# Can we simulate rigid body motion using finite element analysis?

I was wondering if we could model rigid body motion of bodies using finite element models. Particularly I'm interested to know if we can model motion of objects with no constraints or with some degrees of freedom (such as only rotation). Though I've used word 'rigid body' to convey the situations closest to what I'm considering, In reality there will be stress, considering non-uniform application of force on surface/body or because of rotation they undergo, and these are not small enough to ignore.

• Rigid bodies - by definition - have no strain and stress. What are the equations you would like to solve with “no constraints”? – BalazsToth Mar 21 '18 at 9:05
• Thanks. This is about equations of motion - F = m*dx^2/dt^2., and its rotational counter part. Though I've used word 'rigid body' to convey the situations closest to what I'm considering, In reality there will be stress, considering non-uniform application of force on surface/body or because of rotation they undergo, and these are not small enough to ignore. – tired and bored dev Mar 21 '18 at 10:54
• Can you give us an example of what you want to model? – P. G. Mar 21 '18 at 11:06
• Suppose you've a rotating solid sphere, which is has magnetic dipole in it. It's subjected to an external magnetic field. The sphere also has linear motion. – tired and bored dev Mar 21 '18 at 11:09
• Finite element codes that have a nonlinear formulation (i.e. nonlinear strain-displacement relations) are designed to handle arbitrarily large displacements and rotations. Most commercial structural finite element codes have this capability and there are many open source codes that do as well. – Bill Greene Mar 21 '18 at 11:42