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hyper-anisotropic model

 

hello everyone 

does anyone know how to update stress in hyper-anisotropic model in vumat ? 

i am getting the same stress for bi-axial test as my Matlab code and different result for uniaxial test .

anyone one experienced in this area willing to take a look at my vumat  or suggest me a good paper in which the process is outlined?

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Posted by: sam_sh_1 <at> hotmail.com
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Plastic strain is zero in isotropic hardening

 


Hi ,

I want to request an output of the plastic strain components  over my model (tensile test) , but when I do this and view the the results in CAE the plastic strain components are zero everywhere. Im using isotropic hardening Umat.

Can someone help me please 

Thanks pan>


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Posted by: amel.alimi <at> yahoo.fr
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DAMAGE EVOLUTION

 

Dear all

I am trying to simulate a surface based cohesive model in ABAQUS standard. Particularly, a block is moving on a surface while attraction-separation is active during the motion.
 
In this case, 

STEP 1:  the block first slides in a horizontal direction for 4 mm 

STEP 2: block separates vertically from the bottom surface for 3 mm. 

The separation values corresponding to DAMAGE INITIATION is 1 mm ; and the COHESIVE STIFFNESS is also 1. 

So, it means the maximum fracture energy at the failure point in horizontal and vertical are 2 and 1.5 respectively. (the area under traction - separation triangle curve) 

For this case, I think there is two modes of fracture: 

1. in shear plane 
2. in vertical plane

So, I want to implement the fraction of these two modes during the simulation. I could not understand from ABAQUS help how it can be correctly implemented. I applied the below commands:

*DAMAGE EVOLUTION, TYPE=ENERGY, MODE MIX RATIO=ENERGY, SOFTENING=LINEAR, MIXED MODE      BEHAVIOR=TABULAR
 1.5,0,0
 2,1,0
 1.5,0,1
 2, 1, 1

But the main problem is that, when sliding is finished and vertical separation is started (STEP 2) sliding effects still remained !!!!!!!

It seems that there is a problem in fracture energy definition during DAMAGE EVOLUTION definition.

Can somebody help me please, how to overcome this problem.

thanks










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Posted by: Hassan Nazarinezhad <a.nazarinezhad <at> gmail.com>
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translate contact in dyna to abaqus

 

Dear group,


I am trying to translate a model in LS-DYNA (explicit) to Abaqus. I have used the translator utility in Abaqus and Hypermesh but there is plenty more to be done. Translating contact in an accurate way is one of the things I am working on.


As it turns out, interactions in LS-DYNA happen to come with a time variable using which one can turn contact on or off ('birth time' and 'death time'). I can break the Abaqus model in to several steps but it is not an ideal solution because some birth/death times (as defined in LS-DYNA) overlap.


Do you have any suggestions for me? Unfortunately, I do not have the luxury of time to code.

Thank you.


Vikas   

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abaqus √ľnits

 

Hi all


ı have 3d model ınclude all head part, brain skull etc..ı get it from mrı imagines by materiliase mimics and export to 3 matic. ı work in abaqus mm units then export to abaqus as orphane mesh and assmebly etc. ı have to use it sı mm units am ı correct?


if ı right, for example young moduls for brain 2190 mpa ı write 2190 mpa

densty 1040 kg/m3 and ı write 1,04 e-9


when ı do like this its give me a eror exsesive element. and ı try everythink change mesh finner , load rate mass scaling, smooth load amplutude but never fixed it..


if ı use run sı m, runing is completed but the results are so small from literature..


ı suffer so much,


ı hope you help for this prblem...


Fehmi

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Displacement control nonlinear buckling analysis

 

Dear Members,

Can any one suggest me how to perform displacement controlled nonlinear buckling analysis in Abaqus? I am working with plasticity and geometric non-linearity in my model (plate) and want to observe post buckling behavior. 

For this purpose, I would like to apply controlled displacements in incremental way and obtain the corresponding reaction forces to plot force displaceme nt curve.

