Finite Element Analysis (FEA)
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Equivalent Stress Contour Plot Result (Automatic Appearance Settings) |
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What is Finite Element Analysis (FEA)?
Finite element analysis is a mathematical process that can simulate physical, real-world conditions inside of a digital environment. The purpose of FEA is to solve structural, vibrational, and thermal problems in a virtual environment before they become problems in the real world [1]. FEA is a very useful tool in design, as it allows engineers to asses the validity of their model without having to conduct a large number of real-world tests or experiments. Take the design of an armchair for example. If an engineer would like to know the feasibility of their current design, without using any digital simulations, they would have to conduct lengthy physical testing of the chair to determine the eventual modes of failure. This information would be used to improve the design, and the lengthy testing process would begin again. This would continue until the engineer was satisfied with the testing results of their model. However when using FEA, the physical testing conditions can be defined in the software, and the program will simulate 1,000,000 cycles of loading. The results of this time-efficient simulation (modes of failure, cycles before failure, etc.) can then be used to improve the design. Once the design has been changed, the updated parameters can simply be input into the software, and the simulation can be run again. This results in a significantly accelerated design cycle.
FEA Workflow in Ansys
For the Armchair Life Cycle Testing project, FEA simulations were carried out using the Ansys Discovery AIM 2020 R2 software. This software can be used to run many different types of simulations, such as: structural, fluid flow, thermal, and electromagnetic. The necessary steps that must be completed in order to set up and run a structural simulation, as well as properly interpret the simulation results, are described in detail below. The pictures shown throughout correspond to an example structural simulation run on an armchair geometry. There are three main sections to the simulation workflow: "Geometry", "Physics", and "Results".
Geometry
The first step in creating a simulation in Discovery Aim is to import the geometry of the part or assembly that is being studied. This can be done using the following steps:
Once properly imported, the geometry task will display a green "Up-to-date" notification. This signals to the user that no more changes need to be made to this section before the simulation can be run. If needed, there are options under this tab to edit or replace the geometry.
Note: Under the current student version of the software, any geometry imported is subject to a limit of 50 bodies and 300 faces.
Imported Armchair Geometry Example |
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Physics
Material Assignments
In order to run a simulation, every single body in the imported geometry must be given a material assignment. This means that during the simulation calculations, each body will be treated as its designated material with its specific corresponding properties (density, Young's modulus, yield strength, etc.). Material assignments can be set using the following steps:
Armchair Define Example | Use Defined Material to Create a Material Assignment |
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Structural Conditions
The next step in setting up the simulation is the most important. The structural conditions section is where you will define all of the conditions that the geometry will face during the simulations. This tool can be used to define structural conditions such as forces, supports, temperatures, pressures, and many more. Structural conditions can be defined using the following steps:
Note: A support can either be defined as the faces of the geometry that would be resting on the "ground" in reality, or by adding a body to the geometry that serves as the ground (flat slab of concrete for example), and defining that body as a support.
Armchair Loading Example | Armchair Support Example |
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Advanced Setting: Interface Conditions
Interface conditions present in the simulation define how different bodies/faces that are in contact interact. For simpler geometries, this step is often not needed in order to obtain realistic simulation results, as the pre-defined conditions generated by the software are typically adequate. However for more complicated geometries, defining proper interface conditions is important. There are five different types of interface conditions in Discovery Aim 2020:
Actually defining the interface conditions in the simulation can be done using the following steps: