Electromagnetic incremental assembly for large thin-walled ring shells and microscopic mechanisms of dynamic deformation overlap regions

Abstract

This paper introduced an electromagnetic incremental assembly (EMIA) method which employed large thin-walled aluminum alloy ring shells as the processing object and a weak rigidity assembled structure with an irregular cross-section as the support object. By experiments, the effects of discharge frequency, discharge voltage, and coil position parameters on the assembly outcome were investigated. The results show that this method successfully achieved a tight fit between the skin and the assembled structure, as well as effective support. During the EMIA, there were many two-step dynamic deformation overlap regions. This paper also conducted an in-depth study on the microstructure evolution of these deformation overlap regions, revealing that dynamic pre-forming enhanced the strength and plasticity of the material. The enhanced strength was attributed to the higher dislocation density within grain boundaries. The plasticity enhancement was mainly due to two factors: firstly, the more uniform dislocation distributions which promoted homogeneous deformation; secondly, the shear stress on the second-phase particles became more concentrated, and the shear action was enhanced. As a result, a large number of original particles were sheared into multiple segments, and large-scaled particles were also fractured, leading to the accumulation of dislocations that eventually cut through the particles, releasing local shear stress.