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Modelling moving discontinuity using XFEM

February 29, 2012, 6:49 am
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Greeting to all iMechanicians,

I am trying to model motion of discontinuity (grain boundary) using XFEM as it saves me from the computational expense required for mesh adaptation. The material behaviour on the both sides of the discontinuity is different. After any step the discontinuity might cut through an element. Then to compute the stiffness of the element I will have to integrate seperately for the splitted regions and then add them. This is easy when I have a 1-D case but seems difficult for 2-D and 3-D case. Since the discontinuity may take any arbitrary shape, I will have to find out the points in the element that lie on either side of it for which I can use signed distance function. But how do I implement this in ABAQUS. I have a vague idea that I might have to use UEL or UMAT. If somebody has faced a similar situation, please help me out.

Best regards,

Luv

 


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Problem with Abaqus and Umeshmotion

March 16, 2012, 6:54 am
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Hi,

I am currently trying to simulate the wear of a damper within a gas turbine using Abaqus 6.9 and the user-subroutine Umeshmotion. I have managed to get the subroutine to compile correctly but Abaqus does not appear to use it as I can change the wear value within the code and it makes no difference to the results.

Has anyone had the problem where Abaqus does not appear to use a subroutine even though it compiles correctly? Any hints on how to fix this would be greatly appreciated.

 

Many Thanks

 

Joe


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I need some guidance on writing USDFLD subroutine on Abaqus

June 2, 2012, 3:29 pm
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Hey everyone,

I'm very new on Abaqus, and what I'm trying to do is to assign to a model a changing E modulo as a linear function of Z coordinate ( E(Z)=-33936.651*Z+25e06 ).

I tried to gather some knowledge over the web on how to do so, and I found out that It can be done by writing a USDFLD subroutine, I managed to pick of some exapmles the following code:

   SUBROUTINE USDFLD(FIELD,STATEV,PNEWDT,DIRECT,T,CELENT,

  1 TIME,DTIME,CMNAME,ORNAME,NFIELD,NSTATV,NOEL,NPT,LAYER,

  2 KSPT,KSTEP,KINC,NDI,NSHR,COORD,JMAC,JMATYP,MATLAYO,LACCFLA)

C

  INCLUDE 'ABA_PARAM.INC'

C

  CHARACTER*80 CMNAME,ORNAME

  CHARACTER*3  FLGRAY(15)

  DIMENSION FIELD(NFIELD),STATEV(NSTATV),DIRECT(3,3),

  1 T(3,3),TIME(2)

   DIMENSION ARRAY(15),JARRAY(15),JMAC(*),JMATYP(*),COORD(*)

   z=COORD(3)

   CV=-33936.651*Z+25000000

   FIELD(1)=CV

RETURN

END

 

First I will very much appreciate it if someone can say what's wrong with this code or why it won't run on Abaqus/CAE 6.1.

Second, am I missing another step? should I do something about an input file too?

Because as far as I understand the input file is only being created as soon as Abaqus starts running the solution for the job... 

 

I will appreciate any sort of help.

Thanks a lot

Itay 


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Subroutine simulation migration from HETVAL to UMATH

July 13, 2012, 4:15 am
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Hi!

I'm already simulating a shape memory alloy behavior with the aid of the HETVAL subroutine, but I'd like to use UMATHT instead, since the HETVAL can't simulate correctly heat absortion(cooling down).

I've tried to add the required values for UMATHT without achieving a correct phase fraction simulation, and some times even no compilation of the .for file.

Is there any other examples that uses UMATHT besides the Stefan problem?
Any other recommendation about HETVAL to UMATHT migration?

Thanks in advance!

Paulo


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Simple metal cutting example with chip formation in ABAQUS

September 8, 2012, 1:34 pm
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Hello every one....

I am new in abaqus/cae, abaqus/explicit.  I have googled but not able to get any tutorial or example for metal cutting with chip formation. just few youtube animation videos are available on 3D orthogonal cutting, milling. But now such video or doc is available.

So, if any one having any kind of tutorial, example, or short notes.. please please share with me or mail me on my ID badwl24@yahoo.com.

it will be great help for me.  thanks in advance.... please please anyone!!!!!!!!


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FROTRAN subrountines for ABAQUS in bone remodeling simulation

September 18, 2012, 5:47 am
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I'm new in the computer simulation of adaptive bone remodeling (Bone will adapt to the loads it is placed under). And I know many research cases of numerical model were implemented as FROTRAN subrountines for the software package ABAQUS: the bone material properties will be updated by the subroutine.

