Hi

In order to define this pre-stressing force :

In module "Load" click on predefined field>Mechanical>stress.

you can upload your data file or input in manually.

Hi,

In this case you should keep the stresses inside the body and then start the new calculation. For example at the end of the dynamic loading process the internal stresses had to be exported and be used in your next calculation.

http://abaqus.software.polimi.it/v6.12/books/usi/default.htm?startat=pt03ch16s11.html#usi-lbi-iceditors

Dear Sajjad

As i mentioned in my problem statement, i tried using the predefined field option on a simple cantilever beam by defining initial stress values of , say s11, but the variation in results of non-prestressed and prestressed one are arbitrary and illogical.

Dear Ankul

Could you please provide more information? like what was your all predefined stress, did you put shear stress or you just have principal stress?

As for as I got from your model, you want to first analyse the nonlinear model (As you told elastic and plastic! ) and then you want to do the same model for predefined stress for the same analysis. So, in predefined stress you probably have more. what was your output for the same parameter like (S11 =???)

So, how did you compare the results (S11)! How you can declare they are illogical? please clear it so we can able to help you more.

Thanks

Dear sajjad

I tried with a simple problem. a cantilever beam with a point load at the end using shell element and then s11 value was as shown in 1st picture (4.5). in 2nd model i prestresed s11 only by 4.5 and got what is in 2nd picture (point of consideration being same ). what i mean by illogical is change in s11 value which is just 0.25 (from 4.5 to 4.75). Is there some kind of explanation behind this ? or Am i interpreting it wrong way ?

Kumar

If you defined a set for especial element, it may be true. (Is it MPa unit?)

In fact, if you defined a set to take S11, it really depends on the location of element. You need to make sure about MESH, too. Did you use the mesh study to be sure about your meshing seed?

but, in order to make sure about your result, I suggest you to validate with an experimental test, first and then do the prestress for that model. If you do, you can accept your output.

Dear sajjad

let me start from the beginning. I don't have profound knowledge of working in abaqus and especially about predefined field option. I just came to know that one can use this feature to prestress a structure . In my analysis i am not using tendons , i am assigning only concrete properties to the whole structure. so here are my doubts if you can help me out.

1. How does this predefined field option work ? I mean if i enter x value in s11 field and zero in other fields , does it mean that my stress values at each node or element will be affected exactly by x (i.e. increase or decrease by x ) or does it work in some other way ?

2. I will be using time varying load in my analysis. From some of analyses i have done using same method as described above , i found out that that particular stress value, say s11 ( i am providing only s11 value and every other value as zero) tries to come back to zero asap. why is it so ? This can be due to the equilibrium problem but that can not be in real structure as a prestressed structure in real life is already in equilibrium. so how to simulate the same thing in abaqus without using tendons or something like that?

Thanks