1.2 Why do finite element analysis?
To get a feeling for some of the more common advantages and capabilities of the FEM, we cite some material from a NAFEMS booklet entitled Why Do Finite Element Analysis? (Baguley and Hose, 1994). NAFEMS, formerly the National Agency for Finite Element Methods and Standards, is an independent and international association for the engineering analysis community and is the authority on all aspects of FEA. In its view, simulation offers many benefits, if used correctly.
The most common advantages include:
- optimised product performance and cost
- reduction of development time
- elimination or reduction of testing
- first-time achievement of required quality
- improved safety
- satisfaction of design codes
- improved information for engineering decision making
- fuller understanding of components allowing more rational design
- satisfaction of legal and contractual requirements.
We should emphasise early on that all FEA models and their solutions are approximate . Their accuracy and validity are highly dependent on understanding the behaviour of the system being modelled, of the modelling assumptions and of the limits input in the first place by the user.
For example, in the field of stress analysis, which is the most common application of FEA for a typical engineering component or body, the general problem in the first place is to determine the various stresses or strains acting at all points in the body, in all directions, for all conditions of loading and use, and for the actual characteristics and properties of the materials of construction. For all but the most simple of shapes and conditions, this task is humanly impossible, hence the need for setting up simulations and modelling the behaviour.
Straight away, we have to make assumptions; these include the following:
- Are the loads worst-case likely or expected scenarios? We have to choose or specify various options of loads and their application points to embrace the likely real situation that the product may experience in use, transport or assembly.
- How is the component held or restrained? In short, what are the boundary conditions and how are these modelled?
- What are the relevant material properties? Do we know, for example, the material behaviour under stress, heat, static or dynamic loading? Is there a reliable database of material properties that we can draw on?