灰度分布实现了对熔宽的监测,通过对小孔顶部和底部尺寸的监测实现对熔透状态的监测。经过图像处理后的焊接区域同轴监测图像可以清晰的获得熔池轮廓及小孔尺寸,为实现焊接过程中熔池宽度和小孔的穿透状态的监测做准备。针对激光对接焊,提出焊缝跟踪的处理算法,不仅实现了焊接质量包括熔宽与熔透状态的监测,还实现焊接质量与焊缝跟踪一体化监测。     

深熔激光焊接数学模型研究现状

对已有的有关深熔激光的数学模型的类型、建模方法及其应用进行了讨论，评述了深熔激光焊接小孔和熔池形状数学模型的研究现状，对深熔激光焊焊缝形状预测和工艺参数优化人工神经网络模型等典型的模型进行了介绍。     

基于焊缝熔透检测的机器人深熔K-TIG焊接系统

开发了一套基于熔透检测的机器人深熔锁孔非熔化极惰性气体保护焊接(Keyhole tungsten inert gas, K-TIG)系统,实现焊接高度(Contact tip-to-work distance, CTWD)自动调节与熔透状态的在线检测。利用电弧电压与焊接高度的对应关系,通过弧压传感器实时采集电弧电压信号并换算成焊接高度值,然后将实际高度值与预设高度值之间的差值经由过程控制对象连接与嵌入协议(OLE for process control, OPC)通信系统反馈给机器人控制系统,从而控制机器人实现焊接高度的自动调节。同时,构建了熔透检测系统,使用电荷耦合器件(Charge coupled device, CCD)相机采集熔池与小孔图像,从中提取熔池-小孔特征,并建立熔池-小孔特征与熔透状态之间的相关性,在此基础上建立识别熔透状态的反向传播(Back propagation, BP)神经网络,实现不同焊接高度下熔透状态的间接检测,最后根据该检测结果得到最佳的焊接高度。经过试验验证,整个系统可靠稳定,能准确检测焊缝的熔透程度,并实现焊接高度自动调节,从而提高了焊接质量。     

大功率Nd:YAG激光焊接过程同轴视觉传感

利用半透半反分光镜片成功地解决了激光焊接同轴视觉传感技术中同轴成像光信号分离提取难的问题,建立了大功率Nd:YAG激光焊接过程同轴视觉传感系统。针对无辅助照明光的激光焊接同轴视觉图像成像信号的特点,设计了相应的中值滤波和同态滤波来消除图像的低频噪声和增强图像,并基于图像阈值分割技术搜索、检测出了熔池和小孔图像边缘的位置。最后,利用Hough变换对图像边缘进行曲线拟合得到熔池和小孔边缘曲线的拟合方程并从拟合结果中求得熔池和小孔的二维尺寸。     

镀锌高强钢激光深熔焊接温度研究

通过对薄板激光深熔焊接焊缝形状的研究,建立了薄板深熔焊接点线叠加的热源模型.通过对比数值计算和试验测定的焊件表面不同点处温度,验证了理论模型的正确性,为激光薄板焊接优化工艺参数提供依据.     

激光深熔焊接过程实时监测系统设计

基于LabWindows/CVI开发环境,采用红外光、蓝紫光和麦克风3种传感器构成了焊缝熔透状态的实时监测系统。在多传感器的数据融合中,首先对3路测量信号进行时频分析,提取能够反映焊缝状态的特征,然后利用人工神经网络对特征值进行融合计算,得到焊缝是否熔透的判断结果。在对网络权值的训练中采用了随机变异粒子群算法,大大地提高了训练速度和精度。实验结果表明该系统应用于焊接过程的实时质量监测是可行的。     

