﻿ Checklist for Metal Extrusion Simulation
Manufacturing Solutions

# Checklist for Metal Extrusion Simulation

Complete the steps below as a checklist for Metal Extrusion Simulation:

 1 Prepare finite element model for billet, die cavities, bearing, and profile.
 2 Launch HyperXtrude interactively.
 3 Check to ensure that the Extrusion Ratio is correct.
 • If yes, proceed to the next step.
 • If not, the Inflow and Outflow boundaries are not specified correctly. Make a note to fix this and go to the next step.
 4 Display Process Parameters:  Click on Properties and select Process.
 • Check if the units for Geometry, Temperature, and Velocity are correct.
 • Check the remaining data to make sure it is correct. If it is, proceed to step number 6. If not, make a note of errors to be fixed and go to the next step.
 5 Fix the problems identified in the previous two steps.
 6 Run the solver (interactive or batch mode). The solution convergence history is saved in the file: jobname_000.out

## Convergence Checks

 1 Perform the convergence checks: Check if the Norm of Change in Solution (see table below) for Velocity, Temperature, and Pressure is decreasing from one iteration to the next. This may oscillate initially but must decrease steadily after the initial iterations. The solution is said to be converged if the value of Norm of Change in Solution is less than 0.001.

### Norm of Change in Solution

(S)

||S[n]||

||S[n]|| - ||S[n-1]||

||S[n] - S[n-1]||

||S[n-1]||

||S[n-1]||

Velocity

2.888617e-03

2.000727e-05

7.793839e-04

Pressure

2.986197e+02

-3.439566e-04

4.554252e-04

Temperature

1.294574e+01

8.542281e-05

2.123905e-04

Total

2.989002e+02

-3.431516e-04

4.550911e-04

 A slow convergence rate or oscillatory behavior indicates one or more of the following:
 • The mesh is too coarse.
 • Extrusion speed is too high.
 • Temperature boundary conditions are not correct.
 • Material properties are incorrect.
 2 Check if the work piece elements on the boundary between tool and work piece are defined as SolidFluidInterface.
 3 Fix the problem before proceeding to the next step.

## Mass Balance

 1 Check the Mass Balance. Review the Mass Flux table to verify if the mass is conserved.  The mass flux table shows mass flow rate across each boundary. A positive sign indicates material entering through the boundary and negative sign indicates material leaving the boundary. The table also contains average velocity of the material entering/leaving through each boundary surface.
 • Check if the Mass Balance is less than 1 percent
 • Extrusion speed at Outflow boundary (Uexit) must be equal to Extrusion_Ratio*Uram
 • Velocity on solid walls and symmetry must be zero
 • Velocity on free surface and bearing walls must be small (at least less than four orders of magnitude less than extrusion speed Uexit).
 2 If any of these checks fail, verify the boundary conditions.

Mass Flux Across Boundaries

(Kg/sec)

(mm/sec)

ram

1.1980e-02

7.0000e-01

exit

-1.1842e-02

-1.1080e+01

container

0.0000e+00

0.0000e+00

manderwall

-4.7829e-07

0.0000e+00

symmetry

5.2172e-07

0.0000e+00

freesurface

-1.8247e-05

-1.0776e-03

bearing_out

-1.8636e-06

-1.6254e-03

bearing_in

6.5209e-07

6.7218e-04

mass balance (%)

0.9899

## Force Balance

 1 Review the forces on boundaries to verify if the forces are balanced.  A positive sign indicates force applied on a surface and a negative sign indicates response. The table also contains average pressure at each boundary surface.

