自熔式Al—Si—Al—Si复合薄板GTAW焊接质量控制

本文通过电弧线能量、柔性工夹压紧力和交流矩形波参数的取优设计，获得元气孔，无热裂纹的Ａｌ－ＳＩ－Ａｌ－Ｓｉ复合花天酒地板的优良焊缝，根据阴极清理过程分析，提出了阴极清理最小时间的求值公式，借此得到交流矩形波的频率和负半波时间与矩形波周期之比这二个焊接电源设计参数。     

三丝CO2双边角焊全因子试验设计

影响三丝高速CO2双边角焊焊缝成形参数的因素众多,在试验中应集中在影响较大的焊接参数研究.文中以影响其主要的两个焊接参数,即焊接功率和焊接速度为研究对象,建立两因素三水平的全因子工艺试验设计,分析焊接参数对焊缝成形参数的影响.结果表明,下脚长、上脚长和焊缝凸度均受焊接功率和焊接速度的主效应影响,而与交叉效应无关.上脚长的预测范围大约为4mm,下脚长的预测范围大约为2.5mm,而焊缝凸度的预测范围大约为2.5 mm.     

铝板的CO2激光焊接等离子体二维温度分布的测量

利用两个严格同步触发的高速相机,拍摄获取纯铝在CO2激光焊接过程中的等离子体在同一个方向上的二维投影。每个高速相机镜头前均加载了一定规格的滤波片,分别能允许宽度为4 nm、中心线分别为670和589 nm的谱线通过。这两条谱线分别是Al元素的一级和二级电离特征谱线。结合相机标定的原理,对两个特征谱线的二维投影图片进行配准,根据等离子体的热力学方程,使用双谱线比较法,得到了等离子体的二维温度分布。与传统的光谱方法相比,本文的方法可以获得二维温度场,从而可以从更加丰富的角度去分析等离子体的温度与侧吹气体流量等焊接参数的关系。     

基于信度评价的焊缝结构光自适应多次曝光法

利用线结构光主动视觉法获取焊缝尺寸时,被测工件表面的复杂特性会造成局部图像质量下降,严重干扰焊缝尺寸计算.针对此问题提出了一种基于信度评价的自适应多次曝光法.将光条的信度评价作为结构光图像的质量评价参数,根据光条的信度分布自动获得下一次拍摄的曝光参数并判断拍摄结束节点.结果表明,基于信度评价的焊缝结构光自适应多次曝光法应用于角焊缝尺寸检测,具有良好的测量稳定性与测量精确度,并且可以有效避免光条图像质量退化造成的测量误差和测量数据缺失.     

铝合金P-MIG焊接电流对电弧形态的影响

通过对铝镁合金进行脉冲氩弧焊(P-MIG),在相同平均电流和平均电压工作条件下,调节不同峰值电流和基值电流,获得了不同的电弧形态.峰值电流对电弧形态有着重要的影响,而基值电流基本没有影响.基值电流是维持电弧燃烧的参数,在基值时间阶段,必须给定一个足够大的基值电流才能维持电弧的稳定燃烧.文中定义了电弧形态的表征值,针对电流对电弧形态表征值的影响进行了分析.峰值电流是决定电弧温度和脉冲能量的重要参数,铝合金电弧充分燃烧时电弧长度、电弧宽度和电弧纵向截面面积随着峰值电流增加而增加.

Abstract：

Under the same average welding current and welding voltage, by regulating the different based current and peak current, the Al-Mg alloy was welded with Al-Mg filler wire. The photos of welding arc were obtained by using high-speed video photography.Peak current has great influence on the shape and characteristics of the arc. With increasing the peak cunent value, rotated arc appears and pulsed rotated metal transfer behavior occurs. Based current has little influence on the arc shape. Base current is the important parameter for keeping arc burning. At pulse off time, it must be given base current value which is large enough to keep the arc burning stably. In this study, the arc shape is defined by arc length, arc width and arc portrait cross-section area, which will be influenced by the weld current. Peak current is important parameter of arc temperature and pulse energy. The study shows that when the arc is burning at pulse on time, the arc length, arc width and arc pomait cross-section area increase with raising peak current.     

基于卡尔曼滤波的焊缝偏差实时最优估计

建立了基于卡尔曼滤波的焊缝偏差实时最优估计算法.以焊缝中心位置为特征矢量,建立焊缝位置检测的状态方程和测量方程,并依据最小均方差原则建立了卡尔曼滤波最优估计的递推算法.测量噪声协方差由传感器测量误差的统计值得到,假定过程噪声是由于加速度变化引入,通过两点法确定焊缝中心位置的初值.在焊接过程中,应用卡尔曼滤波消除噪声干扰,实现焊缝位置的实时精确预测.计算机仿真和试验结果表明,焊缝偏差信号经过卡尔曼滤波处理后,消除了偶然因素和随机噪声的影响,提高了跟踪精度以及系统工作的稳定性,适合实际工程应用.

