In my work I always try to optimize parts which I make. This require a good knowledge of mechnic and also a lot of calculation.
For some simple models (like bolts, pins, beams) hand calculation is sufficient, however more complex models require a FEA analysis. Easy problems I solve using sheets prepared for this type of calculations, and for more complex I use software like Inventor, Ansys and Nastran (or some open-source software).
This type of software helps a lot, especially with buckling, or non-linear analysis.