POST-PROCESSING A RATCHET WHEEL

Transcription

1 A POST-PROCESS CASE STUDY POST-PROCESSING A RATCHET WHEEL The objective of this case study is to run a post process analysis of a steel ratchet wheel subjected to a set of forces. We will observe the stresses on the material and the resulting deformations. By the end of the study, the user should be able to visualize the analysis results in the GiD post process. 34

2 TABLE OF CONTENTS 1. INTRODUCTION POST-PROCESSING THE PART VISUALIZING THE RESULTS MODES OF VISUALIZATION VISUALIZING THE DEFORMED GEOMETRY CUTS AND DIVISIONS

3 1. INTRODUCTION The model in this study will be the results of an structural analysis located in the directory named "pieza.gid". The object of the study is a ratchet wheel that permits rotation of the axle in only one direction. The aim is to study how the part behaves when subjected to external forces, especially when the wheel is in equilibrium. In this condition, rotation is blocked by the pole, which resists the rotating force coming from the axle. At the same time, the pole exerts an equal and opposite force on one of the teeth. This system is illustrated in the figure A B Ratchet wheel and (in red) pole In order to simulate this condition, a simplification will be made in the following manner: the ends of the axle will be blocked and pressure will be applied to the surfaces of the tooth where the pole resists rotation. The material is steel. The material properties or pressure values the are not important for this sample, only interest show the postprocess options. 36

4 2. POST-PROCESSING THE PART Once the calculation has been run, the post process study may begin. The GiD post process enables the user to visualize the results based on the analysis Visualizing the results 1. Select Files Postprocess. 2. From the Windows menu, choose the View Results option. A window comes up from which the user may visualize the results 1. By default, no result is visualized when the user enters the post process. 3. From the View menu in the View Results window, choose Contour Fill. Window for visualizing the results 4. From the Results menu, choose the NODAL V.MISES option. Click Apply, thus obtaining a graphic representation of the VON MISES calculation, which gives an idea of the stresses on the material. NOTE: In the box labelled Steps, in the View Results window, all the steps of the calculation are listed. The steps normally show the calculations as they evolve. 1 From the options in the View results menu, one may also choose which result to visualize. 37

5 The calculation for the selected step is the one shown. In the present example, there is only one step. Visualization of the VON MISES calculation, using the Contour Fill option 5. The View menu and the Results menu may be combined in order to see the various calculations with each one of the visualization methods. For example, select Contour Lines on the View menu and NODAL STRESS on the Results menu. From the Components menu, choose S x (stress along the X axis). Click Apply. The resulting view is shown. Visualization of the X component of the NODAL STRESS calculation using Contour Lines. 38

6 6. Return to the visualization of the VON MISES calculation using the Contour Fill option. 7. The part will be rendered with a scale of colors covering the range of calculated values. In this example only one interval of the total results range is of interest. The scale of colors must be adapted so that the lower limit is 5.5e7 and the higher limit, 1e9. 8. Choose Options Contour Define Limits 2. The Contour Limits window comes up. In the box labelled Max, enter 1e9. In Min, enter 5.5e7. Click Apply. The resulting visualization is shown in the figure. The color scale of the default values Color scale with the new limits for representing the VON MISES calculation The Contour Limits window Entering the lower limit in the post process Toolbox 2 This option is also available in the post process Toolbox. 39

7 Visualization using the new color scale 9. The olor scale is distributed between the values 1e9 and 5.5e7. All values outside this range are colored blcak. The visualization of these values may be changed. For example, choose these options: Options Contour Min Options Out Min Color Min Color and Options Contour Max Options Out Max Color Transparent. The values below the visualization range are now represented in the same color as the minimum-value color. The values above the visualization range are not drawn; they are perceived as transparent. Visualization using the color scale established in point 9. The calculated values in thr transparent zones are higher than 1e To return to the initial visualization limit values, choose Options Contour Reset Limit Values. 40

8 11. Another option for visualizing the results is Iso Surfaces. This option enables the user to locate the elements of the model that have the same values (Iso). Choose View Results Iso Surfaces Exact NODAL_ V._MISES. GiD asks how many Iso Surfaces to visualize. Enter 2. Then enter the values 1e9 y 5.5e7. This results in a visualization of the surfaces with elements of the values 1e9 o 5.5e7. Visualization in two different colors of surfaces with elements having either the value 1e9. or 55e There are other ways to visualize Iso Surfaces. With View Results Iso Surfaces Automatic NODAL_ V._MISES, the user enters the number of Iso Surfaces to visualize. GiD automatically assigns a color to each Iso Surfaces. 13. Using the option View Results Iso Surfaces Automatic Width NODAL_ V._MISES, enter the incremental step between the values of the different Iso Surfaces. GiD automatically creates as many Iso Surfaces as possible Visualization of 8 Iso Surfaces using the Automatic option Visualization of Iso Surfaces using Automatic Width and an incremental step of 3,4e8. NOTE: The modes for visualizing the Iso Surfaces are located in the Options Iso Surfaces menu. 41

9 14. Visualizing the results using vectors is also an option. A vector is drawn for each element of the mesh. In the View Results window, choose Display Vectors from the View menu and NODAL STRESS from the Results menu. From the Components menu, choose Si (stress along the i axis). Click Apply. Magnify the zone indicated in the image. Visualization of the results using vectors 15. Now select All from the Components menu in the View Results window. Click Apply. A magnification of the surfaces under pressure and visualization of the stresses using vectors Visualization of the the vector compoenents of NODAL STRESS 16. Red vectors indicate traction (tensile stress) and blue vectors indicate compression. 42

