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Double-Cantilevered Bar

Double-Cantilevered Bar. Estimated time for completion : ~20 min Experience Level : Lower. F. F. MSC.Patran 2005 r2. Topics Covered. Creating nodes with Cartesian coordinate system Making curve with two points Equivalence with tolerance cube to remove excessive nodes

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Double-Cantilevered Bar

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  1. Double-Cantilevered Bar Estimated time for completion: ~20 min Experience Level: Lower F F MSC.Patran 2005 r2

  2. Topics Covered • Creating nodes with Cartesian coordinate system • Making curve with two points • Equivalence with tolerance cube to remove excessive nodes • Applying fixed constraint at ends and constant force on a given node • Applying material & element properties • Analyzing the model • Attaching results file • Displaying results

  3. Problem Description • Three separate sections with different material properties & cross-sectional area • Right and left ends are cantilevered • Force of 9,000 Newtons is applied to both top and bottom of the center member (18,000 Newtons total) F 3 1 2 F

  4. Goal • Is any of the section going to yield given the load that is being applied? Yield Stress for Aluminum = 75.8 MPaYield Stress for Steel = 350 MPa • What is estimated magnitude of the maximum displacement for this model?

  5. Expected Results Displacement Fringe Plot Stress Tensor Fringe Plot Max. stress (x-direction) =4.23x107 Pa Min. stress (x-direction) = -1.08x107 Pa Max. Displacement = 1.54x10-5 m Min. Displacement = 0 m

  6. Starting MSC.Patran from Windows To start MSC.Patran from a windows computer you will have to: • Click on start menu • Roll mouse over All Programs • Roll mouse over MSC.Software • Roll mouse over MSC.Patran 2005 r2 • Click on MSC.Patran 2005 r2

  7. Database Creation a • Click File menu / Select New • Enter File Name: bar • Click OK. b c Note: MSC.Patran defaults the working folder to C:/windows/temp. Make sure the folder content is deleted before starting a new database.

  8. Database Settings for the Model • Select Default radio button: Based on Model. • Select Analysis Code to be MSC.Nastran from the drop down menu. • Select Analysis Type to be Structural from the drop down menu since the model that you are about rod elements. • Click OK. a b c d Remember: MSC.Patran does not handle units of measurement, so it is essential to remember to use one consistent system of measurement. In this example, SI units are used with the following measuring units: Input Output Length  meters Force  Newtons Elastic Modulus  Pa Mass  kg Displacement  meters Force  Newtons Stress  Pa

  9. Creating Points to Make Curves f a • Click on Geometryicon. • Select Action to Create / Object to Point / Method to XYZ. • Uncheck the Auto Execute. If checked, the command will execute without clicking on the apply button. • In the Point Coordinate List text field enter [0 0 0]. • Click Apply. • Click the Labels Control icon. • Click Point to show the number of each point. g b c d e

  10. Creating the Remaining Points to Make Curves • In Point Coordinate List text field enter [0.05 0 0] • Click on Apply • Repeat the above procedure with point [0.1 0 0] and then with[0.2 0 0]. a Note: The Curve ID List automatically updates after the successive curve is created. b

  11. Creating Curves by Connecting Two Points • Select Create / Curve / Point from the drop down menus. • From the Option drop down menu select 2 Point. • Uncheck Auto Execute. If checked, the command will execute without clicking on the apply button. • Click in the Starting Point List text field and click on Point 1 (which is the left furthest most point in the viewport window) • Click in the Ending Point List text field and select Point 2 which the point to the right. • Click Apply. a b c d e f Note: When Apply button is pressed, the curve list automatically updates to 2 so that the next curve can be created.

  12. Creating Remaining Curves by Connecting Two Points b • Repeat the procedure from the previous slide to create the two remaining curves by connecting points: 2 & 3 and 3 & 4. • From the Labels Windows click on Curve to see the labels for the curves.

