I want to simulate tensile until fracture. for elastic I input E and v, and for plastic I used true stress and plastic strain value calculated from the stress-strain diagram after elastic until tensile strength. For simulation until fracture, starting from necking and break. I intend to use Damage for ductile model (here I need stress triaxiality, strain rate and eqv plastic strain) How to get these parameters? Can get it from experiment? or I should do UMAT programming? I am using ABAQUS software.
These parameters are given by classical definitions in continuum mechanics
You can find it with Wikipedia.
The triaxiality in case of tensile loading, equals to 1/3.
The strain rate is not useful for you if the material do not present a viscoelastic behavior, then you can use what you want!
The equivalent plastic strain is given by a classical formula : it is the square of 2/3 of the product of the plastic strain tensor by itself.
Regards
These parameters are given by classical definitions in continuum mechanics
You can find it with Wikipedia.
The triaxiality in case of tensile loading, equals to 1/3.
The strain rate is not useful for you if the material do not present a viscoelastic behavior, then you can use what you want!
The equivalent plastic strain is given by a classical formula : it is the square of 2/3 of the product of the plastic strain tensor by itself.
Regards
Hi yves..now its clear..except for eqv strain. I knew the formula but how to calculate it?..do you have any specific example?if you dont mind
OK, for the eqv plastic strain, it is very easy because under tensile loading, the equivalent plastic strain exactly equals to the tensile plastic strain.
It is not true for other type of loadings.
Therefore, you only have to measure it at each step of calculation.
Yves, i might be wrong. I need fracture strain rather than equivalent plastic strain..so, this value can be obtained from stress-strain?or else?
You can measure the total strain at rupture from stress-strain diagram only if the strain is homogeneous into the spécimen, without localization. If you have necking, you cannot take the same value.
In order to obtain the plastic strain at rupture, you should eliminate the elastic strain.
Under small strain, you can make the difference : EPS(plast)=EPS(tot)-EPS(least)
But take care that the elastic strain is given with a Young's modulus which is not the same that the initial one, because of the increase of the damage.
I am not sure to answer to your question....!
Have a nice day!
Yves
Please Mohd refer also to the following article to find damage parameters.
Someone enter a tabular data into the parameters of ductile damage, someone not. I don't understand . Can you explain to me, Yves ? Tks you so much !
Nam Nguyen Viet and others can contact me for Concrete Damage Plasticity Model.
hi , Mohd ! i am to use Damage for ductile model and have the same problem as you . so , could u tell me how should i do if u made it ?
The definition of the damage parameters that go into various parts of the ABAQUS can vary, which makes it difficult to give a definitive answer. However, the general principle is that the damage parameter is a ratio of stiffness of an unload-reload line of the damaged material divided by the stiffness of the undamaged model.
I discuss this topic a little in my PhD thesis, in the context of the concrete damaged plasticity model (CDP). There is a link on my profile.
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