Description

The purpose of this page is to give readers a basic understanding of how to use Ansys Workbench and Mechanical from the Ansys suite. In short, it is a step-by-step guide to conduct the following analyses:

• Static Structural (specifically Quasi-Static)
• Modal
• Response Spectrum (Random Vibration and Shock Vibration)

In addition, I aim to provide the motivation behind each of these analyses, as well as some background information about finite element analysis.

Background Information

What is Finite Element Analysis?

Finite element analysis (FEA) is the process of predicting an object’s behaviour (e.g. stress, strain, deformation) based on calculations performed through the finite element method (FEM) — basically breaking down the object into very small pieces. FEA is used when solid mechanics calculations cannot be done by hand, due to the complexity of a model. The process can be broken down into 8 main steps:

1. Simplify: The CAD model of the object is simplified. Any fine details that are deemed too insignificant to affect the behaviour of the object under load are removed (e.g. small holes, fillets, threads)

1. Define: The material properties of each of the objects components are defined (e.g. modulus of elasticity, yield strength, etc.). Common materials for satellites include Aluminum 6061 and Stainless Steel.

1. Mesh: The essence of the FEM. The model is discretized (made into small elements) through the process of meshing. Most of the work is done automatically by FEA software, but refinements will likely be required to avoid inaccurate results (see “Setting up the Simulation”).

1. Boundary Conditions: When applying loads to a model, it is important to define the ways in which movement will be restricted to most accurately depict its real-life environment. For example, cubesats are placed into cubesat dispensers, which do not allow constant movement in the axial direction. Displacement supports or fixed supports are mainly used for this purpose.
2. Apply Loads: This is the stage where forces/accelerations/etc. will be applied to the model. They may be applied to the whole body or just in a certain location — it depends entirely on the problem at hand.
3. Run: The fun part! Now is the time to harvest the fruits of your labour in setting up this simulation. You can select the types of results you would like to retrieve (e.g. stress, deformation, maximum factor of safety, strain, etc.) and sit back while the software does it for you — this may take a long time, i.e. possibly hours.
4. Interpret: Your work is not done, however. The results you get may not be entirely accurate. Look out for things such as unusally high stresses in specific locations, which are often the result of poor mesh quality.
5. Iterate: This is an important component of the FEA process. It is unlikely that you will acheive the desired results on the first try, since it is almost inevitable that you will discover errors in the interpretation stage.