## General Mechanical

#### Static, quasi static, dynamic, transient

Subscriber

Hi everyone,

Which are difference between static, quasi static, dynamic and transient analysis.

Whether in dynamic and transient analysis need to use the inertia.

Best regards.

• peteroznewman
Subscriber

Static and quasi static both refer to models where there is no dependency on time. Quasi static might be for a mechanism that is moving so slowly, that it is practically static.

Both Dynamic and Transient analysis requires the material have a density so that acceleration loads on the mass of the bodies can be calculated. A Static analysis also needs material with density if you apply a gravity or acceleration load, but it doesn't need density if you are only applying forces.

• Sandeep Medikonda
Ansys Employee

In a static problem, we assume acceleration is zero.

Quasi-static means that at a given instant in time we can assume the problem is static. The fundamental assumption is that the loading is applied so slowly (very low frequency when compared to that of the structure) that basically the structure deforms in a static manner and inertia effects can be neglected. This assumption works well when inertial effects are very low. Also, this helps simplify the non-linear problems to a linear system.

So, In static and quasi-static loading we are solving,  F = KU   and finding the displacements U (Neglect damping, inertia, K is the stiffness matrix)

Note that a load quasi-static for a given structure (made of some material) may not be quasi-static for another structure (made of a different material)

This is not the case in a dynamic analysis where inertia forces are not small enough to be neglected. Inertial forces result from Newton's second law (F = MA). So in a dynamic analysis, we need to account for the accelerations. Where MA is the inertial component and KU is the elastic component (assuming no damping).

In dynamic loading we are solving, F = MA + KU + damping (again we are solving for the displacements in this equation)

Hope this helps!

Subscriber

Hello sir,

I was wondering if you could explain me how to apply dynamic pressure load on a panel??

another question is that how to model this plate out of stripes from different materials?

I wish you could help me

Thanks

• peteroznewman
Subscriber

Please create a New Discussion to ask your questions as they have nothing to do with the topic of this discussion.

Once you have done that, delete your post from this discussion.