Umat error

[Umat]

Dear Abaqus users
  I am working on progressive damage analysis of 3D composites.Do any one has idea how to rectify this error.Abaqus Error: The executable /raid/software/64/abaqus/6.8-1/exec/standard.exe
aborted with system error "Illegal floating point operation" (signal 8).
And more i have checked out the code many times,i didnt find any wrong in the code.
Can anyone please help me out

Thanks
Rajesh

[Dave Lindeman]

It's almost certainly an error in the code.  Add WRITE statements to
check the values being used in any division, square root,
exponentiation, etc. operations.

Regards,

Dave

-------------------------
Dave Lindeman
Lead Research Specialist
3M Company
3M Center 235-3F-08
St. Paul, MN 55144
651-733-6383


Rajesh wrote:

>  
>
> Dear Abaqus users
> I am working on progressive damage analysis of 3D composites.Do any one
> has idea how to rectify this error.Abaqus Error: The executable
> /raid/software/64/abaqus/6.8-1/exec/standard.exe
> aborted with system error "Illegal floating point operation" (signal 8).
> And more i have checked out the code many times,i didnt find any wrong
> in the code.
> Can anyone please help me out
>
> Thanks
> Rajesh
>
>

[maajidchishti]

Hi Rajesh

The floting point error usually occurs if you do not define the numerals in the input file properly as an integer, eg. 5.8.2 (this will give an error because the no. has 2 decimals). Please check your material properties, time, and other values where you think this error may occur. Hope this helps

Regards

Maajid

--- In Abaqus@..., "Rajesh" <rajeshkatta@...> wrote:

>
> Dear Abaqus users
>   I am working on progressive damage analysis of 3D composites.Do any one has idea how to rectify this error.Abaqus Error: The executable /raid/software/64/abaqus/6.8-1/exec/standard.exe
> aborted with system error "Illegal floating point operation" (signal 8).
> And more i have checked out the code many times,i didnt find any wrong in the code.
> Can anyone please help me out
>
> Thanks
> Rajesh
>

[Frank Richter-2]

Dear Group,


we are striving to model shape memory materials. Their stress-strain-curve forms a closed loop.

For you to get a visual impression: Fig. 5 on
http://smart.tamu.edu/overview/smaintro/detailed/detailed.html
This figure depicts tension only.

At lower temperatures the stress-strain-curve also starts with an elastic curve from the origin and then forms a closed loop around the origin (i.e., the rectangle in this figure is shifted both horizontally and vertically).

I want to find out if it is possible to reproduce this curve without a mindboggling UMAT for shape memory materials.

For instance, if I want to model a change of stiffness (entering the 'horizontal' upon tensile straining) at 1% strain I tried:

*ELASTIC,DEPENDENCIES=1
1.0d10,0.0,, 0.0
1.0d10,0.0,, 0.01
1.0d8,0.0,,0.0101
1.0d8,0.0,,0.055

in combination with USDFLD where strain is returned to this parameter list. So far I restricted the loading to simple tension.
Result: the stress drops right to very low values when entering the horizontal. But I need the CHANGE OF STRESS to be very low.

So my concern is:

Is there any way to model this either with *ELASTIC,DEPENDENCIES or with a UMAT for a bilinear constitutive law (i.e, Young's modulus and possibly Poisson's ratio depend on strain or stress) ?

Can anyone share a UMAT for such a bilinear elastic material (yet to be extended for various strain and stress ranges) ?

I am aware that this approach does not constitute physical modeling of shape memory materials. I only want to reproduce the curve, giving the characteristic points where the stiffness is altered.

Thank you all in advance for your expertise

Frank

--
-----------------------------------------------------------------------
Frank Richter
Institute of Materials Science
Ruhr-Universitaet Bochum
Bochum
Germany



GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01

[sridharan.venkataramanan]

 

Dear Frank,

Very interesting topic indeed. I believe abaqus had some material models to simulate SMA especially Nitnol. Look at their support page. On my quick reference I found that sample UMAT/VUMAT for such behavior was also available under answer 1658. You may either use that or use the inbuilt material models if that suits.

