Rigid-plastic Finite Element Simulation Research Articles

Experimental Study and Numerical Simulation of Dynamic Recrystallization Behavior of a High-Strength Steel

In this paper, to research the dynamic recrystallization (DRX) behavior of a high-strength steel (34CrNiMo6), hot compression tests were carried on Gleeble-1500D thermo-mechanical simulator within the different temperatures and strain rates. After hot compression tests, the microstructures of specimens were observed by optical microscope. Based on Kocks and Mecking mathematics model (KM), the DRX kinetic model was established by the flow stress curves during hot deformation. Meanwhile, a grain size model was established by measuring microstructure. Furthermore, combined with the material kinetic model and grain size model, a rigid–plastic finite element simulation was built to analyze the microstructural behavior of 34CrNiMo6 steel during the uniaxial hot compression. The results indicate that the simulation results are in good agreement with the experimental data. The DRX model had an accurately predictive capability for the hot compression process, which could provide a theoretical guidance and process optimization for metal forming processes.

Thermal Deformation Behavior and Formability of High Temperature with Corrosion Resistance Alloy

The aim of present wor is, therfore, to investigated the effect of the damage value prediction equation on the formability of compression specimen and find the optimize forming condition.Although Inconel 625 alloys are excellent materials, Ni-base alloy cannot be formed at room temperature owing to limitation of formability. To improve the formability of Inconel 625, it is necessary to investigate the formability at a high temperature range.A high temperature compression test is performed with a Gleeble 3500 testing machine at various temperatures (approximately 900 1200°C) and strain rates (10/s and 30/s) to obtain high temperature deformation characteristics of Inconel 625. Furthermore, high temperature tensile tests results are used to measure elongations and reductions in the area of Inconel 625.A rigid-plastic finite element simulation is applied to the high temperature compression process to obtain the damage valueThe results of the hot deformation experiment and analysis are presented for various conditions of temperatures and strain rates, and it is expected that damage value will be used in hot forming processes such as hot extrusion and rolling process.

The Finite Element Simulation of Thermal Deformation and Microstructure Evolution Forecast of AZ61 Alloy

In this paper, rigid-plastic finite element simulation software Marc / Auto-forge reflect compression AZ61B magnesium alloy case. Simulation results show that the stress, strain and temperature distribution within the sample is uneven, uneven distribution affect the organization, and with the changes in the deformation process and calculation results with the experimental data exactly. The finite element method can be used in the actual production forecast after tissue deformation components, optimization of process parameters to control the quality of the finished piece.

Rigid-Plastic Finite Element Simulation of Cold Forging and Sheet Metal Forming by Eulerian Meshing Method

A computational technique of rigid-plastic finite element method by using the Eulerian meshing method was developed to deal with large deformation problem in metal forming by replacing the conventional way of applying complicated remeshing schemes when using the Lagrange’s elements. During metal forming process, a workpiece normally undergoes large deformation and causes severe distortion of elements in finite element analysis. The distorted element may lead to instability in numerical calculation and divergence of non-linear solution in finite element analysis. With Eulerian elements, the initial elements are generated to fix into a specified analytical region with particles implanted as markers to form the body of a workpiece. The particles are allowed to flow between the elements after each deformation step to show the deforming pattern of material. Four types of cold forging and sheet metal clinching were conducted to investigate the effectiveness of the presented method. The proposed method is found to be effective by comparing the results on dimension of the final product, material flow behaviour and punch load versus stroke obtained from simulation and experiment.

Improved Rotative Mid-Point Mensuration and Newton-Raphson Method in 2-D Flat Rolling Simulation

Newton-Raphson (N-R) method has been employed to solve the system of simultaneous equations arising in Rigid-Plastic finite element simulation. The combination of the improved rotative mid-point mensuration and the N-R method, named the M-P method is designated to solve the equations of velocity increment in Rigid-Plastic FEM. The CPU times required for calculation by the M-P method and the N-R method are compared and it is found that the CPU time required for calculation of the N-R method is more than the M-P method. The calculated rolling forces by the M-P method and the N-R method are compared and it is found that the former correlates better with the measured value. Numerical tests and application show that the M-P method is feasible and steady.

