电阻点焊过程中动态电阻的变化规律

动态电阻变化是电阻点焊过程中的重要内容．了解不同材料在焊接中动态电阻的变化规律,可以预测点焊接头的形成过程,建立熔核形状与动态曲线的关系,实现对焊点质量的监测,目前．已对低碳钢,镀锌钢板、不锈钢、铝合金和镍合金等材料点焊时的动态电阻变化规律进行了研究。     

不锈钢电阻点焊过程中的动态电阻变化规律分析

对利用自动数据采集技术获取的不锈钢点焊过程中的动态电阻信息进行系统研究.结果表明,不锈钢点焊过程中动态电阻能够灵敏且有规律地反映点焊工艺参数的变化,蕴含着丰富的点焊质量信息.焊接过程中动态电阻变化与熔核生长过程具有明显的对应关系,动态电阻曲线的拐点时间及终点值等特征量分别与熔核出现时间和最终熔核尺寸有很强的相关性.点焊过程喷溅会导致动态电阻骤降,其动态电阻变化率曲线在相应位置出现尖峰,为喷溅的自动识别提供了依据.     

Effects of electrode contact condition on electrical dynamic resistance during resistance spot welding

This study systematically investigates the effects of electrical resistance at the workpiece/electrode interface or electrode face on temperature dependent dynamic resistance during resistance spot welding (RSW). To evaluate temperature transport equations of mass, momentum, energy, species and magnetic field intensity in workpieces, the energy and magnetic equations in the electrode are solved. Contact resistances composed of constriction and film resistances are functions of hardness, temperature, electrode force and surface conditions. The results show that dynamic resistance is complicated due to different variations of film and constriction resistances with temperature at not only the faying surface but also the electrode face in the early stage, i.e. shorter than around 3 cycles. Dynamic resistance in this stage is fortunately insignificant to transport processes. When the power is off, dynamic resistance depends on competition between decreased bulk resistance and increased constriction resistance at the electrode face. Decreased constriction resistance at the electrode face reduces dynamic resistance and temperature.     

精密逆变电阻点焊的应用

首先介绍了精密逆变电阻点焊机系统，包括系统的组成，特点，然后介绍几种典型工件的焊接工艺，结果表明，这种焊机在精密零件 的电阻点焊中有其独持的工艺优势，有很好的推广应用价值。     

分形理论及其在电阻点焊中的应用前景

介绍了分形理论，探讨了其在电阻点焊中的应用前景。分形理论包括分形的基本概念、分形理论的发展、3个分表维数的概念度计算。分形在点焊中的应用包括电极间接触电阻的确定、熔核形成过程中的相变及搅拌运动、点焊中特征信号的提取。     

数学化电阻点焊控制器

根据电阻点焊的控制要求,设计了基于微处理器技术的数字化点焊控制器。控制器基于PHILIPS的80C552单片机设计,具有焊接程序控制、焊接电流波形调制、故障诊断等功能;控制器提供了基于LCD显示与键盘输入的数字化参数设置界面对控制器的可靠性设计进行了分析,采取了硬件和软件的抗干扰措施。试验证明设计的点焊数字控制器具有良好的动态特性。     

点焊过程热膨胀变形分析

用有限元方法模拟了低碳钢点焊过程的热膨胀变形，给出了正常焊接、工件受约束和极限条件下的热膨胀变形的理论计算结果，分析了热膨胀对电极的作用和各种机械约束对热膨胀行为的影响，结果表明：焊接区热膨胀以电极有很在的推动作用，最大位移量在电极轴线方向；焊接热膨胀变形受工件的约束条件，电极压力及焊机机械参数的影响，变形规律有所不同，研究结果为热膨胀法点焊质量实时控制提供了理论指导。     

电阻点焊的单片机控制器研究

研究了AT89C51单片机控制电阻点焊过程，键盘控制输入参数，LED动态显示的新型控制装置。详细介绍了该控制器硬件和软件设计。采用谊控制器可改善焊接循环，提高焊接电流和焊接时间的控制精度，工作性能稳定，程序编制灵活。试验表明．其性能稳定可靠，并具备进一步扩展、开发的能力。     