 

 

 

 

Regards,

V.Sridharan

 

From: Abaqus@... [mailto:Abaqus@...] On Behalf Of Frank Richter
Sent: Monday, October 26, 2009 6:23 PM
To: Abaqus@...
Subject: [Abaqus] Stress vs. strain: closed loop

 

 



Dear Group,

we are striving to model shape memory materials. Their stress-strain-curve forms a closed loop.

For you to get a visual impression: Fig. 5 on
http://smart.tamu.edu/overview/smaintro/detailed/detailed.html
This figure depicts tension only.

At lower temperatures the stress-strain-curve also starts with an elastic curve from the origin and then forms a closed loop around the origin (i.e., the rectangle in this figure is shifted both horizontally and vertically).

I want to find out if it is possible to reproduce this curve without a mindboggling UMAT for shape memory materials.

For instance, if I want to model a change of stiffness (entering the 'horizontal' upon tensile straining) at 1% strain I tried:

*ELASTIC,DEPENDENCIES=1
1.0d10,0.0,, 0.0
1.0d10,0.0,, 0.01
1.0d8,0.0,,0.0101
1.0d8,0.0,,0.055

in combination with USDFLD where strain is returned to this parameter list. So far I restricted the loading to simple tension.
Result: the stress drops right to very low values when entering the horizontal. But I need the CHANGE OF STRESS to be very low.

So my concern is:

Is there any way to model this either with *ELASTIC,DEPENDENCIES or with a UMAT for a bilinear constitutive law (i.e, Young's modulus and possibly Poisson's ratio depend on strain or stress) ?

Can anyone share a UMAT for such a bilinear elastic material (yet to be extended for various strain and stress ranges) ?

I am aware that this approach does not constitute physical modeling of shape memory materials. I only want to reproduce the curve, giving the characteristic points where the stiffness is altered.

Thank you all in advance for your expertise

Frank

--
----------------------------------------------------------
Frank Richter
Institute of Materials Science
Ruhr-Universitaet Bochum
Bochum
Germany

GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01





[Non-text portions of this message have been removed]

[Dave Lindeman]

Frank:

You might want to take a look at Answer #1658 under "My Support" on the
Simulia website.  There is a shape-memory/superelastic material model
available within ABAQUS, but it appears to be accessed using the *USER
MATERIAL interface.  At one time (version 6.4?) I believe you had to pay
to license the material model.  I believe it is now built-in, but
apparently undocumented (I haven't used it, so I'm a little confused...).

Regards,

Dave

-------------------------
Dave Lindeman
Lead Research Specialist
3M Company
3M Center 235-3F-08
St. Paul, MN 55144
651-733-6383


Frank Richter wrote:

>  
>
>
>
> Dear Group,
>
> we are striving to model shape memory materials. Their
> stress-strain-curve forms a closed loop.
>
> For you to get a visual impression: Fig. 5 on
> http://smart.tamu.edu/overview/smaintro/detailed/detailed.html 
> <http://smart.tamu.edu/overview/smaintro/detailed/detailed.html>
> This figure depicts tension only.
>
> At lower temperatures the stress-strain-curve also starts with an
> elastic curve from the origin and then forms a closed loop around the
> origin (i.e., the rectangle in this figure is shifted both horizontally
> and vertically).
>
> I want to find out if it is possible to reproduce this curve without a
> mindboggling UMAT for shape memory materials.
>
> For instance, if I want to model a change of stiffness (entering the
> 'horizontal' upon tensile straining) at 1% strain I tried:
>
> *ELASTIC,DEPENDENCIES=1
> 1.0d10,0.0,, 0.0
> 1.0d10,0.0,, 0.01
> 1.0d8,0.0,,0.0101
> 1.0d8,0.0,,0.055
>
> in combination with USDFLD where strain is returned to this parameter
> list. So far I restricted the loading to simple tension.
> Result: the stress drops right to very low values when entering the
> horizontal. But I need the CHANGE OF STRESS to be very low.
>
> So my concern is:
>
> Is there any way to model this either with *ELASTIC,DEPENDENCIES or with
> a UMAT for a bilinear constitutive law (i.e, Young's modulus and
> possibly Poisson's ratio depend on strain or stress) ?
>
> Can anyone share a UMAT for such a bilinear elastic material (yet to be
> extended for various strain and stress ranges) ?
>
> I am aware that this approach does not constitute physical modeling of
> shape memory materials. I only want to reproduce the curve, giving the
> characteristic points where the stiffness is altered.
>
> Thank you all in advance for your expertise
>
> Frank
>
> --
> ----------------------------------------------------------
> Frank Richter
> Institute of Materials Science
> Ruhr-Universitaet Bochum
> Bochum
> Germany
>
> GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
> Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01 
> <http://portal.gmx.net/de/go/maxdome01>
>
>

