Lianggang Guo

Research on plastic deformation behaviour in cold ring rolling by FEM numerical simulation

Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming parameters, friction, etc. Investigating the plastic deformation behaviour (the plastic deformation state and its development) in the deformation zone during the process is very significant for rapidly predicting the metal flow, controlling the quality of deformed rings and optimizing the cold ring rolling process. In this paper, a decisive factor on plastic deformation behaviour, namely the average amount of feed per revolution , has firstly been ascertained. Then a functional relation, between and various process parameters, has been now established. Lastly, through 3D numerical simulation based on the elastic–plastic dynamic explicit FEM under the ABAQUS software environment, it has been found that there are three kinds of plastic deformation behaviours during cold ring rolling operation. One is that the material in the deformation zone entirely comes into the plastic deformation state at the early stage of the process. Two is that the material in the deformation zone gradually comes into the plastic deformation state during the process. And last is that at the end of the process, there is still a rigid zone in elastic deformation or small plastic strain state near the middle radius of the ring blank. Based on this, the influence of plastic deformation behaviours on metal flow, the degrees of inhomogeneous deformation of ring and force and power parameters in the cold ring rolling process have been explored. The achievements of this study thoroughly reveal the deformation mechanism of cold ring rolling and provide an important basis for the optimization of process parameters and precise control of the cold ring rolling process.

DYNAMIC EXPLICIT FE MODELING OF HOT RING ROLLING PROCESS

Abstract A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions, motion control over guide rolls, and mass scaling. The method has the following features: 1) the elastic-plastic dynamic explicit approach instead of the static implicit approach is adopted to solve the process so as to greatly improve computational efficiency without sacrificing computational accuracy; 2) the coupled thermal-mechanical effect is considered as opposed to the conventional isothermal assumption, which is more practical; 3) in contrast to the simplified 2D or local 3D ring model, the full 3D ring is modeled to simulate the process. Based on the FE modeling method, two cases of hot plain ring rolling are simulated in the FEA software ABAQUS/Explicit. The simulation results are compared with the experimental measurements and the good agreement between them is observed regarding the material flow and the temperature distribution of the ring.

Research on interactive influences of parameters on T-shaped cold ring rolling by 3d-FE numerical simulation

Cold ring rolling is a much complex physical process with multi-factors. Two forming parameters, the feed rate of mandrel and the rotational speed of main roll, affect the quality of deformed ring significantly and the feed amount per revolution of ring in the form of their ratio. By their ratio, the interactive effects of the two forming parameters on the T-shaped cold ring rolling process are explored through 3D-FEM in Abaqus software. The results show: firstly the study objects (roll force, growth rate of diameter, degree of inhomogeneous deformation, filling capability of groove, average side spread and fishtail coefficient) are almost invariable if the two parameters are increased (or decreased) proportionally; secondly whether the ratio is changed by the feed rate of mandrel or by the rotational speed of main roll, the variation of each study object with the ratio is approximately the same; thirdly the increase of the ratio is beneficial to the growth of diameter and the restrictions of inhomogeneous deformation, average side spread and fishtail coefficient, but it causes the roll force to increase and the filling capability of groove to decrease.

Simulation for Guide Roll in 3D-FE Analysis of Cold Ring Rolling

A simple and efficient method has been proposed in order to determine the dynamic speed boundary condition caused by the guide rolls for developing the 3D-FE model of cold ring rolling process rapidly. The concept of the motion track of guide rolls has been put forward firstly and an optimal motion track and track type are given by simulation. Meanwhile, an effect of the guide rolls on the ring tilting and ring circularity was simulated and analyzed. The result shows that the simulation results are in good agreement with experiment results from the literature.

Effect of sizes of forming rolls on cold ring rolling by 3D-FE numerical simulation

Abstract During cold ring rolling process, changing the sizes of forming rolls including driver roll and idle roll will lead to a change of amount of feed Δ h and contact areas between ring blank and forming rolls, thus a change of the shape and dimension of deformation zone located in the gap of forming rolls is found. It has a significant effect on metal flow and the forming quality of deformed ring. So the size effect of forming rolls on cold ring rolling was investigated by three-dimensional dynamic explicit FEM under ABAQUS environment. The obtained results thoroughly reveal the influence laws of the sizes of forming rolls on the average spread, fishtail coefficient, degree of inhomogeneous deformation and force and power parameters etc not only provide an important basis for design of the forming rolls and optimization of cold ring rolling process, but also reveal the plastic deformation mechanism of cold ring rolling.

