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Updated: 21 hours 6 min ago

configure abaqus 6.13.2 in windows7 to run user subroutines

Sun, 2017-02-26 07:51

In reply to configure abaqus 6.13.2 in windows7 to run user subroutines

Please help me with the solution to solve R6034 error for abaqus/explicit VUMAT subroutine.

Thank you

configure abaqus 6.13.2 in windows7 to run user subroutines

Sun, 2017-02-26 07:49

In reply to link instruction -abaqus configuration

Hello,

I also have the same problem running VUMAT due to R6034 error. Can you also send the pdf to me as well?

Thank you

have you found the solution

Sat, 2017-02-25 11:37

In reply to Highlighting contours with Abaqus (XFEM)

have you found the solution to do so?

What is the pull-off for theoretically flat surfaces?

Sat, 2017-02-25 06:12

In reply to On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

An interesting problem is the following:  what happens for a truly flat surface?  Even with a truncated potential, it is easy to show that the decaying adhesive force induces an instability --- even if the surface were flat. I have done the calculation for this instability, and it turns out, for the Lennard-Jones potential, that this instability occurs if we have a periodic wavelenght of the order of 50 a0.  Therefore, not very large at all.  Two flat surfaces would be in equilibrium at distance a0 and show the theoretical Lennard Jones pull-off force (theoretical strength) only if they were constrained not to assume wavy configurations.

This in fact could be an interesting problem to study, which however requires a numerical solution. Anyone interested?

Some arguments on why Pastewka-Robbins is not general

Sat, 2017-02-25 06:10

In reply to On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

First of all, PR use a "truncated potentials", a convenient numerical representation of the Lennard-Jones potential, but certainly a numeric artefact.  Their potential is truncated at a short distance, a0+delta_r where delta_r is of the order of a0 itself (the atomic distance), and therefore, there is an artificial effect there: after 2 atomic steps, there is no longer adhesive force.  This perhaps hides some effects of the rms amplitude?

In a true situation, Lennard-Jones extends to infinity, and it is clear that this fact already lowers the significance of their finding. Even at very long distances, in theory one should always have some attractive force, and this cannot be zero, and this means the area-load bends in the tensile quadrant always. Their criterion therefore has a lot to do with their arbitrary definition of the truncated potential.

 

Restart if max number of increments is less

Thu, 2017-02-23 22:34

In reply to I dont know if you have

Hello,
I have been trying to use the input file solution you outlined. Is it possible to increase the max. number of increments of the step on the job before restarting it? My job was terminated due to this, and I don't want to run the whole thing again. 

Thanks!

Gaurav 
Raleigh, USA

 

Effect of rms amplitude on adhesive behavior of surfaces

Thu, 2017-02-23 07:11

In reply to On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

There is no qualitative contrast between classical asperity models and Persson models or any numerical recent calculation about the slope of area-load curve: the only  geometrical parameter entering the area-load slope is the rms slope of the surface. 

The question arises with adhesion. Pastewka-Robbins suggested that the slope in this case becomes dependent additionally on rms curvature, and not on rms amplitude, whereas asperity models (Fuller-Tabor is the only one, the proper rough random surface one is not in the Literature but we are about to publish it) involve also rms amplitude. 

However, also Pastewka-Robbins do find that pull-off depends on rms amplitude. So in their case there is a curious threshold: for non-sticky surfaces, they say there is no dependence on rms amplitude, whereas for sticky one there is, as they also find.

 

Can you beleive this?

 

Thank you

Wed, 2017-02-22 14:13

In reply to Yes you should double the

Thank you

Superb idea

Wed, 2017-02-22 13:12

In reply to 2007 Timoshenko Medal Acceptance Speech by Thomas J.R. Hughes

Listening to the podcasts or watching videos will be much more interesting and easy than reading a huge write-up. 

Yes you should double the

Wed, 2017-02-22 12:56

In reply to How to apply a traction shear load on a surface

Yes you should double the traction if you fix the other end. But your model should not move. There should be something wrong somewhere.

Not able to apply online

Wed, 2017-02-22 11:57

In reply to Marie Curie Early Stage Researcher (PhD student), Improving the crashworthiness of composite transportation structures

Sir,

I have registered but not able to apply online for this position.

