A static tensile test is simulated using shell elements and a nonlinear, elastic-plastic material model. One end of the specimen is constrained, while concentrated nodal loads are applied at the other end. Uniform stresses develop in the narrowed center section.
Introduction
LS-DYNA Implicit Workshop
Problem #4: Elastic-Plastic Tensile Test
Objectives
* Learn how to observe convergence behavior of nonlinear
equilibrium iterations.
* Learn to use automatic time step control for nonlinear
problems.
* Learn the benefits of force vs. displacement controlled
simulations.
Problem Description
A static tensile test is simulated using shell elements and
a nonlinear, elastic-plastic material model. One end of the
specimen is constrained, while concentrated nodal loads are
applied at the other end. Uniform stresses develop in the
narrowed center section.
Input Filename: tensile2.k
Procedure
Copy the input file to your local directory. Using an editor,
view the input file and answer the following questions:
1. Which material model is used? What is the yield stress?
2. How is load applied?
3. How many steps are used to apply the load?
Run the input deck. Does the job run to completion?
4. At what time does the solution begin to struggle?
Using the postprocessor, plot the X-displacement of an end
node vs. time.
5. What is happening at the time shown above?
6. max end displacement max eff. stress
max eff. strain
Activate the nonlinear print flag to get more information
about the nonlinear solution process, and repeat the simulation.
7. What two methods are available for this?
8. How many cycles are used in the simulation?
Switch from load control to displacement control, and repeat
the simulation (Hint: helpful keywords are commented out in
the original input deck). Using the postprocessor, again
plot the X-displacement of an end node.
9. max end displacement max eff. stress
max eff. strain
10. Why is this problem easier to solve?
Return to the original input deck, and activate automatic time
step control (IAUTO=1 on the keyword *CONTROL_IMPLICIT_AUTO).
Use 200 as the optimum iteration count, and set the maximum
step-size to 0.050. Repeat the simulation.
11. What happens?
12. max end displacement max eff. stress
max eff. strain
Using the ASCII menu, load the GLSTAT database and plot the
step size vs. time.
13. When does the step size change? Why?
Keywords
*BOUNDARY_PRESCRIBED_MOTION_NODE
*BOUNDARY_SPC_NODE
*CONTROL_IMPLICIT_AUTO
*CONTROL_IMPLICIT_GENERAL
*CONTROL_IMPLICIT_SOLUTION
*CONTROL_IMPLICIT_SOLVER
*CONTROL_SHELL
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DATABASE_ELOUT
*DATABASE_EXTENT_BINARY
*DATABASE_GLSTAT
*DATABASE_HISTORY_SHELL
*DATABASE_NODAL_FORCE_GROUP
*DATABASE_NODFOR
$*DEFINE_CURVE
*DEFINE_CURVE
*ELEMENT_SHELL
*END
*KEYWORD
*LOAD_NODE_POINT
*MAT_TRANSVERSELY_ANISOTROPIC_ELASTIC_PLASTIC
*NODE
*PART
*SECTION_SHELL
*SET_NODE_LIST
*TITLE
*KEYWORD
*TITLE
implicit tensile test, elastic-plastic material
$
$ test coupon, 200 mm long, 20 mm width, 2.67 mm thickness, 50.8 mm gauge length
$
$ units; mm, s, ton, N
$
$ By A. Tabiei
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
*CONTROL_TERMINATION
1.0000
$
$========1=========2=========3=========4=========5=========6=========7=========8
$
*CONTROL_IMPLICIT_GENERAL
$ imflag dt0 iefs nstepsb igso
1 0.01 0 0 0
$
*CONTROL_IMPLICIT_SOLUTION
$ nlsolvr ilimit maxref dctol ectol rctol lstol
0 0 0 0.0 0.0 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 0.0 0.0
$ 1 200 0 0.0 0.05
$
$========1=========2=========3=========4=========5=========6=========7=========8
$
*DATABASE_BINARY_D3PLOT
0.0100
*DATABASE_EXTENT_BINARY
$ neiph neips maxint strflg sigflg epsflg rltflg engflg
1 1
$ cmpflg ieverp beamip
$
*DATABASE_GLSTAT
0.0001
$
*DATABASE_NODFOR
0.0001
*DATABASE_NODAL_FORCE_GROUP
2
*SET_NODE_LIST
2
30,31,32,33,38,39
$
$
*DATABASE_ELOUT
0.0001
*DATABASE_HISTORY_SHELL
71,72,73,74,75,76,77,78
79,80
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*CONTROL_SHELL
$ WRPANG ITRIST IRNXX ISTUPD THEORY BWC MITER PROJ
0 0 0 0 0 0 1 0
$
*SECTION_SHELL
$ ID elform
1 16
$ t1 t2 t3 t4
2.670E-00 2.670E-00 2.670E-00 2.670E-00
$
*PART
shell tensile strip
1 1 1
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
*MAT_TRANSVERSELY_ANISOTROPIC_ELASTIC_PLASTIC
$ MID RO E PR SIGY ETAN R HLCID
1 0.780E-08 0.207E+06 0.280E+00 0.200E+03 0.572E+03 0.140E+01 13
$
$ hardening curve: effective stress vs. effective plastic strain
*DEFINE_CURVE
13
0.00000000 200.0
0.00006657 200.5
0.00013650 201.1
0.00020990 201.6
0.00028690 202.2
0.00036780 202.7
0.00045280 203.2
0.00054200 203.8
0.00091670 205.8
0.00136600 207.9
0.00190600 210.0
0.00255300 212.1
0.00472900 217.2
0.00654700 220.3
0.00891000 223.4
0.03259000 250.8
0.04616000 270.5
0.06516000 291.5
0.09176000 313.8
0.13830000 342.4
0.20810001 373.2
0.31279999 406.2
0.46990001 441.6
0.70560002 479.7
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
*LOAD_NODE_POINT
204 1 3 1
205 1 3 1
206 1 3 1
207 1 3 1
212 1 3 0.5
213 1 3 0.5
*DEFINE_CURVE
3
0.00 0.00
1.00 2000.00
2.00 2000.00
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
$*BOUNDARY_PRESCRIBED_MOTION_NODE
$ 204 1 2 4 1.00
$ 205 1 2 4 1.00
$ 206 1 2 4 1.00
$ 207 1 2 4 1.00
$ 212 1 2 4 1.00
$ 213 1 2 4 1.00
$*DEFINE_CURVE
$ 4
$ 0.00 0.00
$ 1.00 7.00
$ 2.00 7.00
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
*BOUNDARY_SPC_NODE
30 0 1 1 1 1 1 1
31 0 1 1 1 1 1 1
32 0 1 1 1 1 1 1
33 0 1 1 1 1 1 1
38 0 1 1 1 1 1 1
39 0 1 1 1 1 1 1
204 0 0 1 1 0 0 0
205 0 0 1 1 0 0 0
206 0 0 1 1 0 0 0
207 0 0 1 1 0 0 0
212 0 0 1 1 0 0 0
213 0 0 1 1 0 0 0
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$
*END
Animated Result
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