Introduction
Objectives: Holistic understanding of the ANSYS workflow, boundary conditions, post processing, and optimization of setup for faster run times (incl meshing, simulating with symmetry, research others)
Learn how to set up realistic + accurate boundary conditions
Learn how to simplify geometry and apply mesh controls to get accurate stress readings
Understand stress, strain, deformation, stress plots
Interpreting post-processing results, what to do with the data
Considerations:
Research fundamentals behind simulation. What do different setups mean? What assumptions are being made about the behavior of the structure with a certain set of boundary conditions?
Work through a few of the ANSYS Mechanical tutorials
Research how other solar teams have simulated their frame, i.e., what elements did they use, what did their boundary conditions look like, etc
Research other ways to refine the setup to be properly constrained and run faster
o Meshing methods
o Element type and size
Simulate a frame (You could pull an FSAE frame off the internet and sim that!)
Deliverable:
Using regulation specified loading conditions in Appendix F of the FSGP regs, set up and execute a front, rear, and side impact loading test
Contextualizing ANSYS
ANSYS is a FEA (Finite Element Analysis) software that simulates using FEM (Finite Element Method).
Essentially, we break up the larger simulation into small parts - “elements” - and solve mathematical and physical differential equations for each element in order to simulate the greater whole. Divide and Conquer.
With ANSYS we can do a ton of things. computational fluid dynamics (CFD, essentially aerodynamics in our context), heat conduction, crash tests, but most importantly for us: static structural analysis.
We use ANSYS so we can save money, time, and energy. Crash-testing something virtually is much less intensive than crash-testing IRL.
Optimizing FEA
Using this article, I’ve got some ideas.
Removing unnecessary features
In CAD a lot of people have fillets and other round things.
But when it comes to FEA, square edges are so much easier to mesh.
Also, these tiny fillets and rounds rarely have a huge impact when it comes to seeing displacement.
By doing this, you can significantly reduce simulation complexity, and thus time, saving resources.
Note: BE CAREFUL THOUGH. SOME features are INTEGRAL to accurate simulation of a system, and so must NOT be removed. This is an example of having strong intuition when simulating, rather than being in complete dependence to the software (ANSYS).
Including effective geometry/constraints
This builds off the second point. We want to remove the unnecessary, but when this isn’t possible, we want to simplify the necessary.
EX: When you need a screw in this place, rather than having the screw with it’s helix pattern and Phillips head… why not just include a cylinder with a hexagonal top?
Proper Mesh Generation - Shell vs Solid Element
If you got geometry where the thickness is insignificant compared to length (smt that’s hella thin).
Or when the deformation due to shear isn’t a big deal (insignificant)
Consider using shell elements.
They’re 2D approximations of 3D elements that store the physical properties of the 3D element.
Doing this can simplify your mesh greatly
Simming a Cantilever Beam - ANSYS
Usually you want to start by opening ANSYS Workbench to outline your simulation and get yourself organized. Think of this as the setup portal.
Notice how many different types of simulations you can do.
Most of frame stuff would be static structural though so mainly go with that.
This is where you identify everything so your sim can be as accurate possible. The identifiers in question are:
Engineering data (pick your material)
Geometry (the shape of the thing you are simming)
Modeling information (a mesh dividing the geometry into a finite number of elements) This is what makes FEA, FEA.
Setup information (ex: boundary conditions and loads)
What do those symbols next to the parameters mean?
This section needs more data.
There’s nothing in this section, need to input data.
The minimum amount of data has been inputted.
Review/modify this section
Some data has changed, so update this section.
Rerun simulation as it was interrupted
There are pending changes, your setup may need more data from you.
Note that these symbols are more for the software than for you. Keep in mind that you still need to make sure the data YOU input is correct - ANSYS will run anything so long as the data exists where it should.
How to change material
Double click on engineering data
Click on engineering data sources
Your top-most tab in the center of your screen should be files of various materials to choose from.
Additionally, you can input your own material properties for ANSYS to take in.
