Rigid-viscoplastic Finite Element Method Research Articles

Numerical simulation of extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube based on finite element method and cellular automaton

FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube is firstly put forward and it can be fabricated by means of isothermal extrusion. Based on Arrhenius constitutive model of FeMnSiCrNi and NiTiNb shape memory alloys, isothermal extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube is simulated by rigid viscoplastic finite element method. It can be found that the deformation zone of the dissimilar shape memory alloy composite tube is always in a three-dimensional compressive stress state during extrusion, and the deformation of the inner tube is obviously higher than that of the outer tube. It is necessary to guarantee the interface compatibility between the inner tube and the outer tube during isothermal extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube. The relationship between macroscopic process variables and microscopic variables during plastic deformation of FeMnSiCrNi shape memory alloy tube at high temperature is established by coupling finite element simulation and cellular automaton simulation. The microstructural evolution of FeMnSiCrNi shape memory alloy in different deformation zones during isothermal extrusion of dissimilar shape memory alloy composite tube is simulated. It can be concluded that the grain size of dynamic recrystallization is reduced with the increase of plastic strain in the deformation zone.

Numerical simulations of twin-roll casting for Mg-AZ31 and AA3003 sheets

Sheets of light-weight alloys, such as aluminum alloys and magnesium alloys, are expected to be used more for interior or exterior panels of passenger cars. Among various manufacturing technologies for the sheets, twin-roll casting has been known to be efficient and economical since it can produce sheets from melt directly. However, the phenomenon occurring in the process is so complicated that various numerical techniques have been explored to analyze it. In the present investigation, the rigid-viscoplastic finite-element method was applied to the analysis of a vertical type of twin-roll casting for production of AA3003 and Mg-AZ31 sheets. As a result, details of melt flow, temperature distribution, solidification, plastic deformation, roll torque and roll-separating force were obtained from the analysis.

An evolution model for elliptic-cylindrical void in viscous materials considering the evolvements of void shape and orientation

The evolution behavior of the internal voids influences the mechanical property of the materials significantly. Considering the void deformation and rotation, the evolution behavior of the elliptic-cylindrical void in power-law viscous materials was investigated by using the representative volume element (RVE) model. The rigid visco-plastic finite element (FE) method was applied to calculate the velocity field in the RVE under different loading conditions, and the instantaneous changing rate of the void radius and orientation were determined by evaluating the evolving of the void profiles at the instant. The calculated results show the deviatoric stress takes an important role in the void radius evolution, and the shear stress influences the change of the void orientation significantly. Based on the investigation, a void evolution model was established to relate the changing rates of the void radius and orientation to the void aspect ratio and the macroscopic stress/strain conditions. This model was incorporated into the FE code to predict the evolvements of void radius and orientation in each step of the deformation history. The predictions agree well with the results of the numerical simulations containing embedded void geometries in the mesh, which demonstrates that this model is capable to evaluate the void evolution behavior under large deformation. As an application, this model was used to predict the closure behavior of the void defects in the large ingot during the hot forging process.

Finite Element Analysis of Cross Rolling on AISI 304 Stainless Steel: Prediction of Stress and Strain Fields

Studies on the effect of strain path during rolling has been carried out for a long time, but the same has not been done using Finite Element Analysis (FEA). Change in strain path affects the state variables in the rolled plate like stress, strain, temperature etc. In the current work, Finite Element Analysis for cross rolling of AISI 304 austenitic stainless steel has been carried out by rotating the plate by 90° in between the passes. To analyze stress and strain fields in the material for cross rolling, a full 3D model of work-roll and plate has been developed using rigid-viscoplastic finite element method. The stress and strain fields, considering von-Mises yield criteria, are calculated by using updated Lagrangian method. In addition to these, the model also calculates the normal pressure and strain rate distribution in the plate during cross rolling. The nature of the variations of stress and strain fields in the plate, predicted by the model, is in good agreement with the previously published works for unidirectional rolling.

Finite element simulation of plate or sheet metal forming processes using tetrahedral MINI-elements

In this paper, finite element prediction of sheet metal forming process is investigated using solid elements. A three-dimensional rigidviscoplastic finite element method with linear tetrahedral MINI-elements is employed. This technique has traditionally been used for bulk metal forming simulations. The solid element approach with remeshing capability is applied to simulating a plate metal forming process to reveal its possible problems. The similar approach is also applied to a typical sheet forming process. Both single- and double-layer finite element mesh systems are studied, with particular attention to their effect on the deformed shape of the workpiece and thickness variation of a cold sheet forming process. The procedure is applied to the well-known problem of the NUMISHEET93 international benchmark. The resulting predictions are compared with experimental observations found in the literature, and good agreement is noted.

