Research On Electromagnetic Heating Strengthening Of Aluminum Alloy Welded Joints With Hole Defects

Aluminum alloy welding is one of the key technologies in the filed of automobile manufacturing, however the defects are easily generated due to the limitations of welding technology itself. Electromagnetic heating crack arrest is a new technology to implement the crack arresting or even healing the wound of metal structures with defects. Applying this technique to aluminum alloy welding fields can improve mechanical property of welded joints better.According to the hole defects existing in the aluminum alloy welding joints, this article takes theoretical analysis, numerical simulation and experiment research to study the hole defects by electromagnetic heating. The research content mainly includes the following several aspects.(1)The theoretical analysis model of aluminum alloy welding containing the hole defect is established.Temperature field distribution at current switching moment near the hole defect is derived with the heat resource method and temperature field boundary conditions. Meanwhile taking an analysis of example to calculate the temperature curve at a certain point near the hole with the time changing.Through the Zhukovsky conformal transformation,the discharging instant thermal stress intensity factor and comprehensive stress intensity factor are calculated.(2)The welding process for butt plates welding of 6061 aluminum alloy is simulated by using ANSYS software,at the same time the effects of welding parameters and welding plate size on the temperature field is analyzed. The finite element analysis model of 6061 welding joints with holes is presented and calculated.The heat-electric-mechanical three coupling calculation method is used to solve the temperature field, stress field and strain field at current switching moment near the hole defect.(3)The welding joints of 6061 aluminum alloy and A356 aluminum alloy are prepared by TIG welding.By the ZL-2 super pulse discharge generator, the welded joints with hole defects are discharged by electromagnetic heating.The micro-structu re,micro-hardness,mechanical properties,micro-fracture and EDS component analysis are analyzed by contrast method,revealing the strengthening mechanism and strengthening effect of electromagnetic heat.This article proves that the electromagnetic thermal strengthening technique is effective to improve welded joint’s mechanical property by the way of theoretical analysis,numerical simulation and experimental research.The research lays the foundation for applying this technique to welding field.