活性剂增加铝合金交流FZ-TIG焊熔深机理

针对铝合金材料提出一种新型活性TIG焊,即分区活性TIG(FZ-TIG)焊,可同时保证焊缝熔深显著增加和焊缝成形良好.利用氦气保护钨极电弧焊观察电弧行为变化,通过分析电弧电压随弧长的变化规律研究活性剂影响电弧的方式,采用焊缝偏移试验分析活性剂对导电通道电阻的影响,进行焊缝表面焊渣X射线衍射分析和热力学计算,分析活性剂与表面氧化膜或熔池金属之间可能的化学反应.通过以上试验研究铝合金交流FZ-TIG焊中活性剂增加熔深的机理,得出活性剂强烈收缩电弧弧根和弧柱是SiO2+FZ108活性剂增加铝合金交流FZ-TIG焊熔深的主要机理.     

Nd:YAG激光+脉冲MAG电弧复合热源焊接参数对焊缝熔深的影响

试验研究Nd:YAG激光 脉冲MAG电弧复合热源焊接过程中焊接参数对焊缝熔深的影响.研究结果表明,复合热源焊缝熔深随电弧功率和激光功率的增大而增大,随焊接速度的增大而减小,并且在相同参数下,复合热源焊缝熔深稍大于激光焊缝熔深而显著大于脉冲MAG焊缝熔深.对于不同焊接电流,光丝间距在0～3 mm内复合热源焊缝取得最大熔深,且取得最大熔深的光丝间距与焊接电流大小有关;复合热源焊缝熔深在离焦量为2 mm时取得最大值.试验结果分析表明,在激光 电弧复合热源焊接过程中激光功率不仅决定复合热源焊缝熔深,而且可以极大地提高焊接速度:MAG电弧也可提高Nd:YAG激光焊的热效率.     

基于铝合金激光深熔焊接温度场研究

采用透过玻璃在线拍摄铝合金激光深熔焊接时小孔形状的方法,得到小孔形状的真实尺寸.随后建立铝和玻璃异种材料激光焊接温度场的数学模型,运用数值模拟法分析了激光深熔焊接铝合金与玻璃的温度场分布,在编制Matlab程序计算时用已观测到的小孔半径数值为基础,保证了数值模拟结果的合理性与正确性,得到了不同材料焊接温度场计算的一般方法.     

基于视觉的机器人智能化焊接技术现状与发展

针对机器人自动焊接技术快速发展的现状,结合机器视觉技术、智能控制技术和信息技术在焊接技术领域应用的特点,归纳综合了弧焊视觉传感技术、激光接缝跟踪技术、熔池视觉形态特征传感与提取技术、熔透与熔深智能控制技术、缺陷监测及控制技术和基于网络的数字化焊接技术的研究现状,分析了激光跟踪传感器结构、熔池与接缝计算机图像处理方法、熔池视觉几何特征提取方法、熔深熔透视觉传感与判断技术、基于网络的焊接信息远程传输与品质评价技术,给出了弧焊机器人智能化和数字化焊接技术优质、高效、柔性、快速、适应性强的特点,探讨了的智能化、数字化焊接技术的主要发展方向。     

Study on the burning loss of magnesium in fiber laser welding of an Al-Mg alloy by optical emission spectroscopy

In order to study the burning loss of magnesium, a specially designed device was used to capture the spectrum emitted from the keyhole plasma in deep penetration laser welding of aluminum alloy 5052. The content of magnesium in the weld bead was measured by an electron probe micro-analyzer (EPMA). The effect of the welding parameters on the spectral intensity of magnesium plasma was examined, and the distributions of the spectral intensity of magnesium plasma in the radial and depth directions of the keyhole were investigated. Finally, the mechanism of the magnesium loss was analyzed. The results indicate that burning loss of magnesium can be monitored by spectral analysis technique. The welding parameters have a great effect on the burning loss of magnesium. The influence of welding speed on the burning loss of magnesium on the top surface is dependent on the penetration regime. The distribution of magnesium in the weld is not uniform. In the radial direction of the weld bead, the content of magnesium increases from the center to the edge of the keyhole. In the depth direction of the weld bead, the content of magnesium decreases firstly and then increases from the top to bottom. The maximum burning loss of magnesium occurs at the middle of the weld bead.     

