Tutorial 13 : Explicit to eigenvalue to implicit

conversion

Case description:

Topics covered:

Explicit to eigenvalue conversion

Eigenvalue to implicit conversion

Files required:

bracket_explicit.k

Step 1: Run the bracket model using LS-DYNA explicit

1. create a directory called "explicit" for "bracket_explicit.k"

2. run "bracket_explicit.k" using single precision LS-DYNA

3. launch LS-PrePost

4. File → Open → Binary Plot

5. open "\explicit\d3plot"

6. hold the Ctrl key and use the left mouse button to rotate the model to a suitable viewing

angle

7. FEM→Post→Fringe Component

8. select "von mises stress" from the list

9. click the Play Ahead (Animate Forward) button in the bottom panel

10. note the stress contour that develops due to the prescribed displacement load

Step 2: Convert the model for eigenvalue analysis

1. create a directory called "eigenvalue"

2. copy "\explicit\bracket_explicit.k" to "\eigenvalue\bracket_eigenvalue.k"

3. launch LS-PrePost

4. File → Open → LS-Dyna Keyword File

5. open "bracket_eigenvalue.k"

6. FEM→Model and Part→Keyword Manager

7. click All

8. select "IMPLICIT_EIGENVALUE" from the list

9. click Edit

10. enter NEIG=10 in the KEYWORD INPUT popup form

11. click Accept

12. click Done

13. select "IMPLICIT_GENERAL" from the list

14. click Edit

15. enter IMFLAG=1 in the KEYWORD INPUT popup form

16. click Accept

17. click Done

18. File → Save Keyword

19. overwrite "bracket_eigenvalue.k"

Step 3: Run an eigenvalue analysis using LS-DYNA

1. run "bracket_eigenvalue.k" using LS-DYNA

2. launch LS-PrePost

3. File → Open → Binary Plot

4. open "\eigenvalue\d3eigv"

5. hold the Ctrl key and use the left mouse button to rotate the model to a suitable viewing

angle

6. FEM→Post→Fringe Component

7. click Ndv

8. select "result displacement" from the list

9. click the Play button in the bottom panel to animate Mode #1

Step 4: View other mode shapes

1. click Previous state /Next state in the animation controls to browse the various mode shapes

2. Mode #10 is shown in Figure

Step 5: Convert the model for implicit analysis

1. create a directory called "implicit"

2. copy "\eigenvalue\bracket_eigenvalue.k" to "\implicit\bracket_implicit.k"

3. launch LS-PrePost

4. File → Open → LS-DYNA Keyword File

5. open "bracket_implicit.k"

6. FEN→Model and Part→Keyword Manager

7. click All

8. select "IMPLICIT_EIGENVALUE" from the list

9. click Edit

10. click Delete in the KEYWORD INPUT popup form

11. select "IMPLICIT_GENERAL" from the list

12. click Edit

13. enter DT0=0.001 in the KEYWORD INPUT popup form

14. click Accept

15. click Done

Step 6: Convert the model for implicit analysis (continued...)

1. select "IMPLICIT_AUTO" from the list

2. click Edit

3. enter IAUTO=1 in the KEYWORD INPUT popup form

4. click Accept

5. click Done

6. select "IMPLICIT_SOLUTION" from the list

7. click Edit

8. select NLPRINT=1 in the KEYWORD INPUT popup form

9. click Accept

10. click Done

11. File → Save Keyword

12. overwrite "bracket_implicit.k"

Step 7:Run an implicit analysis using LS-DYNA implicit

1. run "bracket_implicit.k" using DOUBLE precision LS-DYNA

2. launch LS-PrePost

3. File → Open → Binary Plot

4. open "\implicit\d3plot"

5. hold the Ctrl key and use the left mouse button to rotate the model to a suitable viewing

angle

6. FEM→Post→Fringe Component

7. select "von mises stress" from the list

8. click the Play button in the bottom panel

9. note the stress contour that develops due to the prescribed displacement load

Step 8: Compare stress values between explicit and implicit

runs

1. FEM →Post →ASCII

2. select "elout " from the list

3. click Load (loads "\implicit\elout")

4. select "Sh-1" and "Sh-2" from the middle list (hold down Ctrl for multiple select)

5. select "9-Effective Stress (v-m)" in the bottom list

6. click Main

7. click Plot

8. click File (located above the Load button in the side panel)

9. open "\explicit\elout"

10. select "Sh-1" and "Sh-2" from the middle list

11. select "9-Effective Stress (v-m)" in the bottom list

12. click PAdd

13. right-click Port1 in XY-plot Page Manager

14. click control

15. click icon of Set and change titles/axis labels

16. enter Plot Title: Implicit vs. Explicit Stress

17. enter Legend Title:Element id

18. enter X-Axes Label:Time\

19. enter Y-Axes Label:elout data

20. activate Modify Curve Legend

21. select "Sh-1 (ip=1)" and modify name to "implicit_sh1"(click Apply)

22. select "Sh-2 (ip=1)" and modify name to "implicit sh2"(click Apply)

23. select "Sh-1 Effective Stress (v-m) (ip=1)" and modify name to "explicit_sh1"(click Apply)

24. select "Sh-2 Effective Stress (v-m) (ip=1)" and modify name to "explicit_sh2"(click Apply)