电阻点焊质量监测

电阻点焊质量监测作为一种无损质量检测方法,近年来受到了国内外学术界的广泛关注。阐述了电阻点焊质量监测系统的结构与组成,详细介绍常用的检测信号及其传感器,总结传感器、监测方法及监测系统的最新成果和发展趋势。     

点焊电极工作状态在线监测

对连续点焊过程中电极两端电流、电压和动态电阻进行跟踪测试,并对点焊电极不同工作状态下跟踪测试结果进行对比分析,确定出在线监测点焊电极工作状态的最佳方法。     

利用伺服焊枪实现车身点焊质量的在线检测

伺服焊枪使用带有数字控制的伺服电机,是应用在电阻焊机上的新技术.就伺服焊枪的新特征与传统的气动焊枪进行了对比分析,在此基础上介绍了包括伺服焊枪、机器人和焊接控制器的点焊试验系统,利用伺服焊枪反馈特性实现车身点焊质量的在线检测.     

白车身电阻点焊质量控制技术

概述了白车身电阻点焊质量检测控制的几种技术手段,列举了常见的不同特征焊点的单通道超声波回馈波形,介绍目前最新的矩阵式超声波传感器的特点和动态电阻自适应控制技术工作原理,以及超声波检测技术和动态电阻自适应控制技术在车身电阻点焊质量保证系统中的应用情况及其趋势.     

点焊电极工作状态在线监测

对连续点焊过程中电极两端电流、电压和动态电阻进行跟踪测试.采用DN-100固定式点焊机,在不维修电极的情况下连续焊接550点,并对点焊电极不同工作状态下的跟踪测试结果进行对比分析.发现随着焊点数的不断增加,采集参数中的变压器二次端电压没有发生明显变化,而电极问电压却随之不断地发生改变,从而确定出在线监测点焊电极工作状态的最佳方法.     

基于信号处理对镀锌板的电阻点焊质量的研究

主要研究了点焊镀锌板过程中动态电阻和电极位移的变化趋势及与其对应关系,结果表明,动态电阻、电极位移与焊接过程中存在着直接和间接的关系。同时也研究了在同一焊接工艺参数下点焊镀锌板与低碳钢过程中的信号并加以比较,结果发现,同一点焊工艺下点焊镀锌板的焊接过程信号与低碳钢的变化趋势基本一致。提取电极位移、动态电阻的特征值,作为Som神经网络的输入特征参量,对Som网络进行归类训练,对其训练的网络进行仿真,结果表明,此网络可以对点焊接头进行分类。     

电阻点焊质量在线无损估测

采用动态电阻法建立了低碳钢电阻点焊熔核直径的人工神经网络模型,该模型为3层BP向前网络结构,通过大量正交试验训练获得其模型数据。将模型数据移植到C语言中,建立了熔核直径在线估测系统。该系统有望应用于实际生产的质量监控。     

电阻点焊过程及质量控制方法的研究进展

较为详细地介绍了几种有代表性的点焊质量控制方法的原理及具体应用;重点介绍了动态电阻法和热膨胀电极位移监控法,并简要介绍了点焊质量控制方法的最新发展动态。     

基于混合编程的电阻点焊质量预测

讨论了基于COM组件的混合编程技术在电阻点焊质量预测中的应用,以及Matlab与VB进行有机结合的方法。通过Matlab编写BP神经网络的训练函数和仿真函数,在VB中对函数参数值进行输入与修改,并显示仿真结果。试验表明,该方法在实现电阻点焊质量预测中可起到重要作用。     

微机控制电阻点焊质量探讨

本文阐述利用Cu4800控制器(含恒流控制和动态电阻控制)对电阻点焊的质量控制状况,并介绍了恒流器和动态电阻控制器的原理、特点以及应用。     

Effect of variable electrode force on weld quality in resistance spot welding

Abstract

Resistance spot weldability is defined as the acceptable welding current ranges as determined by the weld lobe in resistance spot welding. Nowadays many studies have focused on the effect of welding current and welding time under constant electrode force on the weld quality and weldability. There is little research on the influence of variable electrode force on the weld quality and weldability because of the difficulty in controlling variable electrode force using pneumatic gun. In the present study, first, the influence of three stages of electrode force, including squeeze force, welding force and forging force, on the quality of welds is analysed. Then a design of experiment approach is applied to analyse the influence of the three stages of electrode force on welding quality and thus to obtain optimum parameter of variable electrode force by controlling the electrode force with servo gun. The comparisons of tensile shear strength, nugget size, weld lobe width and wear rate of electrode tip between variable force and constant force are carried out. The results show that the weld quality and weldability can be increased evidently using optimum parameter of variable electrode force without accelerating the electrode wear rate.     

Improving austenitic stainless steel resistance spot weld quality using external magnetic field

A ring-shaped permanent magnet is applied in resistance spot welding to improve the weld quality of austenitic stainless steel. Under the action of an external magnetic field, the profile of the weld nugget became peanut-shaped instead of ellipsoidal. The crystal orientation near the faying surface was less directional, and equiaxed grains were formed in weld nugget centre. Moreover, the shrinkage cavities tendency in traditional resistance spot welds was reduced. The relatively slow cooling speed could cause element segregation and thus change solidification mode and significantly affect weld microstructures. The mechanical performance of the welds was finally improved by the applied external magnetic field in terms of microhardness and lap-shear strength.     

弹簧钢电阻点焊接头随机回火热处理过程

为更有效地控制弹簧钢电阻点焊接头随机回火热处理过程,以提高弹簧钢电阻点焊接头质量,建立有限元数值模型,对弹簧钢电阻点焊接头随机回火热处理过程进行数值模拟分析.对比分析了弹簧钢电阻点焊接头随机多电流脉冲回火热处理过程及传统的随机单脉冲回火热处理过程.结果表明,采用多脉冲回火热处理方式比采用单脉冲回火热处理方式更容易精确控制随机热处理能量输入,更有效地控制点焊接头回火热处理温度及温度场分布,使弹簧钢电阻点焊接头获得更充分及更均匀的回火热处理.     

