Frequency response analysis of plate using Nastran Sol108

Direct frequency response analysis using Nastran Sol 108 sequence

1. Use the direct frequency response method and determine the frequency response of the flat rectangular plate, subject to 1N (Unit load) load in Z direction at one corner with the exciting frequency-varying in the range of 1Hz to 1000Hz in the step of 1Hz. Use structural damping of g=0.06 Direct Frequency Response ( Nastran SOL 108) FE Model of Plate 100x100x2mm thick Material Steel:- E- 2.0E 5 N/mm 2 , Density = 7.8E -9 tonnes /mm 3 , mu=0.3 Excitation at one end (Node no. 3) One end of plate fixed in ALL DOF)

2. SOL 108 CEND TITLE = FREQUENCY RESPONSE DUE TO UNIT FORCE AT TIP ECHO = NONE SPC = 1 SET 111 = 3, 27, 95, 106 DISPLACEMENT(SORT2, PRINT,PUNCH, PHASE) = 111 SUBCASE 1 DLOAD = 500 FREQUENCY = 100 $ BEGIN BULK param,post,-2 PARAM, K6ROT, 100.0 $ INCLUDE 'plate.dat' $ $ $ SPECIFY STRUCTURAL DAMPING $ PARAM, G, 0.06 PARAM, POST, -2 $ $ APPLY UNIT FORCE AT TIP POINT $ RLOAD2 , 500 , 600 , , , 310 $ DAREA, 600 , 3, 3, 1.0 $ TABLED1, 310, , 0., 1., 1000., 1., ENDT $ $ SPECIFY FREQUENCY STEPS $ FREQ1, 100 , 1.0, 1.0, 1000 $ ENDDATA

3. DLOAD = 500 RLOAD2 , 500 , 600 , , , 310, LOAD DAREA, 600 , 3, 3, 1.0 TABLED1, 310, Dynamic Load Set Selection Frequency Response Dynamic Excitation, Load Scale factor

4. The created loadcol is set as current loadcollector Create load collector

5. Applying Constraints From analysis page menu click on constraints

6. Select nodes for fixing the plate at one end Load type – SPC (Single Point Constraints) Set loadcol as fix

7. The created loadcol is set as current loadcollector Create load collector For applying 1N Load at one end of plate

8. 1N load is applied in Z direction at Node no. 3 Node-3 From Analysis Page select Constraints Apply 1N load in Z direction. Uncheck dof1,2,4,5,6 Load types = DAREA

9. The created loadcol is set as current loadcollector Create load collector For defining frequency range of 1Hz to 1000 Hz Card image = FREQi

10. Define frequency range

11. FREQ1 Frequency List, Alternate Form 1

12. FREQ2 Frequency List, Alternate Form 2

13. The created loadcol is set as current loadcollector Create load collector For defining the table Card image = TABLED1

14. Fill the values in the table

15. TABLED1 Dynamic Load Tabular Function, Form 1

16. TABLED1 Dynamic Load Tabular Function, Form 1

17. Card image = RLOAD2 The created loadcol is set as current loadcollector Create load collector For defining the excitation

18. This box appears after clicking on EXCITED, TB Provide Inputs to RLOAD2 Card as shown below

19. RLOAD1 Frequency Response Dynamic Excitation, Form 1

20. RLOAD1 Frequency Response Dynamic Excitation, Form 1

21. RLOAD1 Frequency Response Dynamic Excitation, Form 1

22. RLOAD2 Frequency Response Dynamic Excitation, Form 2

23. RLOAD2 Frequency Response Dynamic Excitation, Form 2

24. Open the exported file

25. Damping in Direct Frequency Response Damping simulates the energy dissipation characteristics of a structure. Damping in direct frequency response is represented by the damping matrix and additions to the stiffness matrix . The damping matrix is comprised of several matrices

26. sol108_combine_deck.dat

27. sol108_combine_deck.dat

28. Create Node Sets For Plotting the Responses From analysis page menu click on entity sets

29. Create Node Sets For Plotting the Responses Enter name= node_set , car image = SET Select nodes 3,27,95,106 to create a set

30. Create Loadstep from Analysis Page Menu Click create then edit for output requests Specify RLOAD2 loadcol no.

31. Select the Output requests as shown below

32. DAREA Load Scale Factor

33. Scroll to select the parameters This parameter defines the damping. Damping (zeta)is 3% , hence G=2*zeta=0.06

34. Submit Nastran Run Click On the Shortcut to open the file. Select the file In command Info window Type SCR=YES OLD=NO Following files will be created after run completion

35. In Hypermesh From Applications menu Select HyperView In Hyperview Select Hypergraph Click here to see the options

36. Hypergraph Window Used For Plotting the Responses

37. 1. Click Build Plots 2. Click Open to select the . pch file

38. Plot Response At Node-3 in ‘Z’-Direction Select the options highlighted in blue color

39. Plot Response At Node-3,27,95,106 in ‘Z’-Direction Select the options highlighted in blue color Peak Responses are observed corressponding to Natural Frequncies of the Plate. Refer next slide for Natural frequencies & mode shapes of palte Peak Response

40. Plot Response At Node-3 in ‘Z’-Direction With Damping ‘0.0’ Change the PARAM, G value to 0.0 & rerun the model Plot the response of the plate and compare responses with & without damping STUDY

41. Various Mode Shapes Of Rectangular Plate 1 st Frequency – 168.5 Hz 2 nd Frequency – 407 Hz 3 rd Frequency – 1017 Hz 4 th Frequency – 1279 Hz

42. Stress Plot Of Rectangular Plate At 168.0 Hz Frequency With PARAM,G,0.06 With PARAM,G,0.0

43. Stress Plot Of Rectangular Plate At 407.0 Hz Frequency With PARAM,G,0.06 With PARAM,G,0.0