Towards a steady forming condition for radial–axial ring rolling

Radial-axial ring rolling (RARR) is a typical incremental forming process with high flexibility. It is difficult but essential to establish a successful RARR process and remain its stability by properly designing process variables. This paper is an attempt to develop a steady forming condition under which the RARR process can be established successfully and then proceeds stably with qualified ring rolled parts. For remaining process stability by alleviating dynamic contacts and collisions between the ring and the rolls, constant growth velocity condition (CGVC) of the ring is proposed as a design objective of the process variables. Then a mathematical model of the steady forming condition for RARR is developed based on the CGVC. The model describes both the mathematic correlations and the reasonable ranges of key process variables of RARR, and the application and role of the model are illustrated by a case study in detail. For verifying the steady forming condition for RARR, FE simulations and analyses are carried out through developing reliable 3D-FE models for the entire RARR processes under ABAQUS/Explicit platform. The simulation results show that the designed processes based on the mathematical model of the steady forming condition are successfully operated and have good stability. A value of the growth velocity of the ring, which is close to the median of its reasonable range determined by the steady forming condition, is recommended for the design of the process by taking into account the geometry of the rolled ring, material plastic deformation behavior of the ring and process stability.