Forces on Boundaries

 Boundary Name Components of Viscous Force Vector Components of Total Force Vector Average Pressure (MPa) Fx Fy Fz Fx Fy Fz (kN) (kN) (kN) (kN) (kN) (kN) ram 2.5454e+01 7.8440e+01 1.9740e+01 2.5454e+01 7.8440e+01 -7.8244e+03 1.2741e+03 exit 1.0665e-03 5.3531e-03 -6.8977e-02 1.0665e-03 5.3531e-03 -6.8977e-02 0.0000e+00 container 5.3613e+00 3.1117e+00 1.1128e+03 -1.4976e+04 -4.6106e+04 1.1128e+03 1.1674e+03 manderwall -4.6201e+01 4.6323e+01 9.5826e+02 -5.8601e+03 -2.7491e+03 6.3017e+03 6.5564e+02 symmetry 8.3182e+01 2.7992e+01 9.4760e+00 2.0803e+04 4.8745e+04 4.7183e-01 1.0919e+03 freesurface -1.6884e+00 -4.6628e+00 5.2781e-02 -1.6812e+00 -4.6523e+00 5.2781e-02 1.0843e-02 bearing_out -4.8041e+00 -1.5571e+01 8.4259e+00 -4.9994e+00 -1.6622e+01 8.4259e+00 2.6525e+00 bearing_in 2.0909e+00 9.7181e+00 7.7039e+00 2.3798e+00 1.1566e+01 7.7039e+00 5.3868e+00 all walls 6.3395e+01 1.4536e+02 2.1164e+03 -1.2295e+01 -4.1157e+01 -3.9330e+02

 2 Check if each component of total force vector is in equilibrium (<5 percent).
 3 Check if average pressure at Ram (inlet) is within in acceptable range.
 4 Verify the boundary conditions and material properties if either one of these checks fails.

## Energy Balance

 1 Review the Heat Flux table to verify if the energy is conserved.  The heat flux table shows heat transfer rate across each boundary. A positive sign indicates energy input to the system and a negative sign energy leaving through the boundary. The table also contains average temperature at each boundary surface.
 2 Check if energy balance is < 5 percent.
 3 Check if average temperatures are within in acceptable range.
 4 Verify the boundary conditions and material properties if either one of these checks fails.

Heat Flux Across Boundaries

 Boundary Name Heat Trans. Rate Heat Flux Average Temp. (kW) (kW/m^2) (Deg C) ram 7.1830e+00 1.1668e+03 4.3000e+02 exit -7.8366e+00 -2.0383e+04 4.8313e+02 container -2.0564e-01 -4.8707e+00 4.4869e+02 manderwall 3.4233e-02 1.1354e+00 4.7993e+02 symmetry -4.3799e-03 -2.8021e-02 4.5228e+02 freesurface 9.9421e-06 1.6323e-03 4.8313e+02 bearing_out -9.6378e-03 -2.3369e+01 4.8298e+02 bearing_in -6.1217e-03 -1.7543e+01 4.8276e+02 viscous dissipation 1.0753e+00 heat balance (%) 2.7764

## Work Converted to Energy

The amount of heat generated during deformation must be equal to the mechanical work.

 1 Check if β*Pram*Aram*Uram - Φ < 5%

Where,

 • Pram          = Average pressure at ram
 • Aram            = Area of the container
 • Uram                = Ram velocity
 • β                = % of work mechanical converted to energy
 • Φ                      = Work converted to energy (Viscous Dissipation) in the heat balance table

## Profile Deflection

The Norm of Mesh Displacement quantifies the amount of profile deflections. Large value indicates the velocities at die exit are not uniform and this produces large profile deflections. The norm of mesh displacement must be < 0.01 for a good die design.

## Exit Velocity

 1 Check if the velocity is uniform at the exit.
 • Non-uniform velocity will result in profile deflection.
 • If Norm of Mesh Displacement is less than 0.01, the flow is balanced and die design is acceptable.
 • If 0.01 < Norm of Mesh Displacement <0.1 continue additional solution steps to see if the profile deflection calculations converge. Use the profile deflections to correct the die.
 • If Norm of Mesh Displacement is greater than 0.1 stop the analysis and correct the die.

## Profile Surface Temperature

 1 Check if the surface temperature variations are small.
 • Large changes in temperatures (over 15 deg. C) will result in wavy surface.
 • Higher temperatures will result in surface damage.

## Temperature in Weld Zone and Bearing Region

Check the temperature variations near die exit and bearing regions. Large changes in temperature (over 10 deg. C) in thin wall sections and ribs indicate that the material did not weld properly.