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Abaqus Quasi-static induced numerical damping
The Quasi-static method for dynamic problem in Abaqus should be carefully used, because it will automatically induce the numerical damping in your calculation.
This method is very conservative, approximately it will introduce 5% numerical damping (damping ratio).
This method is helpful for contact problem and for convergency. But be careful when using it.
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Effect of Quasi-static method
I also noticed this function in Abaqus. Could you please give me more information on the effect of the quasi-static method? Will the solution be affected a little bit by this method? Thanks.
Yes, the results will be
Yes, the results will be influenced a lot if using Quasi-static method, especially you have defined damping in you model. The model will have double damping, and therefore too damped.
I have compared the solution will experiment data, it indeed affect a lot.
do you mean the result is not trustable
Thanks a lot for your answer! So do you mean the result is not trustable? If the quasi-static method helps the convergence of the simualation, but the result is not trustable, why do we bother to use it?
It may depends on nature of problem
There could be some differences between modeling and experiment. I think it is better for us to compare the results of two difference step types (quasi static and static general) to see the difference between answers. Also it depends on nature of the problem: according to manual, Creep, swelling and viscoelasticity can be modeled in quasi static but not in static general. Also we face fewer difficulties in convergence of quasi static procedure in nonlinear problems especially those cope with complicated contact geometries. But quasi static procedure is not better than static general in all cases. In some cases like surface wrinkling, material instability, or local buckling, you can use stabilization in standard general step.I have modeled a simple steel cantilevered beam under monotonic and cyclic loading and found that there is no difference between responses of these examples. Generally I think quasi static procedure is a good replacement for static general step. Also I will be happy if you introduce me some problems, in them these procedures show different results.
Hi, I just did some detail
Hi, I just did some detailed numerical test on the damping properties using Quasi-static method.
The way I did this is I create a 4 degree of freedom system, without damping, so using Quasi-static method I can get clean numerical damping. And I find that the Quasi-
static will introduce clean STIFFNESS PROPORTIONAL damping. So, the damping value for the nth mode is Cn=a0*phinT*K*phin.
Where phin is the nth modal shape.
K is the stiffness matrix
Yes, you are right for
Yes, you are right for static loading or low speed cyclic loading, but it is a problem during dynamic problems.
I provide some information about the numerical damping in the above thread. Hope it is useful. Your opinion is appreciated.
Hi, I just did some detail
Hi, I just did some detailed numerical test on the damping properties using Quasi-static method.
The way I did this is I create a 4 degree of freedom system, without damping, so using Quasi-static method I can get clean numerical damping. And I find that the Quasi-
static will introduce clean STIFFNESS PROPORTIONAL damping. So, the damping value for the nth mode is Cn=a0*phinT*K*phin.
Where phin is the nth modal shape.K is the stiffness matrix
Hi
Hi. With the information I gained from you problem, I think your problem has dynamic nature, while quasi static procedure is based on stabilized response of the structure to the imposed load.
In addition, the reason for over damping is maybe integration method used by Abaqus. In implicit step, Hilber-Hughes-Taylor method is used while in quasi static procedure, time integration is based on backward Euler method that leads to a higher dissipation than HHT. Perhaps using HHT method with α=0 (Newmark β) will lead to a more suitable answer than Euler method. In addition, you need to control the stability of the solution if you change integration method.