Hi all

 I am modeling a complex muscle with fibre reinforced. The fibre direction is not constant in this muscle. It is changing with the integration point in the model. Is there anyone who got idea on how to simulate the variable fibre directions in Abaqus?  Can user subroutine ORIENT do this?

 Many thanks,

Ben

Cardiff University

Hello everyone,

I am coding a VUMAT for Abaqus/Explicit. I was wondering if the tensor components ordering was ALWAYS different from the one used in ABAQUS/Implicit, or if the special ordering was valid only for the C3D8R element.

In the ABAQUS use subroutines manual Section 1.2.5 the header says the special ordering is used for the C3D8R element, but in the ABAQUS Analysis User's manual section 5.1.2 it is written that the special ordering is used in the VUMAT without any special element specification, so I assume this is applicable to ALL 3D elements of Abaqus/Explicit.

For reminder, the usual ordering for symmetric tensors (used in implici) is 11, 22, 33, 12, 13, 23.

The unusual ordering is 11, 22, 33, 12, 23,  13.

Can someone give me a hint?

Thanks

J.

For my graduation work (student at the Delft university of Technology, The Netherlands), I am trying to model the aeroelastic behavior of a wind turbine rotor. For this end I use an Abaqus model of a wind turbine blade (which is a composite structure with different fiber layers and corresponding orientation). The aerodynamic force is calculated by a BEM code (Blade Element Momentum theory), which is a simplified engineering aerodynamic code: fast but still quite good. Using CFD to calculate the loads is out of the question since it requires far too much time to calculate.

The problem to calculate the aeroelastic response is that by using two separate solvers (Abaqus and the self written but very simple BEM aerodynamic code), they have to communicate with each other. We call this method the staggered approach: the inherently coupled physical problem is split into two and solved one at the time.
I start with an assumed initial loading which is applied on the structure. Abaqus calculates the deformations. The deformations are feed back to the aerodynamic code which recalculates the aerodynamic forces. Forces back to Abaqus for changed deformations etc... This cycle continues till convergence is reached and the true aeroelastic deformation is known. By doing so, the aerodynamic BEM code and Abaqus are run approximately twenty times (depending on how fast the coupled aero structure converge).

As far I understand at the moment (I am nor an Abaqus, nor a FEM expert), there are two ways of implementing this coupled approach in Abaqus: by using user subroutines or via the phyton interface.

For the user subroutines however, some complications emerge. I assume to use the user subroutine DLOAD (defining a distributed load). The actual aerodynamic load varies both span wise and chord wise along the blade (how to implement that on one surface?). To simulate the several coupling steps between Abaqus and the aerodynamic code, I thought of manually defining, say, 35 steps. At each step the user subroutine DLOAD is called to calculate the aerodynamic loads. In order to be relevant, the user subroutine DLOAD should calculated at each step the load as function of the current blade state (deformations). However, is it possible to call the current blade state (deformations) in the user subroutine DLOAD to use as input for the aerodynamic code?
The convergence criteria should be called upon each step as well. It should be able to abstract the deformations of a previous step and compare it with the current. If the convergence criteria are met it should exits the Abaqus analysis and write away the final deformations into the output database.

The python approach seems to be a little less complicated. Calling the model and reading the output database of a previous step, to extract the blade state. Calculate the aerodynamic loading, apply it on the model, write responses into a new output database, to be used for the next step. And so on and so forth. However, could it be that this approach is slower then compared to the user subroutine attack?

Any thoughts on this coupled aeroelastic problem in Abaqus would be greatly appreciated.

I am trying to simulate creep damage in welded components in ABAQUS. I have four different sections in the same model assigned to four different materials. They are weld metal, base metal and Heat affected zones. I have to write a creep subroutine. For all the zones, creep equation is the same , but the parameters or constants change. i want to know how can I assign different parameters for different materials in the fortran source subroutine? what is the variable used for Material 1 , material 2 etc in standard ABAQUS?

Here is a UMAT using an  elastic viscoplastic model for soil

Modifed Cam-clay model coupled with viscosity.

Detailed information can be found in the link

http://www.eng.uwo.ca/research/grc/software.htm

ABAQUS - UMAT (Free Download for Research Purposes)

A user-defined subroutine in ABAQUS for viscous soils.

Introduction:

The ABAQUS subroutine is for viscous soils, which
usually have the following characteristics.

1. Rate-sensitivity. The stress-strain behaviour of
   viscous soils is rate-dependent. Specifically, Two important engineering
   parameters, i.e., undrained shear strength and preconsolidation pressure
   , typically increase with loading rate.

