FEA Meeting Notes - Sept 30th

General Steps

• Import assembly into Ansys
• Simplify your model as much as you can
  • If there are parts that you don't need, don't use them
  • Features like threads might mess things up as well
  • Holes can also mess things up a lot
• Export you assembly as a parasolid
  
  • Parasolids are better than step files because it breaks down into tetrahedral shapes much more easily

• Drag in Static Sims from project selection screen in ansys

  • You can connect the set up, engineering data, and other parameters between sims by clicking and dragging
• Import external Geometry File
  • There will be a lightning bolt icon if there are any issues. Click it to resolve any issues
• Model connections, contacts,and mesh parameters
• Insert Supports, Stresses
  • Add a gravity stress as a baseline sanity check for the model
    • If you see very high stresses, It's usually two bodies contacting at a point or something weird, so check it out
• Set up your mesh:
  • Mesh is very irrelevant compared to the rest of the simulation
  • The mesh can be the difference between a 90% correct sim and 100% correct\
  • Element size can be controlled under element size
  • Mesh is core driven, more coreeeeeees

  • You need to have at least 2 elements through the thinnest bit on your part

  • Ideal element is a cube, so if you can get square elements, thats ideal

• Element midsize notes: Quadratic and Linear
• Supports:
  • Fixed supports allow for fairly conservative estimates
• Loads:
  • You just have to select faces that you want to load
  • You can also use components or vector loading
  • Note: Forcese are always relative to the global coordinate system which is the same as the one in solidworks
• Mesh Independence:
  • Change in stress will approach zero if you continually refine the mesh
  • Mesh refinement auto does not work for weird meshes
  • 5-10% allowable change is a good starting point if you are repeating the FEA sim

General notes

• Reset workspace is a thing, which will bring back all of the menus you have set up
• Ansys can be set up to do pure dynamic, steady state thermal, and static structural sims
• Space Claim
  • Edits models using a workflow similar to Catia or NX
• Design Modeller
  • Edits models much more like conventional CAD
• You can evaluate for a specific block if you want to reduce compute time
• Always check for smooth stress transitions
  • Mesh might not be fine enough if this is not the case
• For sharp geometry:
  • If its welded, you can model in some weld into your part if you have the time, and this will help Ansys resolve the stresses correctly
• Evaluate a contact tool is very useful
• Generally speaking, a lack of constraints will crash Ansys

• Rigid = infinite stiffness

  • This usually represents worst case scenario, and is computationally easier

  • Flexible is usually the go to

• Ansys auto generates contacts
• Just because a body is contacting, doesn't mean that those two bodies will interact
• Pinball region: What elements of your mesh are in contact with your other region

  • It's okay if two bodies may overlap

  • Tolerance values really matter

• Stiffness:

  • If the simulation is not solving, it could mean that your contacts are not stiff enough

• Creating two planes to bisect a part will help you refine an area if you so please:

  • Slice the object into two bodies

  • Once part that is split two bodies is treated is computationally better for the mesh

  • There is a lot of body selection filters in the top bar if you need them

  • You can use this trick to insert a finer mesh on a body you really care about

  • Note: The larger mesh cannot be larger than 2x the fine mesh if you are fine meshing a specific part of the body

• Non-linear Sims:
  • Linear evaluates it as if it has not yielded
  • Energy methods is what is used for non-linear solutions
• Engineering Data

  • Ansys Material data is good for safety factors > 1.3

  • Modulus is very important

• Animations are good sanity checks that everything was set correctly