Doubt about Dynamics of a system from FE analysis

[adas_11]

Hi,

Consider a Single link Manipulator of which I am interested in studying the dynamics as a function of state space formulation like
x_dot = Ax + Bu or x_dot = f(x) + h(x)u for linear and nonlinear case respectively. So when developing the FE, what solver do I need to consider. As I follow, I need to consider an explicit dynamics solver while using ANSYS or an implicit dynamics when using ABAQUS when I am interested to export the Mass, Stiffness, Damping matrix for developing a model for system dynamics. Please clarify if I am correct or not??

 

[FEA way]

Both implicit and explicit solvers can be used for this case. They solve the same equation of motion: [M]{u''}+[C]{u'}+[K]{u}=F and only use different methods for time integration. Also both can solve nonlinear cases. The main difference is that explicit is meant to be used for highly nonlinear problems such as impact. And unlike implicit, it's conditionally stable. For your purpose I would suggest implicit since there's simply no need for such big gun as explicit solver here.

 

[adas_11]

Hi FEA way,

Is this similar when I use a static structural solver in ANSYS. Do I get a similar mass Stiffness matrix for the same equation of motion?

 

[FEA way]

Static structural solvers use simplified version of the equation I presented above: [K]{u}={F}. They can only solve problems where loads do not change in time (are constant) and are applied slowly and gradually until they reach their full magnitude. Thus inertia and damping effects are neglected. Such solvers don’t use mass matrix so you can only get stiffness matrix from them.