2. Time-dependence, including creep and
   relaxation.

A general 3D elasto-viscoplastic (EVP) constitutive
model has been implemented in the user-defined subroutine in ABAQUS. The
objective of developing the subroutine is to make users easily take
account of soil’s viscous behaviours.

The report of AN ABAQUS USER SUBROUTINE INCORPORATING
ELASTIC-VISCOPLASTIC CONSTITUTIVE MODEL here provides more detailed
information about the subroutine and its application. This report first
reviews the theoretical background the EVP constitutive model. The next
section introduces the numerical solution algorithm adopted in the
subroutine. The following section illustrates how to determine the input
parameters according the given viscous soil. Finally, the appendix of
this report provides a series of verification numerical tests in a
format of ABAQUS Benchmark problem and evaluates the obtained numerical
results in reference to the corresponding theoretical solution.

• Benchmark problem 1 - CIU compression tests on NC
  soil at various strain rates

• Benchmark problem 2 - CIU
  compression tests on OC soil at various strain rates

• Benchmark problem 3 - CIU
  compression tests on NC soil at step-changed strain rates

• Benchmark problem 4 – CID (Drained) compression tests
  at various strain rates

• Benchmark problem 5 - ISO compression creep test

• Benchmark problem 6 – Undrained creep test

• Benchmark problem 7 – A case study on a retaining
  wall in soft clay.

This user-defined subroutine is now free to download
for research purposes.

Click here for free
software

Click here
for GRC Report

Click
here for Benchmark Documents

For inquiries, please contact:

Dr. G. Qu

E-mail:
guangfengqu@hotmail.com

Dr. Sean Hinchberger Ph.D.
Adjunct Professor,

Geotechnical Research Centre
Tel:       519-661-3997
E-mail:  shinchberger@eng.uwo.ca

Dear All,

 I think that many students are looking for some tutorials about writing a UMAT in ABAQUS.

You can find a comprehensive tutorial for elastic problems.

This file contains: 

• Motivation

• Steps Required in Writing a UMAT or VUMAT

• UMAT Interface

• Examples

Example 1: UMAT for Isotropic Isothermal Elasticity

Example 2: UMAT for Non-Isothermal Elasticity

Example 3: UMAT for Neo-Hookean Hyperelasticity

Example 4: UMAT for Kinematic Hardening Plasticity

Example 5: UMAT for Isotropic Hardening Plasticity

• VUMAT Interface

• Examples 

Example 6: VUMAT for Kinematic Hardening
Example 7: VUMAT for Isotropic Hardening

Hi,

I'm a fresher in abaqus. Now I'm trying to simulate the damage of brittle kind of materials, like concrete with abaqus on mesoscale. But there are some problems now...

The random meso-structure has already been generated by matlab, but I don't know how to import the information of the geometry which are some coordinates? I find the file formats which could be read by abaqus, like Autocad .dxf,.step...but I'm not sure how to do it exactly since geometry information are in terms of coodinates in matlab.

I also tried to write the coordinates into .inp, but I found the geometry can only be generated with mesh including nodes and elements. So does that mean I need to mesh it manually firstly?

Actually, I want to use lattice model with beam elements in abaqus. however, the beams can only be made on wires target. Does that mean  the mesostructure should be replaced by lattices or wires firstly?

Now, I'm confused completely. Could you help me if you'd like?

You are sincerely appreciated!

Hi,

In an ABAQUS 2D-planar model, is it possible to vary the material properties spatially, say defining modulus (E) as a function of coordinates, E = f(x,y)? One way is to use *DISTRIBUTION feature, but that allows variation based on element-sets and does not allow varying the material properties as function of coordinates. If anyone has solved this or similar problem kindly suggest.

Thank you

Vaibhav

Hi there,

 Has anyone ever used a vumat subroutine with Eulerian elements? it seems that the stress update formulation is different from the way it is in Lagrangian approach! If you have any experience in this regard I'd highly appreciate if you share it with me.

 thanks

Hi,

We are using the user subroutine UMAT in ABAQUS for varying the material properties in a thin plate. For any static analysis this subroutine is working perfectly fine. However, while using UMAT during natural frequency extraction, ABAQUS is not completing the analysis and is giving a very vague following error message in the log file:

Abaqus Error: The executable C:\Program Files\SIMULIA\Abaqus\6.9-3\exec\standard.exe
aborted with system error code 5.
Please check the .dat, .msg, and .sta files for error messages if the files
exist.  If there are no error messages and you cannot resolve the problem,
please run the command "abaqus job=support information=support" to report and
save your system information.  Use the same command to run Abaqus that you
used when the problem occurred.  Please contact your local Abaqus support
office and send them the input file, the file support.log which you just
created, the executable name, and the error code.
Abaqus/Analysis exited with errors

There are no error messages in .dat, .msg or .sta files. Sadly, this error message is not helping in finding the cause of the problem.

