共查询到17条相似文献,搜索用时 265 毫秒
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结合二维数字图像相关技术(DIC),针对焊接电流、通电时间及电极力对电阻点焊过程中工件翘曲变形量的影响规律进行了深入研究和讨论. 结果表明,利用二维DIC技术获得的工件变形过程与电阻点焊各个阶段相吻合,而且具有较高的精确度. 随着焊接电流和通电时间的增大,熔核形成造成的翘曲变形增大;随着电极力的增大,熔核形成造成的翘曲变形减小,同时电极下压造成的变形增大.二维数字图像相关技术在电阻点焊过程中的首次尝试为电阻点焊工艺的研究和焊接质量的提高提供了新的方法,对电阻点焊工艺的发展和完善具有重要意义. 相似文献
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点焊过程中熔核形成过程对焊接结构的强度和耐用性具有非常重要的影响.文中采用高速摄像技术研究了焊接电流和电极压力对铝合金电阻点焊形核过程的影响.结果表明,铝合金电阻点焊熔核首先在工件/工件接触面中心处形成,然后沿着水平方向生长,同时垂直方向也有少量的生长,一直扩展到电极头端面直径.熔核尺寸在点焊前80 ms时迅速长大,120 ms后基本保持不变,表明过长的焊接时间是没有必要的.随着电极力的增加,工件会经历较大的塑性变形,导致没有熔核形成.因此常规点焊时,不应采用过高的电极压力. 相似文献
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为了研究电阻点焊接头质量,分析了铝合金2A12电阻点焊过程中的电极力、电极位移和焊接电流三组动态数据,并绘制了动态数据三曲线图.结果表明,在焊接过程中合格焊点的电极力曲线变化情况是:开始有轻微下凹现象,然后是小幅增长并伴随轻微波动,最后有向下倾斜的趋势,每个阶段不足或过度,则有不合格焊点产生.电极位移曲线的上升率直接与能量供应率有关,电极位移最大时刻与加载锻压力时刻之间的曲线形状与金属熔化量和软化区大小有关. 相似文献
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针对板管间接点焊过程中焊接变形较大,引起接头质量难以保证的问题.通过采集电极位移曲线,研究板管间接点焊过程中膨胀量和变形量的变化规律,分析不同焊接工艺参数(焊接电流、电极力和焊接时间)对该点焊过程的影响.结果表明,板管间接点焊焊接阶段,膨胀过程与变形过程相互耦合;保持阶段,在电极力作用下,焊接变形进一步加大,最大变形量随着电极力的增大和焊接热输入的增多而线性增加.发生喷溅时,电极位移曲线出现阶梯状畸变,可利用位移曲线斜率的变化评判该点焊的喷溅现象.研究结果为板管间接点焊过程在线监测与质量控制提供理论指导. 相似文献
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利用实时监测结构负载声发射信号实现了镀锌钢板电阻点焊过程中的飞溅现象的检测. 以焊接飞溅声发射事件的正峰值和振铃计数为考核指标,通过正交试验设计法设计焊接试验和方差分析法进行显著性检验,研究了镀锌钢板电阻点焊飞溅的主控因素. 结果表明,焊接飞溅释放出的能量当量可由其声发射事件的正峰值和振铃计数两个特征参数定量评估. 影响焊接飞溅的主要因素为焊接电流和电极力,而焊接电流所起的作用比电极力更为重要. 焊接时间和焊接电流与电极力的交互作用对焊接飞溅的影响相差不大. 焊接电流和焊接时间越大,焊接飞溅当量越大;电极力越大,焊接飞溅当量越小. 相似文献
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利用改进的交流电阻点焊监控系统采集电极位移和焊接电流,经分析认为电极位移曲线上的波动是由50 Hz的交流电阻热脉冲引起的.利用电阻点焊中的洋葱环现象分析了电极位移波动特征的机理,认识到电极位移在熔核形成前以热膨胀为主,在熔核形成后以相变膨胀为主,并且都具有波动特征.利用焊接电流曲线提供的晶闸管触发角和导通角依次计算功率因数角、动态电阻和动态电阻热.通过位移波动周波峰值与动态电阻热的对比分析,发现位移波动周波峰值在点焊过程中对热膨胀与相变膨胀有较强的敏感性,能用来反应熔核形成过程的不同阶段. 相似文献
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An indirect resistance spot welding process with single-side electrode access was developed for automotive applications. The variable controls of electrode force and welding current during welding were studied in order to achieve the promotion of weld nugget formation and the suppression of expulsion without sacrificing the productivity and design flexibility of automobiles. The welding experiments were performed on lapped test coupons of 0.7-mm-thick cold-rolled sheet with tensile strength of 270 N/mm2 and 1.6-mm-thick cold-rolled sheet with tensile strength of 980 N/mm2 using a resistance spot welding system consisting a servo-motor-controlled welding gun and an inverter DC power supply. Welding experiments verified that the occurrence of expulsion and formation of molten nugget were significantly influenced by the heat generation and melting process at an initial period during welding and manageable by applying the variable patterns of electrode force and welding current. When welding was performed under the large shunting condition simply with the constant force and current pattern of 400 N in electrode force, the appropriate current range was less than 1 kA. On the other hand, it extended to 2.6 kA when performed with the variable force and current pattern of 800 N in force and 4 kA in current at the first stage and 400 N in force at the second stage, confirming the fact that the variable pattern successfully suppressed the expulsion and promoted the nugget formation. Numerical simulations were conducted to compare the difference in welding phenomena between the constant force and current pattern and the variable force and current pattern and clarified that the effect of variable force and current pattern on the promotion of nugget formation and the suppression of expulsion. 相似文献
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《Science & Technology of Welding & Joining》2013,18(7):563-570
AbstractComputation of the electromagnetic force over a wide range of consumable arc welding parameters is difficult with available models because of the need for experimentally evaluated electrode extension for every individual set of parameters. This becomes more complicated in case of submerged are welding, because the welding arc remains buried beneath flux. This study presents a new approach of integrating mechanistic model of electrode extension with the computational model of electromagnetic force, wherein the apparent electrode extension is obtained by solving the electrode melting rate equation. The proposed approach is demonstrated through a case on submerged arc welding. The effect of current, voltage, electrode diameter, contact tip to workpiece distance and polarity, on the electromagnetic force, is determined and analysed. This investigation shows that detrimental effects of welding electromagnetic force can be restricted without compromising productivity because after initial rapid increase, no considerable change in melting rate is caused by the force under consideration. 相似文献
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《Science & Technology of Welding & Joining》2013,18(8):718-724
AbstractResistance 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. 相似文献
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S. V. Shchetinin 《Welding International》2017,31(11):857-862
The electromagnetic nature of movement of liquid metal in a weld pool is discussed. When increasing the welding speed as a result of decreasing the induction of the magnetic field at the back of the arc and increasing the electromagnetic force directed forward and reducing the size of the active arc spot, the speed of movement of the liquid metal increases in welding in the direction from the current supply and rapidly in welding towards the current supply. This confirms the electromagnetic nature of formation of undercutting. A method is described for high-speed one-sided welding with a compound electrode in which the active spot of the arc becomes larger, the arc and liquid metal of the pool move forward, the electromagnetic forces directed downwards in the area of the side edges of the pool decrease, and the resultant welded joint is of high quality without undercutting, the reverse bead forms on a flux cushion and the impact toughness of welded joints increases. 相似文献