Estimation of mechanical expansion stroke and force and effects of processing parameters on expanding quality for giant ring

Abstract

ABSTRACT Mechanical expansion is the key process in the manufacture of giant metallic ring. The mechanical expansion process of a 10-m-class aluminium alloy ring is taken as the research object in this paper. First, based on the springback theory of small curvature plane bending, the springback ratio formula is derived for the wall thickness centre-line of the ring cross section after unloading, and the mechanical expansion stroke model is established by the mould displacement compensation method. Then, a calculation method for mechanical expansion force is proposed by considering the friction between the mould arc surface and the ring inner wall. Moreover, a finite element model (FEM) is established to simulate the mechanical expansion process of a 10-metre-class aluminium alloy ring using MSC_Marc. The results show that the model proposed in this paper reduces the dimension error of the ring after unloading by 9.19%, and increases the calculation accuracy of the mechanical expansion force by more than 30% under different friction coefficients. Furthermore, the effects of processing parameters, centre angel of the mould segment, relative radius of the mould segment, fillet radius of the edge mould segment, ovality, expansion rate and friction coefficient on the fabricated ring quality are numerically investigated.