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Updated: 16 hours 4 min ago

I suggest that delete the

Tue, 2014-07-29 17:32

In reply to Try creating it in a new file

I suggest that delete the existing step and recreate the Riks step and apply boundary conditions. I hope this would work.

 

Jay

Dear zhigang, thank you for

Tue, 2014-07-29 02:50

In reply to Bioinspiration and biointegration

Dear zhigang, thank you for initiating this intersting topic. As you wrote  when a person steps on a nail, the sensor in his foot sends a signal to his brain, the brain sends a signal to his muscle, and he lifts his foot.  The components of this nevous system can be made of soft materials, which turns the system into a soft machine.

Capacitive sensors made of polymer have advantages in softness, large strain, high sensitivity and small size.  

Viry et al. 2014 Flexible Three-Axial Force Sensor for Soft and Highly Sensitive Artificial Touch.

Stretchable and transparent inoic conductor can serve as the nerve to transport the signal.

Keplinger et al. 2013 Stretchable, Transparent, Inoic Conductors.

"Lifting the foot" needs an actuator, for which electrically active polymers are good candidates.

Brochu et al. 2010 Advances in Dielectric Elastomers for Actuators and Artificial Muscles.

The difficult part may be the processors. Human brain is so powerful and complex that probably no artificial brain can beat it. As Prof. Huang mentioned, human-computer integration can be a good choice. Alternate solution is the indirect control, e.g. human brain controls hands, soft acuators mimic the hands through the transporting signal.

Our group is now targeting to assemble these soft components. I'd like to hear more suggestions from all of you. Thank you! 

1)1st eigen mode is taken

Tue, 2014-07-29 02:20

In reply to Non-linear buckling analysis using static riks method-abaqus

1)1st eigen mode is taken generally...

2) Imperfection can be imposed in the form of % thickness, there are videos available in Youtube on cylindrical shell buckling please check.

3) Dont know exactly....so please refer someone else....still I applied the load as shell edge load hence, when i got the results in eigen value analysis, i just multiplied it by the loading perimeter...For static riks method...sum of the reaction forces at all the nodes will give you the reaction or the actual buckling load, i dnt know if its the critical buckling load....You can get the reactions by giving appropriate field output requests in step and then you can obtain the results from the visualisation module

4) no clue bro

Try creating it in a new file

Tue, 2014-07-29 02:14

In reply to Riks analysis using ABAQUS

Try creating it in a new file instead of replacing the step

SHPB modeling

Mon, 2014-07-28 15:36

In reply to impact velocity,high strain rate impact,

Hello

a few selected publications on SHPB modeling, available freely:

1) in the ABAQUS manual:

Getting Started with Abaqus: Keywords Edition    
9.1 Types of problems suited for Abaqus/Explicit

Getting Started with Abaqus: Keywords Edition    
9.4 Example: stress wave propagation in a bar

2) MODELING AND EXPERIMENTAL INVESTIGATIONS OF THE SHOCK
RESPONSE OF VISCOELASTIC FOAMS
by Richard J. Deigan
Dissertation submitted to the Faculty of the Graduate School of the
University of Maryland, College Park, in partial fulfillment
of the requirements for the degree of
Doctorate of Philosophy
2007

3) 2D Hopkinson bar simulation analysis
Al 6061-T6 specimens
A. Bouamoul
DRDC Valcartier
Defence R&D Canada – Valcartier
Technical Memorandum
DRDC Valcartier TM 2004-363
March 2006

4) Anthony D. Puckett:
Thesis
Fidelity of a Finite Element Model
for Longitudinal Wave Propagation
in Thick Cylindrical Wave Guides
Los Alamos National Laboratory
LA-13753-T

5) Army Research Laboratory:
Numerical Hopkinson Bar Analysis: Uni-Axial Stress and
Planar Bar-Specimen Interface Conditions by Design
by Bazle A. Gama and John W. Gillespie, Jr.
ARL-CR-553 September 2004
prepared by
University of Delaware
Center for Composite Materials
Newark, DE 19716
under contract
DAAD19-01-2-0005

6) BAM-Dissertationsreihe, Band 116
Dipl.-Phys. Hauke Gravenkamp
Numerical methods for the simulation of ultrasonic guided waves
2014, ISBN 978-3-9816380-4-2
from:
http://www.bam.de/de/aktuell/aktuelle_meldungen/index.htm

7) find more on the Internet

Good luck

Frank

impact velocity,high strain rate impact,

Mon, 2014-07-28 14:52

In reply to ABAQUS Tutorial and Assignment #1

Dear all

I am Ali from iraq, I MSc student , I want learn instructions to simulate impact velocity,high strain rate impact (Hopkinson appearus) by abaqus prgram,Please can someone help me? thanks and regards

 

 

 

 

Hi ashkan,

Mon, 2014-07-28 12:56

In reply to One time calculation in UEL

Hi ashkan,

a) you have both matrices, multiply them .. write the code for in your uel file.

b) you can store the values on SVARS. assuming you have three displacements after step 1, then you will need three SVARS.

 

as far as I remember you can use SVARS to store the solution dependent variables.

 

hope this helps

brunda

Hi Brunda,

Mon, 2014-07-28 12:12

In reply to Hi Ashkan

Hi Brunda,

Thanks for your response.