Equal channel angular extrusion of NiTi shape memory alloy tube

As a new attempt, equal channel angular extrusion (ECAE) of nickel–titanium shape memory alloy (NiTi SMA) tube was investigated by means of process experiment, finite element method (FEM) and microscopy. NiTi SMA tube with the steel core in it was inserted into the steel can during ECAE of NiTi SMA tube. Based on rigid-viscoplastic FEM, multiple coupled boundary conditions and multiple constitutive models were used for finite element simulation of ECAE of NiTi SMA tube, where the effective stress field, the effective strain field and the velocity field were obtained. Finite element simulation results are in good accordance with the experimental ones. Finite element simulation results reveal that the velocity field shows the minimum value in the corner of NiTi SMA tube, where severe shear deformation occurs. Microstructural observation results reveal that severe plastic deformation leads to a certain grain orientation as well as occurrence of substructures in the grain interior and dynamic recovery occurs during ECAE of NiTi SMA tube. ECAE of NiTi SMA tube provides a new approach to manufacturing ultrafine-grained NiTi SMA tube.

Finite element simulation of ball spinning of NiTi shape memory alloy tube based on variable temperature field

As a new attempt, ball spinning was used to manufacture the nickel-titanium shape memory alloy (NiTi SMA) tube at elevated temperature. The NiTi bar with a nominal composition of Ni50.9Ti49.1 (mole fraction, %) was solution treated and was used as the original tube blank for ball spinning. Based on the variable temperature field and the constitutive equation, rigid-viscoplastic finite element method (FEM) was applied in order to simulate the ball spinning of NiTi SMA tube. The temperature field, the stress field, the strain field and the load prediction were obtained by means of FEM. FEM results reveal that there is a temperature increase of about 160 °C in the principal deformation zone of the spun part. It can be found from the stress fields and the strain fields that the outer wall of NiTi SMA tube is easier to meet the plastic yield criterion than the inner wall, and the plastic deformation zone is caused to be in a three-dimensional compressive stress state. The radial strain and the tangential strain are characterized by the compressive strain, while the axial strain belongs to the tensile strain. The variation of spinning loads with the progression of the ball is of great importance in predicting the stable flow of the spun part.

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.

The Numerical Simulation of Multi-Directional Forging 6700 Steering Knuckle

The numerical simulation of multi-directional precise contour forging of 6700 steering knuckle was studied in this paper. A 3D thermodynamic coupling finite element method (FEM) was established for each process of the deformation, based on the rigid-viscoplastic finite element method FEM. The results showed that the shape and size of the blanking billet can be optimized and the materials utilization ratio and the dimensional accuracy can be increased dramatically by using multi-directional precise contour forging

Numerical Simulation for Precision Roll-Forging of Automobile Front Axle

Roll forging process for automobile front axle has been simulated by using a rigid viscoplastic finite element method, force-time curve have been obtained and analyzed. On the basis of simulation result, typical characteristics of roll forging process have been explained. It concluded that simulation results could guide the development of roll forging and die design for automobile front axle.

Deformation mechanism of hot spinning of NiTi shape memory alloy tube based on FEM

As a successively and locally plastic deformation process, ball spinning is applied to manufacturing thin-walled Nickel-Titanium shape memory alloy (NiTi SMA) tube at high temperature. NiTi SMA tube blank belongs to the as-cast state which consists of a lot of dendritic grains and a few equiaxed grains. The compression tests of NiTi SMA were carried out at various strain rates at high temperature in order to obtain the constitutive model of NiTi SMA. Because NiTi SMA is sensitive to the strain rates at high temperature, rigid-viscoplastic finite element method (FEM) is used to simulate ball spinning of thin-walled NiTi SMA tube in order to analyze the deformation behavior of ball spinning of NiTi SMA tube. Stress fields, strain fields as well as velocity fields is obtained by means of rigid-viscoplastic FEM, which lays the profound foundations for studying the metal flow rule in ball spinning and forming perfect spun NiTi SMA tube.

Numerical Simulation and Technology Research on the Precision Forging for Inner Ring Gear

Rigid-viscoplastic finite element method was used to analysis the cold extrusion of the external boss and ring gear. Some groups of numerical models were built with different design parameters of die, geometric parameters of gear, processing conditions, and the service loads were investigated. Form the investigation; we predicted the forming defects occurring in the practice. Based on Archard model the lives of dies were predicted. The conclusion above has more guidance to the production.

Numerical Simulation on Thixo-Forging of Magnesium Matrix Composite

The thixo-forging of magnesium matrix composite was analyzed with computer numerical simulation based on rigid viscoplastic finite element method. The constitutive model of SiCp/AZ61 composite was established in our prior literature. Behavior of metal flow and temperature field were obtained. The differences between traditional forging and thixo-forging processes were analyzed. Results indicated that thixo-forging was better in filling cavity than forging. Simulation results were good agreement with experimental ones.

