On the Extrusion in Superplastic Conditions

1975 ◽  
Vol 97 (3) ◽  
pp. 1131-1135 ◽  
Author(s):  
A. Alto ◽  
G. Giorleo
Keyword(s):  
Velocity Field ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Experimental Evidence ◽  
Upper Bound ◽  
Extrusion Pressure ◽  
Slab Method ◽  
Conical Die ◽  
Strain Rate Field ◽  
Superplastic Condition

In this paper the range within which the slab method is accurate enough to calculate the extrusion pressure in superplastic condition has been determined. A realistic velocity field, supported by experimental evidence, has been adopted. A strain rate field has been evaluated and an appropriate constitutive equation has been introduced. The slab method and the upper bound approach, here developed, have then been used to study the superplastic extrusion through a conical die. A comparison of the two solutions thus obtained has been carried out. It has been found that in any case the curves obtained using the slab method run higher than those obtained using the upper-bound approach. The analysis developed may be used to determine the range within the slab method is accurate enough for engineering purposes.

Direct Upper Bound Solution to Rectangular-to-Polygonal Extrusion Through Square Die

1999 ◽  
Vol 121 (2) ◽  
pp. 195-201 ◽  
Author(s):  
S. K. Sahoo ◽  
P. K. Kar ◽  
K. C. Singh
Keyword(s):  
Steady State ◽  
Velocity Field ◽  
Upper Bound ◽  
Velocity Fields ◽  
Extrusion Pressure ◽  
Admissible Velocity ◽  
Bound Solution ◽  
Upper Bound Solution ◽  
Aspect Ratios

This paper is concerned with an attempt to find an upper bound solution for the problems of steady-state extrusion of asymmetric polygonal section bars through rough square dies. A class of kinematically admissible velocity fields is examined, reformulating the SERR technique, to get the velocity field that gives the lowest upper bound. This velocity field is utilized to compute the non-dimensional average extrusion pressure at various area reductions for different billet aspect ratios.

On the Velocity and the Strain Rate Field in Unlubricated Direct and Indirect Axisymmetric Extrusion of Al

2014 ◽  
Vol 611-612 ◽  
pp. 1013-1020
Author(s):  
Sepinood Torabzadeh Khorasani ◽  
Henry Valberg
Keyword(s):  
Velocity Field ◽  
Strain Rate ◽  
Deformation Zone ◽  
Good Accuracy ◽  
Fe Simulation ◽  
Metal Flow ◽  
Fe Analysis ◽  
Extrusion Die ◽  
Strain Rate Field ◽  
Good Agreement

The velocity and strain rate fields in the primary deformation zone ahead of the extrusion die opening are investigated by theory and FE-simulation for direct and indirect Al extrusion. The metal flow obtained in the FEM-models of extrusion is compared with the flow recorded in previous experiments and it is shown that the FE-analysis mimics real metal flow with good accuracy. The velocity and the strain rate fields computed by FEA (using DEFORM® 2D) are described and comparison is made with the idealized spherical velocity field of Avitzur, to see if there is good agreement between the results from theory and FEA, and the correlation between the results from the two is discussed. Moreover, a clear difference in metal flow is confirmed between the two processes direct (FwE) and indirect extrusion (BwE).

A New Formulation of Generalized Velocity Field for Axisymmetric Forward Extrusion Through Arbitrarily Curved Dies

1987 ◽  
Vol 109 (2) ◽  
pp. 161-168 ◽  
Author(s):  
D. Y. Yang ◽  
C. H. Han
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Effective Strain ◽  
Extrusion Pressure ◽  
Grid Pattern ◽  
Forward Extrusion ◽  
Area Reduction ◽  
Theoretical Predictions ◽  
Die Profile ◽  
New Formulation

A new analytic method is proposd for estimating the extrusion pressure, the final effective strain of the extruded billet, and the grid distortion patterns in axisymmetric forward extrusion through arbitrarily curved dies. A generalized kinematically admissible velocity field is derived to formulate an upper-bound solution. The corresponding upper-bound extrusion pressure is then obtained by optimizing the process parameters. The effects of area reduction, frictional condition, die length, and the die profile are discussed in relation to the extrusion pressure, the distorted grid pattern, and distribution of the final effective strain on the cross-section of the extruded billet. In the computation a biquadratic polynomial is chosen for the die profile. The work-hardening effect is incorporated in the formulation. Experiments are carried out for AISI 4140 steel billets at room temperature. The theoretical predictions both in the extrusion load and deformed configuration are in excellent agreement with the experimental results and the results computed by the finite element method.

Influence of Flow Stress and Friction Upon Metal Flow in Upset Forging of Rings and Cylinders

1972 ◽  
Vol 94 (3) ◽  
pp. 775-782 ◽  
Author(s):  
C. H. Lee ◽  
T. Altan
Keyword(s):  
Flow Stress ◽  
Velocity Field ◽  
Strain Rate ◽  
Calibration Curve ◽  
Upper Bound ◽  
Metal Flow ◽  
Computer Programs ◽  
Ring Test ◽  
Stress Distributions ◽  
Upset Forging

An upper-bound velocity field that considers bulging has been applied to cylinder and ring upsetting. Computer programs have been developed to (a) determine strain, strain rate, velocity, and flow-stress distributions, and (b) predict load and bulge profile at various reductions by simulating the upsetting process. The calibration curve for a 6:3:2 ring, the load-displacement curves for ring and cylinder upsetting, and flow stress from the ring test have been predicted. The experimental results, with annealed 1100 Aluminum samples, agree well with theory at the lower and practical range of friction, but they show some disagreement at high friction.

