Workshop D Structural Analysis. Workbench - Mechanical Introduction 12.0 WS ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved.

Transcription

1 Workbench - Mechanical Introduction 12.0 Workshop 4.2 2D Structural Analysis WS4.2-1

2 Workshop Goals Workshop 4.2 consists of a 2 part assembly representing a pressure cap and retaining flange (full model shown below). We will solve it as a 2D axisymmetric model (shown on next page). Pressure Cap Retaining Ring Full Model WS4.2-2

3 Workshop 4.2 Assumptions 2D axisymmetric model assumptions: The retaining ring is fixed at its mounting holes. The contact region between the parts is frictionless. The base of the pressure cap is constrained using a compression only support. Note: due to the presence of the bolt holes the structure is not truly axisymmetric. Pressure Cap Retaining Ring WS4.2-3

4 ... Workshop 4.2 Project Schematic Open the Project page. From the Units menu verify: Project units are set to Metric (kg, mm, s, C, ma, mv). Display Values in Project Units is checked (on). WS4.2-4

5 Workshop 4.2 Project Schematic 1. Double click Static Structural analysis type to add a new system RMB the Geometry cell and request Properties. 2 WS4.2-5

6 Workshop Project Schematic 3. In the Analysis Type field specify 2D. Once this setting is made the properties window may be closed if desired. Note this setting indicates the model to be analyzed is not a full 3D model but represents a symmetry section. It is important that this is set prior to importing geometry as this setting cannot be changed after the import. 3 WS4.2-6

7 Workshop Project Schematic 4. Double click the Engineering Data cell to add material properties With the General Materials library highlighted choose the + next to Stainless Steel to add the material to the project. 6. Return to Project. 6 5 WS4.2-7

8 Workshop 4.2 Geometry Setup 7. From the Geometry cell, RMB > Import Geometry and browse to: Axisym_pressure_2D_12.x_t Double click the Model cell to start Mechanical. 8 WS4.2-8

9 Workshop 4.2 Preprocessing 9. Set the working unit system: Units > Metric (mm, kg, N, s, mv, ma) Change part behavior to Axisymmetric : a. Highlight the Geometry branch b. Change the 2D Behavior under the Details of Geometry to Axisymmetric a. Rename the Parts: Part1: RMB > Rename to Retaining Ring. Part2: RMB > Rename to Pressure Cap. b. WS4.2-9

10 Workshop 4.2 Preprocessing 11. Change the material assigned to the Pressure Cap : a. Highlight Pressure Cap b. Under the Details of Pressure Cap Choose Material > Assignment = Stainless Steel. 11a. 11b. 12. Modify contact behavior: a. In the Details of Contact Region, change the Type to Frictionless 12a. WS4.2-10

11 Workshop 4.2 Contact 13. Generate the Mesh: a. RMB the Mesh branch and choose Generate Mesh. a. WS4.2-11

12 Workshop 4.2 Environment 14. Apply Loads on the model (make sure the Static Structural branch is highlighted): a. Select the 4 inside edges (shown in dashed black lines) of the Pressure Cap. Hint : select one of the edges and use extend to limits b. RMB > Insert > Pressure. c. Set the pressure magnitude = 0.1 MPa. a. b. c. WS4.2-12

13 Workshop 4.2 Environment 15. Apply Supports to the model: a. Highlight the bottom edge of the pressure cap (shown in black dashed lines). b. RMB > Insert > Compression Only Support. b. a. WS4.2-13

14 Workshop 4.2 Environment c. Select the middle line on the top of the retaining ring (shown in black dashed lines). d. RMB > Insert > Fixed Support. Note : Remember, the axisymmetric assumption here is that the retaining ring is a continuous solid. Actually there are bolt holes around its circumference. For this reason, when the model was created in DesignModeler this separate line was intentionally created to provide a location to add our support. c. d. WS4.2-14

15 Workshop 4.2 Solution Solve the model. Notes on axisymmetry : Notice that the model lies completely in +X space with the Y axis as the axis of revolution. This is required for axisymmetry. Axisymmetry assumes that the model is a complete 360 degree model. For this reason no constraints in the X direction are required. The portion of the pressure load acting in the +X direction is assumed to be offset by an equal portion in the X direction. View any warning messages/errors : a. Errors/warning messages are displayed in the Messages tab at the bottom of the graphics screen. b. Double click on the message to view it. Click OK to close the warning window. Note : Note: due to the fact that the pressure cap is constrained using frictionless contact and a compression only support, weak springs are added to prevent rigid body motion WS4.2-15

16 Workshop 4.2 Postprocessing Insert Results into the Solution branch: Highlight the Solution branch, RMB and insert Stress > Equivalent (von- Mises) Highlight the Solution branch, RMB and Insert> Deformation > Total Switch to body select mode, select the pressure cap and repeat steps (a.) and (b.) Solve Note : the last two results are now scoped to the pressure cap. This will allow us to isolate its response. WS4.2-16

17 Workshop 4.2 Postprocessing Highlight each of the result objects to inspect the result. Equivalent Stress on all bodies Total Deformation on Pressure Cap WS4.2-17

18 Workshop 4.2 Postprocessing View Solution time by highlighting the Solution Information branch: The graphics window will change to the Worksheet view. Scroll to the bottom of the solution information and note the Elapsed Time (this will vary by machine). Note, CP time represents the sum for all processors used. In multiprocessor machines it will generally exceed elapsed time. WS4.2-18

19 ... Workshop 4.2 Comparison Solution time comparison using refined 3D symmetry mesh: 2D Elapsed Time = 9.0 seconds. 3D Elapsed Time = 41.0 seconds. WS4.2-19