The aim of this job is to remind FE users, especially young engineers, that behind nice-looking models there is still some mathematics.
The graphic capabilities of modern computers can easily handle models with an enormous number of nodes and their computational power can solve huge systems of equations; thus the tendency is to create models that are geometrically identical to reality, without applying any smart simplification. This is a source of possible errors, especially if the FE user has little experience or none at all. An overview of Solid Mechanics equations for the structural linear elastic problem is given; to better clarify all the process over which the FE method is based, the plane stress status is considered and the Constant Strain Triangle is used to create a very simple 2 elements model of a beam, which is then loaded in bending and axially.
All calculations are clearly explained, performed with an Excel file and finally compared with the results given by a commercial code: the target is to show that an FE model could be theoretically solved “by hand”. Finally some examples of complex models are shown, to illustrate the power of the tool when it is correctly used.