Three-dimensional Rigid-plastic Finite Element Method Research Articles

Numerical Simulation of Material Plastic Deformation Using the Drawing Forming Process of Contoured Internal Surface Tubes

Production of multi-rifled seamless steel tubes employing cold draw process using multi-rifled mandrel is quite a modern technology. The important characteristic of the tube drawing process, unlike the tube with internal rifling, is the corner filling which influences the dimension accuracy of the internal shape of the tube. In this study, the influence of drawing tool dimensions and mandrel shape on to final rifling filling was investigated. Draw process has been simulated by using the three-dimensional rigid-plastic finite element method (FEM) by using DEFORM 3D software. The results of numerical simulation show that the shape of drawing tools and process conditions have a significant influence on the forming process and final shape and properties of the workpiece.

Finite Element Analysis Using Dynamic Material Model to Design Process Variables of Radial Forging

In order to obtain a refined and uniform microstructure in the final billet, the radial forging process needs to be optimized and controlled with various process parameters such as temperature of ingot and die, die size, ram speed, upset ratio, etc. Grain size control is one of the most effective ways for the control of mechanical properties. The change in grain size is significantly related with strain, strain rate and temperature of forged part. To understand material properties and to analyze stability and instability area of forged workpiece, hot compression test of Ti-6Al-4V was carried out within the strain-rate range 10-2 to 10 s-1, and the temperature range 800 to 1100oC. And dynamic material map of Ti-6Al-4V was tabulated. In this study, a three-dimensional rigid-plastic finite element method(FEM) was used to analyze the radial forging process, focusing on the effects of feed rate and rotation angle for appropriate forging pass schedule. And the simulation result was confirmed with dynamic material model of Ti-6Al-4V. The optimal combination of feed rate and rotation angle has been determined by quantifying the radius profile in the longitudinal direction, roundness of the product and uniform strain distribution.

A Three-Dimensional Finite Element Method for Nonsteady State Temperature Distribution in the Rolling Process

The temperature is a key factor that affects the metal deformation and the material property in the rolling process. The metal deformation is often carried along with the variety of temperature. Moreover, the plastic work is converted into the thermal energy during the process of the metal deformation. Therefore, the numerical simulation of the rolling process should take the temperature factors into consideration to improve the prediction accuracy. In this paper, we use the full three-dimensional Rigid-plastic finite element method to predict the temperature distribution which relate to linear or non-linear boundary condition of the free surface. Based on the simulation, the impact of radiant heat-transfer coefficient on the temperature prediction can be obtained. The comparison of the calculated results between the linear and non-linear boundary conditions demonstrates that the temperature obtained on the linear boundary condition has higher accurateness than that obtained on the non-linear boundary condition.

Influence of cooling condition of tools on central deformation of workpiece and tool wear in cross wedge rolling

In this paper, a thermal–mechanical coupled simulation model for two-roll cross wedge rolling (CWR) was developed to investigate the influence of cooling condition of tools on central deformation of workpiece and tool wear by using three-dimensional rigid-plastic finite element method. Based on the simulation results, the information about central deformation of workpiece and tool wear with and without tool cooling was compared and analyzed. The study results indicate that forging quality and tool life can be improved by means of cooling the tools with cooling water. Subsequently, an industrial example of CWR in blank forming for engine connecting rod was presented to verify the feasibility of study results. In this industrial application, higher forging quality and longer tool life were obtained, which benefits the decrease of production cost. This study provides insights into the mechanisms of central deformation of workpiece and tool wear under different cooling conditions of tools in CWR process as well.

THE FORGING PROCESS OF AIRCRAFT ENGINES TURBINE BLADES

The aim of this paper was to obtain information about optimum conditions of the forging process of a blade made from high-temperature creep resisting alloy called Inconel 718. A three-dimensional rigid-plastic finite element method (FEM) of forging process of high-pressure compressor rotor's blade analysis has been performed. Various forging process variants were analysed, including isothermal conditions.

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.

FEM Analysis of Void Closure Behaviour during Open Die Forging of Rectangular Billets

Finite element analysis of open die forging to make rectangular billets has been performed in this study. Three-dimensional rigid-plastic finite element method (FEM) was used to analyse the effects of process variables, forging pass design and die configurations on the void closure phenomena. The major objective was to control the internal deformation for better structural homogeneity and centreline consolidation of the rectangular billet. The effect of die width ratio, die feed rate, die shape, and number of passes on the void closure ratio has been examined. Although it is difficult to optimize process parameters in industrial environments, favourable process conditions are recommended to achieve better product quality.

