Best Practices

Best practices for reliable and consistent results.

Geometry Import/Representation

SimSolid does not have a geometry engine, so when importing your model into SimSolid it is saved as faceted volumes and you can perform analysis on the boundaries created by these faceted volumes. How well the faceted volumes represent the overall geometry is controlled by the import options. SimSolid allows different levels of refinement.

Guidelines for geometry import:


Figure 1.
SimSolid has preset options like Standard, Enhanced and Fine and a Custom option where you can manipulate angular and chordal deviations. Increasing the resolution is going to increase the number of facets and hence it's also going to increase the solution time. Fine or Custom settings may not be best practice for all cases. Choose your import settings wisely based on the geometry that you're working with and the objective of your analysis.


Figure 2.

For example, if your end goal is to perform stress analysis, you may want to avoid rough facets that can introduce stress concentrations. In such cases, go with Enhanced or Fine settings. But if your objective is to look for stiffness, you can get away with standard import settings in most of the cases.

Overall guidelines:
  • Always import with enhanced if not fine for models with thin-walled structures, curvatures and holes or if stresses are of interest.
  • Always check for geometry defects including unwanted voids and sharp facets.
  • Avoid any merged parts.


Figure 3.

Connection Fidelity

Overall guidelines:
  • Use automatic connections wisely, keep tolerances low.
  • Use increased resolution connections only when necessary.
  • Use connection check tools to quick connect groups and locate problematic connections.
  • Connections at the bolt shank should always be sliding.
  • Avoid applying virtual connections to large faces.
Regular Connections:
  • Regular connections are visualized as point clouds at the interface between parts.
  • Can be created automatically or manually.
  • Tuning these two inputs (proximity tolerance and resolution) is key in creating realistic connections which leads to realistic load paths.
Tolerances:
  • Connections are found based on proximity criteria; if two parts have faces within the gap/penetration tolerance window, a connection is established.
  • Too large of a gap tolerance can lead to connections in unwanted areas, over stiff model.
  • Too small of a gap/penetration tolerance can leave parts disconnected or unstable.




Figure 4.
Resolution:
  • Connections are created with a specified resolution (normal, increased, or high) which defines the density of the point cloud.
  • Only use increased/high resolution in areas where it is necessary to fully define the connection.


Figure 5.
Increased connection resolution leads to longer run time, especially when set to High.


Figure 6.
Below are examples of the effect of improper connections.





Tools:

SimSolid has tools designed to make creating proper connections easier.
  • Show disconnected groups – lists all disconnected groups of parts to be either deleted, suppressed, or connected.
    • Select any number of disconnected groups and choose Connect to connect them without having to recreate all others.


Figure 7.
  • Review regular connections – List of all regular connections in the design study with all associated information.
    • Use this to sort connections by found gap/penetration or number of points to isolate problematic connections.


Figure 8.

Seam Welds

Use welds wherever possible for best results.
  • Seam welds are created as prismatic solids at overlapping feature lines between parts.
  • Can be created manually between parts or by using imported CAD welds or lines (.xml file).
  • Using SimSolid welds has better adaption methods as compared to just using a solid body with bonded contact.
  • Two current situations where welds can't be created in SimSolid.
    • Tubes where edges are overhung
    • Imported solids that have center line far away from feature line
    • Convex edges

Solution Adaption

Overall guidelines:
  • Use Adapt to Features to selectively increase degrees of freedom around small features.
  • Use Adapt to Thin Solids to selectively increase degrees of freedom around thin, curved parts.
  • Use local groups when:
    • When high fidelity stresses are of interest at specific locations
    • When there is a huge difference in the scale of parts
    • When combination of stiffer and soft materials are present in the assembly
Adapt thin to solids:
  • Locally increases degrees of freedom around thin, curved areas.
  • Increases accuracy by better capturing curvature in crucial area.


Figure 9.
The following are examples of modal results on a corrugated structure.


Figure 10. Without Adapt for thin solids


Figure 11. With Adapt for thin solids
Adaptive passes:
  • Increasing number of passes increases the number of boundary degrees of freedom which decreases error at the boundary




Figure 12.