It depends on the application and the aspect of the design that you are considering.
Basic force and velocity are straightforward. Beyond that, there is the fluid dynamics for getting the fluid in and out when the cylinder is moving quickly. There is mechanics, when the cylinder has side loading or excessive compression on the rod. There are several methods of calculating the buckling force for the rod.
Cushioning at the end of stroke is a challenge.
Lubricating servo cylinders that are used on simulators can be a PHD thesis.
CFD for the fluid flow, FEA for the mechanics.
Material science for the seals.
Metallurgy for the rod and the chrome plating. Flash chrome or hard chrome?
Tribology for the lubrication.
Tie rod, round line, screwed gland, flanged seal housing, fully welded, displacement cylinders, telescopic cylinders, synchronised telescopic?
Where do you want to start?
