In this guide I will be transferring the frame of a solar car from a 3-D CAD program into ANSYS mechanical 14.1 and performing a simple loading situation that will simulate a frontal collision.
NOTE: This guide will only be beneficial for loading situations of objects composed of tubes. The tubes may be of a different cross-sectional shape and size, I am just using hollow circular 1" tubes for this example.
Step 1: Recommended Programs
Recommended supplemental programs:
Any 3-D CAD program (Inventor, AutoCAD, SolidWorks, etc.)
Step 2: Transferring Information to Excel
Tip: while transferring data to excel start with the keypoints first and list all keypoints, then put in the lines, and lastly put in the arcs. This will keep your spreadsheet more organized and will make it easier to find certain elements if changes need to be made.
This Video will help guide you by showing how to draw simple shapes.
1. Open the file you want to test on the 3-D CAD program you are using and a blank excel speadsheet.
2. In box A1 type "/prep 7"
3. Starting with key points in row 2 in the first box type "k" then the x coordinate in box 2, y coordinate in box 3 and z coordinate in box 4
4. After key points insert the lines joining the key points as shown
5. After the lines finish with the arcs.
Step 3: Opening ANSYS
1. Open ANSYS 14 folder
2. select the Mechanical APDL Product Launcher 14
3. On the simulation environment drop down select ANSYS
4. for the license select ANSYS academic Teaching Advanced.
5. For working directory select the file path where you want the file to be saved.
6. For job name enter the name you want to give to the project
7. Click run
8. Copy and paste the text from notepad into the command prompt. (see movie above)
Step 4: Preprocessor
1. On the left hand side click preprocessor
2. select element type
3. select Add/Edit/Delete
4. Select add, then select beam, then 2-node and click ok
5. Then under element select Material Props
6. Select Material Models
7. there will be 3 columns select structeral in the 1st linear in 2nd and isotropic in 3rd.
8. There will be a box that pops up that says "ex" and "prxy" these values vary depending on what metal you are using and stand for elastic modulus and possan's ratio. For this example I am using 6061 aluminum which is ex=10e^ and prxy=.333
(Note: exponents must be designated with "e" not "^" otherwise you will get an error.)
9. Now click sections under material Props
10. select beam then common sections.
11. A window pops up where you must give a unique ID number for each section (1,2,3 etc..)
12. Next it will ask for a sub type. Sub type is the cross section that you want. For this example i will be using a hollow circular tube.
13. Enter the major and minor diamater of the cross section. ( I am using 1" major and .87" minor)
14. In the command prompt enter "/ESHAPE,1,0" then hit enter
15. Now click meshing under sections and select mesh attributes
16. check the box that says "picked lines" then select the lines of common cross sectional dimensions now, click ok
17. For the lines that you selected find the ID number of the cross sections you made from earlier and hit OK
18. repeat step 16 for each type of unique cross section.
19. Now click the mesh tool on the left hand side under meshing.
20. make sure the smart size box is checked and the bar underneath is scrolled over to 2. Under "mesh" select lines and click all the lines you want to mesh. (or click all lines if you want to mesh all)
Step 5: Solution
1. On the left hand side select "solution" then under solution select analysis type, new analysis, then select static
2. When it asks to define leads select, apply then displacement and then key points.
3. Now select the key points that you want to stay static then hit OK then select all DOF to prevent them from moving in any direction.
4. Now select Force/Moment under displacement on the left hand side.
5. Select apply to nodes and it will prompt you to enter the value of force you want to apply and the direction (x,y,z)
Note: Be careful about signs. If you want to go in the opposite direction make sure you put a negative sign in front of the value. Also if you are applying a force over an area make sure you take the total force you want to apply and divide it by the amount of nodes you are distributing it over and apply that equivalent force over those nodes.
6. Now select solve under the force/moment menu and a box should pop up saying that the scenario is solved. (If not then you have an error. A common error is that you accidentally put 2 lines or key points in the same spot.)
Step 6: General Postproc
This is the part where you can tell the program to plot the results of the loading situation. In this tutorial I will just use the Von Mises stress, although you may select other options to analyze different scenarios such as displacement.
1. Under general Postproc on the left hand side select plot results then contour plot and nodal solution.
2. Your window should now display the image with a key at the bottom showing the stress concentrations on every part of the drawing. One thing to note is that for this example the yield strength is 40 ksi so on the key at the bottom if the number to the far fight is higher than 40,000 psi your model will fail and adjustments need to be made.
Note: if you would like to save the image for documentation you can click the plot controls tab at the top and select capture image then save the image where you would like.