[Milton Deherrera]

The ABAQUS superelastic model has been offered free since about release 6.6
or so. There are some additional features (like plasticity) for which you
still need to pay extra, but the basic model is free.  By the way, it's
available for both Standard and Explicit.

Milton D.

On Mon, Oct 26, 2009 at 9:27 AM, Dave Lindeman <ddlindeman@...> wrote:

>
>
> Frank:
>
> You might want to take a look at Answer #1658 under "My Support" on the
> Simulia website. There is a shape-memory/superelastic material model
> available within ABAQUS, but it appears to be accessed using the *USER
> MATERIAL interface. At one time (version 6.4?) I believe you had to pay
> to license the material model. I believe it is now built-in, but
> apparently undocumented (I haven't used it, so I'm a little confused...).
>
> Regards,
>
> Dave
>
> -------------------------
> Dave Lindeman
> Lead Research Specialist
> 3M Company
> 3M Center 235-3F-08
> St. Paul, MN 55144
> 651-733-6383
>
>
> Frank Richter wrote:
> >
> >
> >
> >
> > Dear Group,
> >
> > we are striving to model shape memory materials. Their
> > stress-strain-curve forms a closed loop.
> >
> > For you to get a visual impression: Fig. 5 on
> > http://smart.tamu.edu/overview/smaintro/detailed/detailed.html
> > <http://smart.tamu.edu/overview/smaintro/detailed/detailed.html>
> > This figure depicts tension only.
> >
> > At lower temperatures the stress-strain-curve also starts with an
> > elastic curve from the origin and then forms a closed loop around the
> > origin (i.e., the rectangle in this figure is shifted both horizontally
> > and vertically).
> >
> > I want to find out if it is possible to reproduce this curve without a
> > mindboggling UMAT for shape memory materials.
> >
> > For instance, if I want to model a change of stiffness (entering the
> > 'horizontal' upon tensile straining) at 1% strain I tried:
> >
> > *ELASTIC,DEPENDENCIES=1
> > 1.0d10,0.0,, 0.0
> > 1.0d10,0.0,, 0.01
> > 1.0d8,0.0,,0.0101
> > 1.0d8,0.0,,0.055
> >
> > in combination with USDFLD where strain is returned to this parameter
> > list. So far I restricted the loading to simple tension.
> > Result: the stress drops right to very low values when entering the
> > horizontal. But I need the CHANGE OF STRESS to be very low.
> >
> > So my concern is:
> >
> > Is there any way to model this either with *ELASTIC,DEPENDENCIES or with
> > a UMAT for a bilinear constitutive law (i.e, Young's modulus and
> > possibly Poisson's ratio depend on strain or stress) ?
> >
> > Can anyone share a UMAT for such a bilinear elastic material (yet to be
> > extended for various strain and stress ranges) ?
> >
> > I am aware that this approach does not constitute physical modeling of
> > shape memory materials. I only want to reproduce the curve, giving the
> > characteristic points where the stiffness is altered.
> >
> > Thank you all in advance for your expertise
> >
> > Frank
> >
> > --
> > ----------------------------------------------------------
> > Frank Richter
> > Institute of Materials Science
> > Ruhr-Universitaet Bochum
> > Bochum
> > Germany
> >
> > GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
> > Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01
> > <http://portal.gmx.net/de/go/maxdome01>
> >
> >
>  
>

[Non-text portions of this message have been removed]

[Frank Richter-2]

Dear Dave,

thanks for your quick reply. I am aware of this model, but I want to get around intricate SMA modeling.

