铝合金TIG焊熔池图像的获取与处理

研究建立了适用于铝合金TIG焊接过程中焊接熔池图像传感系统,探索了获取铝合金熔池图像的条件,详细论述了图像传感系统与焊接电源特性之间的匹配关系。给出了图像传感系统中各个部分之间的空间位置关系。在多种不同的焊接规范下进行了大量的图像获取试验,获得了不同规范下清晰的铝合金熔池正反两面图像。分析了铝合金焊接熔池图像的特征,设计了相关中值滤波和基于统计理论的双期望值阈值方法以及小波变换等方法对焊接熔池图像进行处理,获得了铝合金焊接熔池图像的准确边缘,为焊接过程的智能控制打下基础。     

铝合金双丝脉冲MIG焊双向熔池同步视觉传感及图像处理

铝合金双丝脉冲焊接时,强烈的双弧光强和铝合金的强反射作用造成熔池视觉传感比较困难。建立一套双丝脉冲焊熔池双向同步视觉传感软硬件系统,通过近红外滤光技术和控制电荷耦合器(Charge-coupled device,CCD)快门曝光时间,获得清晰的尾部和侧面同步铝合金熔池图像。针对铝合金双丝脉冲焊熔池图像存在的高频横纹干扰,提出利用巴特沃斯低通加强滤波的方法进行去除,并通过灰度拉伸、阈值分割和边缘提取等图像处理方法,获得双向熔池轮廓。通过熔池几何形态分析,得到双丝脉冲焊前中部熔池形状为椭圆形,尾部形状为抛物线。在获得抛物线和椭圆曲线方程的基础上定义并计算熔池宽度、全长、面积、周长、尾部系数等熔池几何特征参数。     

TIG-MIG双面对称焊焊缝成形机理研究

就纯铝中薄板,通过单面TIG、MIG和TIG-MIG双面对称焊工艺试验对比,利用ANSYS有限元计算软件进行了TIG-MIG双面对称焊熔池的数值模拟,研究了TIG-MIG双面对称焊的熔池特征及焊缝成形规律。研究表明,TIG-MIG双面对称焊的热源静态累积效应和动态热阻效应使得此焊接方法熔深大大增加,TIG、MIG熔池在焊接过程中发生交汇并在电弧力、熔池表面张力和重力等作用下达到平衡,并由此形成焊缝反面成形。TIG-MIG交汇熔池的稳定性决定焊缝的反面成形特征。     

铝壳体纵缝MIG+TIG同步焊工艺研究与应用

针对中厚度铝合金壳体纵缝的焊接,利用现有的焊接设备进行试验,尝试开发了一种能够保证铝合金壳体纵缝气密性探伤要求的焊接方法,采用MIG焊与TIG焊合理配置搭配和工艺参数选择,解决了MIG焊焊接纵缝易产生气孔,探伤合格率低的问题。而TIG焊熔深浅,生产效率低的问题,利用MIG焊和TIG焊各自的优点,在同一台焊接操作架上把MIG焊和TIG焊合理搭配,通过工艺参数的优化选择,实现了利用现有的焊接设备焊接中厚度铝合金壳体纵缝的目的。保证了焊缝质量,提高了劳动效率,经过对比试验后,认为铝壳体纵缝MIG+TIG同步焊焊接中厚度铝合金壳体纵缝是较为经济高效的焊接方法之一。     

GMAW焊熔池图像处理算法

根据GMAW焊的特点,建立焊接熔池图像传感系统,获取了清晰的熔池图像,并对焊缝熔池图像的特征进行分析。采用自适应维纳滤波、GAMMA值增强和Otsu阈值分割进行图像预处理,并采用形态学开运算和Prewitt边缘检测算子对图像进行了后处理。结果表明,这套算法能够对熔池图像进行有效地处理,获得清晰完整的熔池边缘。     