I'm using UEL. Displacements that I'm calculating by UEL are in frequency domain, U(f). I want to change them to time domain, U(t). For doing that I must multiply a trnsfer matrix (n*n) by U (n*1). I'm calculating transfer matrix inside of the UEL and I have access to displacement (U). In history output part of ABAQUS, what I have as displacement is U(f), displacement in frequency domain. Is there anyway that I can add a user-defined history output, let's name it UT, and ask ABAQUS to calculate it for me?

Let's say there is no way to do that. Now I have to write the U(f) and transfer matrix to two files and then in another fortran code call them and multiply them and plot them. Writing transfer matrix to a file is not a big deal but, writing displacement, U, is difficult because it's been calculating in every time incerement. When I'm trying to write it to a file, because for ever time incerement it has a new value, it is been over writing on the value of last incerement. But I need the value of every time incerement to be written in the file. How can I do that?

I really appreciate your consideration. Thanks in advance.

Best Regards,

The rest of the document in

Sun, 2014-07-27 15:58

In reply to A study of conditions for dislocation nucleation in coarser-than-atomistic scale models

The rest of the document in attached in next entry.

2 hints

Sun, 2014-07-27 13:31

In reply to Thanks for your valuable

Hello

in your code replace all TAB with spaces !

Try to get advice from the ABAQUS mailing list
http://groups.yahoo.com/neo/groups/Abaqus/info

This is a moderated list, any posting will be forwarded to subscribers with a delay.

Good luck

Frank

Thanks for your valuable

Sun, 2014-07-27 10:49

In reply to It might be helpful to know

Thanks for your valuable response.

The model I want to code it, is a model for sand (IMAM model). and If the soil be isotropic the STATEV(4) will be zero.

I hope that I can to solve my problem by your response.

Good Luck

 

frequency=0

Sun, 2014-07-27 09:43

In reply to I dont know if you have

is there any way to restart a job if it had "FREQUENCY=0" in the *RESTART command?

 

It might be helpful to know

Sun, 2014-07-27 07:36

In reply to The UMAT problem with no strain and stress

It might be helpful to know what model you want to code.

Mind that

STATEV(4)==0

is a test that works exclusively if statev(4) is an integer.

 

Study these chapters in the manual (section numbers depend on release of your Abaqus !):

13.2.1 USER SUBROUTINES: OVERVIEW

Testing and debugging
When developing user subroutines, test them thoroughly on smaller examples in which the user
subroutine is the only complicated aspect of the model before attempting to use them in production
analysis work.
If needed, debug output can be written to the ABAQUS/Standard message (.msg) file using
FORTRAN unit 7 or to the ABAQUS/Standard data (.dat) file or the ABAQUS/Explicit status (.sta)
file using FORTRAN unit 6; these units should not be opened by your routines since they are already
opened by ABAQUS.
FORTRAN units 15 through 18 or units greater than 100 can be used to read or write other userspecified
information. The use of other FORTRAN units may interfere with ABAQUS file operations;
see “FORTRAN unit numbers used by ABAQUS,” Section 3.6.1. You must open these FORTRAN units;
and because of the use of scratch directories, the full pathname for the file must be used in the OPEN
statement

also:
3.6.1 FORTRAN UNIT NUMBERS USED BY Abaqus
Abaqus uses the FORTRAN unit numbers outlined in the table below. Unless noted otherwise, you should not try to write to these FORTRAN units from user subroutines.
For Abaqus/Standard, you should specify unit numbers 15–18 or unit numbers greater than 100 .
For Abaqus/Explicit, specify units 16–18 or unit numbers greater than 100 ending in 5 to 9, e.g. 105, 268, etc. You cannot write to the.sta file.

Here is an example to write to a self-defined file:

IF (condition fulfilled) THEN
   open(15,file='Exp.rpl',position='append')
   write(15,*) TIME(2), RPL
   close(15)
END IF

I do not remember right now if 'Exp.rpl' is to be preceded by the full path to the file.

To write to the log file:
IF (condition fulfilled) THEN
    print*, NDI
END IF

Good luck

Frank

Re. The UMAT problem with no strain and stress

Sun, 2014-07-27 05:55

In reply to The UMAT problem with no strain and stress

Hi,

There might be multiple reasons for this problem. Please use some WRITE statements and see whether you get proper numbers for the variables that are updated inside UMAT. If the variables returned back to abaqus from UMAT such as STRESS, DDSDDE, STATEV etc by chance turns (NAN) inside the subroutine, then there is probability that these errors come. 

"The selected primary variable is not available in the current frame for any elements in the current display group"

Thanks and Regards,

Rohith

Thanks Profs Christensen and Huang..

Sun, 2014-07-27 05:46

In reply to Professor Christensen published an interesting paper in JAM on the coordination between elasticity theory and failure theory

for sharing this information; I found the paper very inspiring!

vito

 

attach UMAT

Sun, 2014-07-27 04:00

In reply to The UMAT problem with no strain and stress

Dear all,

I attached my UMAT subroutin. Could anybody help me now?

Dear Emilio Martinez

Sun, 2014-07-27 03:54

In reply to Dear Atefe Geramian

Dear Emilio Martinez

Thanks for your response.

But I dont undrerstand your meaning exactly. I attach my UMAT file perhaps you can help me.  

Thanks for posting

Sat, 2014-07-26 22:11

In reply to Thanks for posting such a

Thanks for posting

Help request

Sat, 2014-07-26 22:10

In reply to how to link abaqus with matlab ?

ok

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