ANSYS 英文实用培训教程.docx

1、ANSYS 英文实用培训教程ENSC 895 Assignment 3 TutorialLast updated on: Feb 25th, 2013In this lab, students will learn the basic techniques of FEA analysis. A static structural analysis will be performed on a rack system using ANSYS workbench. Geometry simplification will be introduced to the students. Several

2、 mesh techniques will be briefly introduced to the students. However mapped meshing is the core learning objective. The lab will also introduce the students with basic post-processing techniques needed to interpret the analysis results. Learning objectives:Mid-surface technique: students have to lea

3、rn how to extract the mid-surface to produce high quality mesh. The rule of thumb is that as long as the thickness is 1/5 of the width or length, the body can be simplified to surface body. Surface body uses plane or shell elements such as solid186 or shell181. However, the students dont have to wor

4、ry about which elements to select from since ANSYS will automatically select them. There are two ways to extract mid-surfaces, see tutorials for details.Learn basic defeaturing techniques: Certain unnecessary details should be removed from the analysis in order to obtain better meshing effects. For

5、example, fillets and chamfers that dont play major roles in FEA analysis in many cases can be ignored to generate better local mesh. Students can do a comparative study to see the effect if time permits.Number of divisions per cycle: According to certain industry standard, the circle has to be divid

6、ed into at least 12 elements. Normally ANSYS version 14.5 will automatically detect and divide the circle to 12 elements. If not, one can do it manually. See details from the tutorials. Bonded contact with MPC algorithm: In this assignment all contacts will be automatically generated. But some geome

7、trical preprocessing is needed in order to have effective contacts.Convergence study: A mesh independent study should be performed on the structure to see how mesh qualities can affect the final results. With the improvement of mesh the stress value should approach a steady state meaning its value s

8、hould be within 5%.Check reactions: Learn how to check the reactions after a FEA analysis has been performed. For example, three 1000N forces are added on different level and the reaction at its boundary should be balanced for the structure to be in equilibrium.Entering ANSYSDouble click on ANSYS wo

9、rkbench from desktop.Once you have entered ANSYS workbench drag Static Structural from the Analysis System to the blank area called on the right. Then double click on Geometry to access DM (Design Modeler).Select Millimeter as the desired length unit.Brief Introduction to some functions in DM (Desig

10、n Modeler)The functions below in the red boxes are the commonly used functions in ANSYS preprocessing. These functions are primarily used for geometry simplifications. Geometry simplification is one of the most important tasks in preprocessing. Properly simplified geometry can greatly improve the qu

11、ality of mesh and thus results predicted by the FEA analysis.Mid-Surface: It is used to extract the middle-surface. When a body can be considered as a plate or shell (its shortest dimension is the 1/5 of other dimensions), normally it should be simplified. IThin/Surface: This is a backup choice for

12、Mid-Surface as Mid-Surface fails to work sometimes. It can also be used to achieve other tasks such as forming a cavity.Face Delete: This is used to delete unnecessary faces in order to improve mesh quality. Unnecessary details often impede one from producing high quality mesh.Edge Delete: Same as F

13、ace Delete, but it is for operations on edges.New Plane: Users can establish new planes for all kinds of purposes. However, in this exercise, it is primarily used as reference plane for cutting/slicing.Slice: The purpose of slicing operation ismultiple. In this analysis Slice operations are needed i

14、n order to generate more mappable regions. With mappable regions, the quality of mesh should be higher.Mappable regions: Mappable regions are those surface areas on which mapped mesh can be generated. Mapped meshes typical have high quality and effectiveness. Areas covered by mapped mesh typically l

15、ooks more regular in terms of the shape of the mesh. Use mapped surface mesh whenever applicable.Double click on engineering data.First, click on Engineering Data Sources. Then click on General Materials to see a list of commonly used engineering materials. Then move on to Outline of general materia

16、ls and click on the add sign. Add Aluminum Alloy for later use. (Steel is defaulted material which you dont have to add) Go back to the DM.Double click on Geometry to accessANSYS DM.Import geometry into ANSYS workbench:Click on file and select Import External Geometry File. The location of the paras

