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Research on Inversion Imaging of Nugget Cross-section in AluminumAlloy RSW

Author: XueZhiQing
Tutor: DanPing
School: Tianjin University
Course: Materials Processing Engineering
Keywords: resistance spot welding weld quality quality monitoring inversion imaging regularization method
CLC: TG443
Type: Master's thesis
Year: 2009
Downloads: 28
Quote: 3
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Abstract


Resistance spot welding is a material joining method which is high efficient andeasy to be automotive. However, the physical and chemical characteristic, thedisadvantage of aluminum alloy resistance spot welding machine and its qualitymonitoring system limits its application on the fields where higher quality spot weldis required. The magnitude of current across the nugget, especially the distribution ofelectricity, is one of the key factors that impact the quality of nugget. Therefore, theinverse theory and regularization method are used to the current inversion imaging ofnugget cross-section. The inversion image can be used to evaluate the spot weldintuitively, which is novel evidence on the nugget quality.Theoretical study, numerical experiment and experimental validation arecombined to study the inverse problem. Firstly, the forward model, which describesthe relationship between the current distributions of nugget cross-section, isestablished by Biot-Savart law and superposition principle, and its reliability isverified by experiment. Secondly, inversion model is established and the ill-posednessof the inverse problem is analyzed. Thirdly, the numerical experiment is to verify thecorrectness of the inversion model. In the end, different current is chose for theresistance spot welding experiment. After the magnetic signal is collected, Matlab isused for data processing and the magnetic signal is transformed into current signal,which is shown with the form of image. So, we can analyze the characteristics of theinversion image in different current, the effect of parameters on the inversion resultsand the relationship between inversion image and the nugget quality.Experiment results shows that the forward and inversion model is reliable withina certain error. The inversion image describes the characteristics of nuggetcross-section current distribution to a certain extent, which can reflect the nuggetquality and the weld quality can be evaluated by it. The choices of regularizationparameters impact the accuracy of inversion image. If it is too large or too small, theinversion image will remove from the real ones.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Electric welding
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