Kindly help me how to apply for this position.

Regards,

Sanjay Kumar

FEA developer

Tue, 2017-02-21 15:11

In reply to Several developer positions available at ANSYS

ANSYS just opens several developer positions in aeas of contact mechanics, material modeling, finite element formulation, solver technology. If you are interested, please submit your application on ANSYS company website at 

http://chp.tbe.taleo.net/chp02/ats/careers/requisition.jsp?org=ANSYS&cws=1&rid=5348

Thank you for your reply.

Tue, 2017-02-21 13:51

In reply to Hi

Thank you for your reply.

I am applying it to a unidirectional fiber composite. I am applying transverse load as well as longitudinal shear.

I wanted to apply the shear load to be half of the transverse one. I applied the shear on both surfaces. Each surface has the same magnitude as the transverse.

In the results, I found that the model suffer from free body motion. That is why I thought of fixing one surface.

If I fixed one surface, do I have to apply twice the magnitude with two surfaces?

Thank you

Hi

Tue, 2017-02-21 11:08

In reply to How to apply a traction shear load on a surface

Hi

 

In theory it should not matter if you fix one and apply shear to other surface or if you apply shear half to one surface and half to the opposite surface, but depend on the model, boundary conditions and the system you are studying, it might make some differences.

Amodified form of Pastewka-Robbins criterion for adhesion

Sun, 2017-02-19 16:12

In reply to On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

Amodified form of Pastewka-Robbins criterion for adhesionCiavarellaPapangelo - The Journal of Adhesion, 2017 - Taylor & Francis Abstract

Recent numerical investigation on self-affine Gaussian surfaces by Pastewka & Robbins have led to a criterion for “stickiness” based on when the slope of the (repulsive) area-load relationship appears to become vertical in numerical simulations at a ratio of contact area to nominal one (rather arbitrarily) fixed to 1%. Since pull-off and slope of the area-load are two faces of the same medal, a simple check of the results in terms of pull-off shows that Pastewka & Robbins have many more data which fail their criterion than the ones who satisfy it, and this is evident even in their own Figures. As a small improvement, a proposal to modify the criterion to better fit their own data is put forward. However, the pull-off decay seems rather exponential so that it is unclear if their slope criterion really corresponds to a “thermodynamic” limit, and consequently their conclusion that stickiness should depend only on slopes and curvature may be an artefact of their assumption of defining a secant at 1% contact area ratio, rather than a true important property of rough contact. Both the PR criterion and the present modified one imply that for fractal dimension D<2.4, stickiness should increase with resolution, so the problem of truncation of the spectrum seems ill-defined: in fact, PR define rigid self-affine surfaces with rather smooth and well defined slopes, and not a realistic atomic roughness as first studied by Luan and Robbins.

a mathematica code for surface generation

Sun, 2017-02-19 03:18

In reply to The contact mechanics challenge: Problem definition

anyway, there is already one code in public domain mathematica http://demonstrations.wolfram.com/TwoDimensionalFractionalBrownianMotion/

damage

Sat, 2017-02-18 15:48

In reply to Ductile damage calibration in ABAQUS

Subscribe to and seek assistance from the
ABAQUS mailing list
https://groups.yahoo.com/group/ABAQUS

Search the archive before posting.

For an intro to subroutines get the file
http://imechanica.org/files/Writing User Subroutines with ABAQUS.pdf

Good luck

Frank

Publication in refereed Journals

Sat, 2017-02-18 14:46

In reply to 3rd Indian Conference on Applied Mechanics (INCAM2017, 5-7July, 2017)

Authors of Selected papers (only those which are presented in the conference) will be invited to submit an updated and extended version of their work for possible publication as special issue in following refereed journals (after review as per the norms of the Journal):

Abaqus mailing list

Fri, 2017-02-17 14:59

In reply to ABAQUS: Access stress of integration point of elements during calculation

Subscribe to and seek assistance from the
ABAQUS mailing list
https://groups.yahoo.com/group/ABAQUS

Search the archive before posting.

For an intro to subroutines get the file
http://imechanica.org/files/Writing User Subroutines with ABAQUS.pdf

Good luck

Frank

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