ABAQUS - UMAT Crystal Plasticity

1. Single crystal uniaxial tension

[@fuhuishen358]

Thanks very much for the nice instruction.

[@JoJo-oc6uh]

Hello Enralp, I would like to ask what are the yield criteria of this subroutine(UMAT)? (such as von mises or Hill criteria...) thank you very much. Bests,

[@eralpdemir]

The yield surface in crystal plasticity is governed by Schmid projections. Please see the reference by Weng: link.springer.com/article/10.1007/BF01202946 In this case neither Von-Mises or Tresca, rather a viscoplastic power law which is closer to Tresca but certain crystallographic directions and planes.

[@JoJo-oc6uh]

@@eralpdemir Thank you very much!

[@user-qb3sn8ll2n]

Hello Enralp Could you please provide some documents about the theoretical part of these UMats to introduce the constitutive relations? I saw a description file in the video, but I went to github and found it was not there

[@JoJo-oc6uh]

Hello Enralp, Thanks your instruction. I have a question for CPFEM. How do I draw the yielding surface or know the yielding surface from CPFEM? Bests. JoJo

[@eralpdemir]

Hi JoJo, That is an important question. - First the yield point shall be located, one of the best way to look at total plastic strains which is stored as a scalaer in the variable "statev_totgammasum". The time that it starts taking non-zero values indicates yield. - Second, yield surfaces are in stress space. You need the location of your stress state. Macro stress for a polycrystal can be simple uniaxial but the stresses in the grains can be complex. You may use that information to plot the yield surface for each integration point with complex stress states. The stress components are stored within "statev_stress" you need to find the principal stresses. The critical thing is that you need to find the stress state at the point of yield which might be different for each integration point. Hope this helps, Eralp

[@JoanJiang-rn8ul]

Hi, I observed that the slip rate has positive or negative value. If the value of the slip velocity of (111)[1-10] is negative, does this mean that the crystal moves in the [-110] direction? Thanks a lot! Bests, Joan

[@eralpdemir]

Hi Joan, Yes that is correct, slip can take negative or positive depending on the applied stress. As you say, slip being negative means simple shear direction is along [-110] while keeping the plane the same (111). Bests, Eralp

[@ZengCQ]

Hello Enralp, Thank you for sharing your work,and I have a question about "statev_output(1)". I have set the statev_output(1) to 1 (the statev_output(10) remained 1)and added the number of SDV to 30, but it seems that I still cannot get the values of g^t in the odb file. Only SDV 1-SDV12 get values and other SDVs keep 0. I don't know why. I would appreciate it if you could answer my question.

[@eralpdemir]

Hi Zeng, Thanks for your notice. I have looked into this as an issue. I downloaded the software from github and run it again. Please make sure to increase the number of DEPVAR. I got the 9 components of gmatinv matrix. Please feel free to raise an issue in the Github page if you have any other issues. If you raise an issue I can send the inp file and others to you as attachments. Best, Eralp

[@anmolbakshi613]

@@eralpdemir increase number of DEPVAR to how much as even after setting to 30, i am not getting the 9 components in ABAQUS visualization? Also, where to get the final values of the SDVs in text form?

[@eralpdemir]

@@anmolbakshi613 Hi Anmol. The outputs become visible if you thick the SDV boxes in the field variables option of the model. A text file is generated only for the legends of the list of SDV defined by the user. The outputs are not written to a text file. Hope this helps, Eralp

[@anmolbakshi613]

@@eralpdemir Thanks a lot, it solved my problem.

[@user-xg7bk5fl8t]

Hello Enralp, Thanks for sharing your work, your insights have proven to be incredibly valuable in my research endeavors. I am currently exploring the simulation of phase transitions during loading, particularly the transition from FCC to BCC. In this context, I am considering introducing small BCC crystals at grain boundaries, initially setting their parameters to match those of the surrounding FCC phase. As the simulation progresses and certain conditions are met, my aim is to alter the material properties of these small crystals to simulate the transition to a BCC structure. Do you find this assumption reasonable? I would greatly appreciate any suggestions or insights you may have regarding the implementation of dynamic phase transitions within the framework of crystal plasticity. Furthermore, as I continue with my research, I am eager to delve deeper into your scholarly contributions to enhance my knowledge. Could you kindly recommend a few of your key papers or publications? Your recommendations would greatly assist in my ongoing studies and provide valuable references for future citations in my work.

[@eralpdemir]

Thank you so much for your interest. That is a very interesting application. For example for deformation twinning, there are continuum models available (doi.org/10.1016/S0022-5096(97)00051-3). The current code can not work with dynamic changes, but you need to learn how to implement and make related modifications in the computation framework which is in "cpsolver.f". I have put some relevant papers on the Github page. The publication related with this code is under prep. I will share once published. Best wishes

[@user-xg7bk5fl8t]

@@eralpdemir I am immensely grateful for the invaluable assistance you've provided. Thank you so much! I have another question and would greatly appreciate your insights. I wanted to inquire about whether crystal plasticity finite element analysis is generally associated with static analyses? Regarding the time increment used in static analyses, can it be considered as a process akin to dynamic analysis under the assumption of small deformations? Thank you once again for your time and expertise.

[@liangsu-fg7kh]

Hello Enralp, Thanks your instruction. I have a question for CPFEM. When I run the job by ABAQUS, it appear the error 'Abaqus/Standard Analysis exited with an error - Please see the message file for possible error messages if the file exists' as soon. I use other model and UMAT, it has the same error. If possible, could you kindly assist me in resolving this problem?I would greatly appreciate any assistance you can provide. Thank you in advance.

