Finite Element Analysis (FEA) is just one of many tools in the engineers’ toolkit used to help solve problems and find answers. The applications for FEA just about cover everything where the effects of forces, impact, shock, earthquakes, temperature, noise, vibration, friction, durability, stiffness and weight are of interest.
FEA programs generally import CAD geometry and create a mesh to divide the volume or area into smaller volumes or areas called elements.
Think of each element acting like a spring with each spring connected to each other to form one large spring. The benefits of this methodology are that any CAD model of any shape or form can be checked for stress and deflections before making a prototype. In other words, FEA is virtual prototyping.
FEA provides the ability to explore a wide range of prototype options and designs quickly and cheaply. This makes FEA an essential tool to improve product performance, cut costs and reduce project lead time.
If you build and test a prototype you may find that the prototype suddenly breaks at 50% load. You will then build another prototype, make the failed section thicker and re-test. You may then find that your prototype fails at 75% load in a different place. The design and test cycle is repeated until you reach 100% load without any failures or damage.
On the other hand, your prototype may pass first time without using FEA but you will not know what your reserve factors are unless of course you test to destruction. If you decide to test to destruction you will need several prototype components for each design iteration. For example, if you have three design options in three similar materials and three load cases you would need to test at least 27 prototypes to destruction.
You will never really know what is your optimum design because the cost and lead time of making such a large number of prototypes and test rigs will be unacceptable.
One of the advantages of FEA is that you can find the stress on any part of the CAD model before you make a prototype therefore you can predict what area is likely to fail first and what is the second and third areas that could fail with higher loads. By properly applying FEA you are effectively performing design iterations on a simulation model rather than a physical prototype. Another advantage of FEA is that you can see things that you can't see by going down the build and test route. For example, if you overload a grey iron casting, the deflections may be unnoticeable before it suddenly cracks or fractures. Now if you wish to make it stiffer in a certain direction, it will be difficult to measure such small deflections on the test rig. With FEA the deflections are easy to see, this helps you to understand load paths and stiffen the structure in the most effective way.
It is very expensive to build and test prototypes for large components and structures. Imagine how much a test rig would cost to demonstrate reliability for earthquake motions on an overhead travelling crane that is 20 metres long and is carrying 50 tonnes. FEA on the other hand has no restrictions on size or weight.
Something else to consider with plastic components is your prototype may be in a different material to your manufactured component. Injection mounded tooling for high volume production is very expensive so you may only be able to build and test your component made with a similar material and not the production material. Similar plastics can have very different mechanical properties especially when subjected to high or low temperatures and repeated load cycles. FEA will give you the opportunity to explore different material options quickly for minimal cost.
FEA is particularly useful when applied to components used in highly regulated industries where safety is a priority such as pressure vessels. There are many design codes and standards that require accurate stresses to be calculated so that they can be checked against allowable stresses. Some sections of the ASME codes allow stress from FEA to be directly applied to check compliance against the required standards.
FEA is just a tool and like any other tool requires an engineer who is experienced enough to understand how to use it properly. The most important attribute of any FE Analyst is not their ability to drive a software package but their ability as an engineer.