Finite element analysis and experimental validation of flashless cold forging of propeller hubs and blade of autonomous underwater vehicle

In this paper three-dimensional finite element method analysis and experimental flashless cold forging of aluminium front and back hubs, and the blade of an autonomous underwater vehicle propeller are presented. The rigid—plastic finite element simulation is performed using Deform F-3V6.0, to estimate the optimum load required for the flashless cold forging. The complex profiles of the hubs and blade are modelled using Solidworks SP4.02007, which is also used for the modelling of the workpiece and die-punch assembly. The workpiece used is of AISI AL6061 and the die material is die steel (AISI D2). The process is optimized to form the propeller back and front hubs, and the blade. For all the models, three workpieces with different specifications are selected and investigated to obtain the optimum workpiece that gives flashless cold forging with no underfilling. Based on the simulation results, the flashless cold forging is successfully done on a 100 tonne C-type machine. The experimental forged samples conform well with the simulated models.

Rigid-Plastic Finite Element Simulation of Deformation Mechanisms during Rolling of Complex Sheets Containing an Inclusion

Using rigid-plastic finite element DEFORMTM 2D software, this study simulates the plastic deformation of complex sheets at the roll gap during the sheet rolling process. Specifically, the study addresses the deformation of complex sheets containing inclusion defects. Under various rolling conditions, the present numerical analysis investigates the damage factor distributions, the void length at the front and rear of the inclusion, the deformation mechanisms, and the stress-strain distributions around the inclusion. The relative influences of the thickness reduction, the roll radii, and the friction factors on the void length at the front and rear of the inclusion, respectively, are systematically examined. Additionally, the correlation between the front and rear void lengths and a series of damage factors is explored. The simulation results appear to verify the suitability of the DEFORMTM 2D software for modeling the rolling of complex sheets containing inclusions.

A study on the cold ironing process for the drum clutch with inner gear shapes

This paper describes a 3D FE simulation of the cold ironing process for forming the drum clutch, the main part component of the automatic transmission. The process of the drum clutch with inner gears that was employed in this study consists of 12 steps associated with nine deep drawing processes and three ironing processes to form the inner gear shape. The ironing processes were focused on this study in order to estimate the dimensional accuracy of the inner gear shape according to the process variables such as the punch shape, the approach angle of the punch, and the thickness reduction ratio. A rigid-plastic finite element simulation was applied to analyze the deformation characteristics of the ironing processes and to determine the optimum parameter for selected conditions. Finally, an experiment on the whole drum clutch forming process was carried out to examine the validity of the analytical results and the chosen parameters.

Finite Element Simulation of Canned Forging on TiAl Alloy Containing High Nb

A rigid plastic finite element simulation method on canned forging was introduced to explain and optimize the large ingot deformation of TiAl alloy containing high content of Nb. By this method the process of deformation and the distribution of stress and strain especially on the interface can be obtained, thus the influence of capsule on the deformation and final shape of ingot can be easily explained and an appropriate processing of canned forging was ingot.

Precision Extrusion Methods with Double Axis Servo-Press using Counter Pressure

Cold extrusion methods for manufacturing products with high dimensional accuracy utilizing a servo-controlled press are studied. Experiments using lead as a model material are carried out on a servo-controlled double axis press against a flat tool supported by counter pressure. The proposed extrusion methods are analysed with the rigid-plastic finite element simulation by accommodating the pressure-supported tool. It is found that a counter pressure of 50-60 % of the flow stress is needed to flatten the front surfaces of the extruded part. To obtain a long extruded part without under-filling defect at the front corner, reverse extrusion is carried out by pushing back the extruded part after forward-backward extrusion. The proposed extrusion methods are verified with gear parts.

A finite element model for hydrodynamic lubrication of cold extrusion with frictional boundary condition

In this paper, based on elastic–plastic hydrodynamic lubrication theory and metal-forming mechanism, a model of hydrodynamic lubrication during cold extrusion is established. The frictional boundary condition during rigid-plastic finite element simulation of cold extrusion is dealt with using the proposed model. In addition, the distribution of strain in the billet during cold extrusion is analyzed by FEM. The numerical result is discussed and compared with the experimental result.