  13. Using Mesh Seeds to Control Mesh Density A finite element “mesh” gets its name from the appearance of the elements connected together as shown in the figure on the right. Mesh seeds are “planted” on the geometry to specify the boundaries of elements. The examples below show how the number of elements in your model can be controlled by the location and number of mesh seeds used. Mesh Seeds ( ) Planted Mesh Seeds ( ) Planted 12 Elements Created 3 Elements Created 2 3 1 1 2 3 4 5 6 7 8 9 10 11 12

  14. Creating the Mesh Seed from Curves a The creation of a mesh seed is required to be able to create the mesh in the next few steps and be able to define the element type • Click on Elements icon. • Select Create / Mesh Seed / Uniform from the drop down menus. • Select Number of Element radio button and enter 1 in the Number text field. This will create each curve into one element • Make sure the Auto Execute checkbox is off. • Click on the Curve List text field. To select all 9 curves by click and dragging a square over the curves or type in Curve 1:3 • Click Apply. b c d e f Note: When Apply is button is pressed, the only change is the curves become orange

  15. Creating the Mesh Create the finite element mesh on the 3 curves you crated using the mesh seeds you just defined. a • Select Create / Mesh / Curve from the drop down menus. • Select Topology: Bar2. Note: Bar2 defines a linear displacement variation along the elements versus quadratic (Bar3) or cubic (Bar4) • Click in the Curve List textbox and Select all three curves. • Click Apply. b c d Note: When the Apply button is pressed, the only change you will see is that the lines turn yellow.

  16. Equivalence the Element Nodes Created Equivalencing is an extremely important, and often forgotten, step in the modeling process. When elements are created, nodes are also created at the element vertices and, in some cases, in-between the vertices as shown above For models with multiple elements, nodes co-exist at the same location where elements are adjacent. Lets take an example such as the illustration below: • 9 elements x 4 nodes per element = 36 nodes • Equivalencing deletes redundant nodes and ties the elements together through the sharing of common nodes • 9 elements  16 nodes (there was 20 redundant nodes that were deleted) 1 2 3 4 5 6 7 8 9

  17. Equivalencing the Nodes with Tolerance Cube • Select Equivalence / All / Tolerance Cube from the drop down menus. • In the Equivalencing Tolerance textbox enter 0.001. • Click Apply. • Note in the History Window 2 nodes have been eliminated. This is because each bar member has two nodes (one at each end). Since the bar element are connected at the joints only one node is needed, so the overlapping nodes gets removed. a b c d

  18. Creating Boundary Conditions of Fixed Support Ends a b • Click on Loads/BCs icon. • Select Create / Displacement / Nodal from the drop down menus. • Enter New Set Name to be RLClamp. • Select: Input Data • In the Translations <T1 T2 T3> text field enter <0 0 0>. This will constrain the <x y z> directions from any movement. • Click OK button. e c f d

  19. Creating Boundary Conditions of Fixed Support Ends • Select: Select Application Region • Select Geometry Filter: Geometry. • In the Picking Filter window click on Point or Vertex • In the Geometry Entities textbox click on Points 1 (left end of the model). • In the Selection Choice window click on Point 1. • Click Add. • Repeat steps (d) through (f) with the Point 4 (right end of the model). • Click OK. • Click Apply. b d f h a e c

  20. Creating Nodal Force Load Shortcut file provided with this procedure completed under “shortcut” folder • Select Create / Force / Nodal from the drop down menus. • In the New Set Name textbox enter axial. • Click on Input Data …button. • In the Force <F1 F2 F3> textbox enter <1.8e4 0 0> • Click OK button. • Cklick on Select Application Region .... Button. • Under Geometry filter choose the Geometry radio button. • Click on the Select Geometry Entities textbox and click on Point 3 (second node from the right). • In the Selection Choice Windows select Point 3. • Click Add. • Click OK. • Click Apply. g a d h j e b Point 3 Curve 2 Curve 3 k c f l i

  21. Summarizing Load/BCs • Both ends have the x,y,z direction constrained as illustrated by 1,2,3 • The force is being applied to point 3 and to the positive x-direction. Note: At this point it would be a good time to save the database. Go to File menu and Save. If your model does not look as illustrated to the right you may want to go back and re-do the steps or read in the shortcut files provided. To read in the shortcut files, close the current database file by clicking on File menu and Close. Then go to the default file and erase all the files there. Copy the files provided as a shortcut to that folder. To load such files, go to File menu and Open. Double click on the file named bar.db. a b a

  22. Creating Material Properties for Steel a • Click on Materials icon. • Select Create / Isotropic / Manual Input from the drop down menus. • In the Material Name text field enter Steel. • Click on Input Properties …button. • From the Constitutive Model select Linear Elastic from the drop down menu. • For Elastic Modulus text field enter 2.0e11 • For Poisson Ratio text field enter 0.3. • Click OK button. • Click Apply button. b e f g c d h i

