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reference about mesh dependency in cohesive elements

 

I'm working in double cantilever beam model in Abaqus. I did the model using two beam instance and another instance the middle which is the adhesive instance with cohesive elements. I tied the instances and define the elastic properties of the beam and the adhesive (cohesive element). The point is that the input parameters that I used to define the properties of the cohesive element (Kn, Gn, and Tmax) are different when I plotted displacement vs traction.

I read a little bit about mesh dependency in cohesive elements and I'm wondering if anyone can recommend me a good reference that help me to identify which are the real parameters in the cohesive elements that are working in the simulation.

Thanks in advance


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Posted by: mgchavez77 <at> yahoo.com.mx
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Homogenization in ABAQUS/Explicit

 

Dear all,

I would like to do homogenization in ABAQUS. At the moment, I can do it in ABAQUS/Standard, but I cannot do it in Explicit because I cannot ask for integration point volume (IVOL) in Explicit. If you know how to solve the problem, please kindly let me know. Every input is highly appreciated!

Kind regards,
Ken
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Posted by: Ken Lippmann <kenlippmann <at> gmail.com>
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(unknown)

 

hi everybody, i am doing a project work in upset forging process. i have modelled the process in abaqus by providing displacement. i want the same result (not exactly) but instead of applying displacement i need to apply load. if i apply load on the rigid element compression/bulging doesn't takes place. can anybody help me? herewith i attached the model with displacement provided on the y axis.

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

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Posted by: David Blessley Blessley <sdblessley <at> rocketmail.com>
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Re: Coupled-Temp-Discpl Step convergence

 

I think I know what the issue was, but I am not sure exactly why this is an issue - when the body heat flux is held constant, and every nodal temperature is constant but different from its neighbour I get the error. When, however, I have ramp up the body heat flux by a tiny amount, this error disappears.

Could someone please explain why?

Thank you!

A


On Tue, Aug 26, 2014 at 7:17 PM, Anna Antoniou <anna.antoniou <at> gmail.com> wrote:
Hi Dave,

Thank you for your response.

The thing is, the two parts do not come in contact - the expansion that I am currently using is too small to allow for this to happen. They do however expand and thus come closer together and the gap becomes smaller (non zero value). As my gapcon definition is inversely proportional to the distance between the two parts, it increases as they come closer together. I had to define an interaction as a surface-to-surface contact in order for me to be able to use the GAPCON subroutine for the conductance in the gap.

I do output the key values from the subroutine in a dat file (distance between the surfaces, temperatures, gap conductivity etc etc) and it appears that I am not getting anything out of the ordinary. I made sure there are no divisions by 0 in my subroutine. When I use a lower body heat flux, everything runs smoothly and the subroutine appears to be doing what I designed it to do. 

I attached my subroutine and the input file in this message. If you can have a look, let me know if there's anything weird. With the current small expansion, the parts do not come in contact and thus only the first IF loop in the subroutine is entered. 

Regards,
Anna



 


On Mon, Aug 25, 2014 at 3:40 PM, Dave Lindeman ddlindeman <at> mmm.com [Abaqus] <Abaqus <at> yahoogroups.com> wrote:
 

In an analysis involving contact and heat transfer, the "TEMP. CORRECTION TOO LARGE COMPARED TO TEMP. INCREMENT" warning occurs when there is no conduction between the bodies (i.e., they're no longer in contact).  If your heat flux is applied to one body, and your convection to the other, then when the gap conductance goes to zero, the temperature in the body with the heat flux will become infinite.  If you can, check to see what's happening with the gap conductance value during your third load step.

Regards,
Dave Lindeman Lead Research Specialist 3M Company 3M Center 235-3G-08 St. Paul, MN 55144 651-733-6383
On 8/11/2014 8:00 AM, Anna Antoniou anna.antoniou <at> gmail.com [Abaqus] wrote:
 
Dear all,

I have an axisymmetric model made of two parts and three steps.
The first step is linear and involves the application of pressure.

Step-2 is a coupled-temperature-displacement step the total time of which is 20 hours and I linearly ramp up a Body Heat Flux (BHF) up to 3E+8 W/m^3 using the *Amplitude command. In the same step the two bodies are allowed to exchange heat via the Gapcon subroutine and one of the surfaces loses heat via a Surface Film Condition.

Step-3 is the same as step-2 (20 hours)  but the BHF is not held constant. All the boundary conditions and interactions and loads are propagated from Step-2.

The BHF is controlled using the *Amplitude command and use the Total Time to give tabular values for the entire simulation such as

*Amplitude, name=Amp-2_thermal-load, time=TOTAL TIME
             0.,              0.,            100.,              0.,          72100.,              1.,         144100.,              1.

where 72000 seconds is the equivalent of 20 hours, and hence:

** LOADS
** Name: BHF   Type: Body heat flux
*Dflux, amplitude=Amp-2_thermal-load
_PickedSet67, BF, 3e+08


In both steps the timestep and maximum allowable temperature change per increment are:

*Step, name=Step-2, nlgeom=YES, inc=8000000
*Coupled Temperature-displacement, creep=none, deltmx=80.
0.72, 72000., 7.2e-06, 720.


Step-2 is successful but Step-3 does not converge. The warning in the message file is:

TEMP.    CORRECTION TOO LARGE COMPARED TO TEMP.    INCREMENT

I am not sure how to fix this. I tried a couple of things to no avail.