Are we missing something, like initial conditions, to be defined in UMAT? If somebody has used UMAT during eigenfrequency analysis, kindly suggest.

Thank you

Vaibhav Yadav

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Hi there,

I'm trying to model crack growth under special conditions using MPC
subroutine in Abaqus6.9. The procedure is simple:

In a 2D half-symmetric model, a virtual FIXED node has been defined out of
the body and all nodes in crack direction (symmetric line) in the body have
been tied to the virtual node (only one DOF tied in normal direction). Below
command line was used in *.inp file:

*MPC, USER (default=DOF)

1,1,10
2,2,10

...

where the first "1" is the identifier used in subroutine, the
second "1" is the node 1 in the body which is tied to "10",
the virtual FIXED node out of the body. In the subroutine, I found that the
simple definition of

A(1)= 1

A(2)=-1

JDOF(1)=2

JDOF(2)=2

is ended with 5 unsuccessful attempts to converge and an error; whereas
defining

A(1)= 1

A(2)=0

JDOF(1)=2

JDOF(2)=2

leads to a proper node release in the model based on the defined criterion
without problems in convergence. The constraint form in my model is U1-U10=0
where U is my desirable DOF identifier for nodes 1 and 10. So simply A(N)
constants based on Abaqus docs are expected to be 1 and -1 for a 2D problem.

I'm just wondering what is the proper way to obtain A(N) constants? Or are there some tricks
for node release in a symmetric line using a fixed virtual node that i must include? What would be
wrong in both ways of A definition mentioned above?

Thanks for your helps.

Regards,

Hamed

Hello, Everyone!

     This is the first time that I come here to ask for help,so I wish that I can get the answer!

     I'm modeling with ABAQUS, My problem is how to use a subroutine which contains two external functions ?I need your help, Thank you!

       SUBROUTINE UTRACLOAD(ALPHA,T_USER,KSTEP,KINC,TIME,NOEL,NPT,
     1 COORDS,DIRCOS,JLTYP,SNAME)
C
      INCLUDE 'ABA_PARAM.INC'
C
      CHARACTER*80 SNAME
      DIMENSION T_USER(3), TIME(2), COORDS(3), DIRCOS(3,3)
     
      pi=2.*ASIN(1.0)
      ALPHA=200*pulse(TIME(1))+10*pulse_u(TIME(1))
      T_USER(1)=1
      T_USER(2)=0
      T_USER(3)=0 
           
      RETURN
      end
     
      function pulse(t)
      pulse=0.0
      if(t.ge.0.and.t.le.0.50)then
      pulse=4*pi*cos(4*pi*t)-4*pi*cos(8*pi*t)
      else
      pulse=0.0
      endif
      end function
     
      function pulse_u(t)
      pulse_u=0
      if(t.ge.0.and.t.le.0.50)then
      pulse_u=sin(4*pi*t)-0.5*sin(8*pi*t)
      else
      pulse_u=0.0
      endif
      end function
     

Hi,

I managed to find a way to debug UMAT step by step. I tested it on ABAQUS 6.9 using intel fortran 11.0 which is integrated with Visual Studio 2005 or 2008 running on Win 7/x64. The process is the same for other versions and other user subroutines (The same process should also work in linux, but with different debugger).

The whole idea is to attach your "ABAQUS standard" process to a debugger. To do so, you must compile and link your UMAT code in debug mode.
So you should compile your user-subroutine file as if you want to create an exe console application and do not pay attention to the last linker error, saying that your file does not contain the main subroutine. Here, it is much easier to use the pre-compiled obj file instead of the original fortran file while running an abaqus job (because the debug-information file is created in a fixed location and not in the temp folder that abaqus creates each time at different folders). 