钛合金胶接点焊与电阻点焊接头性能对比分析

分别对1.5 mm厚的钛合金板进行胶接点焊和电阻点焊连接,获得了不同焊接电流下的胶接点焊和电阻点焊接头,从熔核的C扫描图像、接头的失效载荷和断口形貌等方面,对比分析了胶接点焊和电阻点焊的接头强度及失效样貌. 结果表明,通过观察A扫描信号的变化与C扫描图像的特征,能够很好的划分接头的热影响区、熔合区、熔核区以及检测出接头的熔核直径和焊接缺陷. 随着焊接电流(7.0～10.0 kA)的逐渐增大,接头熔核直径及失效载荷呈递增趋势;当焊接条件相同时,胶接点焊接头的熔核直径普遍大于电阻点焊接头,但接头的强度相当. 当电流在7.0～8.5 kA时,接头强度不足,熔核区的断口处出现大小不等的韧窝,呈现出韧性断裂特征;当电流为10.0 kA时,接头强度较高,主要呈现出韧性断裂与准解理断裂特征.     

Effect of aluminium sheet surface conditions on feasibility and quality of resistance spot welding

A study investigating the effect of sheet surface condition on resistance spot welding (RSW) of aluminium has been carried out. This concentrates on two automotive aluminium alloys; AA5754 and AA6111, used for structural and closure applications respectively. The results show the marked effect that surface condition can have on the RSW process. For AA5754 sheet incomplete removal of a ‘disrupted surface layer’ prior to surface pretreatment is shown to have a detrimental effect on the RSW process. The solid wax lubricant used to assist metal forming leads to unpredictable changes in contact resistance, and consequently affects the process stability. For AA6111 closures the final surface topography can influence the RSW process. Standard ‘mill’ and electro-discharge textured (EDT) finish sheet surfaces were examined and preliminary results suggest that both are suitable for welding. The successful application of RSW of aluminium sheet requires careful consideration of the sheet surface condition. This requires close collaboration between material suppliers and automotive manufacturers.     

The influence of spot weld position variation on geometrical quality

The body of a car is typically joined by thousands of spot welds. The spot welds guarantee the strength of the car, but their positions also affect the geometrical quality of subassemblies and the final product. In practice, the positions of the weld points often deviate from nominal position. By analyzing industrial scanning data, deviations of spot weld positions are found to be of magnitudes up to 19 mm. In this paper, the influence of variation in position of spot welds is investigated with respect to geometrical quality, by simulating and analyzing the geometrical variation of an A-pillar assembly.     

点焊过程工艺参数采集及缺陷信息分析

采用基于图形化语言的虚拟仪器开发工具LabView开发了界面友好、操作简单的虚拟仪器——电阻点焊参数采集及缺陷信息分析系统。该系统实现了对铝合金点焊过程工艺参数的实时采集、数据传输与存储、波形同步显示，以及对工艺参数的分析和处理，对点焊过程中发生的缺陷状况做出评定和分析。在分析研究所采集的焊接电流和电极电压的基础上，建立了基于电压曲线斜率变化的判读飞溅缺陷的算法和基于积分变化的判读脱焊缺陷的算法。所建立的算法应用于实践，可准确地判读飞溅和脱焊缺陷。     

高强钢与铝合金电阻点焊性能

针对高强钢DP590和铝合金Al6061利用电阻点焊专业有限元软件SORPAS进行模拟分析,分析了钢-铝点焊熔核形成过程的三个阶段,阐述了钢-铝电阻点焊的非对称温度场分布特点及由此产生的熔核偏移和双熔核特征;通过EDS等检测手段结合宏微观金相组织及试验过程中实测的焊接区动态电阻,揭示出点焊接头形成过程即熔融成液态的铝合金在钢-铝界面处向高强钢润湿铺展并扩散而形成熔-钎焊接头;焊接过程中铝原子扩散到钢中的原子分数达到40%左右,形成钢铝晶间化合物的厚度小于2μm.     

静音钢板的焊接性能研究

研究MSC公司研发的厚0.84 mm、1.14 mm的静音钢板与1.0 mm厚度的DC06的点焊工艺,对焊接接头的组织与力学性能进行分析.试验结果表明,点焊后的焊核组织为贝氏体,热影响区为铁素体与少量的贝氏体组织,熔合区结合良好,由于熔核结合面上存在着锌或锌铁合金,在静音钢板一侧焊后熔核中心存在明显的分界线;在焊接后接...     

Online quality inspection of resistance spot welded joint based on electrode indentation using servo gun

Abstract

Resistance spot welding is one of the major joining techniques widely used for car body assembly. Weld quality may significantly influence the durability and reliability of the automobile body. Automotive manufacturers often rely on destructive testing and monitoring variables which indirectly reflected weld quality to assess the weld quality and control the welding process. However, these approaches have inherent limitations and are difficult to be implemented in plant environments. Therefore, it is imperative to develop an online inspection method to evaluate weld quality. In the present study, a method of producing a series of substantially uniform spot welds between two metal parts using a servomotor driven movable electrode and an axially opposing fixed electrode is proposed. The indentation in the workpiece surface is suitably measured by the displacement of the movable electrode as it applies an electrode force and welding current is passed through the weld site of the workpiece. The optimal indentation range is determined by peel test and metallographic examinations with respect to various sheet gages and grades. Consequently, online weld quality inspection results are achieved based on developed optimal indentation range.