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1、WORKSHOP 1 3- BAR TRUSS OPTIMIZATION SUBJECT TO STATIC LOADING,Design Model Description Objective Function: Weight minimization Design Variables: Cross-sectional area A1 and A2 Constraints: Stress Allowable: 20 ksi tension 15 ksi compression Displacement at grid 4:X direction 0.2 in Y direction 0.2
2、in,Suggested Exercise Steps Open a new database and call it wkshp1.db. Turn on all the labels and select front view. Create new nodes for the model. Create bar elements from the previous nodes Make a new material called alum and sets its properties. Create a 1-D rod with property set named prop_1 an
3、d sets its material property to alum with area of 1. Create another 1-D rod with property set named prop_2 and sets its material property to alum with area of 2. Under Loads/BCs, create a new nodal displacement called disp_1 and sets its translation and rotation parameters. Create another nodal disp
4、lacement called disp_2 and sets its parameters. Create a nodal force called force_1 and sets its force property and application region. Create another force called force_2 and sets its force properties and application region. Create a load case called case_1 and sets its properties. Create another l
5、oad case called case_2 and sets its displacement and force properties. Create design variables using 1-D rod with prop_1 and prop_2 and associated areas. Create design objective from the design study pre-processing tools. Create design constraints on X displacement, Y displacement, and axial stress.
6、,Suggested Exercise Steps Create a design study called opt_1 by including design variables, objectives and constraints. Review the design study contents using the Design Study Summary option. Create an input file for optimization Set necessary parameters. Select the existing design study and global
7、objective. Create the subcases by including desired constraints. Select subcase for the job. Generate the analysis Bulk Data file: wkshp1.bdf Compare wkshp1.bdf with the sample input file. Compare wkshp1.bdf with the sample input file (contd). Compare wkshp1.bdf with the sample intput file (contd).
8、Submit the wkshp1.bdf for Nastran analysis and check for errors. Compare the results with the sample output. In Patran, read the result file using Nastrans generated file, wkshp1.op2. Plot the Design Variable History on the XY plot. Plot the Objective Function History on the XY plot. Plot the Maximu
9、m Constraint History on the XY plot. Quit MSC.Patran.,Figure 1.2 Constraints and Applied Forces (Case 1),Figure 1.3 Constraints and Applied Forces (Case 2),Figure 1.1 Geometry and Finite Elements,Table 1.1 Material Properties,Step 1. Create a New Database,Open database. File / New. Enter wkshp1 for
10、File Name. Click OK. Under New Model Preferences, select Based on Model Tolerance. Select MSC.NASTRAN for Analysis Code. Select Structural for Analysis Type. OK.,a,Step 2. Show All Labels,Show labels and change the view to front view. Show all entity labels Front view Whenever possible, deselect Aut
11、o Execute option.,b,a,Step 3. Create New Nodes,Create new nodes Elements Create/Node/Edit Deselect Associate with Geometry Enter -10 0 0 for Node Location List Apply Repeat the same steps a c with 0 0 0 for Node Location List and click Apply Repeat the same steps a c with 10 0 0 for Node Location Li
12、st and click Apply Repeat the same steps a c with 0 -10 0 for Node Location List and click Apply,b,c,d,e,z,a,Step 4. Create bars,Create bars Elements Create/Element/Edit Select Bar for Shape Select Node 1 from the viewport for Node 1 = Enter Node 4 from the viewport for Node 2 = Apply Repeat steps a