To create the object file in debug mode, I use a command like this (you might need to modify it a bit based on the paths of your VS):

ifort /nologo /debug:full /Od /gen-interfaces /warn:interfaces /module:"compiled\modules\\" /object:"compiled\\" /traceback /check:bounds /libs:static /threads /dbglibs /Qvc8 /Qlocation,link,"c:\Program Files (x86)\Microsoft Visual Studio 8\VC\bin\amd64" "Umat-Test.f90"

In my foldering, I say the compiler to create module files in "compiled\modules" and the object files in this folder: "compiled". You might have your owns. By running this command, the linker also creates the file needed for debug, which is (in MS-VS) a file with pdb extension.

After compiling, you can find the file "Umat-Test.pdb" in the same folder as that of your fortran file.

I should say that Abaqus links each created obj file to the file "standardU.dll" which is re-created after submitting each job. This file is the main output of the linker command in abaqus_v6.env file, which is loaded by Abaqus. So you must modify the linker command to create it in debug mode as well. To do so, I just copied link_sl and link_exe from the main abaqus_v6.env file and put it in my user-level abaqus_v6.env file. Then I added the switch /debug:full to the origial command. Your commands should look like this:

link_sl='cmd /c "LINK /nologo /debug:full /INCREMENTAL:NO /subsystem:console /machine:AMD64 /NODEFAULTLIB:LIBC.LIB /NODEFAULTLIB:LIBCMT.LIB /DEFAULTLIB:OLDNAMES.LIB /DEFAULTLIB:LIBIFCOREMD.LIB /DEFAULTLIB:LIBIFPORTMD.LIB /DEFAULTLIB:LIBMMD.LIB /DEFAULTLIB:MSVCRT.LIB /DEFAULTLIB:kernel32.lib /DEFAULTLIB:user32.lib /DEFAULTLIB:advapi32.lib /FIXED:NO /dll /def:%E /out:%U %F %A %B oldnames.lib user32.lib ws2_32.lib netapi32.lib advapi32.lib && mt /manifest %U.manifest /outputresource:%U;2 && del %U.manifest"'

link_exe='cmd /c "LINK /nologo /debug:full /INCREMENTAL:NO /subsystem:console /machine:AMD64 /NODEFAULTLIB:LIBC.LIB /NODEFAULTLIB:LIBCMT.LIB /DEFAULTLIB:OLDNAMES.LIB /DEFAULTLIB:LIBIFCOREMD.LIB /DEFAULTLIB:LIBIFPORTMD.LIB /DEFAULTLIB:LIBMMD.LIB /DEFAULTLIB:MSVCRT.LIB /DEFAULTLIB:kernel32.lib /DEFAULTLIB:user32.lib /DEFAULTLIB:advapi32.lib /FIXED:NO /LARGEADDRESSAWARE /out:%J %F %M %L %B %O oldnames.lib user32.lib ws2_32.lib netapi32.lib advapi32.lib && mt /manifest %J.manifest /outputresource:%J;1 && del %J.manifest"'

Then the settings are ready. Go to VS, create a fortarn project and add you fortran source code file to the project. DO REMEMBER that your compiled file MUST match with your code while debugging.

Then go to Tools->Options->Debugging->Symbols, add the path of your pdb file to "Symbol file (.pdb) location" section.

These procedures are needed to be done just once.

Now submit your job, and wait for a while to see Standard.exe in the list of your processes (use the task manager of win for example) then switch to VS and go to Debug-> Attach to Process.
Select standard.exe from the list of the running processes. If you did all the steps flawlessly, VS would successfully load the debug symbols from the pdb file and you must be able to debug your code line by line, as I did.

Here are some useful hints: Put a one-time delaying command (like sleep) to buy some time to switch to VS environment and attaching the debugger to the process (standard.exe). You can put your break points after that line. If you have difficulties going through these steps, you may want to drop me an email.

 Here is a screenshot of what it looks like after attaching the process to the debugger:

Explanation: In my code above, InitializationDone is a common variable which I use once to catch the process after 10 secs sleep. 

Here is a simple sample you can try (Umat-Test.f90):
 

SUBROUTINE UMAT(stress,statev,ddsdde,sse,spd,scd,rpl, ddsddt, drplde, drpldt, &
  stran,dstran,time,dtime,temp,dtemp,predef,dpred,cmname,ndi,nshr,ntens,nstatv, &
  props,nprops,coords,drot,pnewdt,celent,dfgrd0,dfgrd1,noel,npt,layer,kspt,kstep,kinc)

  include 'aba_param.inc'
  integer::nTestNum

  nTestNum = 0

  ! wait for 10 seconds
  CALL sleep(10)
 
  ! put your break point here:
  nTestNum = nTestNum + 1

! you can use add watch to inspect the values. Enjoy!

