Influence of Tool Runout on Force Measurement During Internal Void Monitoring for Friction Stir Welding of 6061-T6 Aluminum
Influence of Tool Runout on Force Measurement During Internal Void Monitoring for Friction Stir Welding of 6061-T6 Aluminum
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DOI：
10.1115/1.4051009
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发表时间：
2021-04
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影响因子：
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通讯作者：
D. Franke;M. Zinn;S. Rudraraju;F. Pfefferkorn
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文献类型：
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作者：
D. Franke;M. Zinn;S. Rudraraju;F. Pfefferkorn
本研究的目的是研究在控制工具肩的倾斜量（振荡过程力的驱动因素）的同时改变摩擦搅拌工具的偏心量如何影响在地下空隙相互作用期间过程力瞬态的产生。所获得的知识将有助于提高基于力的空隙监测方法的准确性，从而有可能减少焊后检查的需要。在地下孔隙形成过程中，对具有不同幅度运动跳动的多个工具进行了过程力瞬态测试。刀具的偏心运动在刀具旋转频率上产生了加工力的振荡，当刀具探头上的特征（平面）与空体相互作用时，这种振荡会变得扭曲，在刀具旋转频率（对于三个平面刀具）的三倍处产生力信号的振幅。较大的刀具偏心会在刀具旋转频率下产生较大的力信号振幅，从而在空隙相互作用过程中产生较大的失真。一旦空洞变得足够大，产生的三次谐波幅值大于没有相互作用的焊缝中旋转频率幅值的30%（仅为旋转频率幅值），工具肩的后缘就不能完全巩固空洞，也就是说，它将留在最终焊缝中。此外，一旦空洞超过一定的尺寸，在完全固结时，第三次谐波的幅值达到旋转频率幅值的70%。通过确保肩部（倾斜）相对于旋转轴的任何几何缺陷被移除，隔离了偏心探头和亚表面空隙之间的相互作用。结果表明，在开发基于这种性质的力瞬变的空隙监测方法时，必须了解与工具旋转轴相关的几何缺陷（偏心和倾斜）。
The goal of this research was to examine how altering the amount of friction stir tool eccentricity while controlling the amount of slant in the tool shoulder (drivers of oscillatory process forces) effects the generation of process force transients during sub-surface void interaction. The knowledge gained will help improve the accuracy of force-based void monitoring methods that have the potential to reduce the need for post-weld inspection. Process force transients during sub-surface void formation were examined for multiple tools with varying magnitudes of kinematic runout. The eccentric motion of the tool produced oscillations in the process forces at the tools rotational frequency that became distorted when features (flats) on the tool probe interacted with voided volumes, generating an amplitude in the force signals at three times the tool rotational frequency (for three flat tools). A larger tool eccentricity generates a larger amplitude in the force signals at the tool’s rotational frequency that holds a larger potential to create a distortion during void interaction. It was determined that once void becomes large enough to produce an interaction that generates an amplitude at the third harmonic larger than 30% of the amplitude at the rotational frequency in a weld with no interaction (amplitude solely at rotational frequency), the trailing edge of the tool shoulder cannot fully consolidate the void, i.e., it will remain in the final weld. Additionally, once the void exceeds a certain size, the amplitudes of the third harmonics saturate at 70% of the amplitude at the rotational frequency during full consolidation. The interaction between the eccentric probe and sub-surface void was isolated by ensuring any geometric imperfection in the shoulder (slant) with respect to the rotational axis was removed. The results suggest that geometric imperfections (eccentricity and slant) with respect to the tool’s rotational axis must be known when developing a void monitoring method from force transients of this nature.