  23. Creating Material Properties for Aluminum a d • Select Create / Isotropic / Manual Input from the drop down menus. • In the Material Name text field enter Aluminum. • Click on Input Properties …button. • From the Constitutive Model select Linear Elastic from the drop down menu. • For Elastic Modulus text field enter 7.0e10 • For Poisson Ratio text field enter 0.3. • Click OK. • Click Apply. e f b g c h

  24. Applying Material Properties to Bar 1 a • Click on Properties icon. • Select Create / 1D / Rod from the drop down menu • In the Property Name text field enter bar1. • Click on Input Properties … button. • Click the Mat Prop Name button. • Select Steel for the material for bar1. • In the Area text field enter 4e-4. • Click OK button. • Select Members: Select the left most curve (Curve 1). • Click Add button. • Click Apply button. b e g f c d h i j k

  25. Applying Material Properties to Bar 2 d a • Select Create / 1D / Rod from the drop down menu • In the Property Name text field enter bar2. • Click on Input Properties … button. • Click the Mat Prop Name button. • Select Aluminum for the material for bar2. • In the Area text field enter 2.5e-3. • Click OK button. • Select Members: Select the center curve (Curve 2). • Click Add button. • Click Apply button. f e b g c h i j

  26. Applying Material Properties to Bar 3 d a • Select Create / 1D / Rod from the drop down menu • In the Property Name text field enter bar3. • Click on Input Properties … button. • Click the Mat Prop Name button. • Select Aluminum for the material for bar3. • In the Area text field enter 1e-4. • Click OK button. • Select Members: Select the right most curve (Curve 3). • Click Add button. • Click Apply button. f e b g c h i j

  27. Running the Model in Nastran a d • Click on Analysis icon. • Select Analyze / Entire Model / Full Run from the drop down menus. • Click on Translation Parameters… button. • Make sure the checkbox for XDB is ON and Print is OFF. The remaining options are left at as default. • Click OK button. • Click on Solution Type … button. • Make sure that Linear Static radio button is on. • Click OK. • Click Apply. b g c h f i Note: When the model finishes running, you will hear your computer do a double beep e

  28. Loading Output Results File from Nastran a • Select Access Results/Attach XDB / Results Entities from the drop down menus. • Click on Select Results File … button. • Click bar.xdb. • Click OK button. • Click Apply button. c d b e

  29. Displaying Displacement Fringe Plot a • Click on Results icon • Select Create / Quick Plot from drop down menus. • Under Select Results Cases click on DEFAULT, A1:Static Subcase. • Under Select Fringe Result click on Displacements, Translational. • In the Quantity drop down menu select Magnitude. • Under Select Deformation Result click on Displacements, Translational. • Click Apply button. b c d e f Note: Maximum and Minimum values are displayed here. g

  30. Displaying Stress Fringe Plot • Under Select Fringe Result click on Stress Tensor. • From the Quantity drop down menu select von Mises. • Under Select Deformation Result click on Displacements, Translational. • Click Apply button. a b c d

  31. Outcomes • Maximum stress occurs at node 1 with a value of 4.23x107Pa. • Minimum stress occurs at node 6 with a value of -1.08x107 Pa. • Maximum displacement occurs at node 4 with a value of 1.5x10-5 m. • Minimum displacement occurs at node 1 with a value of 0 m.

  32. Important Skills Acquired • Creating nodes with Cartesian coordinate system • Making curve by connecting two points • Equivalence with tolerance cube to remove excessive nodes • Applying fixed constraint at ends and constant force on a given node • Applying material & element properties • Analyzing the model • Attaching results file • Displaying results

  33. Further Analysis (Optional) • Would the stresses and displacement be the same if the force were to be applied in the opposite direction (negative x-direction)? • What would happen to the stresses and displacement if the far end corners were only constrained in the x-direction?

  34. Best Practices • Always remember to do a equivalence with the tolerance cube of your model to remove excess nodes in the mesh • Remember to be consistent with the system and unit of measurement through out the analysis • Remember to attach the result files so that post processing procedures can be achieved • Name loads, boundary conditions, and properties with useful labels. Avoid labels that have spaces in their names to avoid problems. Use “_” when a space is needed • Start each finite element analysis on a new folder that is empty to avoid any confusion of files while working on the model

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