  RETURN
END SUBROUTINE UMAT

-- 

Cheers,

Hamidreza,

Sir,

 I am new to abaqus software. How can i import a subroutine file into abaqus software.while running a .inp file  added to job it asks for a sobroutine file.while editing the job file in general tab there is an option to include a subroutine file but while selecting a .f file to it. it asks for importing a .for or .obj file . what can i do now. I am studying about heat generations due to friction in contacts .the .inp file i imported into job is ufricxxy.inp and .f file is ufricxxy.f from help .please help me in solving these problems.

thanking you

yours faithfully

maneesh .T

maneesht88@gmail.com

Thank you asim sir,

I am sorry to say that i am still getting the error message.I have attached the picture of  procedure and error  messages i gets.please correct my procedure.

I use

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C:\SIMULIA\Documentation\docs\v6.8\books\eif\ufricxxy.f

as the inpu file

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C:\SIMULIA\Documentation\docs\v6.8\books\eif\ufricxxy.f

 as subroutine file

Hi,

I'm stucking with my subroutine. May ask anybody to have a look the the file. 

I run a simple model that and try to run it,but an error message was appeared as below;   ***ERROR: USER SUBROUTINE UEL MISSING

I don't know what is the problem. I did locate the input (.inp) and user (.f) in the same folder and run it (abaqus job=.... user= ...ff int )

Hope to get help from anybody...

Aida

Hello

I am working on the simulation of ring rolling. I have written the subroutine for the plasticity part in the subroutine VUHARD and have set the PLASTIC part in material definition to USER.
I dont have HARDENING PROPERTIES so i have set it BLANK. i have set the path of the subroutine in the job defintion part too. But abaqus crashes whenever i try to do DATA CHECK
It says ABAQUS KERNEL EXITED WITH AN ERROR.I dont know why this problem arises?. I am stuck.

The curve i want to define is yieldstress=K*plasticstrain^m*plasticstrainrate^n

I have defined the yield,Dyieldeqps(k,1)Dyieldeps(k,2) as abaqus has told.
Abaqus has told to define Statenew too.I dont know how to define it.

This is my subroutine :

c-----subroutine for plasticity
subroutine vuhard(
C Read only -
* nblock, 
* jElem, kIntPt, kLayer, kSecPt, 
* lAnneal, stepTime, totalTime, dt, cmname,
* nstatev, nfieldv, nprops, 
* props, tempOld, tempNew, fieldOld, fieldNew,
* stateOld,
* eqps, eqpsRate,
C Write only -
* yield, dyieldDtemp, dyieldDeqps,
* stateNew )
C
include 'vaba_param.inc'
C
dimension props(nprops), tempOld(nblock), tempNew(nblock),
1 fieldOld(nblock,nfieldv), fieldNew(nblock,nfieldv),
2 stateOld(nblock,nstatev), eqps(nblock), eqpsRate(nblock),
3 yield(nblock), dyieldDtemp(nblock), dyieldDeqps(nblock,2),
4 stateNew(nblock,nstatev), jElem(nblock)

parameter( one=1.0d0,small=1.0d-8)
C
character*80 cmname

double precision a,b,c

k=100.0d0
m=0.30d0
n=0.15d0
C
C
do km = 1,nblock

plstrain=eqps(km)
plstrnrt=eqpsRate(km)

C 

yield(km)=k*(plstrain**m)*(plstrnrt**n)
dyieldDeqps(km,1)=k*m*(plstrain**(m-one))*(plstrnrt**n)
dyieldDeqps(km,2)=k*n*(plstrain**m)*(plstrnrt**(n-one))

end do
C
return 
end

I would be grateful if someone could help me figure out the error. 

hi, someone know how run abaqus models using user subroutines, I can run one umat with one model, but i need to run two umats in an unique model in a simple step..Thanks for you help!!

Luis. 

Hello

I have a sensor in VUAMP subroutine to measure the diameter of a ring. I want to compare the current value with the sensor value 10 seconds ago.

Is there a way to store the sensor values and retrieve them in abaqus?

Thanks

ravikumar. 

Hello everyone,

 I am implementing a uel user subroutine in ABAQUS. This uel is for modeling contact in X-FEM framework. Thus, it's a nonlinear problem and I need to store some solution dependent variables during each iteration. I know I can store SDVs in SVARS. But this vector will update at the end of each step, and not during iterations. Anybody knows about this problem?

 I really appreciate if anybody can help me with this.

    Thanks

    Ehsan