Effects and Optimization of Roll Sizes in Hot Rolling of Large Rings of Titanium Alloy

Abstract In hot rolling of large rings of titanium alloy (LRTs), the ratio of roll radii R 1 / R 2 , i.e., the ratio of the radius of the driver roll R 1 to that of the idle roll R 2 , has a significant effect on the geometric shape of the deformation zone (GSDZ) which plays a decisive role in achieving LRTs with high quality. In the study, an analytical description of the GSDZ is presented, and quantitative relationships between the GSDZ and R 1 / R 2 are determined. Then a validated coupled thermo-mechanical 3D-FE model of the process is developed in the dynamic explicit code ABAQUS/Explicit. Finally, an investigation is conducted regarding the effects of R 1 / R 2 on the quality of LRTs from the view point of GSDZ using FE simulation. The results show that there is an optimized range of R 1 / R 2 for obtaining LRTs with better end-plane quality and more uniform strain and temperature distributions.

Some advances in local loading precision forming of large scale integral complex components of titanium alloys

Abstract The large scale integral complex components of titanium alloys have been attracting increasing applications in the aerospace industry because they can meet the requirements of high performance, lightweight and high reliability. The local loading method which can control unequal deformation is an essential way to form such components. There are key problems to be solved urgently in the research and development of local loading method, and finite element numerical simulation in combination with theoretical analysis and experimental investigations has been playing a more and more important role in this field. This paper presents the state of the art of some local loading forming technologies and their applications in manufacturing titanium components, including the isothermal local loading forming of large scale integral rib web components, hot rolling of large seamless rings and hot spinning of thin walled shells.

Wrinkling Limit Based on FEM Virtual Experiment during NC Bending Process of Thin-Walled Tube

A definition of forming limit is given with minimum centerline radius min R before wrinkling for NC bending process of thin-walled tube. Based on the developed FEM wrinkling prediction system TBWS-3D, an effective searching algorithm of wrinkling limit is proposed and forming limit can be obtained conveniently. Thus influence laws of main forming parameters on wrinkling limit are investigated and revealed. Measures to improve forming limit is put forward consequently. The achievements may help to both practice of thin-walled precise tube bending and research of plastic wrinkling.

Key Technologies for 3D-FE Modeling of Radial-Axial Ring Rolling Process

Nowadays, 3D-FE Modeling and simulation is an indispensable method for the optimum design and precise control of radial-axial ring rolling process for its complexities. In this paper, the unique forming characteristics of radial-axial ring rolling have first been summarized, and then some key technologies for 3D-FE modeling of the process have been presented and their solution schemes have been given out, lastly the modeling and simulation of radial-axial ring rolling process have been realized using elastic-plastic dynamic explicit procedure under ABAQUS environment. The work provides an important basis and platform for the future investigations, such as forming mechanism and laws, process optimum design and precise control.

Research on the influences of material properties and forming parameters in T-shaped closed cold ring rolling process

The influences of the material properties (hardening exponent, Young modulus and yield stress) and the forming parameters (feed amount per driving roll revolution and friction coefficient) on the T-shaped closed cold ring rolling process have been investigated through 3D-FEM. The results show that, the roll force, the roll moment and the diametrical expansion of ring lie on the hardening exponent, the roll force and the roll moment hoik, but the growth rate of ring diameter drops quickly with the increase of hardening exponent; the ring deforms more uniformly with the increase of hardening exponent, yield strength or the feed amount per driving roll revolution or with the decrease of Youngs modulus; the filling capability of groove improves with the increase of yield strength but worsens with the increase of the other four variables. The achievements may serve as an important guide for selecting rolling equipment and determining the forming parameters of the process. As compared with the experimental data, the 3D-FE model of T-shaped cold ring rolling is valid, ensuring the necessary accuracy of the obtained results.