Any advice/suggestion would be highly appreciated.
 
Mahmudur Rahman
Masters Student (ID No: s14me127)
Structural Mechanics & Dynamics Lab
Saitama University
, 255 Shimo-Okubo,
Sakura-ku, Saitama-shi, 338-8570 JAPAN.


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Posted by: Mahmudur Rahman Limon <limonkcivil <at> yahoo.com>
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Steady State Dynamics (Modal) - visualising frequency response function

 

Dear users,


hello. I am a mechanical engineering student now learning finite element method and Abaqus.

I have searched on this forum, but I haven't found an answer for my problem.

I'd really appreciate any suggestion, idea or improvement by you about the following Abaqus analysis.


What I wanto to obtain:

Frequency Response Function (FRF) of a plate when I load a point in the structure and measure the displacement response at the loaded point. Hence, a graph like the one depicted below


What I did:

Steady State Dynamics (Modal), plot of the nodal displacement of interest vs frequency, absolute value of the displacement, logarithm of the absolute value divided by the absolute value of the applied force

Then, I have tried to plot generalised displacement, add all the generalised displacement plots


 Issues:
-the displacement plot is both positive and negative, therefore it is zero somewhere at resonances. As I take the logarithm the value goes to -infinity at resonances;
-in the sum of generalised plots I can no lenger see the antiresonances as Abaqus gives me generalised quantities only for whole model and not for the single point I need.

As I said, any idea or suggestion would be really appreciated.
Have a nice day,

Italian


 

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Erosion loss calculation using Abaqus

 

Hello,

Anyone have any idea about getting mass loss of erosion wear due to particle impact on metal using Abaqus.

Your help would be greatly appreciated.

Regards

Shahanur

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Posted by: shahanur hasan <shahanur2 <at> yahoo.com>
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Gravity Load Abaqus CAE

 

Hello, 


I searched for similar issues but I did not found the exact same situation I am facing. 


When submitting a simple analysis in a static step to an acceleration I am using the option of gravity load. 


Suppose this is an acceleration in the X axis. 


If the system of units being used is metric ton / second / mm, and obviously the density is in ton/mm^3,  the question is how to correctly define the gravity load magnitude. 


In the .inp file that section is written  :


*Dload

accel-1_eset-10, GRAV, 9810., 1., 0., 0.

The question is , if I want a 1G acceleration in X Axis what do you have to put as magnitude:


  • Use 9810 as it is consistent with the system of units mm/s^2 and the density units. (I believe this is the correct approach). Although I am having issues with elements distorting excessively.     

*Dload

accel-1_eset-10, GRAV, 9810., 1., 0., 0.

  • Use 9.81 as magnitude. Although this is incosistent with all the other units as gravity is here in m/s^2
  • ul>

    *Dload

    accel-1_eset-10, GRAV, 9.81, 1., 0., 0.

    • Use 1 as magnitude. In some places I read that as you have all your consistent units, you only put how much Gs you are using, in this case 1G, or if it is for example 25G you would put 25 in magnitude.

    *Dload

    accel-1_eset-10, GRAV, 1., 1., 0., 0.



    Thank you for your help.




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Errors message in Abaqus

 

Hello everyone,

I got this error message after submitting a job
Unable to open the file <rank=0,arg_name=tmpdir>Bridge.scr

I do not know what is the reason, because yesterday, it was fine. However, yesterday, I left the computer run with abaqus, and this morning I came to my office, run the abaqus again with that error. The error happens to any model, even a simple model.

Could you please help me about this.

Thank you so much!

Regards
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Posted by: Hai Bang Phan <phanhbang <at> gmail.com>
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overclosure

 

Hi all


İ work dynamic explict in abaqus about tbi. There are contact problem. İ should do overclosure. İt is easy in standart sorfacce to surfac contact but i dont know how can i do dynamc contact...


Can you help me?

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Gmane