Impl Expl Switch

A cantilevered strip of shell elements is loaded using the static implicit method. The analysis type is then switched to explicit, the load is removed, and the dynamic response is simulated. The first fundamental response frequency is verified by eigenvalue analysis.

Problem #7: Implicit Explicit Switching

Objective
* Learn to use the implicit method for static initialization
of an explicit simulation.
* Learn to switch formulations during a simulation.
* Learn to perform a simple eigenvalue analysis.

Problem Description
A cantilevered strip of shell elements is loaded using the
static implicit method. The analysis type is then switched
to explicit, the load is removed, and the dynamic response
is simulated. The first fundamental response frequency is
verified by eigenvalue analysis.

Input Filename: ie_shell.k

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

1. How is the implicit explicit switching activated
2. When does the simulation run implicit? Explicit?
3. How many implicit steps will be taken?
4. How is load applied? When is load removed?

Run the simulation, and postprocess the results. Plot the
Y-displacement of a tip node vs. time.

5. Estimate the period of response for the first fundamental
mode: seconds.

Modify the input deck to conduct an eigenvalue analysis.
Solve for the lowest five eigenvalues. Repeat the simulation.
Observe the names of the two new output files which are
created for eigenvalue analyses.

6. Which two new output files are created?

View the file elout using a text editor.

7. What is the period of the first fundamental mode?

Postprocess the binary file d3eigv using LS-POST. View the
mode shapes.

8. What is the meaning of the time associated with each
mode shape?

*CONTROL_IMPLICIT_AUTO
$*CONTROL_IMPLICIT_EIGENVALUE
*CONTROL_IMPLICIT_GENERAL
*CONTROL_IMPLICIT_SOLUTION
*CONTROL_IMPLICIT_SOLVER
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DEFINE_CURVE
*ELEMENT_SHELL
*END
*KEYWORD
*LOAD_NODE_POINT
*MAT_ELASTIC
*NODE
*PART
*SECTION_SHELL
*TITLE

  *KEYWORD
  $
  *TITLE
  cantilevered shell strip w/ end load
  $
  $--------------
  $
  *CONTROL_IMPLICIT_GENERAL
  $   imflag       dt0      iefs
          -9    0.0005         0
  $
  *DEFINE_CURVE
           9
   0.00000, 1.0
   0.00999, 1.0
   0.01000, 0.0
   1.00000, 0.0
  $
  *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
  *CONTROL_IMPLICIT_SOLVER
  $   lsolvr   prntflg    negeig
           0         0         0
  *CONTROL_IMPLICIT_AUTO
  $    iauto    iteopt    itewin     dtmin     dtmax
           0         0         0      0.00         0
  $$
  $*CONTROL_IMPLICIT_EIGENVALUE
  $$     neig
  $         5
  $$
  $--------------
  $
  *CONTROL_TERMINATION
       0.025
  $
  *DATABASE_BINARY_D3PLOT
      0.0001
  $
  $--------------
  $
  *MAT_ELASTIC
           1 7.000E-04 3.000E+07 3.000E-01
  $
  *SECTION_SHELL
           1         6 8.333E-01 3.000E+00 3.000E+00 0.000E+00         0
   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
  $
  $--------------
  $
  *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
    0.00000,   0.0
    0.01000,  50.0
    0.01001,   0.0
    1.00000,   0.0
  $
  $--------------
  $
  *END