how to can be define drucker-prager ballast property in abaqus 1

[mojtaba pourgholami]

I want to model a rail way with geocell in abaqus look like the attach article . in article witch has stated to use the another experimental article that article is also attached to. how I can Defining Drucker-Prager hardening form that article.

https://files.engineering.com/getfile.aspx?folder=14b0ace9-b4be-4845-9e09-57a44c973577&file=p1.pdf

https://files.engineering.com/getfi...a0-ba64-0eeed3be37fc&file=leshchinsky2013.pdf

 

[FEA way]

In the first article they say that they used hyperbolic Drucker-Prager yield criterion. Thus in Abaqus you should choose:

*DRUCKER PRAGER, SHEAR CRITERION=HYPERBOLIC
β, p_t, , φ

where: β - material angle of friction, p_t - initial hydrostatic tension strength, φ - dilation angle

 

[mojtaba pourgholami]

I need Drucker-Prager hardening how i can define it from result of Triaxial test

 

[mojtaba pourgholami]

 

[FEA way]

Hardening for this yield criterion can be defined this way:

*DRUCKER PRAGER HARDENING
yield stress, plastic strain

Now the type of yield stress that needs to be specified depends on the parameter TYPE added to the keyword. If TYPE = COMPRESSION (default) you have to give uniaxial compression yield stress. If TYPE = TENSION you need to specify uniaxial tension yield stress. For TYPE = SHEAR give cohesion.

Triaxial test data can be used to calibrate Drucker Prager model but only for *DRUCKER PRAGER, SHEAR CRITERION = EXPONENT FORM. In this case you include additional keyword:

*TRIAXIAL TEST DATA
σ_1 = σ_2, σ_3


If you specify both hardening and triaxial test data for Drucker Prager model then the value of hydrostatic tension strength obtained from calibration will be omitted and Abaqus will obtain it from hardening data.

 

[mojtaba pourgholami]

now how can i define ballast property in abaqus look like article.
I use hyperbolic drucker-prager and input Internal Angle of Friction and Angle of Dilation

but my analyses is aborted with an error that say *drucker prager requires the use of *drucker prager hardening.
how can fix it.
in article say the ballast shear strength properties were obtained from this article is attached.

 

[FEA way]

In this window that you show here there's a button called Suboptions. Click it and you will be able to choose Drucker Prager Hardening. There you can specify the data I mentioned in previous post. It will eliminate the error. Also if you select the box named "Use Suboption Triaxial Test Data" you will be able to specify the data obtained from triaxial test. But this is for exponential form.

 

[mojtaba pourgholami]

I'm sorry I cant understand this. Can I only use Triaxil test result to define? and Due to the result I mentioned in previous post
What numbers should I enter in the form below?

 

[FEA way]

Yes, you can use this triaxial data suboption to define Drucker-Prager model (but you will have to switch to exponential type). In those two fields put σ_1 = σ_2 and σ_3 values respectively (include signs too). Parameters a, b and pt are optional, you don’t have to put them. If you add hardening too then pt will be taken from hardening data and this field here (in triaxial data suboption window) will be ignored.

 

[mojtaba pourgholami]

in exponent form need a and b.what is this ?

 

[FEA way]

When you use exponent form of Drucker Prager model together with triaxial test data then you only have to specify the dilation angle. Remaining two parameters (a and b) can be omitted.

 

[mojtaba pourgholami]

hello
I cant fix this problem after a wile time
I want to define ballast properties in abaqus with durcker-Prager hyperbolic shear criterion . I had internal angle of friction and dilation but I cant Understand correctly how can i define hardening .as I mentioned in previous post i have the result triaxial comperetion test. know What amounts i must enter in rows of hardening stress and strain.