TUTORIAL 1 LS-DYNA MODEL PREPARATION

1. TUTORIAL 1LS-DYNA MODEL PREPARATION

3. Note: As in the other tutorials, all menu items that need to be selected will be preceded by a maroon right arrow: >User action. Mouse buttons are indicated as follows: -- 1B = First (left) button -- used for selecting items-- 2B = Second (middle) button -- used for "OK"-- 3B = Third (right) button -- used for View Manipulation & pop-up menusNormally 1B is used, unless otherwise. Table Of Contents SectionPage Step1. Import Nastran Deck. 3 Step2. Check Model Statistics. 4 Step3. Modify Part. . 5 Step4. Modify Material Properties. 6 Step5. Create X-Y Plots. 7 Step6 . Import X-Y Plots. 8 Step7 . Penetration checking. 9 Step8 . Penetration Fixing. 10 Step9 . Quality Check On Element Length Criteria. 11 Step10. Fix the element lengths . 12 Step11. Delete un-needed entities from Nastran model. 13 Step12. Change Units. 14

4. Step1. Import Nastran Deck. • Launch MSC.SOFY according to your local configuration. • Select >LS-DYNA mode from entry screen. • You'll be importing and converting a Nastran deck. • First, set the units to match the file being imported: - Select >Options menu >Units Mgr. • In the Units Manager dialog box :- Select >Standard Units button >which brings up another pop-up with several choices of units. • Choose >NASTRAN (without WTMASS card) >OK. • Check that the derived units are appropriate, as well. • For example, you should choose >N-mm for torque to maintain a consistent set of units. • When finished, >Exit the dialog box. • Now to import the NASTRAN deck,:- Select >File menu >Import >NASTRAN. • In the dialog box "Select Nastran file to merge" navigate to the file .../DEMOS/Tutorials_NASTRAN/Tut_N-1_floor.nas and then >Open. • Watch the message area at the bottom for any error messages. • When complete, a text editor window should pop up with a file "MSC.SOFY.err" showing any Nastran cards which failed to convert to LS-Dyna. • You should have the following model on the canvas. n f

5. Only entities currently displayed are included in the Statistics Step2. Check Model Statistics. b Find out some statistics about the model • Select >Statistics icon from tool bar. • An information panel comes up with the statistics about the current scene, such as number of parts, number of elements, and so on. • The Nastran material cards were all converted to type 024 Piecewise Linear Plasticity and all RBE2 rigids were converted to Nodal Rigid Body elements. a

6. Step3. Modify Part. Let's examine and modify some of the parts in the model. • From Collection block> Type> Part should already be displayed. • Click with >3B over the part name: >PNL_RR_FLR • Then from the pop-up> select >Modify. • In the Modify Part dialog, if you hover your mouse over each field, its description appears at the bottom. • In some cases you can double-click on the field to Select / Modify/Create. d c

7. Step4. Modify Material Properties. b • Double click in >MID (Material ID) > select >Modify. • Another dialog opens with the card image of the 024 MAT card. • You can type in any field to replace the values shown, or again, in some fields you can double-click to Select / Modify / Create. • Double-click in >LCSS field (Load Curve, Stress-Strain) • Select >Create. • Choose >DEFINE_CURVE from the next pop-up and >OK. f

8. Step5. Create X-Y Plots. • The MSC.SOFY Grapher is now launched. • You can enter in X-Y pairs of data on the right side, or select points graphically, as follows: From >View >Set Range. • Enter in an appropriate min/ max range of Stress & strain values. • Then to define the curve Edit >Current Curve >Add Point. • Define graph points with the mouse on the graph. • Click> Modify then >Exit the panel. b f

9. Step6. Import X-Y Plots. b • If you have existing Load Curves, you can import them by Click >File Open icon in the MSC.SOFY Grapher window. • Browse to the location of your x-y plot file (*.plt) • Click >Open. • In this fashion, you can do multi-level traversing through card images. • Alternatively, you can access Materials, Load curves, etc. from the Collection block. • Click >Type >Material. • For example. Right-click (>3B) over any material on the list to access the Modify panel, as above. • Click >3B over the list area also gives you the opportunity to >Create new materials. • Change >Type to >Load Curves to access and Modify the Load curve you created in above.

10. Step7. Penetration Checking. e b Let's check and fix penetration between parts. • From top menu bar >Modules> select >Penet.>Check. • In Pick block> click drop-arrow> pick >Among Picked Parts. • Now from the canvas, select the floor panel, >PNL_RR_FLR and the >xsill_rr . • Confirm with >2B. • The elements which have penetration are saved in a Set, and a Collection block clone pops up. • Click >3B over one of the Sets gives you a choice to Highlight the elements. or • Select >Equal to keep only those elements in the display. f

11. Step8. Penetration Fixing. d To view and change options for penetration fixing • Select >Modules >Penet >Set Options. (Also available from >Param button in Pick block.) • These options set maximum movement allowed (% of part thickness) at the part, surface, and local levels. • Accept the default values >click >OK. • Now to fix the penetration, Select >Modules >Penet >Fix • Pick the same two parts as before.(>PNL_RR_FLR and >xsill_rr .) • Click >Done. • The message are will indicate if the penetration is fixed. g

12. Step9. Quality Check On Element Length Criteria. d e In LS-Dyna analysis you may want to control the minimum length of shell elements. Let's perform a quality check, focusing on the element length criterion. • From >Element menu>select >Quality >Check Quality. • This opens up a Quality check form. • Disable (un-check) all element and model checks, except for >Length Degeneracy (collapsed elements), and >Element Length. • Set Minimum Length Dengeracy at >1.0. • For Element Length set Min at >3.0, Max at >35, and Ideal at >10. • At bottom of form click >More Options. • On right side, set Minimum Good at >4 and Maximum Good at >25. • At bottom, check the box >Output File? • Click >Apply >OK. • A text editor window pops up with the file quality.out, showing all elements which failed the quality check. • Close the window, and note that the elements are also highlighted on the canvas. g j

13. Step10. Fix The Element Lengths. Now to fix the element lengths: • In Collection block >Select>Type >Set. • Click with >3B over the set >Elem. Length • Click >Equal. • This leaves only the failed elements on the canvas. • Click the >Grow Mesh icon a few times to bring up the surrounding elements. • Now go to >Element >Quality >Enhance Quality. • In Pick block> click >Disp to select the displayed elements, • Click >Done. • In the Quality Enhancer Dialog, accept the default values >click >Enhance. • After the quality enhancement is complete another pop-up summarizes the results. • Most likely all elements are not fixed on the first pass, although in this case over 90% were fixed. • It may be useful to add more element checks to the Quality Check form and re-execute the Quality Check and Enhance steps.

14. Step11. Delete Un-Needed Entities From Nastran Model. b Delete some un-needed entities that were imported with the Nastran deck. • In Collection Block>Select>Type to >BC Sets. (Boundary Condition sets). • Click >All On button. • Now go to >Edit menu >Delete FEM. • In Pick block there are several entity types to select from. • To delete all the Loads and Constraints from NASTRAN, Select >BC Sets. • Click >All and >Done.

15. Step12.Change Units. You can change the units to your own preference. • From >File menu> select >Units Mgr. • Click on the >Standard Units button. • From the pop-up> select >Crash units • Click >OK. • Now >Exit the Units Manager . • Save the file as a SOFY database: File >Save As and enter in a file name: >floor_dyna.sof into the appropriate directory. • Click >Save. Exit MSC.SOFY: >File >Quit. c Congratulations!!! You have just completed LS-Dyna Tutorial 1.