17、olid geometry (x_t) will be given to you.The geometry will look like this if it is imported correctly.Extracting Middle SurfacesMid-surface command will be used to extract middle surface of the sheet metal. Select face pairs by clicking on the front and back side of the column bar. After successfull

18、y selected, it will be highlighted in purple.However, in order to select as many legitimate surface bodies as possible, one can exploit its auto-selection capability by changing the selection method from manual to automatic. Note you should click on “Finding surface pairs now” once in order for this

19、 to work. Then all available surface bodies will be selected all at once which will save you considerable amount of time.There are occasions that Mid-surface will fail to work due to the complexity of thegeometry. Fortunately, there is another method we can use in order to bypass this issue. Thin/Su

20、rface can be used as a tool to extract surface body while Mid-surface fails to work. Click on the surface bodies while holding the ctrl key this allows you to select as many surface as you might need. Change the Selection Type to Faces to Keep as indicated below. Since the bottom plates have thickne

21、ss of 3 mm, in order to serve as middle surfaces the face offset should be half of it which is 1.5mm. DefeaturingNormally geometries imported from CAD software are too complicated and have too many details to capture. As a FEA analyst, you have to know how to remove unnecessary details as it will im

22、prove the quality of mesh.Surface-delete is a technique to delete unwanted surfaces. For example, in many cases fillets and chamfers dont play a major role in stress analysis and thus can be deleted.Edge-delete is similar to Surface-delete in which it removes unnecessary edges instead of surfaces.Se

23、tting up the thickness: When Thin/Surface is used to extract middle surface it will lose information on its thickness. Go to ANSYS Design Simulation (DS) by double clicking on Model. All “part 3” are bottom holding plates, it should be noted that “part 3” are with question marks before setup. Select

24、 all of “part 3” and set the thickness to 3mm.The next step is quite crucial for generating high quality mesh. In order to produce high quality mesh, the geometry should be made to be mappable (Sometimes Sweepable in the case of solids). In order to have as many mappable region as possible, Slice fu

25、nction is used to separate the geometry to simpler shapes and thus more likely to be mappable.Slice can be performed under the condition that the geometry or a part of that geometry is frozen. While the geometry is first imported to the DM, it is defaulted to be frozen. Therefore slice can be applie

26、d to each body directly.There are several slicing methods. Commonly used in this exercise are two: 1) Slice by Surface; 2) Slice by plane.Slice by Surface: Select the surface that you want to use as a tool surface. Click on Slice and change Slice Type to Slice by Surface and apply. As indicated belo

27、w, the geometry will be sliced about the top level surface. Do this repeatedly for 3 different levels.Slice by Plane: In order for this slicing method to work, a new coordinate system needs to be constructed. Click on to create a new coordinate system. The new coordinate system will be established o

28、n the corner. In order for slicing plane to work, one has to re-orient the coordinate system such that the red and green axis forming the plane of slicing. In other words, slicing plane will be perpendicular to the blue axis.The new coordinate system will be shown. Change Type to From Point and Norm

29、al. As point-normal method will be the most convenient way to construct a coordinate.Base point will be the origin of the coordinate system and click on the vertex as indicated below. Click on Normal Defined by and then go to geometry to click an axis that you want to specify as the normal axis. A b

30、ig red arrow will be shown in the screen to indicate the direction your selected normal line. It doesnt matter as to what direction the blue arrow is pointing at, as long as the red and green axes form the plane of cutting it should be working correctly.The next step is to use the coordinate system

31、that you just created as a reference to slice the plane.Select Slice function and choose the Slice Type as Slice by Plane this time. Change the Base Plane to the plane that you want to slice about. (Normally if you have just created a coordinate system, it will be defaulted to Base Plane. Click on g

32、enerate to see the effect (you can press F5 as well).Create a coordinate system again for another corner this time. Just repeat the procedure described above until all 4 sides have been covered.And then use slice based on the coordinate system just created.This is what it looks like when you have sliced two sides.If 4 sides are slices correctly, you should geometry should resemble the one shown below.Create a new coordinate system as shown.Slice based on the coordinate just created.If you have done it