Three Dimension Rigid-plastic Finite Element Simulation for Two-Roll Cross-wedge Rolling Process

Cross-wedge rolling (CWR) is a metal process of ro ta ry forming. To produce a part, one cylindrical billet should be placed between t wo counterrotating and wedge-shape dies, which move tangentially relative each other. The billet suffers plastic deformation (essentially, localized compressio n) during its rotation between the rotating dies. Compared to other numerical si mulation methods, the finite element method (FEM) has advantages in solving gene ral problems with complex shapes of the formed parts. In cross-wedge rolling, t here are four stages in the workpiece deformation process, namely knifing, guidi ng, stretching and sizing stage. It is time-consuming and expensive to design t he CWR process by trial and error method. The application of numerical simul ation for the CWR process will help engineers to efficiently improve the process development. Tselikov, Hayama, Jain and Kobayashi, and Higashimo applied the sl ip-line theory in study of CWR process analysis. Zb.pater studied CWR process i ncluding upsetting by upper-bound method. The above numerical simulation were b ased on the two-dimensional plain-strain assumption ignored the metal flow in workpiece axial direction. Therefore, the complex three-dimensional stress and deformation involved in CWR processes were not presented. Compared to other nume rical simulation methods, the finite element method (FEM) has advantages in solv ing general problems with complex shapes of the formed parts. As yet, a few 3-D finite element simulation studies on CWR process have been reported in literatu res. In this paper, the process of cross wedge rolling (CWR) has been simulated and analyzed by 3D rigid-plastic finite element method. Considering the charact eristic of CWR, the static implicit FEM program is selected. The models proposed in this study uses the commercial code DEFORM 3D to simulate the CWR process. T his is an implicit Lagrangian finite element code, which includes many new enhan cements functions. A new method of utilizing multiple processors using the MPI s tandard has been implemented. Automatic switching between the two different defo rmation solvers (Sparse Solver and Conjugate Gradient Solver) has also been impl emented in order to increase the speed of simulations. In this paper, all stages in CWR process are simulated to be able to closely understand and analyze the a ctual CWR process. For simulating all forming stages in CWR process, the dynam ic adaptive remeshing technology for tetrahedral solid elements was applied. T he stress distributions in cross section of forming workpiece are analyzed to in terpret fracture or rarefaction in the center of workpiece. Authors also analyze d the time-torque curve and the laws of load changing.

Mechanism of necking defect of 6082 aluminium alloy rolled by cross-wedge rolling method based on material thermal properties

Necking defects have long troubled the application of cross-wedge rolling technology in aluminium alloy shaft parts.To accurately predict necking defects,new judgement conditions are established based on the thermal performance of 6082 aluminium alloy.The limit-sectional shrinkage without necking defects is achieved by combining theoretical calculation and finite-element model analysis,which couples heat transfer and deformation.In this paper,a 6082 aluminium alloy extruded rod with a 40 mm diameter rolled at a preheated temperature of 500℃and a rolling angular velocity of 1 rad/s is taken as an example.The simulation and experimental results show that necking defects do not occur on the rolled pieces if the sectional shrinkage is below the limit-sectional shrinkage but will occur when the sectional shrinkage is above it.The results prove that the prediction model of necking defects in cross-wedge rolling of 6082 aluminum alloy is feasible,and this research provides a theoretical basis for the qualified aluminum alloy shafts produced by the cross-wedge rolling.

Effect of cross wedge rolling on the microstructure of GH4169 alloy

The metal microstructure during the hot forming process has a significant effect on the mechanical properties of final products. To study the microstructural evolution of the cross wedge rolling （CWR） process, the microstructural model of GH4169 alloy was programmed into the user subroutine of DEFORM-3D by FORTRAN. Then, a coupled thermo-mechanical and microstructural simulation was performed under different conditions of CWR, such as area reduction, rolling temperature, and roll speed. Comparing experimental data with simulation results, the difference in average grain size is from 11.2% to 33.4% so it is verified that the mierostructural model of GH4169 alloy is reliable and accurate. The fine grain of about 12-15 p.m could be obtained by the CWR process, and the grain distribution is very homogeneous. For the symmetry plane, increasing the area reduction is helpful to refine the grain and the value should be around 61%. Moreover, when the roiling temperature changes from 1000 to 1100℃ and the roll speed from 6 to 10 r.min-1, the grain size of the rolled piece decreases first and then increases. The temperature may be better to choose the value around 1050℃ and the speed less than 10 r-min-1.

Evolution of microstructure of aluminum alloy hollow shaft in cross wedge rolling without mandrel

During the process of cross wedge rolling of aluminum alloy hollow shaft, the evolution of its microstructure has an important influence on the mechanical properties of the rolled piece. In order to obtain the microstructure evolution law of aluminum alloy hollow shaft in cross wedge rolling without mandrel, a finite element model is constructed through the finite element software Deform-3D. The influences of rolling temperature, sectional shrinkage,spreading angle and forming angle on the average grain size of rolled piece are studied by numerical simulation of microstructure evolution. The cellular automata method reveals the inherent relationship between the process parameters and the evolution of the microstructure, and provides a reference for optimizing the rolling process parameters of aluminum alloy hollow shafts and improving the forming quality. The results show that the average grain size of the rolled piece increases with the increase of the rolling temperature, decreases with the increase of the sectional shrinkage,and decreases first and then increases with the increase of the spreading angle, and changes little with the increase of the forming angle.

