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Springback II

This exercise involves two simulations. First, a cantilevered strip of shell elements is loaded using a dynamic explicit simulation. An output file named dynain is created at the end of this simulation. A second, implicit simulation is then performed which reads the dynain file and computes the springback deformation. Download is available in the download section of this document

Introduction

LS-DYNA Implicit Workshop

Problem #8: Springback using DYNAIN file

Objective
* Learn to generate a DYNAIN output file at the end of a
simulation.
* Learn to apply artificial stabilization in a multi-step
springback simulation.

Problem Description
This exercise involves two simulations. First, a cantilevered
strip of shell elements is loaded using a dynamic explicit
simulation. An output file named dynain is created at the
end of this simulation. A second, implicit simulation is then
performed which reads the dynain file and computes the springback
deformation.

Input Filename: cant_dynain_load.k, cant_dynain_springback.k

Procedure
Copy the input files to your local directory. Using an editor,
view the first input file and answer the following questions:

1. What keyword is used to create the DYNAIN file?
2. What material model is used?

Run the first simulation, and postprocess the results.

3. What is the initial Y-coordinate for all nodes?
4. What is the maximum effective stress at the end of the
loading?

View the contents of the DYNAIN file which was created at
the end of the first run.

5. Which keywords are used in the DYNAIN file?

View the contents of the second input file, and answer the
following:

6. Could this file be easily created from the first input
file? How?

7. How many steps will be used in this simulation?

8. How is load applied in this simulation?

Run the second input file, making sure the DYNAIN file produced
by the first run is available for *INCLUDEing, and postprocess
the results.

9. Is the termination time reached? Why?

Activate automatic time step control and artificial stabilization,
and repeat the simulation. Postprocess the results, and plot
the Y-coordinate of a tip node vs. time.

10. Does the springback deflection occur uniformly, or abruptly?

11. After springback:
max. effective stress =
max. Y-coordinate =

Modify the artificial stabilization scale factor to SCALE =
0.050, and repeat the springback simulation. Postprocess,
and plot the Y-coordinate of the tip node again.

12. How has the evolution of springback deflection changed?

13. After springback:
max. effective stress =
max. Y-coordinate =

Modify the nonlinear convergence test to compare the displacement
increment to the total displacement over the current step
(DNORM=1), repeat the simulation, and postprocess.

14. After springback:
max. effective stress =
max. Y-coordinate =

Keywords

*BOUNDARY_SPC_NODE
*CONTROL_IMPLICIT_AUTO
*CONTROL_IMPLICIT_GENERAL
*CONTROL_IMPLICIT_SOLUTION
*CONTROL_IMPLICIT_STABILIZATION
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DEFINE_CURVE
*END
*INCLUDE
*INTERFACE_SPRINGBACK_LSDYNA
*KEYWORD
*LOAD_NODE_POINT
*MAT_ELASTIC
*PART
*SECTION_SHELL
*SET_PART_LIST
*TITLE

Reduced Input

  *KEYWORD
  $
  *TITLE
  springback of elastic cantilevered shell strip
  $
  $--------------
  $
  *INCLUDE
  dynain
  $
  $--------------
  $
  *CONTROL_IMPLICIT_GENERAL
  $   imflag       dt0      iefs
           1    0.2500         0
  $
  *CONTROL_IMPLICIT_SOLUTION
  $  nlsolvr    ilimit    maxref     dctol     ectol     rctol     lstol
           0         0         0      0.00      0.00         0         0
  $    dnorm   divflag   inistif   nlprint
           0         0         0         0
  $        1         0         0         0
  $
  *CONTROL_IMPLICIT_AUTO
  $    iauto    iteopt    itewin     dtmin     dtmax
           0         0         0      0.00         0
  $        1         0         0      0.00         0
  $
  *CONTROL_IMPLICIT_STABILIZATION
  $      ias     scale    tstart      tend
           0       0.0         0         0
  $        1      0.00         0         0
  $
  $--------------
  $
  *CONTROL_TERMINATION
        1.00
  $
  *DATABASE_BINARY_D3PLOT
        0.01
  $
  $--------------
  $
  *MAT_ELASTIC
           1 7.000E-04 3.000E+07 3.000E-01
  $
  *SECTION_SHELL
           1        16         0         2
   1.000E-01 1.000E-01 1.000E-01 1.000E-01 0.000E+00
  $
  *PART
  cantilevered shell     
         1       1       1       0       0       0       0       0
  *END
  $$$$$$$$$$$$$$$$$$$$$$
  $$ 2nd file
  $$$$$$$$$$$$$$$$$$$$$$$$
  *KEYWORD
  $
  *TITLE
  cantilevered shell strip w/ end force
  $
  $--------------
  $
  *INTERFACE_SPRINGBACK_LSDYNA
  $     psid
           7
  $
  *SET_PART_LIST
  $     psid
           7
  $      pid
           1
  $
  $--------------
  $
  *CONTROL_TERMINATION
       0.050
  $
  *DATABASE_BINARY_D3PLOT
       0.001
  $
  $--------------
  $
  *MAT_ELASTIC
           1 7.000E-04 3.000E+07 3.000E-01
  *SECTION_SHELL
           1        16         0         2
   1.000E-01 1.000E-01 1.000E-01 1.000E-01 0.000E+00
  *PART
  cantilevered shell     
         1       1       1
  $
  $--------------
  $
  *LOAD_NODE_POINT
  $     nsid       dof      lcid        sf    
          16         2        98       0.5
          32         2        98       1.0
          48         2        98       0.5
  $
  *DEFINE_CURVE
          98
  0.000,   0.0
  0.050,  50.0
  1.000,  50.0
  $
  *BOUNDARY_SPC_NODE
  $      nid       cid        dx        dy        dz        rx        ry        rz
           1         0         1         1         1         1         1         1
          17         0         1         1         1         1         1         1
          33         0         1         1         1         1         1         1
  $
  $--------------
  $
  *END

Figures

image01.gif

image02.gif

Animated Result

Result