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)
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Using regulation specified loading conditions in Appendix F of the FSGP regs, set up and execute a front, rear, and side impact loading test
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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.
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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?
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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.
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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
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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)
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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.
Meeting notes from 11/27/2024 w/Ryan G. From Combustion
Ideal workflow for static structural sims:
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This way you can have multiple sims referencing the same geometry/model.
If you think that there’s a place where two points that should be in contact aren’t, run a modal simulation. It’s good for troubleshooting contacts, and your frame in general.
Make sure to hit the “share” button in spaceclaim when using beam elements.
Solution → insert → beam results → axial force. Helps to show places of interest on the frame.
Meshing Methods
Right click mesh + show + sweepable bodies shows which bodies u can use sweep (the most efficient meshing method)
for areas that are unsweeapable try to do quads/hex mesh (less expensive, but less accurate for some geometries, essentially less complex geometry is good for this)
multizone mesh method is a mix b/w sweep and face meshing
cartesian is coordinate-centric
layered tetrahedrons for mainly 3d printing we're not gonna use much
Primemesh is python based (interesting uncharted territory)
patch conforming is gen triangles out and go in (newer, and more efficient)
patch independent is gen triangles in and go out (vv of patch conforming)
Additional Points
make sure to set element order to quadratic - more simulation accuracy (set to this by default)
but for crash sims you want linear because of how expensive those sims are
Splitting beam elements??
“You can put a coordinate system at those locations and then you should be able to apply a remote force along that coordinate system
Do this by in workbench view->properties, then you click on the geometry and you can go over to the right and click the checkbox to turn on coordinate systems” - Ryan
“Or if you split the tube at those locations when you extract as a beam it should give you a point to apply this load” - Ryan
Basically, split tube BEFORE extracting as a beam.