[@eralpdemir]

Hi Liangsu, if you would send me you .inp file, I could try to point the problem. email: [e-mail] Bests

[@anmolbakshi613]

Thank you for developing this whole thing. I used the following commands to generate 5 grains in neper: neper -T -n 3 -dim 2 -domain "square(1,1)" -morpho gg -ori "file(orientations.txt)" -oriformat plain -oridescriptor e -o square_2d neper -M 2d_square.tess -statelset area -rcl 1 -elttype quad -order 1 -interface continuous -format inp -o abq_tet_2d -format msh where orientations.txt containing phi1, PHI, phi2 are as: 199.1 44.1 59.6 325.1 48.2 33.2 276.2 45.9 60.9 270.8 46.0 68.3 188.7 32.0 69.6 Then, I am converting neper .msh file to abaqus .inp file using your MATLAB code. Then when viewing in ABAQUS PROPS, the angles values are not remaining same. Where am I going wrong?

[@eralpdemir]

Hi Anmol, I have prepared the Neper to Abaqus converter for 3D meshes. It may go wrong or miss something in the input file for 2d cases. Please feel free to modify the code for your purpose. Best

[@anmolbakshi613]

@@eralpdemir I am getting the discrepancy in case of 3D meshes also. Can u help me?

[@eralpdemir]

@@anmolbakshi613 Hi Anmol, I tested the code for linear tetragonal elements. Please try the same code as in the example. You may convert to different element types using Abaqus after generating the polycrystal mesh. Best

[@anmolbakshi613]

@@eralpdemir Ok thanks for the help.

[@anmolbakshi613]

in useroutput , there is one state-variable as "Elastic strains in the crystal frame", how to know "Plastic strains in the crystal frame"?

[@eralpdemir]

Hi Anmol, This you may obtain from "Fp". For that you need to write a custom output using statev_Fp.

[@anmolbakshi613]

@@eralpdemir Ok ok. One more doubt, here " State variable-4 if (statev_outputs(4) == 1) then ! do i = 1, 6 ! count = count + 1 ! select case(i) ! case(1) ij = 'xx' case(2) ij = 'yy' case(3) ij = 'zz' case(4) ij = 'xy' case(5) ij = 'xz' case(6) ij = 'yz' ! end select ! ! ! write(100,'(A7,I3,A36,A2,A6)') + 'STATEV-', count, + ': Elastic strain in crystal frame-', ij, ' [MPa]'", why MPa as strain is unitless?

[@eralpdemir]

@@anmolbakshi613 could be a copy-paste typo. If you check the magnitudes, you should see strains not the stresses.

[@MultiSaded]

Please, how can install Neper in Windows?

[@eralpdemir]

Neper is a linux based software. You should first get install linux with windows subsystem.

[@vikramroy7471]

Hello Enralp, I'm currently working on developing a crystal plasticity code with similar functionalities. However, I encountered some issues when running your code. Here's the log file output Begin Compiling Abaqus/Standard User Subroutines 2023-05-27 9:42:10 AM Intel(R) Fortran Intel(R) 64 Compiler Classic for applications running on Intel(R) 64, Version 2021.8.0 Build 20221119_000000 Copyright (C) 1985-2022 Intel Corporation. All rights reserved. End Compiling Abaqus/Standard User Subroutines Begin Linking Abaqus/Standard User Subroutines Creating library standardU.lib and object standardU.exp libirc.lib(fast_mem_ops.obj) : warning LNK4210: .CRT section exists; there may be unhandled static initializers or terminators End Linking Abaqus/Standard User Subroutines 2023-05-27 9:43:44 AM Begin Analysis Input File Processor 2023-05-27 9:43:44 AM Run pre.exe 2023-05-27 9:43:49 AM End Analysis Input File Processor Begin Abaqus/Standard Analysis 2023-05-27 9:43:49 AM Run standard.exe 2023-05-27 9:43:49 AM Abaqus Error: Abaqus/Standard Analysis exited with an error - Please see the message file for possible error messages if the file exists. Begin SIM Wrap-up 2023-05-27 9:43:50 AM Run SMASimUtility.exe 2023-05-27 9:43:51 AM End SIM Wrap-up Abaqus/Analysis exited with errors. While I am able to run other subroutines on my workstation, I'm having trouble understanding the issue with my PC. If possible, could you kindly assist me in resolving this problem? I hope this helps you understand the issue I encountered while running your code. I would greatly appreciate any assistance you can provide. Thank you in advance.

[@eralpdemir]

Hi Vikram, Thank you for your efforts in running our code. If it happens at the very first step it is usually an input issue. It could be related with the model. UMAT reads the Job-1.inp file and this can happen usually if it cannot find that file. I recommend setting the flag "readinpfile=0" in userinputs.f and set the defaultnumel=??? and defaulteltyp='???' in the same file. Please also make sure to check the 6 inputs UserMaterial and the outputs in Depvar. Let me know if this solves the issue. Best wishes, Eralp

[@phamthanhwru]

I have the same problem, have you solved it?

[@user-qb3sn8ll2n]

Hello Enralp Could you please provide some documents about the theoretical part of these UMats to introduce the constitutive relations? I saw a description file in the video, but I went to github and found it was not there

[@eralpdemir]

The paper is under preparation now, I will soon provide the reference for it. I will keep you posted once published. Thanks

[@user-qb3sn8ll2n]

thank you so much @@eralpdemir