Three-dimensional finite element analysis of multi-stage hot forming of railway wheels

Three-dimensional finite element analyses has been carried out using DEFORM 3D software on multi-stage hot forming of railway wheels involving the processes of upsetting, forging, and punching of wheels. Thermal analysis related to heating the blank in furnace and all intermediate heat transfer stages between deforming operations have been conducted. Rigid viscoplastic finite element method has been utilized for coupled thermo-mechanical analysis of the processes. Modeling of punching the wheel bore has been carried out using Cockcroft and Latham fracture criterion. Evolution of thermo-mechanical parameters at selected points within the workpiece has been studied in detail. The method of simulating the effects of various process parameters has been explained using relevant mathematical relations. This study shows that design, optimization, and analysis of process perturbations for multi-stage railway wheel manufacturing process can be done efficiently in three-dimensional finite element simulations instead of conventional time and cost intensive trials. It might be necessary to use the results of finite element analysis in shop-floor to enhance productivity and reduce wheel rejection.

Development of severe plastic deformation by various asymmetric rolling processes

Rolling is the most appropriate process to produce a severe plastic deformation in the sheet or plate type of materials. Compared to symmetric rolling, asymmetric rolling is more efficient in producing plastic deformation since it develops additional shear strain for a given reduction in thickness. In the present investigation, various asymmetric rolling processes were analyzed by the rigid-viscoplastic finite element method. The results of the analyses were compared to each other in terms of plastic deformation: effects of asymmetries due to the differences in size, rotational speed and frictional condition between upper and lower rolls. Rolling pressure distribution, rolling force and rolling torque were also compared.

Coupling Thermomechanical and Microstructural FE Analysis in Plate Rolling Process

Using three-dimensional rigid-viscoplastic finite element method (FEM), a coupling multivariable numerical simulation model for steel plate rolling has been established based on the physical metallurgy microstructural evolution rule and experiential equations. The effects of reduction, deformation temperature, and rolling speed on the deformation parameters and microstructure in plate rolling were investigated using the model. After a typical rolling process of steel plate 16Mn is simulated, the strain, temperature, and microstructure distributions are presented, as well as the ferrite grain transformation during the period of cooling. By comparing the calculated ferrite grain sizes with measured ones, the model is validated.

Predicting polygonal-shaped defects during hot ring rolling using a rigid-viscoplastic finite element method

We applied a rigid-viscoplastic finite element method to investigate polygonal-shaped defects that occur during ring rolling and developed an improved analysis model with relatively fine finite elements near the roll gap to reduce the computational time, along with a scheme to minimize the volume change. We also simulated the formation of a polygonal-shaped defect during hot ring rolling of a ball bearing outer race. The results were in good qualitative agreement with actual experimental phenomena.

계층적 접촉 탐색방법을 이용한 3-D 초소성 성형/확산접합의 공정설계(I)

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a 3-D rigid visco-plastic finite element method. A constant-triangular element based on membrane approximation and an incremental theory of plasticity are employed for the formulation. The coulomb friction law is used for interface friction between tool and material. Pressure-time relationship for a given optimal strain rate is calculated by stress and pressure values at the previous iteration step. In order to improve the contact searching, hierarchical search algorithm has been applied and implemented into the code. Various geometries including sandwich panel and 3 sheet shape for 3-D SPF/DB model are analyzed using the developed program. The validity fer the analysis is verified by comparison between analysis and results in the literature.

Finite Element Simulation of Hot Strip Continuous Rolling Process Coupling Microstructural Evolution

Using the nonlinear rigid-viscoplastic finite element method (FEM), a finite element simulation of the hot strip continuous rolling process was done, which completely integrates different phenomena such as the metallurgical behavior of the strip and the thermo-mechanics in the strip based on the physical metallurgical microstructural evolution law. By combining with the process parameters of certain 2 050 mm hot strip rolling, an actual rolling process of low carbon steel SS400 was simulated using the FEM model. Based on the simulation results, the distributions of the strain field, the temperature field, and the microstructure were presented. Meanwhile, the simulated rolling force, temperature, and microstructure are in good agreement with the measured results.

Research on deformation and microstructure evolution during forging of large-scale parts

Based on the rigid-viscoplastic finite element method (FEM), an investigation on large-scale forging parts deformation was carried out with the mode of twist-compression deformation adopted in this study. The processing model coupled thermal, mechanical and microstructural phenomena, in which some empirical equations for recrystallization evolutions were obtained using the Gleeble-3500 thermomechanical simulator. Through FEM simulation, the distributions of different field-variables, such as force, strain and grain size and so on, were obtained. After different forging parameters were employed, one can know that twist-compression deformation style can decrease the deforming pressure effectively and make deformation more homogeneous through analyzing these results. And it is worth mentioning that compared with upsetting this changed forming style makes grain sizes in the metal inner decrease and their distributions more uniform. Thus, the comprehensive properties of large-scale forging parts will be improved.