Question:
What are the options for simulating lattices?Answer:
There are three main methods for simulating lattices in nTop. They are using Solid Elements, Beam Elements, or Homogenization. The pros and cons of each method are listed in the table with an example workflow below.| Type | Pros | Cons |
|---|---|---|
| Accuracy, Edge effects considered, Locatable maximum stress point | Computationally expensive, Requires meshing of the lattice (challenging), Dependent on mesh quality, Large file size | |
| Fastest, Accepts field-driven beam thickness | It only works on beam-based lattice structures, No edge effects, No stress concentrations, Ignores blend lattice-wall radius | |
| Faster, Works for any lattice, Works on large and high-density lattice structures | More setup steps, Least accurate, No edge effects, No stress concentrations, Ignores blend lattice-wall radius, Lattice must be uniform |
Solid Elements
Solid elements are volumetric finite element mesh of the entire lattice structure.- A finer mesh is required to capture the detail of the lattice
- Use Remesh Surface block after Mesh from Implicit Body
- Volume Mesh block may fail; if so, you can repair the mesh through Mesh from Implicit Body and Remesh Surface or use the slower, more robust, Robust Tetrahedral Mesh.
Beam Elements
Beam elements are finite element nodes along lattice vertices connected by lattice beams. This method greatly reduces the number of elements from a typical volume mesh but ignores certain mechanical behavior like edge effects and stress concentrations in the lattice. FE nodes will be placed at the endpoints of each beam, along with node(s) and the subdivisions of the beam. You can choose the number of subdivisions as input to the FE Lattice Mesh block, which will be arrayed as demonstrated in the image below.
- Use Trim Lattice to ensure the lattice elements lie within the volume of the Lattice Structure.
- If you get a warning about short lattice beams, use Collapse Lattice Vertices with a threshold much lower than the unit cell size.
Homogenization
To create a homogenized simulation, run a Solid FEA simulation on a single unit cell of the lattice, and generate effective material properties of the unit cell. Next, run a second Solid FEA simulation on the bulk lattice structure volume using the effective material properties (from the first simulation). Use Solid Domain with the Material chip from the Homogenization block.- Works best with many unit cells
- Good for comparing different lattice types
Comparison
To compare these methods, we’ve created a BCC Lattice between two panels. Look for the download of this Case Study at the bottom of this article.