13、 c with: Node 2 for Node 1 = Node 4 for Node 2 = and click Apply. Repeat steps a c with: Node 3 for Node 1 = Node 4 for Node 2 = and click Apply.,z,b,c,e,d,f,a,Step 5. Create and Define the Materials properties,Define a material using the specified modulus of elasticity and allowable stresses. Mater
14、ials Create/Isotropic/Manual Input Enter alum for Material Name Input Properties Enter 10e6 for Elastic Modulus = Enter 0.3 for Poisson Ratio = Enter 0.1 for Density = OK Apply,b,c,d,e,f,g,h,i,a,Step 6. Create a 1-D Rod and Set its Properties,Create a 1D rod with aluminum properties. Properties Crea
15、te/1D/Rod Enter prop_1 for Property Set Name Input Properties Select alum in the Select Material databox for Material Name. Enter 1 for Area OK For Select Members, click on Beam Element icon and select rod elements 1 and 3 from the view port. Add j.Apply,e,f,g,a,Step 7. Create another Rod and Set it
16、s Properties,Create another property with the new input properties. Properties Create/1D/Rod Enter prop_2 for Property Set Name Input Properties Select alum in the Select Material databox for Material Name. Enter 2 for the Area OK For Select Members, click on Beam Element icon and select Elm 2 for S
17、elect Members Add j.Apply,b,c,d,h,i,j,e,f,g,a,Step 8. Create a Load/BC,Create a nodal displacement called disp_1. Loads/BCs Create / Displacement / Nodal. Enter disp_1 for New Set Name Input Data Enter for Translations Enter for Rotations OK Select Application Regions Select FEM under Geometry Filte
18、r Drag the mouse to select Node 1, Node 2, and Node 3 from the viewport for Select Nodes Add OK Apply,m,l,k,j,i,h,g,f,e,d,c,b,a,Step 9. Create a Load/BC (Cont.),Create another nodal displacement called disp_2. Loads/BCs Create / Displacement / Nodal. Enter disp_2 for New Set Name Input Data Enter fo
19、r Translations Enter for Rotations OK Select Application Regions Select FEM under Geometry Filter Select Node 4 from the viewport for Select Nodes Add OK Apply,m,l,k,j,i,h,g,f,e,d,c,b,a,Step 10. Apply Forces on X and Y,Create a new nodal force called force_1. Loads/BCs Create/Force/Nodal Enter force
20、_1 for New Set Name Input Data Enter for Force OK Select Application Region Select FEM under Geometry Filter Select Node 4 from the viewport for Select Nodes Add OK Apply,k,j,i,h,g,f,e,d,c,b,l,a,Step 11. Apply Forces on X and Y (Cont.),Create another nodal force called force_2. Loads/BCs Create/Forc
21、e/Nodal Enter force_2 for New Set Name Input Data Enter for Force OK Select Application Region Select FEM under Geometry Filter Select Node 4 from the viewport for Select Nodes Add OK Apply,k,j,i,h,g,f,e,d,c,b,l,a,Step 12. Create Load Cases,Create a new Load Case called case_1. Load Cases. Create En
22、ter case_1 as Load Case Name Input Data Under Select Individual Loads/BCs databox, select Displ_disp_1 Displ_disp_2 Force_force_1 OK Apply,g,f,e,d,c,b,a,Step 13. Create Load Cases (Cont.),Create another Load Case called case_2. Load Cases. Create Enter case_2 as Load Case Name Input Data Under Selec
23、t Individual Loads/BCs databox, select Displ_disp_1 Displ_disp_2 Force_force_2 OK Apply,Note: The viewport stays the same.,g,f,e,d,c,b,a,Step 14. Create Design Variable from Tools,Use Tools to create the Design Variables for the model. Tools/Design Study/Pre-Process Create/Design Variable/Property S
24、elect 1D for Dimensions Select Rod for Type Select prop_1 from Select Property Set databox Select Area from Select Property Name databox Apply,a,g,f,e,d,c,b,Step 14a. Create Design Variable from Tools (Cont.),g,f,e,d,c,b,Use Tools to create the Design Variables for the model. Tools/Design Study/Pre-