アルミニウム板のせん断加工特性に及ぼす側圧の影響

In order to improve sheared edge quality of aluminum sheets, shearing tests were conducted under various axial stresses at the shearing region, and the effect of the axial stress was investigated. Numerical simulations of the shearing process were carried out using a rigid plastic finite element simulation code developed by the authors. In the simulation, the Jeong expression was used as a fracture criterion of aluminum sheet. The distributions of fracture value and mean normal stress at the shearing region of the sheet were calculated. The experimental and simulation results showed that the rollover depth and fracture surface length decrease, but the burnish surface length increases with increasing additional axial compressive stress. When the axial compressive stress was applied, the mean normal stress becomes lower at the shearing region. Therefore, the fracture value was decreased, and the crack initiation was delayed. The experimental results were in good agreement with the simulation results.

Rigid-Plastic Finite Element Simulation of Peening Process with Plastically Deforming Shot

To simulate not only plastic deformation of a workpiece but also that of a shot in a peening process, the effect of the interaction between the shot and workpiece in the collision is included in the dynamic rigid-plastic finite element method. In the formulation, the equilibrium equations of nodal forces are solved simultaneously with velocity boundary conditions at the interface between the workpiece and shot for sliding and non-sliding contacts. Axi-symmetric plastic deformation in peening of a circular workpiece with a single shot is computed. The calculated shapes of the workpieces and the shots are in good agreement with the experimental ones for plasticine workpieces and shots. It is shown that almost no plastic deformation of the shot occurs under actual shot-peening conditions for steel workpieces when the flow stress ratio of the shot to the workpiece is larger than two.

Rigid-Plastic Finite Element Simulation of Peening Process with Plastically Deforming Shot.

To simulate not only plastic deformation of a workpiece but also that of a shot in a peening process, the effect of the interaction between the shot and workpiece in the collision is included in the dynamic rigid-plastic finite element method. In the formulation, the equilibrium equations of nodal forces are solved simultaneously with the boundary condition for velocity at the interface between the workpiece and shot. Both sliding and non-sliding contacts in the interface are dealt with, and the law of Coulomb friction is assumed for the sliding contact. Axi-symmetric plastic deformation in peening of a circular workpiece with a single shot is computed. The calculated shapes of the workpiece and the shot are compared with the experimental ones for the workpiece and a shot made from plasticine whose flow stress is controlled by temperature. It is shown that almost no plastic deformation of the shot occurs under actual shot-peening conditions for steel workpieces when the flow stress ratio of the shot to the workpiece is larger than two.

Theoretical and experimental analysis of drawing of steel rods covered with copper

The problem of the drawing of the steel rods covered with the copper sleeve is investigated in the paper. The theoretical analysis of the process is based on the thermal-mechanical rigid-plastic finite element simulation. Experimental part includes drawing of the bimetal rods prepared by the explosive welding and by the rolling in the oval-vertical oval grooves. The samples after each drawing pass were investigated and the properties of the sleeve and the core were measured. It has been observed that the copper sleeve allows to obtain the reduction of the rod diameter which cannot be achieved in the conventional drawing.

アルミニウム薄板の延性の向上に対する変形中の焼なましの影響

Interstage annealing is often employed as a method to increase the forming limit of sheet metals. This paper describes the effect of interstage annealing on the surface roughening and the improvement of limit strain of aluminum sheets. A rigid-plastic finite element simulation of plane strain tension was firstly made to predict how the limit strain could be increased by the interstage annealing and how the surface roughening would develop with plastic strain after the interstage annealing. Uniaxial tension, plane strain tension and hole expansion tests were then carried out to confirm the result of simulation. The simulation and experimental results show that the interstage annealing contributes to the recovery of ductility, but on the contrary, the increase in plastic strain due to the annealing causes the development of the surface roughening which induces a localized necking. As a result of these two effects which oppose each other, the total strain achieved is limited even if the number of interstage annealing is increased.

Increase in limiting drawing ratio by using partially thickened blanks

Deep drawing of a partially thickened blank, the thickness of which is somewhat larger at the punch head portion than at the flange portion, is investigated in an attempt to increase the limiting drawing ratio (LDR). A rigid-plastic finite element simulation is firstly used to predict the effect of the partially thickened blank on the increase in LDR. To confirm the result of the simulation, deep drawing experiments are carried out using partially thickened blanks that are produced by machining. In addition, spot welding and forging process methods are employed to produce partially thickened blanks. The finite elements simulation and experimental results show that when a partially thickened blank is used, the LDR increases appreciably compared with that for a normal blank of uniform thickness.