Mechanical APDL is intended for solving practical engineering problems. Many theoretical problems are not realistic in that the assumptions necessary to obtain a closed-form analytical solution make the mathematical model depart from a practical application problem. Examples of these assumptions are: step force changes, step temperature changes, perfectly plastic impacts, infinitely rigid supports, etc. Imposing these conditions in a finite element analysis often requires more effort to duplicate the theoretical result than would be required to solve the "real world" problem.

Theoretical solutions are generally based on a continuous or differential approach. In some cases, an exact comparison with a finite-element solution would require an infinite number of elements and/or an infinite number of iterations separated by an infinitely small step size. Such a comparison is neither practical nor desirable.

Some of the Mechanical APDL solutions in this document are also compared against experimental data obtained from textbooks or technical publications. The experimental measurements are often presented in the form of graphs of relevant parameters. Hence the simulation results are also presented as graphs so that the corresponding values can be compared on the same graph. Experimental data represent the real-world physics reproduced in a controlled manner, and provides more complex details than theoretical solutions.

The examples in this document have been modeled to give reasonably accurate comparisons ("engineering accuracy") with a low number of elements and iterations. In some cases, even fewer elements and/or iterations will still yield an acceptable engineering accuracy. There are also cases where larger differences may exist with regard to references, for example when comparing against experimental solutions. These differences have been examined and are considered acceptable. A survey of the results comparisons in this document shows an average accuracy within 1-2% of the target solution.