How to upload/import new materials
Ensure your file with the new material(s) is in .XML format
Go to “Engineering Data” tab in ANSYS Workbench Project
Select “File” --> “Import Engineering Data”
Select your indicated XML file w/materials
Select open
Your materials should be there now
Lets start with Geometry.
Right click Geometry → New SpaceClaim Geometry.
Usually we will import, but for now it’s time to get familiar with ANSYS spaceclaim.
This is kind of like SolidWorks but with less freedom. I started by drawing a 40mm X 1000mm rectangle constrained around the origin and ended the sketch.
Note: “Fill” will make selected lines a surface. SolidWorks does this automatically.
After that I extruded using the pull tool to 40mm along Y. Now have 1000x40x40 mm beam.
In this simulation I’m going to load the beam at a 20mm section in the center of the beam. To do this I use the split tool since ANSYS does not allow point loads. (pressing tab in the split mode lets you input specific value instead of percent)
Now our engineering data is good. Next, lets move onto “Model”. This is where ANSYS mechanical starts.
We’re gonna create a mesh first.
On the left side, under the “Outline” window select “Mesh”.
Then go to “Mesh” on the top bar, and select sizing.
From there click the green box to select a body.
Press “No selection” next to Geometry on the bottom left and press apply so Software knows what geometry is being simmed.
Then in same area define Element size as 10mm (enter 0.01 because units in meters).
Press generate mesh.
Now lets apply the load.
Select Static Structural in the feature tree.
Go to Environment top tab and press fixed in supports, then select each square end of the beam and press apply for geometry in the bottom left.
Now press force. Select Split area.
Define the force by components, not vector (bottom left)
Apply -2000 N force to Y component.
Now let’s sim.
Press solve on top left.
This basically tells the simulation to compile and interpret your inputted data.
Now lets click “Solution” and go to “Deformation” and select total.
Lets click “Stress” and press “Equivalent Stress”.
What we just did here is tell ANSYS what exact data we want to see from it. Note that there are so many diff types of things we could test for.
Now lets click solve AGAIN so we can get a visual.
Our current visual is not representative of the true deformation. Click the pink highlighted drop-down and press “True Scale” to see the what it would look like IRL.
I just simmed my first sim!
Notes and Observations:
This software is a lot more complex than SolidWorks simulation. There’s so much to do it’s definitely easy to get overwhelmed, but the possibility is also exciting. I’ve only scratched the surface at this point.
SpaceClaim doesn’t really seem worth it to 3D model. SolidWorks, even OnShape, is way better.
Woahhhhh colors O.o
11/9/2024 Torsional Rigidity - Static Structural Deformation Analysis on Early 22-24 Frame Iteration
Process:
7mm Mesh on entire structure
This frame was a .SLDPRT and not .SLDASM so did not have to individually select each pipe member.
Completely fixed the back panel of the frame (rectangle with asterisk shaped cross brace pattern at the back
This section will NOT move at all
Applied +1500 N y-direction force on the front left hardpoints
Applied -1500 N y-direction force on the front right hardpoints
Solved first time
Solved for “Equivalent Stress” and “Total Deformation”
Screenshot above is total deformation (see top left)
Notes and Observations:
This frame is not torsionally rigid enough
Make sure to keep your element size realistic
If you have elements smaller than 7mm, don’t try to set element size to 7mm because you can’t mesh empty space
ANSYS is a D1 RAMmaxxer - make sure your applications are closed during “solve” period
If you don’t think you have sufficient RAM for solve to complete, close ALL other applications. The solve WILL terminate w/o sufficient RAM
Useful tool to debug solves is checking the Solution Information sheet under the “Outline” tree
Helped me understand the RAM issue
When you select multiple points/edges/faces that aren’t connected to each other (in terms of selection), the indicated force will apply at the centroid of the selection
Ex: my selection of the hardpoints to sim torsional rigidity
Oftentimes, the force will appear at the first selected point/edge/face, even though it’s actually at the centroid.