对接TIG焊熔池正面几何形状参数的检测

研制出连续电流对接TIG焊熔池正面形状参数实验检测装置。利用普通CCD摄像机，通过光学参数的优化和采集参数的动态调整，拍摄出了清晰度和分辨率都较高的对接TIG焊熔池正面图像。根据对接TIG焊熔池图像特点，设计出图像处理算法，检测出了焊接熔池的整个边缘，得到了不同工艺条件下对接TIG焊熔池几何形状参数的实际尺寸。     

脉冲MIG焊熔池行为的数值模拟研究

基于流体力学、热力学及电磁学等理论建立二维脉冲MIG焊熔池数学模型，在Fluent软件中通过用户自定义程序(UDF)添加模型所需的热源、动量源项以及定义材料的物性参数，对焊接过程进行数值模拟，分析各驱动力对脉冲MIG焊熔池行为的影响以及熔池在脉冲周期内的变化规律。模拟结果表明，在焊接过程中马兰戈尼力对熔池影响最大，其次为电弧压力，然后为电磁力，浮力影响相对较小。在各驱动力复合作用时，熔池表层的熔池形态以马兰戈尼力为主导，熔池内部以电磁力为主要作用力，造成熔池内形成了两种不同方向的环流。熔滴冲击力主要作用于熔池表层，对熔池内部影响较小。脉冲MIG焊高速摄像试验表明，实际熔池形态与模拟结果吻合良好，验证了熔池模型的合理性。     

城轨车辆铝合金空调板激光MIG复合焊工艺研究

正一、概述铝合金型材焊接最初多采用MIG自动焊焊接,但由于MIG焊热输入高,焊接变形大,焊接产品的一致性难以控制,所以目前重视研究采用搅拌摩擦焊以及激光MIG复合焊等热输入小的新型焊接工艺,用于薄壁铝型材的焊接。激光MIG复合焊作为一种高能束焊接方法,其光束功率密度高、热输入小、深宽比大、热传导快、焊接速度快,能很好的实现高效自动化,又具有焊接变形小的优点,因此铝合金型材激光MIG复合焊的前期工艺研究对今后该新工艺的工程化应用具有较     

基于非负矩阵分解的熔池图像识别方法

为探求视觉传感智能识别焊接缺陷技术，利用电荷耦合器件(CCD)相机采集了熔化极气体保护焊(GMAW)熔池图像，分析了不同工艺条件下熔池动态变化过程及所对应的焊接缺陷，提出利用非负矩阵分解法对熔池图像进行解析，得到熔池图像的特征矩阵。通过最小二乘法计算未知焊接过程测试图像在特征矩阵的投影值，给出了焊接缺陷的自动识别方法。研究结果表明，焊接质量和熔池稳定程度有关联，熔池紊乱表现为熔池轮廓波动、浮渣离散等特点，熔池稳定程度下降伴随着焊接质量的下降，以及焊缝出现缺陷。利用非负矩阵分解法得到的熔池图像特征矩阵，能够对原始图像进行整体性描述(如熔池轮廓)和局部性描述(如浮渣区域、电弧区域等),具有物理可解释性，可用于识别焊接缺陷。     

脉冲MIG焊建模仿真分析及弧长控制

针对脉冲MIG焊过程中的电弧稳定性问题,建立基于尖端不稳定熔滴过渡理论的焊丝熔化动态电弧模型,并对焊接过程中的电弧电压、电弧长度及熔滴过渡尺寸进行仿真,得到与实际焊接相似的电弧电压波形,分析脉冲电流下熔滴过渡频率及影响电弧稳定性的因素,且进行弧长稳定控制的仿真研究,在此基础上运用快速原型技术建立铝合金脉冲MIG焊控制系统,采用电弧电压反馈对铝合金脉冲MIG焊过程进行送丝调节的弧长控制试验。研究表明:所建立的铝合金脉冲MIG焊焊丝熔化动态电弧模型很好反映了实际焊接过程,揭示出脉冲MIG焊焊接过程中熔滴过渡时间间隔具有一定的不确定性和电弧长度的不稳定性,通过电弧电压反馈控制可显著改善铝合金脉冲MIG焊过程电弧系统的稳定性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.