Abstract：

The optimal estimation algorithm for real-time welding deviation based on Kalman filtering is presented. The state equation and measurement equation for detecting the weld position is established, and the optimal estimation of the Kalman filtering recursive algorithm also is established according to the principle of minimum mean square error. Measurement noise covariance is obtained from the statistical value of measurement error, and after the process noise is supposed to derive from the changes in acceleration, the initial values of the welding center position are determined by the twopoint method. During the welding process, the welding position is accurately predicted while the noise interference is eliminated by Kalman filtering. The computer simulation and experiment results show that the weld deviation signal processed by the Kalman filtering can eliminate the disturbance of causal factors and random noise,improve the tracking precision and the stability of system, and be suitable for the practical engineering applications.     

脉冲熔化极气体保护焊熔滴过渡电信号特征及建模

脉冲熔化极气体保护焊(GMAW-P)熔滴过渡形式对焊接质量有着重要的影响,同时脉冲参数是影响GMAW-P熔滴过渡行为的主要参数.利用高速数字摄像技术,记录熔滴过渡过程,同时采集焊接过程的电流、电压信号,并将各个信息传输到PC机中,实现数据的保存.综合分析熔滴过渡图片与对应的电信号的关系,提取了GMAW-P熔滴过渡过程特征电信号.通过统计分析建立了GMAW-P熔滴过渡逻辑回归模型.结果表明,此模型预测熔滴过渡的正确率达93%,为实现一脉一滴最佳脉冲熔滴过渡形式闭环控制开辟了新的途径.

Abstract：

Metal droplet transfer mode which is influenced by the pulse parameters such as pulse current ( I_p ) , pulse time ( t_p ) , base current ( I_b ) and pulse frequency (f) has play an important role in the weld quality. An experimental system based on the Lab VIEW virtual instrument and high speed photography technology was developed to sample the transient electrical parameters and record the images of droplet transfer process simultaneously. A transition voltage U_(dd) in the pulse voltage drop edge of electrical waveform was discovered according to analysis of synchronous electric and image signals. The relationship between the metal transfer mode and the slope of the transition voltage was proposed. The result of experiments shows that the model can be used in closed-loop controlling of one droplet per pulse transfer mode and also can help for optimizing the welding parameters.     

Analysis on the stability of the single weld pool formed during the triple-electrode high speed CO2 welding

The pinch instability theory with free surface and wave superposition principle was applied to understanding the critical disturbance wavelength and the theoretical bead width for the single weld pool formed during the triple-electrode high speed CO2 welding.In addition,the reason for higher stability in the single weld pool was analyzed.Then single-,twin-,and triple-electrode overlaying experiments were conducted,it was found that triple-electrode CO2 welding can improve welding efficiency greatly without reducing the weld quality.The results indicated that the oscillation frequency of the weld pool increased,oscillation wavelength decreased,and bead width increased with the increase of welding electrodes under the same disturbance circumstances.     

DSP+MCU数字控制脉冲GMAW铝合金焊机研究

铝合金在工业中的广泛应用促进了铝合金脉冲GMAW焊接工艺及焊接设备的大发展,数字化技术为研发适合高效焊接铝合金工艺新电源提供了契机。文中基于数字信号处理器(DSP)和MCU双核数字控制,研制了数字化脉冲GMAW铝合金焊机。基于模块化设计思想,DSP主要处理焊接过程信号和焊接输出波形控制,MCU主要处理人机交互信息,双核之间采用通讯方式进行信息交互。设计的数字化控制电源具有焊接电源输出波形控制、熔滴过渡控制、电弧性能控制、专家系统等功能,适合各种铝合金不同场合的应用。焊接试验结果表明,焊接工艺性能良好,焊缝成形均匀一致,建立的焊接电源数字控制平台可用于铝合金焊接工艺的研究。     

Touran轿车天窗框架冲压成形的数值模拟

应用LS-DYNA有限元软件,对Touran轿车天窗框架冲压成形过程进行了数值仿真,研究了框架易于失效沟槽处材料的变形行为,并预测了开裂产生的原因,同时对其成形后的厚度变化、变形安全裕度及天窗框架的材料选择进行了分析.仿真结果与实际冲压结果取得了较好的一致,证明了所建立的天窗框架仿真模型的合理性及计算结果的准确性,同时也进一步说明了材料性能对成形化具有显著的影响,为天窗框架冲压材料的选择提供了科学依据.