Failure criterion of cohesive beam

[dxvn818]

Hello all,

I would like to ask about the failure criterion of beam. In Beam class, I saw the parameter "maxStress_" and the following code:

if (maxStress_   > 0.  && currentStress_ > maxStress_)
        Bond::Disable();

Is it right that the rankine failure criterion is used in GranOO ? However, I do not see where "maxStress_" is calculated. In my test, the beam seems to be broken earlier than experiment and I want to make some change. Could you please show me the file name of this calculation ?

Thank you in advance.

Regards,
Vinh

[jeremie.girardot]

Dear Vinh,

you will find what you want in the same file but just a little before on line 352 :

      currentStress_ = (currentNormalStress_ + sqrt(pow(currentNormalStress_,2.) + 4.*pow(currentTorsionStress_,2.)))/2.;

You can see that the "currentStress" is computed thanks to the rankine criteria and compared to the scalar value "MaxStress" you give in your .inp file.

Do not hesitate to test other criterion !

regards

[dxvn818]

Hello Jeremie,

My question means when I did not input the value of MaxStress, I do not understand how its value is calculated. For example, the input file in my test case has the form:

<PlugIn Id="_ConvertElementPairToPlasticBeam"
            YoungModulus="Eu" RadiusRatio="Ru" PoissonRatio="poisson" DampingFactor="damp"
            MaxElasticElongation="maxElasElong" MaxElongation="maxElong"/> 

I have no input value for MaxStress, but instead I input value of MaxElongation. In this case, how GranOO calculates the MaxStress ?

Regards,
Vinh

[Damien André]

Hello Vinh,
You can set directly in your input file a MaxStress value. It is set through  the inheritance mechanism because PlasticBeam inherits from Beam.

<PlugIn Id="_ConvertElementPairToPlasticBeam"
            YoungModulus="Eu" RadiusRatio="Ru" PoissonRatio="poisson" DampingFactor="damp"
            MaxElasticElongation="maxElasElong" MaxElongation="maxElong" MaxStress="10e6"/> 

I don't test the above code but it should work.
Damien.

[dxvn818]

Hello Damien,

Thank you. I tested and it works.

Vinh