铝合金电阻点焊过程的有限元模拟

建立了铝合金电阻点焊过程的有限元分析模型，采用基于显微接触理论的接触电阻模型模拟点焊过程中试件与试件界面上的接触电阻。计算获得了焊接过程中电极／试件和试件／试件接触界面上接触半径的变化，以及试件间界面上压应力、电流密度和温度的分布。试验考察了熔核的形成和长大过程。比较表明，计算与试验测量结果符合很好，证实了所采用的接触电阻模型在铝合金电阻点焊模拟中的正确性和适用性。     

A mathematical model of rough surface contact characterization in spot welding

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Filling technique for keyhole of friction stir spot welding based on the principles of resistance spot welding

Keyhole at the end of a weld prepared by friction stir welding(FSW) is one of the major issues that impede the application of FSW. To address this issue, a keyhole filling technique was proposed in this paper, which is based on the principles of resistance spot welding(RSW). A three-phase secondary rectifier resistance spot welder was applied as the experimental instrument for filling the keyhole in the center of friction stir spot weld(FSSW). The test sheet is a 2024-T4 aluminium alloy with a thickness of 6.0 mm. The experiments results show that the filled joint strength is improved by 26.12% since the area is increased for the plug in the keyhole. And there are two kinds of dimples in the tensile fracture—equiaxial dimples and long dimples. The filled joint involves the fusion welding zone(FWZ), pressure welding zone(PWZ), melted plug zone(MPZ), and plastic deformation zone(PDZ). The FWZ and the PWZ is the melting bond and diffusion bond between the plug and keyhole, respectively. The MPZ is the center part and the PDZ is upper or lower part of the plug.     

Quality estimation of resistance spot welding of stainless steel based on BP neural network

The end value of the dynamic resistance curve of stainless steel was proved to have strong correlation with nugget size by experiments, so it was an important factor for estimation of weld quality. BP neural network was employed to estimate the weld quality. The end value of the dynamic resistance curve, welding current and welding time were selected as the input variables while the nugget diameter, which is closely related to weld quality, was selected as the output variable. Testing results shows that such network has fine fault tolerance and real-time quality estimation is possible.     

基于嵌入式系统的电阻点焊飞溅信息在线判读

钢材的电阻点焊过程中,动态电阻的变化表征了丰富的焊接质量信息.采用嵌入式系统实时监测焊接过程动态电阻的变化有利于提高对焊接质量的认识.设计了嵌入式监测系统,系统同时监测焊接电流、电极间压力和电极间的电压、电极位移信号.分析了双相钢DP600焊接过程中的动态电阻变化与焊点熔核之间的关系,并阐明用焊点两端的电压信号替代动态...     

低碳钢点焊喷溅的动态电阻特征参量

针对电阻点焊车间生产,开发了一套点焊过程动态数据采集装置,用以采集和分析点焊过程喷溅行为的动态特征.利用系统对试验室环境下的点焊过程进行数据采集,分析了焊接电流、电极力、焊件表面状态、小边距及分流影响下喷溅的动态电阻曲线特征.结果表明,低碳钢点焊过程喷溅发生时,其动态电阻及其变化率曲线形式、峰值的大小、峰值点到达时刻和停留时间、峰值下降量等都有所不同;曲线在不同阶段有不同程度的突变,前期突变程度较大,后期较为平缓;提取的喷溅动态特征参量为动态电阻曲线及其变化率曲线的不同程度突变.     

