|Figure 1: SOLIDWORKS Simulation Tetrahedron Mesh on a Part|
Meshing is one of the most recognizable tools that we use in simulation. We often look at components that have been meshed and see a map of triangles (tetrahedron elements) that are used to provide us with analytical results. But, what exactly is a "mesh?" Specifically in SOLIDWORKS Simulation, what does the mesh consist of? How is it used to provide us with all of these simulation results we see? I want to give a brief overview of the anatomy of the mesh, how it calculates results, and explain the pros and cons of the different element types.
|Figure 2: Solid Elements in SOLIDWORKS Simulation|
The mesh is broken down into two main areas: elements and nodes. The element is the overall "triangular" shape that you see throughout the model in Figure 1. Nodes are a part of the element, and is best shown by Figure 2, where nodes are called out by the red points. Figure 2 shows the two types of solid elements we can use in SOLIDWORKS Simulation. The left part of the image shows the draft quality mesh, which is a 4-node tet (tetrahedron) element. The right of the image shows our higher order 10-node tet element. When we run a finite element analysis, we are essentially calculating deflections for the nodes in our elements. Overall, the goal is to typically calculate stress and strain values, which is a derivative of the displacement. The following equation is run by the computer to calculate deflection values:
|Figure 3: Finite Element Stiffness Equation|
Figure 3 shows the equation that is used to calculate the deflections in our FEA models. "K" is the stiffness matrix, "U" is the displacement, and "F" is force. When we rearrange the equation, we set the output to be the deflection, "U," where "U" is a function of the stiffness. The stiffness is what makes all the difference between the draft quality element and the default, higher-order element type. Due to the lack of nodes for the draft quality element (4-node tet), the overall stiffness of that element is amplified, and less likely to give more accurate results relative to the higher-order element for stress values. If you are running a final analysis, always use the higher-order elements. However, draft quality elements do help out if you want to run a quick analysis to ensure that you have working FEA model. Due to the smaller number of nodes, there is less calculation and therefore you receive results much faster. Once you've run a "draft" run with draft quality elements, go over to the property manager and uncheck the box for draft quality elements.