A cooperative control strategy of resistance spot welding process by combining the constant current control with the DRC method

The modeling control method based on the dynamic resistance characteristics of good nuggets, that is the DRC method, is an improvement on the dynamic resistance threshold method for the quality control of resistance spot welding. But there is still a control blind area in the initial four cycles. For this reason, the quality of every weld nugget could not be fully ensured. Thus a new fuzzy cooperative control method is put forward. It uses a multi-information time-control mechanism by combining the constant current control technology with the DRC method in a relay way. This whole-process control strategy has led to a good control effect and produced the dual-identical results in the weld nugget quality and the welding time.

6061铝合金FSW接头组织与耐蚀性能的研究

对4 mm厚的6061-T6铝合金板进行了搅拌摩擦焊接,通过浸泡腐蚀试验和电化学腐蚀试验研究焊缝腐蚀性能,采用金相显微镜、透射电镜等观察接头的微观组织。结果表明:6061铝合金FSW焊核区晶粒显著细化,晶界第二相较少;焊核区的耐剥落腐蚀和晶间腐蚀性能优于热影响区的;焊核区比热影响区的腐蚀电位较高,腐蚀电流密度较小,焊核区表现出更好的耐腐蚀性能。

搅拌针表面螺纹头数与轴肩下压量对金属轴向迁移的影响

研究搅拌针表面螺纹头数与轴肩下压量对8mm厚的LY12铝合金板材在搅拌摩擦焊过程中焊缝塑性金属在搅拌针轴向的迁移量的影响。结果表明:螺纹内的塑性金属因受到螺纹表面挤压力和螺纹表面与金属间摩擦力的共同驱动而在搅拌针轴向产生迁移,单位时间内塑性金属的轴向迁移量取决于引起金属迁移的驱动力大小和单位长度螺纹内携带金属的量。增加搅拌针表面螺纹头数和增大焊缝所受轴向的挤压力均能使焊缝塑性金属的轴向迁移量增加,其宏观表现为呈"洋葱瓣"花纹状的焊核横截面积增大。

电阻点焊接头熔核面积的预测

以电阻点焊接头表面的数字图像作为信息源,探索了一种新的点焊接头质量无损检测方法。首先通过图像特征分析,将焊点表面图像划分为三个特征区域,提取三个同心圆的面积作为表征接头熔核面积的特征参量。其次,以提取的特征值作为输入向量,以接头横截面处的熔核面积作为评判标准,建立点焊接头熔核面积的SVM(支持向量机)等级分类模型。实验结果表明,该模型可以有效地对熔核面积进行预测分类,实现了对电阻点焊接头质量的无损评判,经验证其准确率可达96.667%。