Failure of a steel
Failure of a steel
(OP)
I've a problem.
I must study the load capacity of a steel.
I must use an elasto-plastic costitutive law.
My problem is that: i'm not able to define the failure of my steel. When i launch the job, the program continues to increase the plastic deformation without that the material crashes!!!
I want that when the material arrives to a deformation that i define, the element crashes and the analysis stops.
How can i define this failure criteria?
Please help me!
I must study the load capacity of a steel.
I must use an elasto-plastic costitutive law.
My problem is that: i'm not able to define the failure of my steel. When i launch the job, the program continues to increase the plastic deformation without that the material crashes!!!
I want that when the material arrives to a deformation that i define, the element crashes and the analysis stops.
How can i define this failure criteria?
Please help me!





RE: Failure of a steel
The "failure" of your steel depends on many things:
* the type of steel,
* the temperature,
* the structure or component it is made into,
* detailed geometrical detail: such as the presence of a stress concentrating feature, or even a crack.
There are damage models and facilities available in ABAQUS that allow "failure", but you must first consider the above and decide the damage mechanism(s) that operate in your circumstances.
Regards,
MRG
RE: Failure of a steel
I concur with what MrG said.
Also, if you want material failure in your model, you need to be looking at the *DAMAGE INITIATION and *DAMAGE EVOLUTION options. These are only available in Explicit though (section 11.6.1 of the Analysis Users Manual)
I assume that you are using a *ELASTIC and *PLASTIC material model? The *PLASTIC model will not give failure at the last specified *PLASTIC point - ABAQUS will extrapolate the data forward, so the material never actually 'fails' as we would expect in real life.
Martin
RE: Failure of a steel
I have only this version
RE: Failure of a steel
corus
RE: Failure of a steel
RE: Failure of a steel
There is *FAIL STRESS and *FAIL STRAIN - but these are generally used with composites (see section 10.2.3 of the ABAQUS Analysis Users Manual).
It sounds to me like you want to have the elements removed from the model as they fail by setting a failure stress. As far as I know, this is only possible in Explicit with the dynamic failure models. If there is a way to do it in Standard, I can't find one.
Martin
RE: Failure of a steel
RE: Failure of a steel
Now I see what you're trying to do
Unfortunately, I don't think there is any way of stopping an ABAQUS/Standard analysis at a specific value of stress. If anyone else knows a way, then I will learn something new aswell.
You may have to fall back on examining the principal stresses and plastic strains (PEEQ) to figure out how close you are to failure of the material.
Regards
Martin
RE: Failure of a steel
RE: Failure of a steel
The strain at which necking occurs is called the 'instability' strain, look up plasticity books on it, Im not sure if ABQ manuals say anything about it. There is a formula to determine it based on the plastic properties of the metal defined by the Ramberg-Osgood plasticity formula.
RE: Failure of a steel
Couldn't you let the results run past failure and then plot the stresses vs. load to determine at what load the failure occurs?
Gurmeet