Has anyone come across this before? I need some help.

Best,
A.



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Elastic Foundation Output

 

Hello all!


I'm modelling a simple concrete slab (Elastic Property only) over an elastic foundation. It is a Linear Perturbation STEP using CAE.


Is there anyway to visualize the force on the springs? Reaction Forces do not work and I can't assign Spring Output since there are no Springs explicity defined.


It would also be nice to visualize spring "Tension" as Spring Force divided by it's Area of Influency. Is it possible?


Thank you.



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How to include damping effect from geometric stiffness in wires using Rayleigh damping?

 

Hi,


I have a problem with too little damping at high frequencies in a cable-system I'm working on.


I have used Rayleigh damping with alpha and betta values, but this includes only damping proportional to the material stiffness and mass, and not the sum of the material and geometrical stiffness, and the mass.

Does anyone have a solution for this problem? How can I get the correct damping contributions from the geometric stiffness?


Petter Nåvik

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cyclic loading and bucklingsandwiched buckling-restrained brace??????

 

hi 
I model sandwiched buckling-restrained brace in abqus But I have several problems 
1- how to app ly The cyclic loading and buckling together in this example ?
2- Why do not stress in analysis buckling?
3- how to Define interaction Between the concrete , bolt , core and......?
4- Buckling of the brace should be used for buckling analysis or static analysis alone can be used?
help me 
thanks

http://d01.megashares.com/dl/lq76UAk/aaa.png



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Writing Results to Existing ODB file

 

Dear Abaqus Users,


I would appreciate your help with the following;


I am using standard Field outputs (LE, S, etc) to calculate a certain strain result that I am interested in. I would like to write these results back to the ODB file so I can view the contour plot in the CAE Visualization module.


I am new to scripting so I started off with just a simple cube part, meshed with a single 8 node element, and generated an ODB for a straight forward compression analysis. Then I tried to write a new field output variable to the ODB.

I am trying the following commands in the Abaqus (ver 6.12) command line interface;


import odbAccess

odbName = 'C:/Users/jejohnson/Desktop/Newfolder/test1.odb'

odb = session.openOdb(name=odbName, readOnly=False)

instance1 = odb.rootAssembly.instances['TEST1-1']

frame1 = odb.steps['load'].frames[-1]

field1 = frame1.FieldOutput(name='Mod', description='none', type=SCALAR)

nodeNO = [1,2,3,4,5,6,7,8]

nodeData = [(0.05),(0.05),(0.05),(0.05),(0.05),(0.05),(0.05),(0.05)]

field1.addData(position=NODAL, instance=instance1, labels=nodeNO, data=nodeData)

odb.save()

odb.close()


When I try to create the new field output "field1", I get the following error;

NameError: name 'SCALA R' is not defined


I do not understand why I get this error since the Scripting Reference Manual mentions that that is a possible value for "type"

I also tried;

field1 = frame1.FieldOutput(name='Mod', description='none', type='SCALAR'), but then I get

TypeError: type; found string, expecting SCALAR


Any suggestions/comments would be greatly appreciated. If there is a better/more efficient way to do this, that would also be appreciated.


Thank you very much for your help,


Joshua

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Posted by: joshua.e.johnson2 <at> gmail.com
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bothioan@yahoo.com [Abaqus] | 26 Aug 19:14 2014
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Thermal analysis of slab

 

Dear All,

I am trying to model a fiber reinforced concrete slab on steel beams. I have applied the load in the first step and applied thermal conditions (convection and radiation) in the second step. The analysis reached 400seconds (tops) ( I was expecting 7000s). I have modeled the structure with solids. Slab tied to the beam.
the analysis was run with Abaqus Standard. I have tried the same model using Explicit but the second step won't even start due to convergence. I tried contact between slab and beam.
I have tried the same structure with shell elements but still "no go".

Does anyone have references related to the topic? Thank you for any advice!

Regards everyone,


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Abaqus ver 6.13 - FSI modelling - CONFLICT error for CONTROLS keyword

 

Hi,

Getting an error when trying to emulate the FSI example from Getting Started with Abaqus: Interactive Edition manual : Appendix E: Flow through a bent tube

Section E.6.5 requires the addition of the following to the keywords, just after *Co-simulation Controls option block keyword

*Controls, type=FSI
, , , 1.1

However, the data-check on fluid model fails with following message

Error: in keyword *CONFLICTS, file "??????.inp", line ????: Keyword *Conflicts is generated by Abaqus/CAE to highlight changes made via the Keywords Editor that conflict with changes made subsequently via the native GUI.

The conflict is listed as the *Controls keywords added. The example runs successfully in version 6.12

Has anyone else had the same issue or been successful in running FSI modelling in version 6.13. Please advise what changes to the keyword file worked.

Thanks,

Miten

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Posted by: miten.patel <at> imperial.ac.uk
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Condition Number of Stiffness Matrix

 



I am dealing with laminated materials differing quite a lot in thickness and
stiffness of the layers. I have a full model with all layers in extra elements to determine non-linear shear, too.

Thus, I want to *extract the condition number of the global stiffness
matrix*.

I only found the element matrix output of the whole stiffness matrix, but
not the condition number!

Does anyone know a way?

And how about pre-conditioning?

Thanks a lot!

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Posted by: =?UTF-8?B?TWF0dGhpYXMgS2zDpHJuZXI=?= <matthias.klaerner <at> gmx.de>
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Gmane