I know FROTRAN is excellent at handling large data sets for scientific coumputing and requires less resources, but I haven't learned the FROTRAN.I wonder what else irreplacable advantages of  FROTRAN in the bone remodeling? 

And whether I could implement my algotiyhms by the Matlab code? It will be more easier and I can get step result directly. 

Thanks. 

 

 


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FROTRAN subrountines for ABAQUS in bone remodeling simulation

September 18, 2012, 9:25 am
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I'm new in the computer simulation of adaptive bone remodeling (Bone will adapt to the loads it is placed under). And I know many research cases of numerical model were implemented as FROTRAN subrountines for the software package ABAQUS: the bone material properties will be updated by the subroutine.

I know FROTRAN is excellent at handling large data sets for scientific coumputing and requires less resources, but I haven't learned the FROTRAN.I wonder what else irreplacable advantages of FROTRAN in the bone remodeling?

And whether I could implement my algotiyhms by the Matlab code? It will be more easier and I can get step result directly.

Thanks.


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How to learn user subroutines in ABAQUS by FORTRAN?

September 18, 2012, 9:53 am
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I'm a freshman in biomechanic and apply to learn user subroutines in ABAQUS by FORTRAN.

I have installed the ABAQUS 6.11, VS2008 and IVF 11.1.

But I don't know how to call the subroutines in ABAQUS, so I will be very appreciate if someone give me some suggestion or simple tutorials about this.

THANKS!


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Education

November 7, 2012, 3:50 am
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ABAQUS UEL SUBROUTINE_Abnormal termination signal_Signal 6

January 17, 2013, 4:08 am
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Dear valuable members,





Thanks for the kind help in advance.





I would submit a well known error that I got in my run of
the UEL subroutine which has additional dof. the error is:





Abaqus Error: The executable
/abaqus/6.11-2/exec/standard.exe








aborted with system error "Abnormal termination
signal" (signal 6).
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.





 noting that my run is only for four elements 2D/4node/3dof,
and all the initial values are correct before submitting the AMATRX and RHS to
ABAQUS!





 Your inputs are highly appreciated





Best regards




Msekh





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How to export NODAL DISPLACEMENT in a UAMP subroutine in ABAQUS?

August 5, 2013, 11:28 pm
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DEAR ALL,

    I am a new user in ABAQUS. I want to do an analysis on a cantilever beam, where force applied to the beam deforms it, and depending on its deformation the direction of the force changes.

In order to calculate the change in direction of the force I need DISPLACEMENT INFORMATION at two different set of nodes where forces are being applied. I am planning to use UAMP for

this purpose, by varying the x and y component amplitude of the forces, I can calculate the resultant force acting on a particular node. For this I need to export the DISPLACEMENT DATA of

atleast two different node set from which I can calculate the angle at which the force is acting as θ = atan[(Uy2-Uy1)/(Ux2-Ux1)], and finally calculate the force components as Fx=F*Cos(θ)

and Fy=F*sin(θ), where F is to be calculated in FORTRAN subroutine. I intend to do it in a FORTRAN SUBROUTINE and then transfer this values to ABAQUS. Iwant to inquire about the folowing

things,

1. I am planning to do it in the load defining step using UAMP by varying the amplitude. Can I define two different amplitudes for CF1 and CF2 in the edit load window? Is there any other better way of doing this?

2. In whatever way I intend to do this, I will need to export the NODAL DISPLACEMENT VALUE to the FORTRAN subroutine in order to calculate the angle theta? How can I export the nodal displacement data to a FORTRAN subroutine?

I am attaching a figure with this for further reference....

 

Thank you very much all for your help and support...

 

 

 


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About Dflux of abaqus

August 19, 2013, 6:24 pm
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I would like to use Dflux to give a Temperature and dT/dt related heat flux. Can Dflux be used for this purpose? I am not sure how to get dT/dt ? Or other subroutine can fulfill this purpose?

 

Thank you 


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A Very silly abaqus question... applying a wind load

September 17, 2013, 12:02 am
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Dear All,

Sorry to ask such a silly question but I am quite new to Abaqus... I am trying to model a tower exposed to wind. I know how the wind pressure varies according to height, but what I dont know is how to model it in abaqus... Also, if i apply a pressure load, then the load will act normally at all points on the surface, right? But in actuality wind doesnt act that way... Could anyone help me out on this one?

 

Thanks and Regards,

Lekshmi 


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Abaqus "system error code 884"

October 7, 2013, 2:32 pm
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Hello again

 

Im running a simulation on Abaqus and i got the next text message:

 

Abaqus Error: The executable C:\SIMULIA\Abaqus\6.11-PR3\exec\standard.exe 

aborted with system error code 884. 