ヘリカルロール加工された管材のひずみ分布と微小亀裂におよぼす成形条件の影響

Steady-state analyses of helical rolling of tubes were carried out by the three-dimensional rigid-plastic finite element method. The analysis results were validated by comparison with hot rolling experiments on steel tubes. Using the calculated velocity field and distribution of equivalent strain rate, equivalent strain and Cockcroft's damage factor were integrated along the streamline. The maximum equivalent strain occurred on the outer surface of the rolled tube and the minimum one occurred at the center of its thickness. The maximum damage factor occurred on the inner surface of the tube. The experimental result for Ni-base alloy tubes showed small cracks on the inner surface. This large damage factor was mainly accumulated just in front of the region of contact with the mandrel, because the wall of the tube bulged out in the radial direction between rolls. The analysis results showed that the increase in drawing velocity and t1/D1 (t1 and D1 denote the thickness and diameter of the rolled tube, respectively) makes the maximum damage factor decrease. There were no cracks on the inner surface of the Ni-base alloy tube that was rolled under the proposed forming condition.

Optimization of open die forging of round shapes using FEM analysis

A three-dimensional rigid-plastic finite element method (FEM) analysis has been performed to optimize an open die forging process in the production of circular shapes (i.e. round bars, spindles, rotors, etc.). In producing circular shapes by open die forging, it is difficult to achieve the optimal set of process parameters by trial and error within an industrial environment. In this study, the finite element method was used to analyze the practice of open die forging, focusing on the effects of feed rate and rotation angle for optimal forging pass design. The optimal combination of feed rate and rotation angle has been determined by quantifying the radius profile in the longitudinal direction and roundness of the product. From an analysis of the results, optimal process conditions are proposed for the production of circular shapes with good dimensional accuracy by open die forging.

Simulation of Mannesmann piercing process by the three-dimensional rigid-plastic finite-element method

Simulation of the Mannesmann piercing process is performed for the first time by the three-dimensional rigid-plastic finite-element method. Firstly, a method of analysis is proposed for the steady-state formulation in the case that the sides of the finite elements cannot be made to coincide with the streamline of the material flow. Secondly, the simulation of the Mannesmann piercing process is performed under the variation of rolling conditions such as the feed angle, the minimum roll gap, the maximum plug diameter, the plug advance and the guide shoe diameter, and the effects of the rolling conditions on various rolling properties such as the outer diameter, the inner diameter, the roll force, the mandrel force, the equivalent strain distribution and the equivalent strain rate distribution are demonstrated. Finally, the results of the analysis are compared with the results of an experiment using Plasticine. The dimension in the rolling condition of the experiment is scaled to one-third of the dimension in the rolling condition in an actual Mannesmann piercing process. The analytical results agree with the experimental results and the validity of the method of analysis is confirmed.

Simulation of deformation and temperature in press roll piercing

A method of analyzing deformation and temperature in press roll piercing has been proposed. The method can be utilized for the pass design in the press roll piercing process. The method of analyzing deformation is ordinary three-dimensional rigid-plastic finite-element method (FEM), while for the analysis of temperature, three-dimensional FEM is primarily used; one-dimensional FDM is also used since three-dimensional FEM requires a large amount of computation time and memory capacity. Analysis was performed by varying the following rolling parameters: the pusher velocity, the plug position, the plug diameter, the plug top radius and the frictional factor between the material and the plug. Furthermore, the analysis of a perfectly rigid-plastic material was also performed. The effects of these rolling conditions on the roll force, the mandrel force, the material shape, the equivalent strain distribution and the temperature distribution are demonstrated. The roll force, the mandrel force and the material shape calculated from the analysis agree with those obtained by experiments.

Optimisation of spiral forging process design for ensuring uniform quality of forged round billet by three-dimensional rigid–plastic finite element analysis

Focusing on the spiral forging stage of the hot open die forging process, which is the final stage of finishing round billets from ingots, the influence of operational conditions on the distribution of equivalent plastic strain has been numerically analysed using a three-dimensional rigid–plastic finite element method. The mechanism via which equivalent plastic strain is accumulated at the surface of the workpiece during spiral forging is clarified. The independent influence of each major operational parameter, i.e. rotational angle and feed, is revealed, and the optimum combination of these two parameters is clarified. The influence of the coefficient of friction is also discussed, and, as a result, a fundamental scheme to optimise spiral forging process design is suggested, taking account of not only uniformity of quality but also dimensional precision of the forged round billet.