25、Process Create/Design Variable/Property Select 1D for Dimensions Select Rod for Type Select prop_2 from Select Property Set databox Select Area from Select Property Name databox Apply Close,h,a,Step 15. Create Design Objective from Tools,Create Objective for the Design Study. Tools/Design Study/Pre-
26、Process Create / Objective Select Global as the Solution. Select Weight as the Response. Enter Total_Weight as the Objective Name Select minimize under Min/Max selection box. Apply,e,d,c,b,f,g,a,Step 16. Create Design Constraints from Tools (Cont.),Create Design Constraints for the Design Study Tool
27、s/Design Study/Pre-Process Create /Constraint DISP_1 for Constraint Name Select Node 4 for Select Node Select TX option under Displacement Component Enter 0.2 for Lower Bound Enter 0.2 for Upper Bound Apply DISP_2 for Constraint Name Select Node 4 for Select Node Select TY option under Displacement
28、Component Enter 0.2 for Lower Bound Enter 0.2 for Upper Bound Apply,a,h,f,d,c,b,i,g,j,k,l,m,e,n,Step 16a. Create Design Constraints from Tools (Cont.),Create Stress Constraints for the Design Study Tools/Design Study/Pre-Process Create/Constraint Select Stress for the Response. STRESS_1 for Constrai
29、nt Name Select FEM under Constraint Region Select 1D Select Rod Under Select Finite Element, drag your mouse to select Element 1, Element 2, and Element 3 from the viewport For Select Component, select Axial Enter 15000 for Lower Bound input box. Enter 20000 for Upper Bound input box Apply,a,g,f,e,d
30、,c,b,i,h,j,k,l,Step 17. Create Design Study from Tools,Create Design Study and set its properties. Tools/Design Study/Pre-Process Create / Design Study Enter opt_1 for Design Study Name Select Design Variables For prop_1_Area, enter 0.1 under Lower Bound and press Enter, and 100 under Upper Bound an
31、d press Enter for For prop_2_Area, enter 0.1 under Lower Bound and press Enter, and 100 under Upper Bound and press Enter for OK Select Objective Select Total_Weight for the study Close Select Constraints Select desired constraints (all of them for this study). Close Apply,f,e,d,c,b,a,g,i,j,l,n,m,h,
32、k,Step 18. Design Study Summary From Tools,Review contents in a Design Study. Tools/Design Study/Pre-Process Summary / Design Study Select opt_1 from Design Study Listbox Review various contents of the design study. Close,d,c,b,a,e,Step 19a. Create an Input File for Analysis Translation Parameters,G
33、enerate an input file and sets its parameters for analysis. Analysis Optimize/Entire Model/Analysis Deck Enter wkshp1 for Job Name Translation Parameters For Data Output, select OP2 and Print For MSC.Nastran Version, enter 2005 OK,a,g,f,e,d,c,b,Step 19b. Create an Input File for Analysis Optimizatio
34、n Parameters,Generate an input file and set its parameters for analysis (Cont.) Optimization Parameters Enter 10 for Maximum Number of Standard Design Cycles (DESMAX) = Enter 1 for Print Design Data (P1) every n-th cycle where n= Enter 1 for Print Analysis Results(NASPRT) every n-th cycle where n =
35、OK,a,e,d,c,b,Step 20a. Create an Input File for Analysis Design Study Select,a,b,Select the Design Study Design Study Select Select opt_1,Step 20b. Create an Input File for Analysis Global Objective Select,a,c,b,Select a Global Objective Global Objective Select Select Total_Weight,Step 21a. Create a
36、n Input File for Analysis Subcase Create,Select constraints Subcases Select case_1 from the Available Subcases Select Constraints/Objective Select Constraints Select all of the existing constraints. OK Apply Select case_2 from the Available Subcases Repeat steps c.-g. for case_2. Cancel,a,d,c,b,f,e,
37、g,h,i,j,Step 21b. Create an Input File for Analysis Subcase Select,Generate an input file and sets its parameters for analysis Subcase Select Select 101 LINEAR STATIC for Solution Type Under Subcases Available, select case_1 and case_2 OK Apply An MSC.Nastran input file called wkshp1.bdf will be gen
