Radial Ring Rolling Research Articles

Effects of axial rolls motions on radial–axial rolling process for large-scale alloy steel ring with 3D coupled thermo-mechanical FEA

Radial–axial ring rolling (RARR) is an advanced plastic forming technique which is widely used to manufacture large-scale seamless rings. Compared with pure radial ring rolling, a pair of axial rolls are added to control the axial deformation of the ring during the RARR process. The motions of the axial rolls are very important to the RARR process since they have enormous influence on the stability of the process as well as the quality of the rolled ring. But during the RARR process, the motions of the axial rolls are very complicated, and how to reasonable control them always is a difficulty in the actual RARR production which limits the development and application of the RARR. In this paper, the ranges of motion parameters of the axial rolls are reasonable determined firstly, then a 3D elastic–plastic and coupled thermo-mechanical FE model of RARR is explored using the dynamic explicit code ABAQUS/Explicit. Based on the reliable 3D FE model, the effects of the axial rolls motions on the RARR process are investigated. The research results provide valuable guidelines for the motion control of the axial rolls in the actual RARR production.

A One-Point Quadrature Element Used in Simulation of Cold Ring Rolling Process

A single-point load will be applied on the ring in the cold ring rolling process when the ring vibrates violently. This arouses hourglass in finite element simulation of the process using reduced integration element. A one-point quadrature element with hourglass control developed by Hu is used, and the user-defined control parameters are not required. Hourglass energy can be reduced to 3 percent of the internal energy. The element is applied to simulation of a pure radial cold ring rolling with rectangular section. Compared with the experimental results, the simulation results are proved to be accurate. Key-Words: one-point quadrature; Hourglass control; finite element; cold ring rolling

Change of Plastic Hinge Position in Radial Ring Rolling without Guide-Roll

Radial ring rolling is an unsteady plastic deformation process. Internal stress of the ring is foundation of formation of the plastic hinge. The radial wall thickness of ring changes gradually along ring circumferential direction. Theoretical analysis and FE simulation show that: the plastic hinge is not always exactly opposite to the rolling deformation zone in ring rolling process without guide-roll. The plastic hinge position angle β0 is affected by ratio of rolling entrance wall thickness H0 and rate of wall thickness change η. Curve of β0-H0/η is shaped as double U staggered relative to each other. With the H0/η increasing, β0 reduces gradually and approaches to π in the range of H0/η>6.28. H0/η>14.6H0/R2. Only when the rolling process is steady, and H0≈R2, β0 is greater than π, and approximates to π. The β0 fluctuates dramatically when H0/η≈5.71. In some cases, H0/η may fluctuate in 0 to 6.28, leading to the instability of plastic hinge position.

Effect of the Guide-Roll Positional Angle to the Stability of Radial Ring Rolling

Non-stability factors affect stability of radial ring rolling process, and lead to fluctuating of ring position. This decreases rolling precision. Evaluating stability of the process is very important. A stability evaluating method is proposed. The stability can be measured with the mean square root of sequence of oscillation of ring geometrical centerline displacement. Using ABAQUS/Explicit, the stability is analyzed. It is showed that guide-roll position angle has the significant effect to the stability. If guide-roll is located at the tangential position to the ring’s fringe, the stability will vary with the angle between two planes. One passes through axes of guide roll and ring blank, and another passes through axes of drive roll and ring blank. The stability is highest when guide roll is situated at the position angle of 100˚to 130˚at exit side of ring rolling mill.

Design of Profile Ring Rolling by Backward Simulation Using Upper Bound Element Technique (UBET)

The upper bound element technique (UBET) is used to determine the optimum intermediate shape for profile ring rolling using backward simulation. The lowest energy rate is the key issue in achieving the optimal intermediate shape as well as the backward simulation of the process. The plastic flow of material in ring rolling is assumed to be a sequence of successive closed-die forging processes. The ring is divided into features, which provide an approximated profile consisting of a number of rectangular elements. The simulation of the profile ring rolling was tested with different profiles of rolls, and two such cases are presented here. The present method was validated using an experimental radial ring rolling mill designed and fabricated in the Dept. of Mechanical Engineering at Ohio University for the investigation of both cold and hot ring rolling processes. As the results show, this technique is capable of solving the backward simulation of profile ring rolling problems in a much shorter time compared to the finite element method (FEM), which cannot easily simulate profile ring rolling. Moreover, as an engineering tool, this approach can be applied effectively to the profile ring rolling process and can serve as a useful tool in industrial applications.

Simulation of ring rolling using a rigid-plastic finite element model

This paper describes details of a finite element model for analysing three-dimensional flow in the roll gap during radial ring rolling between plain cylindrical rolls. The model considers such factors as curvature of the workpiece, unequal roll diameters and the fact that the inner roll or mandrel is unpowered. The results of the analysis compare favourably with experimental observations. Fishtailing is predicted satisfactorily, also the form of the pressure distribution in the roll gap, which shows twin peaks under some rolling conditions. The method has the merits of easy handling and short calculation time. It should be a useful aid to the design of ring rolling and other asymmetric rolling processes.

Spread and flow patterns in ring rolling

Tellurium lead and aluminium alloy rings were rolled on an experimental radial ring rolling mill to reductions as great as 70% to determine the spread when taking into account the various ring rolling factors. Both plain and profiled rings were rolled. In the case of the profile ring rolling, a T-shaped section was formed from an initially rectangular cross-section, the undriven mandrel being grooved and the main roll plain. The mode of deformation for plain and profiled rings was also examined and is reported.