A Design of Distributed Coils System for Electromagnetic Bulging in Large Aluminum Alloy Rings

Large aluminum alloys rings processing and manufacturing inevitably introduce residual stress due to the uneven thermal and mechanical loading of large-scale structural forming. Residual stress will cause a decrease in mechanical strength and dimensional accuracy. Existing large-ring stress relief methods are trace cold deformation after aging treatment. However, aging treatment of large workpieces requires expensive and large-scale equipment, and the heating could be uneven easily. At the same time, traditional mechanical bulging machines with defects in terms of processing capacity and size make it difficult to achieve cold deformation on large-diameter aluminum alloy rings. In this paper, a method of using distributed coils to bulge large rings is proposed, which can achieve cold deformation and eliminate residual stress. An electromagnetic bulging system is designed for aluminum alloy rings with an outer diameter of 10 m. The coil type and spatial magnetic field distribution are simulated and verified by numerical simulation. Simulation results show that smaller size distributed coils can produce better pulsed currents. Using the adjacent coils through current with the same direction can realize more obvious deformation results than the reverse current. Furthermore, about 20 MJ electromagnetic energy can generate 0.1% plastic strain of the aluminum alloy ring at a single discharge.