面能量对激光—电弧复合焊接焊缝及熔滴过渡的影响

引入面能量的定义,从激光功率、电弧参数和焊接速度等方面来研究面能量的变化对焊缝熔深、熔宽、焊缝成形系数和熔滴过渡的影响,试图建立激光能量与电弧能量之间的最佳配比关系以及面能量与熔深的定量关系。采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化,并采集焊接过程中的电弧和熔滴图像;利用激光共聚焦显微镜观察焊缝形貌,并测量焊缝熔宽、熔深等数据。试验研究发现:激光与电弧两热源之间存在最优匹配范围;电弧电压与焊接电流之间存在U(15 1)0.05I的关系式;焊接速度的降低与焊缝熔深的增加并非线性关系,可选择的焊接速度是一个区间,该区间内存在一个最佳的焊接速度,并对应一个最佳的面能量。因此,在具体的激光—电弧复合焊接中,需要根据板厚、接头形式等确定激光与电弧的能量参数,选择合适的面能量。     

RELATIONSHIP BETWEEN PLASMA OPTIC SIGNAL AND PENETRATION DEPTH FOR PARTIAL-PENETRATION LASER WELDING

Through sampling and analyzing of plasma optic signals of 400-600 nm emitted from partial-penetration laser welding processes, how the penetration depth is related to the welding parameter and the plasma optic signal is studied. Under the experimental conditions, the plasma optic signal has good response to variety of the weld penetration, and the signal's RMS value increases with the penetration in a quadratic curve mode. The inherent relation between the plasma optic signal and the penetration depth is also analyzed. It is also found that, between the two common parameters of laser power and welding speed, laser power has more influence on penetration while welding speed has more influence on weld width. The research results provide theoretic and practical bases for penetration real-time monitoring or predicting in partial-penetration laser welding.     

激光焊匙孔特征的近红外与X射线传感分析

由于多传感匙孔特征参数可以有效地反映大功率激光焊接质量状态,本文研究了匙孔特征信息的提取方法并建立了焊缝成形预测模型。以大功率盘形激光焊接304不锈钢为试验对象,应用近红外高速摄像机和X射线视觉成像系统同时提取了焊接过程中的熔池动态图像,并分割出匙孔区域。针对近红外图像,应用矩方法导出匙孔的不变矩特征,同时定义并提取匙孔面积和最前端点纵坐标两个特征;针对X射线图像则提取匙孔深度和熵两个特征。在不同激光功率条件下得到匙孔特征并进行特征融合分析,然后建立了3个BP神经网络焊缝成形预测模型。探索了匙孔形态、焊接条件和焊接状态三者之间的联系,实现了对焊接过程的在线监测。试验结果表明,将两个传感器获取的匙孔特征信息融合并进行主成分分析变换后,熔宽和熔深的预测绝对误差平均值分别为0.18mm和0.57mm,比基于单个传感器获取匙孔特征建立的BP神经网络分别减小了0.03mm和0.31mm,显示提出的方法能够有效在线监测大功率盘形激光焊接状态。     

铝合金激光焊接的研究现状

综述了铝合金激光焊接技术的新近发展。列举了铝合金激光焊接的优越性和常见的焊接缺陷，重点分析了激光焊接气孔的复杂性和特殊性，给出了现今有关小孔研究工作的新进展。激光焊接的主要优点是高效率，尤其体现在大厚度的深熔焊接上。要想成功实现大厚度铝合金的深熔焊接，必须解决小孔所造成的气孔缺陷问题。     

Numerical modeling of heat transfer and fluid flow in hybrid laser–TIG welding of aluminum alloy AA6082

