Nowadays Finite Element Analysis (FEA) is an important procedure before the production process. The analyst can know in advance whether the structure will withstand the loads it was designed for. Here is a step-by-step basic methodology setup of a FE Analysis.
Step 1: Geometry
FEA starts with CAD (Computer-Aided Design). CAD is a 2D or 3D design that seems like the prototype component which the analysis is made for. The job of a CAD engineer is different from an Analysis engineer. The first wants to make the CAD just like the prototype, and the second wants to simplify it as much as possible, to run the simulation quickly, without much computational cost.
The geometry in our case is shown below:
Figure 1: Geometry of a boom.
This part is a component of an Excavator Boom that is lifting 350kg mass. To understand the model better, Figure 2 illustrates a real-life Excavator.
Figure 2: Excavator’s boom.
In Simcenter 3D the CAD file is .prt (part file) and you should not do any changes to that file. You can do modifications in the i.prt (idealized part) as described in the next step.
Step 2: Geometry modifications
In the i.prt you may modify the CAD to make the model simpler. In this file, you can use the command “mid-surface” to generate an approximation of the part’s medial surface between pairs of surfaces. You can then perform your CAE analysis directly on that mid-surface, rather than on the original solid model. The process is: you select the solid body on which to create the mid-surface, the program creates face pairs, and finally, creates a surface in the middle of those face pairs. The mid-surface procedure has a drawback that creates voids between attached planes. So, requires further processing to join these gaps, such as extended faces. The following figure explains that:
Figure 3: The gaps left from the mid-surface procedure.
After expanding, the surfaces the result looks like this:
Figure 4: The geometry after the expansion.
Step 3: Mesh and Stitches
The next step is the meshing procedure. In FEA, a mesh grid is used to represent the geometry of the component. For this job, the used file is .fem file. Meshing is the stage of the finite element modeling process in which you divide a continuous structure into a finite number of regions. These regions are known as elements and are connected by nodes. There are several factors to consider when meshing geometry, such as element type, element size, and mesh density.
This model consists of surfaces, so the elements that we use to discretize, are Shell 2D. At the end of the boom, there is a concentrated mass that can be modeled by the 0D element. Also, 1D elements are used as well to attach the 0D element to the boom surface.
Figure 5: Mesh grid.
One more important task in this step is stitching. “Stitch Edge” is the command that joins two surfaces, edge to face or edge to edge. You can see which edge is stitched and which is not by the Model Display, on the Polygon Edges section area. Your model should look like Figure 6.
Figure 6: Unstitched Edges-(Left), Stitched Edges-(Right)
Last but not least, in the .fem file, you can define the material properties. Simcenter 3D is equipped with a library of materials that the user can use.
Step 4: Set the Solution
You are almost at the end of the setup. The final file that you are going to use, is the .sim file. Here you specify the restrictions, connection, and loads of your analysis.
Figure 7: Constraints and Loads for the simulation.
In this case, connections were not useful. Some connections are surface-to-surface contact/gluing, edge-to-edge contact/gluing, edge-to-surface gluing etc. All these choices make the results more accurate. Now you are ready to press the solve button.
Step 5: Post-Process
This is the last step. The best way to understand the results is to visualize them. Post-processing displays are created directly in the graphics window. Simcenter 3D allows you to create cross-section and cutting-plane views, graph results, animations, results identification, and display multiple views.
Figure 8: Post-Processing example.
We at FEAC hope that this blog post has been interesting and that you will be able to create a nice FE Analysis after reading this. If you have any questions, you are always welcome to contact us at email@example.com