Introduction

LS-DYNA Implicit Workshop

Problem #5: Door Beam

Objective
* Learn to perform a spring back simulation using an entirely
static implicit analysis.
* Learn to specify key points during the solution which must
be reached exactly.
* Learn about the available displacement convergence norm options.

Problem Description
A doorbeam subassembly is deformed by a rigid pole. Shell
elements are used throughout, and nodal rigid bodies are used
to spotweld the components of the doorbeam. The pole is
displaced to deform the doorbeam, then retracted to evaluate
springback.

Input Filename: doorbeam.k

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

1. What type of contact interface is selected? Why?

2. Why is the doorbeam chosen as the slave side?

Run the simulation and observe the convergence behavior.
Activate the flag IGAPF=2 on optional card C in the *CONTACT_
keyword. Repeat the simulation.

3. Which gap flag produces the best convergence behavior?

Postprocess the results, and plot the slave interface force.
Save the interface force curve as file curve1.

4. What is the strategy for solving the springback problem?
How is the applied load removed?

5. At what time is the full load applied? (HINT: Check the
input file.)

6. Why are the maximum reaction force and springback
predictions from this simulation misleading?

Define a key point at time=1.0 using the
*CONTROL_IMPLICIT_AUTO keyword. Use a maximum step size of
0.05 throughout the entire simulation. Repeat the simulation,
and plot the new interface force curve. Save this curve as
file curve2. Compare these results to curve1.

7. Is the peak load computed at the correct time?

8. Why is the force-deflection behavior not smooth?

Select the alternate displacement tolerance scheme using
DNORM=1 on *CONTROL_IMPLICIT_SOLUTION, and repeat the simulation.

9. Does the alternative displacement tolerance become ( )
more or ( ) less strict when total displacements are large,
as they are at the end of this problem?

10. Is the force-deflection curve more smooth? Why?

11. What is the springback deflection at the center of the
doorbeam?