Wall thickness control in multi-stage hydroforming of multiwave seal ring with small diameter

Abstract

Thinning rate is a crucial factor in forming quality of the thin-walled seal ring with complex features. To control the excessive thinning by altering the stress state during the material deformation, a new multi-stage three-dimensional (3D) hydroforming technology was proposed in this work. Based on the characteristics of the seal ring and the used superalloy strip, a multi-stage internal pressure forming process was established through finite element analysis (FEA) and forming experiment verification. In addition, the distribution of wall thickness in every stage was discussed. And the influence of the width of deformation zone and the pressure loading path in the cavity on the wall thickness of the part in each step was studied. Finally, the optimal forming parameters of each step that can achieve a stable state of metal flow were obtained. The experimental results demonstrated that the developed 3D hydroforming technology can accurately control the material flow in the multi-stage forming of the multi-wave seal ring with small-diameter and ultrathin wall thickness. For the optimized parameter combination, the blank dimensions of deformation zone are 8 mm in the first step and 18 mm in the second step, while the pre-bulging pressure is 9 ~ 12 MPa and the maximum pressure is 100 MPa in the two steps.

Experimental Research for Open Die Polyurethane Forming of Corrugated Thin-walled Machinery Sealed Rings

“…When the appropriate viscous medium is used as the core material, the viscous medium and the metal billet are deformed synchronously to form a composite billet. Yan et al [5] used the problem of wall thickness control in multi-step three-dimensional hydroforming to reduce the rate of thinning by adjusting the stress states of axial compressive and circumferential tensile stresses during multi-pass threedimensional hydraulic expansion feed expansion. With the axial and circumferential stress states properly matched, the required deformed material in the circumferential direction can be supplemented from the axial direction, thus effectively suppressing the wall thinning.Wang et al [6] used this method to form two different shapes of corrugated meridian thinwalled rings, and the maximum wall thickness reduction of the formed parts was less than 8%.…”

A Review of Characterization and Modelling Approaches for Sheet Metal Forming of Lightweight Metallic Materials

“…He detailed the formability of sheet metals and presented various mathematical modelling techniques for forming limit predictions. Another important role of simulation is to quantitatively evaluate the influence of forming process parameters on the mechanical properties of formed parts through the calibrated simulation model to provide effective guidance for subsequent forming process optimization [ 67 , 68 , 69 ]. There have been numerous studies and reviews of SMF simulations, from fundamental plasticity theory to the optimization of FE models [ 31 , 70 , 71 , 72 ].…”