Inversed Imaging Of The Nugget In Aluminum Alloys Spot Welding Based On Magnetic Field

Aluminum alloy spot welding is wildly implemented in auto and aerial industry because it is a welding technique which is easy to be automatized. Owing to the physical and chemical characteristic of aluminum alloy and restricted by the welding machines, aluminum spot welding is a process with high non-linearity, coupled with many parameters and affected by lots of random factors. Besides, the forming process of the nugget can not be inspected directly. Therefore, it has vital significance to inspect the forming process.The inverse problem, basic principles of Computerized Tomography, and reconstruction algorithm are analyzed in this research. The related theories are imported in aluminum alloy spot welding at the first time. According to the Biot-Savart law and related electromagnetic theory, mold parameters and predigestion conditions are brought forward based on the characteristic of aluminum alloy spot welding. A forward model of magnetic filed in aluminum alloy RSW are set up.A data sampling system based on virtual instrument LabVIEW, DAQ2000 series data acquisition hardware and Holl sensors array is designed to inspect the magnetic field. The scientific computing software Matlab is implemented to setup a mathematical model and make data processing. This data sampling and processing system actualized the high speed sampling and high precision data processing.On the foundation of forward model, a reversed model is set up by discrete method. The reversed model established the function relationship between plate current intensity of the nugget and magnetic intensity in 3D space. Eventually, all the data processing will be actualized with Matlab program. In this research, a new method was put forward to inspect the forming process of the nugget. And the feasibility of validity of the model and related algorithm was confirmed by experiments.