Forming thin-walled circular rings with corrugated meridians via quasi-bulk deformation of metal blank and viscous medium

Abstract Excessive thinning of wall thickness caused by the unstable deformation of metals is the main failure mode in the manufacturing of thin-walled circular rings with complex section. A novel quasi-bulk forming method is proposed in this work to deal with this problem through achieving a stable state of metal flow. Metallic materials and viscous medium with different strain rate sensitive exponents ( m ) were respectively employed as core materials (i.e. pressure-carrying medium) in finite element analysis (FEA) to investigate the effects of core materials on the deformation behaviors of ring-shaped metal blank. Numerical results indicate that viscous medium and metal blank deform synchronously like a composite billet when appropriate viscous medium acts as core material. It is attributed to the adhesive attraction between viscous medium and metal blank caused by the high viscosity of viscous medium. In this condition, the composite billet easily fills the die cavity, which is similar to the way that round billets fill the die cavity in bulk forming processes. In order to verify the validity of quasi-bulk forming method, two types of thin-walled circular rings with corrugated meridians were formed through proposed method in the forming experiments. The maximum wall thickness reduction of formed parts is less than 8%. The present study demonstrates the quasi-bulk forming method can not only inhibit wall thickness thinning of thin-walled parts but simplify the process control. Thus, it may become a key process to fabricate thin-walled circular rings with large diameter variation per unit axial length ( ψ ).