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

 

 do you know what is this error? ive been looking on ABAQUS documentation and in the web and i cant find information

 

Thanks for your help

 

Juan Carlos Martinez

 


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How to use USDFLD request variables from other elements in ABAQUS

October 10, 2013, 7:19 am
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Hi all,

 I want to use USDFLD to have diffusion and mechanical coupling analysis. The model is building a cohesive zone between two parts. Before the calculation is  executed in each increment, I need to get the stress information of last increment of one element and the other two element next to it in the same cohesive zone. After geting this, I can update the parameters of cohesive zone and a following mechanical analysis will be executed. How can I save the variables of desired elements for each increment? Or how can I request other elements' information in the USDFLD subroutine ?


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UMAT input DROT not identity even with local direction

November 21, 2013, 3:30 pm
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Hello,

 

    While debuggin my UMAT code for Fung material for Simple shear mode I saw that UMAT is receiving a DROT matrix as input that is not identity. Since I have specified *orientation as show below, I was expecting that I should see DROT to be a n identity matrix. ( ref. abaqus user subroutine manual 1-1-40-9). As this UMAT code agrees with abaqus built-in Fung model for tension tests but not for simple shear, I was wondering if it has to do with the finite rotation aspect. 'DROT' not being identity hints that my material fiber directions are not being specified correctly. Is that right?

Has anyone faced situation like this? 

Are possible other scenarios when DROT can be non-identity for simulation with local fiber directions specified ?

Or is there anything wrong in the way I specify material directions in the excerpt from .inp file given below:

---------------------------

*Element, type=C3D20RH

1,  5,  6,  8,  7,  1,  2,  4,  3, 12, 11, 10,  9, 13, 14, 15,

   16, 18, 17, 19, 20

*Elset, elset=SET-2

 1,

*Orientation, name=Ori-1,local directions=3

 1., 0., 0., 0.,1.,0., 0., 0., 0.

3, 0.0

1.,0.0,0.0

0.0, 1.0, 0.0

0.0,0.0,1.0

** Section: Section-1-SET-2

*Solid Section, elset=SET-2, orientation=Ori-1, material=UMAT_MTRL

1.0,

*End Part 

-------------------- 

 

 

 

 

Thanks, 


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Writing User Subroutines with ABAQUS

February 11, 2010, 1:26 am
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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


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Non-uniform expansion coefficient alpha in UEXPAN (ABAQUS)

December 16, 2013, 1:56 am
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I want to define the expansion coefficient alpha as a function of the depth, alpha(z)=f(z). How can I achieve this in UEXPAN? I cannot find a way to incorporate coordinates in UEXPAN.


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material points will change while using subroutine in ABAQUS

February 17, 2014, 9:25 am
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This subroutine using VUSDFLD is to
determine position of damage and provide evolution of damage surface, when some
elements failed. The “outer” damage status will transfer to “inner” damage
status.

Now the problem is that when I read the
coordinates of material points, using coordMp（k,1),coordMp（k,1),coordMp（k,1), it returns wrong locations. Then I
tried a very simple loop:

Do
k=1,nblock
        stateNew(k,7)=nblock
end Do

I found the number of material points
(namely, nblock) varied! First time
I ran this loop, I got the contour of state variable 7 (SDV7) shown below. The
SDV7 were various. But from the subroutine they were supposed to be same.

 

Then I coarsen the mesh, and get a
different result, SDV7 of every element were same (equal to the material point
number=125)! Shown below:

 

Then I substituted coordMp(1,1) for nblock
in the above-mentioned loop, and found similar phenomenon.

 

I wonder if the number of material points
and their coordinates will vary in a loop? Those results are beyond my expectation.
Is that Fortran grammar problem or misunderstanding on subroutine in Abaqus?

 

I attached the subroutine "position.for" and its "Job-1.inp" below. But I switch their extensions into .txt for uploading.

Thank you all.


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Calling a File inside of the UEL

February 17, 2014, 9:32 am
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Hi everybody,

I'm writing a User Difined Element (UEL) for my research.

Would you please let me know if it's possible to call a file (txt, dat, etc) inside of the UEL or not?

Example:

    IF (LFLAGS(3)=1) THEN
        OPEN (UNIT = 10, FILE = "AAA.dat", STATUS = "OLD")
        READ (10, *), StiffnessTable
        AMATRX=StiffnessTable
    END IF

Thanks in advance,

Ashkan


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