Difference between results of Linear static and Non linear quasi static.

hiranwale_bharat

Hello,

 

I was carrying out analysis on a model in which load vs deflection results were to be found out.

 

Material was defined by MATHE card with stress -stretch curve , and some contacts were present.

 

First I used Linear static loadstep and then I used Nonlinear quasi static step for same model and BCs.

 

Results of both cases were very much different (more than 50%).

 

Can anyone tell me what is the case?Is linear static neglecting the effects of contact and material non linearity?

 

Regards,

Bharat

tinh

Yes, ofcourse Linear Static does not take into account the contact - it is nonlinear, generally all nonlinearity affects including:

- material nonlinearity: stress is above yield point

- geometric nonlinearity: stiffness matrix sensitive with geometry deformation

- boundary nonlinearity: contact

And also 'static' means no dynamic affect can be captured, so every loads must be applied slowly

Rahul Rajan_21763

Hi,

MATHE is a Hyperelastic material.

HyperElastic materials behave differently compared to isotropic materials and their properties are extracted through strain energy potential.

Hence linear static will not take account of MATHE card.

 

Regards

Rahul R 

hiranwale_bharat

Hello Rahul and Tinh,

 

Thanks for the help,

 

Regards,

Bharat

hiranwale_bharat

Hello guys,

 

What can you say about transient, Random and frequency response analysis. I have heard that random and frequency response are linear analysis. What if these cases have material defined by MATHE and has contacts in it?

 

Regards,

Bharat

Altair Forum User

Hi Bharat,

 

FRF, modal, linear transient, random response are linear dynamic when we talk in Solid mechanics terminology.

 

You can either do a implicit or explicit dynamic analysis for instance a drop test for nonlinear transient analysis.