Here is the background; I dropped it in my previous posting because I didn't want to make it excessively complicated:

We do have a SMA model using UMAT.

I am striving to validate the stress distribution and the like by formal interpretation of SMA behavior as an elastic- ideally plastic material. Means: I want to compare the SMA results to those from a simulation on an elastic- ideally plastic material.
This, however, is hampered by the fact that PLASTIC preserves the volume, whereas our model does not. The difference arises as soon as the stress horizontal is entered.

Workaround: strive to define
*ELASTIC,DEPENDENCIES
with a very low modulus along the horizontal and a Poisson's ratio of zero.

or: bilinear elastic UMAT - but I couldn't dig up one.

Is there a way to get this done ?

Thanks again to all who take an interest here !

Frank


-------- Original-Nachricht --------
> Datum: Mon, 26 Oct 2009 11:27:37 -0500
> Von: Dave Lindeman <ddlindeman@...>
> An: Abaqus@...
> Betreff: Re: [Abaqus] Stress vs. strain: closed loop

> Frank:
>
> You might want to take a look at Answer #1658 under "My Support" on the
> Simulia website.  There is a shape-memory/superelastic material model
> available within ABAQUS, but it appears to be accessed using the *USER
> MATERIAL interface.  At one time (version 6.4?) I believe you had to pay
> to license the material model.  I believe it is now built-in, but
> apparently undocumented (I haven't used it, so I'm a little confused...).
>
> Regards,
>
> Dave
>
> -------------------------
> Dave Lindeman
> Lead Research Specialist
> 3M Company
> 3M Center 235-3F-08
> St. Paul, MN 55144
> 651-733-6383
>
>
> Frank Richter wrote:
> >  
> >
> >
> >
> > Dear Group,
> >
> > we are striving to model shape memory materials. Their
> > stress-strain-curve forms a closed loop.
> >
> > For you to get a visual impression: Fig. 5 on
> > http://smart.tamu.edu/overview/smaintro/detailed/detailed.html 
> > <http://smart.tamu.edu/overview/smaintro/detailed/detailed.html>
> > This figure depicts tension only.
> >
> > At lower temperatures the stress-strain-curve also starts with an
> > elastic curve from the origin and then forms a closed loop around the
> > origin (i.e., the rectangle in this figure is shifted both horizontally
> > and vertically).
> >
> > I want to find out if it is possible to reproduce this curve without a
> > mindboggling UMAT for shape memory materials.
> >
> > For instance, if I want to model a change of stiffness (entering the
> > 'horizontal' upon tensile straining) at 1% strain I tried:
> >
> > *ELASTIC,DEPENDENCIES=1
> > 1.0d10,0.0,, 0.0
> > 1.0d10,0.0,, 0.01
> > 1.0d8,0.0,,0.0101
> > 1.0d8,0.0,,0.055
> >
> > in combination with USDFLD where strain is returned to this parameter
> > list. So far I restricted the loading to simple tension.
> > Result: the stress drops right to very low values when entering the
> > horizontal. But I need the CHANGE OF STRESS to be very low.
> >
> > So my concern is:
> >
> > Is there any way to model this either with *ELASTIC,DEPENDENCIES or with
> > a UMAT for a bilinear constitutive law (i.e, Young's modulus and
> > possibly Poisson's ratio depend on strain or stress) ?
> >
> > Can anyone share a UMAT for such a bilinear elastic material (yet to be
> > extended for various strain and stress ranges) ?
> >
> > I am aware that this approach does not constitute physical modeling of
> > shape memory materials. I only want to reproduce the curve, giving the
> > characteristic points where the stiffness is altered.
> >
> > Thank you all in advance for your expertise
> >
> > Frank
> >
> > --
> > ----------------------------------------------------------
> > Frank Richter
> > Institute of Materials Science
> > Ruhr-Universitaet Bochum
> > Bochum
> > Germany
> >
> > GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
> > Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01 
> > <http://portal.gmx.net/de/go/maxdome01>
> >
> >

--
-----------------------------------------------------------------------
Frank Richter
Institute of Materials Science
Ruhr-Universitaet Bochum
Bochum
Germany



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