【文章內(nèi)容簡介】 .Approach and Assumptions Assume the side of the wing connected to the plane is pletely fixed in all degrees of freedom. The wing is solid and material properties are constant and isotropic. Solid modeling is used to generate a 2D model of the crosssection of the wing. You then create a reasonable mesh and extrude the crosssection into a 3D solid model which will automatically be meshed. Additionally, the mesh used in this example will be fairly coarse for the element types used. This coarse mesh is used here so that this tutorial can be used with the ANSYS ED product. .Summary of Steps Use the information in this description and the steps below as a guideline in solving the problem on your own. Or, use the detailed interactive stepbystep solution by choosing the link for step 1. Input Geometry 1. Read in geometry input file. Back To Top Define Materials 2. Set preferences. 3. Define constant material properties. Back To Top Generate Mesh 4. Define element type. 5. Mesh the area. 6. Extrude the meshed area into a meshed volume. Back To Top Apply Loads 7. Unselect 2D elements. 8. Apply constraints to the model. Back To Top Obtain Solution 9. Specify analysis types and options. 10. Solve. Back To Top Review Results 11. List the natural frequencies. 12. Animate the five mode shapes. 13. Exit the ANSYS program. .Input Geometry .Step 1: Read in geometry input file. You will begin by reading in a file that includes the model. 1. Utility Menu File Read Input from ... 2. File name: UNIX version: /ansys_inc/v130/ansys/data/models/ PC version: \Program Files\Ansys Inc\V130\ANSYS\data\models\ 3. [OK] .Define Materials .Step 2: Set preferences. You will now set preferences in order to filter quantities that pertain to this discipline only. 1. Main Menu Preferences 2. (check) “Structural” 3. [OK] .Step 3: Define constant material properties. 1. Main Menu Preprocessor Material Props Material Models 2. (doubleclick) “Structural”, then “Linear”, then “Elastic”, then “Isotropic” 3. “EX” = 38000 4. “PRXY” = 5. [OK] 6. (doubleclick) “Density” 7. “DENS” = 8. [OK] 9. Material Exit .Generate Mesh .Step 4: Define element types. Define two element types: a 2D element and a 3D element. Mesh the wing crosssectional area with 2D elements, and then extrude the area to create a 3D volume. The mesh will be extruded along with the geometry so 3D elements will automatically be created in the volume. 1. Main Menu Preprocessor Element Type Add/Edit/Delete 2. [Add...] 3. “Structural Solid” (left column) 4. “Quad 4node 182” (right column) 5. [Apply] to choose the Quad 4 node ( PLANE182) 6. “Structural Solid” (left column) 7. “Brick 8node 185” (right column) 8. [OK] to choose the Brick 8 node ( SOLID185) 9. [Options] for Type2 SOLID185 10. Choose “Simple Enhanced Str” for the element technology. 11. [OK] 12. [CLOSE] 13. Toolbar: SAVE_DB .Step 5: Mesh the area. The next step is to specify mesh controls in order to obtain a particular mesh density. 1. Main Menu Preprocessor Meshing Mesh Tool 2. “Size Controls Global” = [Set] 3. “Element edge length” = 4. [OK] 5. [Mesh] 6. [Pick All] 7. [Close] Warning. 8. [Close] Meshtool 9. Toolbar: SAVE_DB In designing this problem, the maximum node limit of ANSYS ED was taken into consideration. That is why the 4node PLANE182 element, rather than the 8node PLANE183 element was used. Note that the mesh contains a PLANE182 triangle, which results in a warning. If you are not using ANSYS ED, you may use PLANE183 during the element definitions to avoid this message. Note: The mesh you see on your screen may vary slightly from the mesh shown above. As a result of this, you may see slightly different results during postprocessing. For a discussion of results accuracy, see Planning Your Approach in the Modeling and Meshing Guide. .Step 6: Extrude the meshed area into a meshed volume. In this step, the 3D volume is generated by first changing the element type to SOLID185, which is defined as element type 2, and then extruding the area into a volume. 1. Main Menu Preprocessor Modeling Operate Extrude Elem Ext Opts 2. (drop down) “Element type number” = 2 SOLID185 3. “No. Elem divs” = 10 4. [OK] 5. Main Menu Preprocessor Modeling Operate Extrude Areas By XYZ Offset 6. [Pick All] 7. “Offsets for extrusion” = 0, 0, 10 8. [OK] 9. [Close] Warning. Using SOLID185 to run this problem in ANSYS ED will generate the warning message. If ANSYS ED is not being used, then SOLID186 (20node brick) can be used as element type 2. Using PLANE183 and SOLID186 produces a warning message about shape warning limits for 10 out of 160 elements in the volume. 10. Utility Menu PlotCtrls Pan, Zoom, Rotate 11. [Iso] 12. [Close] 13. Toolbar: SAVE_DB .Apply Loads .Step 7: Unselect 2D elements. Before applying constraints to the fixed end of the wing, unselect all PLANE182 elements used in the 2D area mesh since they will not be used for the analysis. 1. Utility Menu Select Entities 2. (first drop down) “Elements” 3. (second drop down) “By Attributes” 4. (check) “Elem type num” 5. “Min,Max,Inc” = 1 6. (check) “Unselect” 7. [Apply] .Step 8: Apply constraints to the model. Constraints will be applied to all nodes located where the wing is fixed to the body. Select all nodes at z = 0, then apply the displacement constraints. 1. (first drop down) “Nodes” 2. (second drop down) “By Location” 3. (check) “Z coordinates” 4. “Min,Max” = 0 5. (check) “From Full” 6. [Apply] 7. Main Menu Preprocessor Loads Define Loads Apply Structural Displacement On Nodes 8. [Pick All] to pick all selected nodes. 9. “DOFs to be constrained” = All DOF 10. [OK] Note that by leaving “Displacement” blank, a default value of zero is u