Hi, Navid! n ANSYS your problem is solved very simply. One solution is to use a multi-step mechanism for the calculation.The first step is to solve task of forming a pre-load, and the next - to specify conditions for the solutions of the required the main task. The result will be the one about which you write.

I wish you success.

Hi Alexander,

Thanks very much for your explanation. However, I am not sure I got your point. I was wondering if you could explain it a little bit more.

Thanks again,

Navid

So, pre-stressed state is the result of some impact which is defined by a set of boundary conditions and / or some specified temperature distribution. That is why on the first step problem is solved, resulting in a desired stress distribution. And at the second step, you decide the main task with predefined stresses.

Thank you again. As I do not know what is the initial shape of my model (before generation of the prestress), I cannot start from the initial step. I have the geometrical properties of a fairly complex model, in which I also know the stress profile. I want to start from this step and apply another loading on my model to see what will happen next.

Sorry if I didn't get your point again!

Cheers,

Navid

Well, Nvid!.

I do not know all the features of your application, so I will do simpler - I will recommend to see the following sections of a general guide ANSYS:

2.6.13. Initial Stress Loading

2.6.13.1. Initial Stress File Format

2.6.13.2. A Sample Initial Stress Problem Using ISFILE

Wishing you success.

The answer depends strongly on that do you mean as "prestress". Stress is a tensor, so definition of spatial stress field is very complicated.

If you mean only values of local tension of compression, a simply answer to your question is defining the spatial temperature field in the structure to develop local compression stress (raised temperature) or local tension stress (lowered temperature). Local stress will be proportional to change of temperature.

Temperatures can be defined as a first structural step (to see resusultant prestress field), or just in main load step.

If you need smooth distribution of temperature, structural (stress) step should be preceded by heat transfer step with local definition of temperatures. After this step, you will get smooth temperature field as input for structural analysis with prestressed structure.

I hope it is clear enough to help you.

I do not know details of your model.

In principle, you could prescribed displacement along the outer boundary of your domain

assessed on the basis of constitutive elasticity relationships, to generate the desired stress states.

As you can see, everyone has different understanding yours "prestress". It can be many different things, and for each there is different answer.

For example it can be:

1. internal stress state state after plastic deformation (stamping)

2. initial stress by externally applied force/displacement before main load

3. internal thermal stress from non-uniform temperature change

4. initial stress caused by centifugal forces

5. any combination of above

6. others...?

Be more precise and specific, please.

Hi,

Big thanks to all for your answers.

I really need to apologize for being such late in responding since I was expecting to receive notifications from this website in case anybody put a comment on my question, but I didn't receive any email.

Back to my problem, I have to say I have a hole in a thick hyperelastic plate (Fig 1), and I know the stress profile across the thickness direction of this thick plate in this configuration. As shown in Fig 1 a bush was fitted inside the hole of plate. In this configuration (the only configuration we have), we also know the lateral pressure profile which is shown in FIG 2. Now, we are going to apply an external tension or bending on the thick plate to see how stress will change and what will be the deformation in existence of the initial stress I described before. The tension or bending will be applied on the surrounding boundary.

With this explanation I guess I have "initial stress by externally applied force/displacement before main load" in my model.

So I have attached 2 figures here showing 1- the geometry of the plate and the bush, 2- corresponding initial stress. AS I am doing this in ABAQUS software, it would be more appreciated if I could have your suggestion about how to do it in abaqus. BTW, I know the model should be 1/4 of the current model, because it is an axisymmetric model. I hope I explained enough, otherwise let me know.

Thank you very much for your help.

Navid

Sorry the first FIG is attached now

If its just a steel cylinder pushed into rubber plate, you can do it in abaqus in two steps:

1. place cylinder in rubber with no stress and cool down the rubber material (or heat up the cylinder) to get correct stress in rubber -> prestress

2. apply external load to the rubber in second step

Thank you Artur. However,

1- Using either of the ways, the bush diameter, since it is not much stiffer than the plate, also changes, and I do not want this.

2- I cannot get the non-uniform stress profile I showed above with changing the temperature, can I?

3- What is your idea about using predefined stress field option in ABAQUS?

I am using it now but again I have the same issues as above.

Any further help would be much appreciated.

Navid

Did you find answers for your questions on "how to apply non-uniform pre-stress distribution in Abaqus"?

Please share your finding..!

I am also intereseted in this topic. I assume the original question went in the direction of how to apply a prestress condition into a FEM model without performing the initial loading step...etc. E.g. if residual stresses are known to be 500MPa over a certain area of the 3D geometry (as measured) - how to assign these to the FEM model in order to perform other analyses (such as Modal, etc).

In ABAQUS, from load module, use create predefined field in the initial step. it is very easy to apply however you need to know the stress tensor for every element in the set that you are imposing the pre-stress BC.