Mixed Meshing in SolidWorks Simulation - Top Tips for Large Assemblies by Brian Zias (Part 5 of 5)
In the previous four parts of this series(see below for links), I have stated how critical it is to use the proper element types and modeling techniques. When it comes time to apply Simulation to a larger, full-scale assembly, there are unique challenges and frustrations the user may face. To close out this series, here are several of my Top Tips to get your simulation completed successfully:
1. Be cognizant of every body in every component. Remember, the body is the lowest-common denominator in a Simulation. If your part has a solid and a surface body, then Simulation will see two separate bodies, and mesh one solid and one shell. It's extremely helpful to use configurations to manage solid vs. surface versions of a part. Name the configurations appropriately, and the top-level assembly tree can be scanned easily to verify configuration name of each component instance.
2. Fix all the components in place. As we idealize and hack away features, mates will break. Set all the assembly components to ‘Fix' and suppress all the mates (this can be a separate assembly configuration).
3. Suppress all components and start with just a handful. It is very daunting to start with the entire large assembly, and troubleshooting what is failing and why becomes next to impossible. Create a test study and apply a simple gravity load. Mesh, solve, and verify deformation. Methodically un-suppress your components a few at a time. Repeat meshing and solving after adding each set of components. This will save quite a bit of confusion when creating many contact sets, and makes narrowing down the missing ones an easy process instead of an overwhelming one. Make sure and use the ‘Update all Components' command if the body list doesn't update in your study. This approach keeps creating contact sets manageable.
4. Turn on ‘soft spring' in study properties. Also, apply only a light gravity load until the entire assembly is verified. Soft spring will usually grab any rigid-body motion of an under-constrained component. Remember rigid-body modes cause static analyses to fail, typically reporting a ‘Singular Matrix' solver error. If soft spring keeps failing, then go back to your previous iterations (see step 3) and make a smaller un-suppression step. If you have Professional, you can use frequency study type to identify rigid-body modes of components. Any frequency that is zero (or near-zero) is a rigid-body mode, and the mode shape will display this behavior.
5. Mesh and run test studies with a coarse, draft-quality mesh. There's no point in refining the mesh or solving high-quality elements at this point. Look only for proper contacts, restraints, and deformation. If a component will not mesh with a coarse mesh, think twice before refining the mesh. If you have to make large refinements at this point, will you have enough RAM with all components resolved?
6. Use mesh controls appropriately. Remember that the element size in a mesh control must always be finer than the global mesh. Therefore the global should represent your ‘big' mesh size.
7. Use Connectors. Bolt, pin, and spring connectors are there to reduce DOF. However, remember that bolt connectors require a contact set (no penetration). Therefore, on very large assemblies, it's sometimes easier to treat all connections as bonded, then add the connectors later.
8. Take advantage of the ‘Run all studies' command. Once the assemblies is ready to go, apply your loads, make different studies with different conditions, and run them all overnight.
9. Use new functionalities such as ‘Fix' and ‘Treat as Rigid' (both new in 2009) which allow you to further reduce DOF and simplify larger models.
10. Use Display States to manage results presentation. Simulation uses the assembly's hide/show states to determine whether the results are hidden or shown on the contour plot. Large assemblies can use Display States to look at different areas of the assembly. It's a nice, organized way of managing the results. Be sure and use the chart option ‘display min/max on shown parts only'.
11. Use Iso-Clipping to show critical volumes in the final results. This will make it clear where there are issues without painting the entire assembly.
12. Last, but most important: Attend our regularly-scheduled Simulation training. All of these tips are incorporated into the lectures and exercises. You can view our training calendar here.
To review any previous article in this SolidWorks Simulation Mixed Meshing Series, please use the links below.
Meshing Advice in SolidWorks Simulation (Part 1 of 5)
Mixed Meshing in SolidWorks Simulation - What's New in 2009 (Part 2 of 5)
Mixed Meshing in SolidWorks Simulation - Contact Sets (Part 3 of 5)
Mixed Meshing in SolidWorks Simulation - Maximizing RAM and solving "Out of Memory" issues. (Part 4 of 5)