Multiaxial simulations

[Samuel Alfred]

Hello everyone. 

Is it possible to do multiaxial simulations in crystal plasticity and PRISMS in particular?

I will like to simulate a uniaxial case and also add a Torsion loading to it. Thanks.

Samuel 

[Yaozhong Zhang]

Hi Samuel, 

It's possible to do multiaxial simulation. I've done torsion-tension combined loading with PRISMS-Plasticity. It's realized by enabling the Torsion BCs in the .prm file and use Neumann BCs to apply the tension.

Use a BC.txt file like usual to fix one end, then on the other end, you can apply tension and torsion together.

To enable Torsion BCs, add the following lines where the Tabular Time Table are the time the rotation is applied and the Tabular BCs are the rate of ratation in rad/s for that time:

set Use Torsion BCs = true
set Torsion Axis  x 0  y 1  z 2  = 2
set Tabular Time Table for Torsion = 0, 5, 10, 15
set Tabular Torsion BCs = 0, 0.1, -0.1, 0.1
set Center point for Torsion= 0.5, 0.5

To enable Neumann BCs, add the following lines:

set Use Neumann BCs = true
set Tabular Neumann Boundary condition filename = NeumannBCs.txt
set Number of time data for Tabular Neumann BCs = 3
set Number of tabular Neumann boundary conditions = 1
# Boundary IDs following the displacement IDs convention presented in documentation.
set Boundary IDs of Neumann BCs = 6
# DOF that the load is applied, here 0 means along x.
set dof of Neumann BCs = 2
set Tabular Time Neumann BCs = 0, 5 ,15

NeumannBCs.txt just contains the stress (MPa) you want to apply at the specified the tabular time, for example:

0 100 100

Hope that helps!

Yaozhong Zhang

[Samuel Alfred]

Thanks a lot

[TIMOTHY NGIGI]

Hello, everyone. I also would like to carry out multi axial fatigue simulation (with cyclic torsion and static compression). The problem is that the simulation is return an error particularly 

----------------------------------------------------
Exception on processing:


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Exception on processing:


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Exception on processing:

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Exception on processing:

--------------------------------------------------------
An error occurred in line <1999> of file </home/timoshenko/dealii-candi/tmp/unpack/deal.II-v9.5.2/source/base/parameter_handler.cc> in function
    void dealii::ParameterHandler::scan_line(std::string, const std::string&, unsigned int, bool)
The violated condition was:
    skip_undefined
Additional information:
    Line <86> of file <prm_0.prm>: No entry with name <Torsion Axis x 0 y
    1 z 2> was declared in the current subsection.

Stacktrace:
-----------
#0  /home/timoshenko/dealii-candi/deal.II-v9.5.2/lib/libdeal_II.so.9.5.2: dealii::ParameterHandler::scan_line(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int, bool)
#1  /home/timoshenko/dealii-candi/deal.II-v9.5.2/lib/libdeal_II.so.9.5.2: dealii::ParameterHandler::parse_input(std::istream&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bool)
#2  /home/timoshenko/dealii-candi/deal.II-v9.5.2/lib/libdeal_II.so.9.5.2: dealii::ParameterHandler::parse_input(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bool, bool)
#3  ../../../main: userInputParameters::userInputParameters(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, dealii::ParameterHandler&)
#4  ../../../main: main
--------------------------------------------------------

Aborting!
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I am suspecting the problem might be on definition of torsional axis and/or center point for Torsion, (see in bold above - the error returned on command lie). 

P.S i have used the prm file from the compression-Neumann folder i downloaded from Prism plasticity Github page. I have also followed the instructions from Yaozhong Zhang. I am also carrying out rate-dependent simulation. 

Thank you in advance

[Chaitali Patil]

Hi Tim,

Can you share the prm file you edited?

-Regards,

Chaitali

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[TIMOTHY NGIGI]

Hi Chitali,

Thank you for your response. i have attached the prm file, the NeumanBcs.txt file and the BCinfo.txt file. 

Thank you 

Regards,

Tim

[Chaitali Patil]

Hi Tim, 

The input line strings should be matched exactly as : 

set Torsion Axis  x 0  y 1  z 2  = 2

I changed it in your input file,  which should resolve above error. 

-Regards,

Chaitali

[Timothy Ngigi]

Thank you very much Chaitali, it is working now. However, I still cannot point out my mistake. The input string is the same. Did you add or remove character spacing

Timothy Ngigi Ngeru

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