38、erated. This process of translating your model into an input file is called the Forward Translation. The Forward Translation is complete when the Heartbeat turns green. MSC.Nastran users should proceed to the next step.,a,e,d,c,b,e,Step 22. Generated Input File,Look for the generated input file name
39、d wkshp1.bdf. It should be similar to the output below.,SOL 200 TIME 600 $ Direct Text Input for Executive Control CEND TITLE = MSC.Nastran job created on 25-Apr-05 at 13:06:35 ECHO = NONE MAXLINES = 999999999 DESOBJ(MIN) = 1 ANALYSIS = STATICS $ Direct Text Input for Global Case Control Data SUBCAS
40、E 1 $ Subcase name : case_1 SUBTITLE=case_1 SPC = 2 LOAD = 2 DISPLACEMENT(SORT1,REAL)=ALL SPCFORCES(SORT1,REAL)=ALL STRESS(SORT1,REAL,VONMISES,BILIN)=ALL DESSUB = 21 $ Direct Text Input for this Subcase SUBCASE 2 $ Subcase name : case_2 SUBTITLE=case_2 SPC = 2 LOAD = 4 DISPLACEMENT(SORT1,REAL)=ALL S
41、PCFORCES(SORT1,REAL)=ALL STRESS(SORT1,REAL,VONMISES,BILIN)=ALL DESSUB = 22 $ Direct Text Input for this Subcase BEGIN BULK PARAM POST -1 PARAM PRTMAXIM YES PARAM NASPRT 1 $ Direct Text Input for Bulk Data $ Elements and Element Properties for region : prop_1 PROD 1 1 1.,Step 23. Generated Input File
42、 (Cont.),$ Pset: prop_1 will be imported as: prod.1 CROD 1 1 1 4 CROD 3 1 3 4 $ Elements and Element Properties for region : prop_2 PROD 2 1 2. $ Pset: prop_2 will be imported as: prod.2 CROD 2 2 2 4 $ Referenced Material Records $ Material Record : alum $ Description of Material : Date: 25-Apr-05 T
43、ime: 08:32:04 MAT1 1 1.+7 .3 .101 $ Nodes of the Entire Model GRID 1 -10. 0. 0. GRID 2 0. 0. 0. GRID 3 10. 0. 0. GRID 4 0. -10. 0. $ Loads for Load Case : case_1 SPCADD 2 4 6 LOAD 2 1. 1. 1 $ Displacement Constraints of Load Set : disp_1 SPC1 4 123456 1 2 3 $ Displacement Constraints of Load Set : d
44、isp_2 SPC1 6 3456 4 $ Loads for Load Case : case_2 LOAD 4 1. 1. 3 $ Nodal Forces of Load Set : force_1 FORCE 1 4 0 20000. -.8 -.6 0. $ Nodal Forces of Load Set : force_2 FORCE 3 4 0 20000. .8 -.6 0. $ Referenced Coordinate Frames $ .DESIGN VARIABLE DEFINITION $ prop_1_Area DESVAR 1 prop_1:11. .1 100
45、. 1. $ prop_2_Area DESVAR 2 prop_2:22. .1 100. 1. $ .DEFINITION OF DESIGN VARIABLE TO ANALYSIS MODEL PARAMETER RELATIONS DVPREL1 1 PROD 1 A 1 1. DVPREL1 2 PROD 2 A 2 1.,Step 24. Generated Input File (Cont.),$ .STRUCTURAL RESPONSE IDENTIFICATION DRESP1 1 W WEIGHT $ DCONADD21 DCONADD 21 1 2 3 $ DCONAD
46、D22 DCONADD 22 1 2 3 $ DISP_1 DRESP1 2 DIS2 DISP 1 4 $ DISP_2 DRESP1 3 DIS3 DISP 2 4 $ STRESS_1 DRESP1 4 STR4 STRESS ELEM 2 1 2 3 $ .CONSTRAINTS DCONSTR 1 2 -.2 .2 DCONSTR 2 3 -.2 .2 DCONSTR 3 4 -15000. 20000. $ .OPTIMIZATION CONTROL DOPTPRM DESMAX 10 FSDMAX 0 P1 1 P2 1 CONV1 .001 CONV2 1.-20 CONVDV
47、 .001 CONVPR .01 DELP .2 DELX 1. DPMIN .01 DXMIN .05 ENDDATA 3951b41d,Step 25. Submit the Model to Nastran for Analysis,If you have MSC.NASTRAN on your Network, you can submit the wkshp1.bdf for analysis. Open MSC.NASTRAN. Find and Open wkshp1.bdf . Open. Run. Check for fatal errors by opening up wk
48、shp1.f06 file as a text document and searching for the word FATAL. If no fatal errors exist, then the analysis completed successfully. If no matches exist, search for the word WARNING. Determine whether existing WARNING messages indicate modeling errors.,a,c,b,Step 26. View Results in the f06 File (Cont.),* S U M M A R Y O F D E S I G N C Y C L E H I S T O R Y * (HARD CONVERGENCE ACHIEVED) NUMBER OF FINITE ELEMENT ANALYSES COMPLETED 7 NUMBER OF OPTIMIZATIONS W.R.T. APPROXIMATE MODELS 6 OBJECTIVE AND MAXIMUM CONSTRAINT HISTORY -