Dong Jihong, Huang Yiming, Zhu Jialei, Guan Wei, Yang Lijun, Cui Lei
Beijing Institute of Petrochemical Technology, Beijing 102617, China.
Beijing Academy of Safety Engineering and Technology, Beijing 102617, China.
Materials (Basel). 2023 Feb 3;16(3):1312. doi: 10.3390/ma16031312.
As a direct reflection of the interaction between the stirring tool and the base metal in the friction stir welding process, the force signal is an important means to characterize welding quality. In this paper, the variation mechanism of three-dimensional force and its relation with welding quality were explored. The acquired signals were subject to interference from high-frequency noise, so mean filtering and variational mode decomposition were applied to obtain the real signals. The denoised signals were analyzed and the results showed that the traverse force was ahead of the lateral force by a ratio of π /4, while the phase difference between the axial force and the other two forces changed with the process parameters. Through application of the least square method and polynomial fitting, the empirical formulas of three-dimensional force were obtained, and these were applicable regardless of tunnel defects. The minimum value of the lateral force increased several times more than that of traverse force when the welding speed increased from 80 mm/min to 240 mm/min. When the pole radiuses of most data points had a value greater than 4, tunnel defects were highly likely to generate. In order to predict welding quality more accurately, a prediction model based on long short-term memory was constructed. The model recognized the various modes of good welds and tunnel defects with 100% accuracy. The identification ability for large and small defects was relatively poor, and the average accuracy of classifying the three categories of welding quality was 84.67%.
作为搅拌摩擦焊过程中搅拌工具与母材相互作用的直接反映，力信号是表征焊接质量的重要手段。本文探究了三维力的变化机理及其与焊接质量的关系。采集到的信号受到高频噪声干扰，因此采用均值滤波和变分模态分解来获取真实信号。对去噪后的信号进行分析，结果表明横向力超前于侧向力，相位差为π /4，而轴向力与其他两个力之间的相位差随工艺参数变化。通过最小二乘法和多项式拟合，得到了三维力的经验公式，且这些公式适用于无隧道缺陷的情况。当焊接速度从80 mm/min增加到240 mm/min时，侧向力的最小值增加幅度比横向力的增加幅度大几倍。当大多数数据点的极点半径值大于4时，极有可能产生隧道缺陷。为了更准确地预测焊接质量，构建了基于长短期记忆的预测模型。该模型对良好焊缝和隧道缺陷的各种模式识别准确率为100%。对大小缺陷的识别能力相对较差，对三类焊接质量进行分类的平均准确率为84.67%。