Dynamic simulation of resistance spot welding of zinc-coated steels

A model was developed to simulate the temperature distribution and nugget formation during resistance spot welding （ RS1V） of zinc-coated steels. It employs a coupled thermal-electrical-mechanical analysis simulating the dynamic RSW process. Temperature-dependent thermal-electrical-mechanical material properties were considered including contact-resistance. The contact area was determined from a coupled thermal-mechanical analysis. A layer of transition elements was used to represent the change of contact area by killing or activating elements. The heat generation and temperature field were computed in a coupled thermal-electrical model. All these analyses were solved using the commercial finite element method （FEM） based on ANSYS code, and some advanced functions were used by writing a paragraph of codes by the authors. Compared with the results from only coupled thermal-electrical model in which contact area was uniform during the whole process, the result matches better to the experimental results.     

博世UIR技术在汽车高强钢电阻点焊上的应用

根据高强钢板的物理特性,介绍高强钢板电阻点焊的难点,通过优化焊接参数,如增大焊接压力、延长焊接时间、减小焊接电流、增加焊前预热、减小修磨间隔点等可以有效消除高强钢点焊过程中的焊点毛刺、焊点裂纹和熔核缩孔等缺陷。简述博世UIR系统的动态电阻检测原理、恒功率补偿原理和焊点质量监控原理。采用UIR系统采集并建立焊点的标准动态电阻曲线,根据标准动态曲线对点焊过程进行能量补偿,有效弥补高强钢点焊常见的飞溅导致的能量损失,提高焊点质量。通过UIR系统监控功能有效保障焊点质量和点焊过程的稳定性,满足高强钢实际生产需要,并延长电极使用寿命。     

铝合金点焊的多场耦合建模与动态过程数值模拟(英文)

基于铝合金点焊的热、机、电及相变原理,建立热电力耦合场的轴对称有限元数值仿真模型,实现对焊接区温度场、电场、应力应变的动态模拟。发现了焊接电流变化激发的铝合金动态电阻"瞬态逆向虚变效应",揭示了过程热电耦合瞬态与稳态差异性作用机理,阐释了焊接电流增加而瞬态电阻骤降的反常现象。基于铝合金点焊稳态仿真与实验结果修正了动态电阻数值计算模型。AA5182的计算与实验结果表明,考虑动态电阻"瞬态逆向虚变效应"的动态仿真模型能够精确描述焊接电流调整过程中的电参数动态变化和铝合金焊点熔核的生长过程。     

镁合金电阻点焊接头组织结构特点

为了提高镁合金电阻点焊接头的力学性能,采用光学显微镜、激光共聚焦扫描显微镜、x射线衍射仪研究了接头的微观组织和相组成.结果表明,接头主要由熔核和热影响区(HAZ)所构成.熔核一般包括两种不同的组织形态,即熔核边缘的胞状树枝晶和熔核中心的等轴树枝晶.熔核是由大量的α-Mg相和少量的β-Mg17Al12相所组成.相对于未熔化的母材晶粒,热影响区晶粒变粗,并伴随晶界熔化.当焊接电流为23 kA,焊接时间为8个周波,电极力为4.5 kN时,熔核边缘的胞状树枝晶细化,而熔核中心的等轴树枝晶有向等轴晶转化的倾向,且平均晶粒尺寸为12.96μm.     

低碳钢点焊动态过程的模型化控制

ＤＲＣ法点烛质量监控技术关键之一是恰当地设定和描述表示点焊熔核形成过程最优动态品质的给定动态电阻特性。本文在深入试验研究和理论分析的基础上，确立了标识最优动态品质动态电阻特性的总体模型及其特征参数，据此实现了低碳点焊热过程的模型化控制。     

镁合金电阻点焊接头中的缺陷

研究了新型轻质镁合金在电阻点焊中的主要缺陷,分析了焊接缺陷的形貌特点、形成原因和危害,为提高镁合金点焊接头质量提供了依据.结果表明,在镁合金电阻点焊接头中的裂纹为结晶裂纹,与电流特性、结晶时的应力状态和成分偏析有关;缩松和缩孔的产生主要与焊接过程中金属热膨胀及焊接后期锻压力大小有关;电极粘附和焊接喷溅是镁合金点焊中最常见的缺陷,产生的主要原因是电极与工件以及工件与工件界面处局部过热造成的.