10 2.2. Modes of visualization 1. Choose Windows View Style. A window labelled Select & Display Style comes up in which to change the options for visualizing the geometry. This window is composed of various menus, each characterizing some aspect of the visualization of the model. All these menus can be combined to achieve a suitable visualization. The Select & Display Style window NOTE: In the post process, the elements of the mesh are classified into Meshes, Sets and Cuts. A new Set is created for each group of surfaces that share the same material. There is a Mesh for each group of volumes sharing the same material. Cuts are sections made into the geometry during the pot process. The categories Meshes, Sets and Cuts are at the top of the window in the figure. For each category the user may choose a color using the Color Change option. Each one may be clicked On or Off 3, or deleted (Del). In the present example there is only one volume. Therefore, only one Mesh appears. It is named "Mesh1". The Style, Render, Culling and Conditions menus as well as the Massive and Transparent options affect the visualization of the entire mesh. 2. Try out the various options offered in the Style 3. Click Apply to see the results. 3 This option is also located in the post process Toolbox. For further information on the tools in Toolbox, click on the corresponding icon with the right mouse button. 43

11 Visualization using Style Boundaries. Visualization using Style All Lines. Visualization using Style Hidden Lines. Visualization using Style Body. Visualization using Style Body Bound. Visualization using Style Body Lines. 3. Try out the various options offered in the Culling 3 menu combined with the Conditions menu and the Transparent and Massive options. Click Apply to see the results. Culling Front Faces. Culling Front Faces with the Massive option Culling None, Conditions Geometry aand the Transparent option 44

12 2.3. Visualizing the deformed geometry 1. Choose Windows Deform Mesh. The Mesh Deformation window comes up. 2. From the Style menu in the Select & Display Style window, select Boundaries. 3. From the Mesh Deformation window, select Deformation, under the heading Main Geometry. Under the heading Reference Geometry select Original. Click Apply. In order to better distinguish the two geometries, select Body Bound from the Style menu in the Select & Display Style window. NOTE: Changes carried out in the Select & Display Style window do not affect the reference geometry (in Reference Geometry in the Mesh Deformation window.). NOTE: The factor box in the Mesh Deformation window indicates the multiplying factor of the real deformation. NOTE: In the Steps boxes in the Mesh Deformation window, the user may select the steps to be visualized. The Mesh Deformation window The (yellow) deformed geometry (Body Bound) versus the original geometry (Boundaries) 45

13 4. Now the deformed geometry may be visualized. For example, in the View Results window, select Contour Fill and NODAL V.MISES. Click Apply. Visualizing the results of the deformed mesh (colored) 46

14 2.4. Cuts and divisions 1. In the GiD post process, the user may cut or divide the mesh to visualize the results on the interior of the part. Begin the cutting process by choosing Do cuts Cut plane 3 points Using the Join C-a option on the Contextual menu, located on the mouse menu, select the three points indicated in the image to define the cutting plane. 3. A Cut is made. To visualize it, click Off "Mesh1" in the Select & Display Style. The cutting plane defined by three points "Mesh1" is Off. The section resulting from the cut NOTE: The sections (Cuts) made in the original mesh also deform when the mesh deforms. And vice versa, the cuts made in the deformed mesh deform when the mesh returns to its origianal state. 4 Another option is Do cuts Cut plane 2 points. Here, the cutting plane is the plane perpendicular to the screen that passes through the line defined by the 2 points. The cutting options are also located in the post process Toolbox. 47

15 4. Starting from the View Results window, select Contour Lines from the View menu, and select NODAL V.MISES. from the Results menu. Click Apply, thus visualizing the results within the cut. Visualizing the results within the cut 5. From the mouse menu, choose Label Select Results. Select several nodes, thus obtaining the numeric value of the VON MISES module for each node selected. Visualizing the numeric values of the VON MISES module 6. To return to the previous visualization, choose Label Off from the mouse menu. 7. In the Select & Display Style window, click "Cut1" Off and "Mesh1" On. Choose Rotate planexz from the mouse menu. 48

16 8. Choose Do cuts Succession. This tool enables the user to make a specific number of equidistant cross-sections along an axis. Enter two points to define the axis. Defining the axis 9. A window comes up in which to enter the number of cuts to make. For the present example, enter 20. In the Select & Display Style window, click "Mesh1" Off. Cuts made using Do cuts Succession with no visualization of the results The Select & Display Style window with a list of all the cuts made 10. Use the View Results window and the Select & Display Style window to visualize the results in the cuts made. NOTE: With the option Files save cut, the cuts may be saved in a file in order to be used during another GiD session. 49

17 NOTE: Using Options Iso Surfaces Convert to cuts, the Iso Surfaces may be converted into Cuts. 11. In the Select & Display Style window, select all the cuts and click Del to delete them. Click "Mesh1" On. Choose the Rotate planexy option from the mouse menu. 12. Choose Do cuts Divide Mesh 2 points. Using this option the mesh is divided by a plane, without cutting the elements. (The plane may be defined by two or three points and the right or left portion of the model may be selected. A new mesh is created that contains the selected portion. The cutting line. 13. Enter two points to define the plane that will divide the part, as shown. Click on the right portion of the model to indicate that this is the side to select. After clicking "Mesh1" Off, the result will be that shown in th figure. 50

18 A visualization of the divided mesh using VON MISES and Contour Fill. NOTE: The dividing tools are classified in three groups: Divide mesh, Divide Sets and Divide lines. In the three cases, entities may be divided by defining 2 or 3 points. 51