Influence of process parameters on the microstructural evolution of a rear axle tube during cross wedge rolling

In the shaping process of cross wedge rolling（CWR）, metal undergoes a complex microstructural evolution, which affects the quality and mechanical properties of the product. Through secondary development of the DEFORM-3D software, we developed a rigid plastic finite element model for a CWR-processed rear axle tube, coupled with thermomechanical and microstructural aspects of workpieces. Using the developed model, we investigated the microstructural evolution of the CWR process. Also, the influence of numerous parameters, including the initial temperature of workpieces, the roll speed, the forming angle, and the spreading angle, on the grain size and the grain-size uniformity of the rolled workpieces was analyzed. The numerical simulation was verified through rolling and metallographic experiments. Good agreement was obtained between the calculated and experimental results, which demonstrated the reliability of the model constructed in this work.

Analysis of Metal Forming in Two-Roll Cross Wedge Rolling Process Using Finite Element Method

A simulation model for two-roll cross wedge rolling （CWR） was presented by using three-dimensional rigid-plastic finite element method （FEM）. The whole forming process of CWR, including knifing zone, guiding zone, stretching zone, and sizing zone, was simulated using the model in which dynamic adaptive remeshing technology for tetrahedral solid elements was used to fix element distortion. Based on the simulation results, the distributions of metal flow field, strain field, and damage field, and the geometry of the workpiece＇s end were analyzed. These results could provide theoretical guidance for realizing net shaping and reasonable design of tools.

Novel evaluation method for metal workability during cross wedge rolling process

This study presents a novel method using a disk-like sample to assess the workability of metal during the cross wedge rolling(CWR)process.Using this method,we can quantitatively evaluate the moment destruction which occurs at the center of the sample during CWR.In this study,45 steel was selected to demonstrate the proposed method.Firstly,we designed a model for the tools and sample,conducted finite element simulations to analyze the distribution regulations of metal flow,stress,and strain,and evaluated the relationship between the damage and moving distance of the tool during the forming process.Then,we obtained the optimal deformation temperature range,rolling speed,and geometry parameters for the tool.Finally,experiments were conducted from 20℃ to 1200℃ to verify the accuracy of the developed model.It was demonstrated that the model was significantly accurate in accessing the workability of 45 steel in the CWR process.The proposed method could be generalized to investigate the CWR process for other materials,such as aluminum alloys,superalloys,titanium alloys,etc.

Effect of tempering on bonding characteristics of cross wedge rolling 42CrMo/Q235 laminated shafts

To further improve the comprehensive properties of 42CrMo/Q235 laminated shafts produced by cross wedge rolling.theheat treatment of the shafts was studied.Tensile and bending tests were carried out to compare the changes in mechanicalproperties before and after heat treatment.The results showed that the interfacial bonding strength increased most aftertempering at 350℃for 45 min.The microstructure of the interface was observed using a digital microscope.The resultsshowed that the dispersed oxides on the interface were basically eliminated by using the scheme of tempering at 350 cand holding for 45 min.The reasons for the change in mechanical properties were explained from the point of theinterfacial microstructure.Scanning electron microscopy was used to analyze the micro-morphology of the tensile fracture.lt was observed that after tempering at 350℃and holding for 45 min,the dimple holes became larger and deeper,and thestructure of fracture became more uniform and stable.From the point of the tensile fracture morphology.the reasons for thechange in mcchanical propcrties wcrc explained as well.

Multi-Wedge Cross Rolling of Balls

The multi-wedge cross rolling process of forming balls is described. The process tool for rolling 8 balls with a diameter of 35 mm is presented. The course of the rolling process, distributions of forming forces as well as maps of effective strain and temperature in the obtained balls are presented by finite element modeling （FEM）. Ex- perimental tests of simultaneous forming of 4 balls with a diameter of 22 mm conducted in laboratory conditions at Lublin University of Technology have proved that the balls obtained in multi-wedge cross rolling are of good quality and can therefore be used in both ball mills and rolling bearings.

Research and industrialization of near-net rolling technology used in shaft parts

Shaft part rolling is an efficient and green near- net shaping technology offering many advantages, includ- ing high production efficiency, high material utilization rate, high product quality, and excellent production environment. In this paper, the features of shaft part rolling are introduced along with the working principles of two main shaft part rolling technologies, namely, cross wedge rolling （CWR） and skew rolling （SR）. In relation to this technology, some R＆D achievements gained by the University of Science and Technology Beijing are summarized. Finally, the latest developments in shaft part rolling are presented, including SR steel bails, precise forming of camshaft blank by CWR, SR phosphorous copper balls at room temperature, and CWR hollow axle sleeve. Although the shaft part rolling technology has been widely used in China, it only accounts for about 15% of applicable parts at present. Nevertheless, this technology has broad application prospects.

Microstructural Evolution of NiTi47.7Cu6.3 Alloy during Hot Deformation

In the present work, the hot workability and microstructural evolution of NiTi47.TCu6.3 （at.%） shape memory alloy were investigated by using wedge-rolling test. The wedge specimens were subjected to hot rolling at the temperatures of 700-1000℃. The microstructural evolutions at the strains of 0.05, 0.15, 0.2, 0.25 and 0.3 were then characterized by optical microscopy and scanning electron microscopy （SEM） as well as energy dispersive spectrometry （EDS） technique. Depending on the deformation temperature and strain, the dynamic recrystallization （DRX） could occur, leading to the refining of the microstructure. At low temperatures of 700 and 800℃ there was no sign of DRX at all studied strains. At these temperatures, the formed fine needle-like precipitates pinned the grain boundaries and prevented them from bulging/migration. By contrast, at higher temperatures of 900 and 1000℃, the DRX took place at the critical strains lower than 0.25 and 0.15, respectively. However, at higher temperatures, strain-induced-boundary-migration （SIBM） mechanism resulted in the formation of DRX grains.