3차원 강소성 유한요소법을 이용한 환상압연공정중 형상결함의 예측

3차원 강소성 유한요소법을 이용한 환상압연공정중 형상결함의 예측

Optimization of open-die forging process design to ensure homogeneous grain size refinement of cast structures by three-dimensional rigid-plastic finite element analysis

Focusing on the rough-forging stage of the hot open-die forging process, the influence of pass schedule on the equivalent plastic strain distribution at the surface of a forged billet has been numerically analysed using a three-dimensional rigid-plastic finite element method. By analysing the circumferential distribution of the strain obtained by one forging pass, it has been clarified that the distribution is strongly influenced by the cross-sectional shape of a workpiece. By utilizing the analytical results, a new method has been developed to predict the cross-sectional shape and the strain distribution without numerically analysing all passes. As a result, a new pass schedule has been proposed to ensure homogeneous grain size refinement of cast structures and the effect of the pass schedule was verified by a real hot open-die forging experiment.

Theoretical and experimental analysis of the rolling process of bimetallic rods Cu-steel and Cu-Al

In this study, the authors present the results of their theoretical and experimental analysis of the rolling process of bimetallic rods in stretching passes. The bimetallic rods had different ratios of the yield stress between components. The original rods were round (21.7mm diameter) steel and aluminium rods, covered with 2.8mm copper layer. A numerical model for hot stretching passes rolling was proposed. In the model, the deformation of a bimetallic material was analysed by three-dimensional rigid–plastic finite-element method. The model simulated metal flow during rolling of bimetallic rods in round–oval series. The results of the experiments were compared with the finite-element calculations of the stress distribution and spread of Cu-steel and Cu-Al rods in the deformation zone. The analysis demonstrated that an appropriate selection of shape and size of oval pass allows production of even distribution of the copper layer in the bimetallic roll products. The results of comparison of calculated spread and experimental data confirmed good ability of proposed mathematical model, that is recommended for roll pass design at rolling of bimetallic rods.

Optimisation of spiral forging process design for ensuring dimensional precision of forged round billets by three-dimensional rigid–plastic finite element analysis

Focusing on the spiral forging stage of the hot free forging process, which is the final stage to finish round billets from ingots, the optimisation of the operational conditions for ensuring dimensional precision of the final round billet has been carried out mainly by numerical analysis. In the analysis, a three-dimensional rigid-plastic finite element method was used and the validity of the analysis was examined by laboratory experiments using lead billets. The independent influence of each chosen major operational parameter, i.e. the rotational angle and the feed, has been clarified and critical and suitable ranges of the operational parameters for ensuring dimensional precision have been specified. As a result, the optimum combination of rotational angle and feed has been clarified and a fundamental scheme to optimise spiral forging process design has been suggested taking account of not only dimensional precision but also productivity. Moreover, it is suggested that the optimum rotational angle can be determined independently of the anvil geometry.

A 3-D finite element method analysis of cold rolling of thin strip with friction variation

In this paper, a three-dimensional rigid-plastic finite element method (FEM) model to simulate the cold rolling of thin strip with different friction models is described. The effects of rolling parameters, such as work roll diameters and reductions, are analysed in this study. The simulation and experimental values of rolling pressure and spread (the difference of strip width before and after rolling) show a good agreement when friction variation in the roll bite is considered. The roll separating force, spread and forward slip for constant friction and friction variation models are also compared. The friction variation in the roll bite has a significant effect on the simulation results.

652 穿孔圧延の変形及び温度解析

−. We have proposed a method of numerical simulation for hot caliber rolling, in which the deformation of the material is analyzed by the conventional three-dimensional rigid-plastic finite-element method, while the temperature distribution in the material is calculated using a new combined method of the three-dimensional finite-element method and the onedimensional finite difference method. In this paper, the method of numerical simulation for

강소성 유한요소법을 이용한 링 압연 공정에서의 폭 퍼짐량 및 접촉영역 예측

The ring rolling process involves three-dimensional non-steady material flow and continuous change of radius and thickness of the ring workpiece. In this study, the deformation analysis and geometric updating algorithm of the ring rolling process were verified by using the three-dimensional rigid-plastic finite element method. Manufacturing processes for plain ring and T-shaped ring were investigated by comparing experiments with simulation results, especially in side spread, load-stroke and pressure distribution, showing a good agreement. It was concluded that the simulation method would be a useful tool for the design of a ring rolling process.

Analysis of the non-steady state vertical–horizontal rolling process in roughing trains by the three-dimensional finite element method

The vertical–horizontal rolling process is often used to accomplish width reduction so as to provide a synchronising operation between the continuous slab casting and hot rolling processes. Numerical simulation of the non-steady state deformation behaviour around the head and tail ends during this process is made by the full three-dimensional rigid–plastic finite element method. An explanation is provided in the theory for the ‘thin element technique’ at the inlet surface of velocity discontinuity. To deal with the interpolation of friction within a surface of an element contacting partly with the roll, a new term, so-called ‘pseudo shape function’, is presented and a related new equation formula is deduced. The calculated shape of the slab edge, the separating force and the rolling torque are consistent with those measured experimental ones for the model material lead.