The influence of strain rate on the cavitation time and deformation of an underwater impulsively rectangular plate

2021 ◽  
pp. 030932472110208
Author(s):  
Habib Ramezannejad Azarboni ◽  
Abolfazl Darvizeh
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Rectangular Plate ◽  
Total Pressure ◽  
Elastoplastic Deformation ◽  
Underwater Explosion ◽  
Strain Rate Effect ◽  
Linear Solution ◽  
Explosion Load ◽  
Explosive Forming

The effect of strain rate on the cavitation time and elastoplastic deformation of steel rectangular plate subjected to underwater explosion load is analytically and numerically investigated in this study. At the cavitation time, the total pressure of the explosion is eliminated so that the cavitation time plays a significant role in the elastoplastic deformation of underwater explosive forming of plate. Taking into account the strain rate effect, the Cowper-Symond constitutive equation of mild steel is employed. Exact linear solution using the Eigen function and numerical linear and nonlinear solution using finite difference method (FDM) of dynamic response of impulsively plate is obtained. Implementing the linear work hardening, the stress, strain, displacement, and velocity in any steps of loading are calculated. The time of cavitation can be recognized in elastic or plastic regimes by applying the Cowper-Symond constitutive equation. Considering the strain rate influence, the effects of charge mass and standoff are investigated to occur of cavitation and time dependent deflection and velocity of a rectangular plate.

Radial Flow Velocity Field for Predicting Upper-Bound Solutions for Plane Strain Extrusion

1968 ◽  
Vol 90 (1) ◽  
pp. 45-50
Author(s):  
R. G. Fenton
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Flow Velocity ◽  
Plane Strain ◽  
Upper Bound ◽  
Radial Flow ◽  
Flow Velocity Field ◽  
Wide Range ◽  
Ram Pressure ◽  
Considerable Range

The upper bound of the average ram pressure, based on an assumed radial flow velocity field, is derived for plane strain extrusion. Ram pressures are calculated for a complete range of reduction ratios and die angles, considering a wide range of frictional conditions. Results are compared with upper-bound ram pressures obtained by considering velocity fields other than the radial flow field, and it is shown that for a considerable range of reduction ratios and die angles, the radial flow field yields better upper bounds for the average ram pressure.

A Yield Criterion of Porous Materials With Anisotropy Caused by Geometry or Distribution of Pores

1991 ◽  
Vol 113 (4) ◽  
pp. 425-429 ◽  
Author(s):  
T. Hisatsune ◽  
T. Tabata ◽  
S. Masaki
Keyword(s):  
Velocity Field ◽  
Porous Materials ◽  
Upper Bound ◽  
Volume Fraction ◽  
Yield Criterion ◽  
Longitudinal Direction ◽  
Axisymmetric Deformation ◽  
The Other ◽  
The Matrix ◽  
Spherical Cells

Axisymmetric deformation of anisotropic porous materials caused by geometry of pores or by distribution of pores is analyzed. Two models of the materials are proposed: one consists of spherical cells each of which has a concentric ellipsoidal pore; and the other consists of ellipsoidal cells each of which has a concentric spherical pore. The velocity field in the matrix is assumed and the upper bound approach is attempted. Yield criteria are expressed as ellipses on the σm σ3 plane which are longer in longitudinal direction with increasing anisotropy and smaller with increasing volume fraction of the pore. Furthermore, the axes rotate about the origin at an angle α from the σm-axis, while the axis for isotropic porous materials is on the σm-axis.

Hot Compression Deformation Behavior of Spray-Formed AlSn20Cu Alloy

2021 ◽  
Vol 1035 ◽  
pp. 189-197
Author(s):  
Bao Ying Li ◽  
Bao Hong Zhu
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
Phase Distribution ◽  
True Stress ◽  
Hot Compression ◽  
Test Machine ◽  
Hot Compression Deformation ◽  
Compression Deformation

The hot deformation behavior of spray-formed AlSn20Cu alloy during hot compression deformation was studied, and the constitutive equation of AlSn20Cu alloy was established. The samples of spray-formed AlSn20Cu alloy were compressed on Gleeble-3500 thermal simulation test machine. The error of the true stress caused by adiabatic heating effect in the experiment was corrected. The constitutive equation of spray-formed AlSn20Cu alloy could be represented by Zener-Hollomon parameter in a hyperbolic sine function. The results showed that the deformation temperatures and strain rates had a notable effect on the true stress of the alloy. At the identical deformation temperature, the true stress increased with the increase of strain rate. When the strain rate was constant, the stress decreased with the increase of deformation temperature. After hot compression deformation, the tin phase was elongated along the direction perpendicular to the compression axis with short strips and blocks. With the increase of deformation temperature and the decrease of strain rate, Sn phase distribution became more homogeneous.

Simulation of Influence of Friction Coefficient on Extrusion of TC4 Alloy

2013 ◽  
Vol 470 ◽  
pp. 244-249
Author(s):  
Chang Dong Liu ◽  
Yi Du Zhang
Keyword(s):  
Friction Coefficient ◽  
Strain Rate ◽  
Effective Strain ◽  
High Stress ◽  
Extrusion Process ◽  
Extrusion Pressure ◽  
Tc4 Alloy ◽  
Stress Zone ◽  
D Model ◽  
High Stress Zone

Based on Simufact11.0, a 3-D model of T profile extrusion is established and the extrusion process of TC4 is investigated using finite volumemethod(FVM) of Euler mesh description. Effects of different friction coefficients on the effective stress, extrusion pressure, effective strain and effective strain rate have been studied. The study shows that there is a high-stress zone at a certain distance from the entrance of the forming area and a high strain rate zone around that area. With the increase of friction coefficient, the value of the stress increased and the deformation is more uneven. The track of extrusion pressure shows that extrusion increase with the increase of friction coefficient.

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