Li Wen Zhang

Finite Element Simulation of Vacuum Hot Bulge Forming Process of Reactor Coolant Pump Rotor-Can

In this paper, a 2-D nonlinear thermo-mechanical coupled finite element model was developed to simulate the vacuum hot bulge forming process of rotor-can with the aid of finite element software MSC.Marc. Thermal physical and mechanical properties of materials vary with temperature in the model. In addition, the effects of high temperature creep properties of materials on the vacuum hot bulge forming process of rotor-can were considered. The temperature field, the stress-strain field and the displacement field of rotor-can during vacuum hot bulge forming process were calculated. This work is beneficial to understand the vacuum hot bulge forming process of rotor-can and lays a good foundation for future work.

Influence of hot working parameters on dynamic recrystallisation of GCr15 bearing steel

Abstract A modified cellular automaton model is constructed for dynamic recrystallisation of GCr15 bearing steel. The effects of the solutes on dislocation density evolution and grain growth are taken into account for accurate predictions of the microstructural evolution during dynamic recrystallisation. The model can predict the recrystallisation kinetics and macrostress–strain of metallic materials. It is found that dynamic recrystallisation inclined to occur under a high temperature and low strain rate conditions. The effects of hot working temperature and strain rate on microstructure were studied, and the simulated results compared with the experimental results for GCr15 bearing steel.

Modeling of the Influence of Initial Grain Sizes on Dynamic Recrystallization Using a Cellular Automaton Model

A two-dimensional modified cellular automaton (CA) model was developed to simulate the dynamic recrystallization (DRX) behaviour during thermo-mechanical processing. It provides a link for multiscale modeling to bridge the mesoscopic dislocation activities with the macroscopic mechanical properties. This model is applied to investigate the effect of initial grain sizes on DRX process in commercial pure copper. The simulated results indicate that the stable size of recrystallized grain is independent on initial grain sizes. However, the percentage of DRX is not only related to the thermo-mechanical parameters, but also influenced by the initial microstructure. It is concluded that larger initial grain sizes promote a delay in the DRX occur on commercial pure copper. The calculated results compare well with the limited number of experimental observations and theoretical conclusions.

3D Rigid-Viscoplastic FEM Simulation of Forging Process of a Gas Turbine Rotor Blade

Analysis of the forging of gas turbine rotor blades is a complex operation because of the complicated three-dimensional geometry and the non-steady state contact between the workpiece and the die surface. As a result, the simulation of blade forging performed so far has been restricted to two-dimensional plane-strain problems or simplified three-dimensional deformational cases throughout which some simplifications and assumptions are employed. In this paper a three-dimensional analysis of the non-isothermal multi-stage forging process of a gas turbine rotor blade from a cylindrical billet to a complicated product is presented, using 3D rigid-viscoplastic FEM. The simulation results of the blade forging processes are summarized in terms of deformed configurations, the material flow net pattern of typical cross-sections, the distribution of different field variables such as strain and stress, and the load-stroke relationships for each operational stage, in this way the forming laws during forging process of a gas turbine rotor blade being revealed. The validity of simulation results has been verified through comparisons with forging tests, which show good agreements with numerical simulation results. The simulation results may be effectively applied to other types of three-dimensional turbine blade forging processes.

Modeling and Simulation of Dynamic Recrystallization of GCr15 Steel Using Cellular Automaton Method

A modified two-dimensional (2-D) cellular automaton (CA) model was constructed to simulate dynamic recrystallization (DRX) process of GCr15 steel. Particle stimulated nucleation (PSN) was incorporated into the CA model to determine the influence of dispersed particles on the nucleation of DRX. In addition, the model included the effects of particles on increasing the dislocation density and pinning the grain boundaries for accurate determination of micro-structural evolution during DRX. The model was applied to simulate the DRX process of GCr15 bearing steel. DRX grain size and volume fraction were simulated using the CA model. The simulated results indicated that the simulated stable grain size of particle-containing model is closer to measured value than particle-free model. It was observed that DRX kinetics depends on both thermo-mechanical parameters and initial grain sizes. The calculated results were compared with the experimental findings in GCr15 bearing steel, the predictions show very good agreement with the experimental results.

Effects of Mandrel Structure on Ring Rolling Process for Large-Scale T-Sectioned Ring with Numerical Simulation

The process parameters including the mandrel structure of radial-axial ring rolling is in close relationship with the forming defects such as over-high axial spread and the folding defect in the connecting part of the big and small ring. In this paper, a 3D rigid-plastic and coupled thermal-mechanical finite-element model (FEM) of radial-axial ring rolling for large-scale T-sectioned ring was developed using commercial software of DEFORM-3D. By changing the chamfer radius of mandrels work roll, the effects of mandrel structure on the height of axial spread which considerably affects the stability of the ring rolling process were investigated. The folding defect was also simulated. The numerical simulation results showed that with the decrement of the chamfer radius r, the metal increasingly accumulated in the big ring and the axial spread height increased. Consequently, the ring rolling process became unstable. Also, the folding angle augmented.

Simulation and Optimization of Die Forging Process for High Pressure Valve Bonnet

In this paper, the multi-stage die forging process of a high pressure valve bonnet was simulated by 3D coupled thermal-mechanical rigid-viscoplastic finite element (FE) method. The deformation and the metal flow field of billet were obtained. Based on the simulation, two optimized schemes were put forward for improving the yield. Both of them can save material and ensure the stability of billet during the forging process. The study can provide scientific theory foundation for practical engineering applications.

FE Simulation of Die Forging Process for High Pressure Valve Body

In this paper, based on the finite element (FE) software Deform 3D, the simulation of the die forging process of a high pressure valve body was conducted. The deformation field and the metal flow field of billet were obtained and analyzed in detail. In addition, the effect of upsetting depth on the die forging process of high pressure valve body was also discussed. This study can provide a good guide for the following researches and practical industry.

Finite Element Simulation of Vacuum Hot Bulge Forming of Titanium Alloy Cylindrical Workpiece

Vacuum hot bulge forming (VHBF) is becoming an increasingly important manufacturing process for titanium alloy cylindrical workpiece in the aerospace industries. Finite element simulation is an essential tool for the specification of process parameters. In this paper, a two-dimensional nonlinear thermo-mechanical couple FE model was established. Numerical simulation of vacuum hot bulge forming of titanium alloy cylindrical workpiece was carried out using FE analysis software MSC.Marc. The effects of process parameter on vacuum hot bulge forming of BT20 titanium alloy cylindrical workpiece was analyzed by numerical simulation. The proposed an optimized vacuum hot bulge forming process parameters and die size. And the corresponding experiments were carried out. The simulated results agreed well with the experimental results.

Finite Element Simulation of Microstructural Evolution during Inertia Friction Welding Process of Superalloy GH4169

During the inertia friction welding (IFW) process of superalloy GH4169, the main mechanism for microstructural evolution is dynamic recrystallization (DRX). In order to investigate the microstructural evolution during the process, a finite element (FE) model coupled with the DRX model of the alloy was developed on the platform of MSC.Marc. Equivalent strain was introduced into the DRX model to improve the computational precision. As a result, the IFW process with microstructural evolution was simulated. Simulated results reveal that DRX region is very small. Fully recrystallized region and fine grains appear near the weld line. Dynamically recrystallized fraction (DRXF) decreases and grain size increases with the increase of the distance from the weld line. Predicted results of microstructural distribution agree well with experimental ones.