Welcome to part 5 of our Getting Started with SOLIDWORKS Simulation series. This time we will be showing you how to break your model into smaller entities, otherwise known as meshing.
If you haven't seen our previous entries, here is where to get caught up:
Once you’ve finished defining your fixtures and loads, the next step before running the simulation is to divide the model into small entities called elements. This process is called "meshing", and it's one of the foundational concepts in FEA. Meshing is what allows the computer to solve the underlying math problem and give us results.
You can think of mesh elements as “virtual Lego blocks” that are used to represent the model. If you use big Legos, you can build a copy of the model very quickly with a relatively small number of blocks, but it will only be a rough approximation of the true shape. On the other hand, if you use very small Legos, you can get a more accurate representation of the shape, but it will require a lot more Lego blocks and take longer to construct.
The same is true with your mesh. The smaller the elements, the more accurate your results will be, but the longer it takes for the simulation to run.
Therefore, your goal is to strike a balance between accuracy & run time by choosing an element size that will give you an acceptable level of accuracy while still using the fewest number of elements possible.
Finding this balance can sometimes be a challenge for new users, but it's a skill that can be learned over time.
In our simulation training classes at Alignex, we teach several techniques for developing an efficient mesh that delivers accurate and fast results.
A great feature for those new to SOLIDWORKS Simulation is the automesher. The automeshing tool allows the software to quickly & automatically divide the model into elements. You can use this slider bar to set an approximate mesh density, or you can expand the Parameters section and specify an exact element size.
There are three automeshers to choose from: Standard, Curvature-based, or Blended curvature-based.
The Standard mesher is ideal for creating a symmetrical mesh with very uniform element sizes. However, it can sometimes be challenging to represent small features or highly curved geometries.
Next, the Curvature-based mesher uses a variable element size that makes it much more flexible and robust when dealing with complex geometry or small features. It’s also the fastest of the three meshers.
Finally, the Blended Curvature-based mesher can be used when the curvature-based mesher fails or produces poorly shaped elements.
One technique for creating an efficient mesh is to use mesh controls. This allows you to create small entities in specified regions of the model. Mesh controls allow you to use smaller elements in areas of interest without needing to use them in less critical areas where stresses are much lower. This decreases the total number of elements, thus decreasing solve time.
Because the accuracy of your stress results relies heavily on the quality of your mesh, it's always a good idea to run what’s called a mesh convergence study. The idea is to run your simulation multiple times using smaller elements with each subsequent run. If the maximum stress changes significantly from one run to the next, this can indicate that your elements are not small enough. Once your stress values converge, or level out, you can have more confidence in the quality of your mesh and your results.
If your stress results do not converge, but instead begin diverging to infinity then your model probably has what is known as a stress singularity. No, we aren’t talking about a black hole that will consume the planet, but the concept is actually somewhat similar.
Stress singularities occur in all FEA software. There are many online resources that explain why they occur and how to resolve them. A full discussion of stress singularities is beyond the scope of this video, so if you’re interested in learning more I encourage you to check out some of the SOLIDWORKS help documentation or attend an Alignex training class.
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Written by Sean Stiehm
Sean Stiehm is a Product Specialist at Alignex, Inc. His days are spent showing businesses how they can leverage SOLIDWORKS ancillary tools to streamline specific processes, get products to market faster and reduce costs associated with product development, prototyping & manufacturing. When not working, you're most likely to find him flying his sUAS or wandering a trout stream somewhere in the driftless region.