This paper describes a three-dimensional numerical model based on finite volume method to simulate heat transfer and fluid flow in laser–tungsten inert gas (TIG) hybrid welding process. To simplify the model and reduce the calculation time, keyhole dynamics are not considered; instead, a new modified volumetric heat source model is presented for the laser source to take into account the effect of the keyhole on the heat transfer into the workpiece. Due to the presence of arc current, an appropriate electromagnetic model based on the Maxwell equations are also solved to calculate electromagnetic forces in the weld pool. The results of computer simulation, including temperature, current density, electromagnetic, and melted material velocity field, are presented here. Furthermore, several dimensionless numbers are employed to recognize the importance of fluid flow driving forces in the weld pool. It is deduced that the fluid flow has an important effect on the weld pool shape. It is also founded that among the driving forces, Marangoni force is dominant fluid force in the weld pool. Besides, calculated results of hybrid welding process are compared with those of TIG and laser welding processes. The weld pool depth is relatively the same, but the width of the weld pool is highly larger in hybrid welding than lone laser welding. Eventually, the presented model is validated by comparison between calculated and experimental weld pool shape. It is founded that there is a good agreement as the capability of this model can be proved.     

Effect of gap on plasma and molten pool dynamics during laser lap welding for T-joints

The aim of the present research is to discuss the effect of gap on plasma plume, keyhole, and molten pool dynamics during laser lap welding for T-joints. The authors observe plasma plume, keyhole opening, and molten pool images by high-speed camera in different gaps during CO₂ laser overlap welding of T-joints. The results show that gap causes beam energy fluctuations in the keyhole and leads to the instability of welding process. In laser spot welding, zero-gap and small gap greatly affect the stability of plasma and keyhole, which causes the formation of cavities in the weld metal, while a proper gap can help prevent porosity formation. In laser continuous welding, the disruption and closure of front keyhole wall at the gap periodically changes with the gap, which causes the formation of plenty of porosities at the gap. The instability of keyhole is closely related to dynamics of plume and molten pool, which gives an insight into the mechanism of porosity formation during laser overlap welding.     

活性剂增加铝合金交流A-TIG焊熔深机理研究

采用多组元活性剂AF305进行铝合金交流A-TIG焊时,熔深达到传统TIG焊的3倍以上。进行了交流、直流正接和直流反接A-TIG焊,发现极性不同时活性剂对熔深的影响也不同。研究了强制电弧收缩对交流焊熔深的影响,发现弧根整体收缩并不是AF305增加交流A-TIG焊熔深的主要机理,熔深显著增加主要与焊渣成片分布有关。对焊渣进行了SEM形貌观察和EDS成分分析,并采用氦弧焊证实了焊接过程中焊渣在熔池表面成片分布,电弧斑点极大收缩。向AF305活性剂中添加铝粉改变焊渣分布,研究焊渣分布与熔深的关系,证实了焊渣成片分布能增加焊接熔深。认为焊渣成片分布使得电弧斑点极大收缩,斑点压力以及电弧和熔池内的Lorentz力增强,最终焊接熔深显著增加。     

大功率盘形激光焊焊缝背面宽度预测

提出了通过视觉传感获取焊接过程中的焊接特征信息并利用神经网络模型预测焊缝背面宽度的方法。利用大功率盘形激光器焊接了低碳钢SS400焊件,在焊接过程中改变焊接功率、焊接速度和焊接路径,并利用两台高速摄像机同步获取焊件正面和侧面出现的焊接特征信息。对获取的图像进行色彩空间转换、分层、滤波去噪和空域图像处理,提取飞溅、熔池和金属蒸气等焊接特征信息,观察焊接路径对各个特征的影响。最后,建立了一个三层的LMBP(LevenbergMarquardt Back Propagation)神经网络模型,将提取的特征信息作为输入量,预测焊缝的背面宽度。结果显示:当熔透不稳定或出现未熔透状态时,LMBP神经网络拟合度大于0.83,最大训练误差均值为0.002 8mm,最大实际误差均值为0.225 6mm。试验结果表明所建立的预测模型具有良好的准确性和稳定性。