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Updated: 7 hours 12 min ago

Is updated lagrangian

Wed, 2017-07-19 21:51

In reply to Question reg ABAQUS-VUMAT and Updated Lagrangian formulation.

Is updated lagrangian formulation automatically toggled while solving in ABAQUS/Explicit wherein NLGEOM is ON by default? 





Wed, 2017-07-19 11:09

In reply to Error in openning ODB file in ABAQUS CAE



I have the same problem. It occurred on a job where I used an HPC cluster server to solve the job. When i try to open it in my local machine, I get the same error. Any solutions?





That is also my opinion "Not

Tue, 2017-07-18 05:05

In reply to Can we predict when the Larsen-C ice shelf will fail?

That is also my opinion "Not yet".
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Sun, 2017-07-16 02:17

In reply to Re: Unaddressed problems from mechanics



Re: Unaddressed problems from mechanics

Sat, 2017-07-15 19:57

In reply to Re: Unaddressed problems from mechanics

Unfortunately, it was my own money and time.  Can't say it was a waste though.  I learnt a lot in the process about what works and what doesn't and have a better nose for spotting bullshit academic papers as a result.

-- Biswajit

Re: Unaddressed problems from mechanics

Sat, 2017-07-15 14:06

In reply to Can we predict when the Larsen-C ice shelf will fail?


I understand you wasted a lot of American (or, at any rate, Utahian) tax-payer's money.

I wish other mechanicians did the same, too!




Nice one Teng. Thanks for

Fri, 2017-07-14 05:27

In reply to How to post a video?

Nice one Teng. Thanks for taking such time, dedication and effort in sharing the information on how to post video in iMechanica. I'll keep in mind the step by step instructions.
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Re: Tall order

Thu, 2017-07-13 16:56

In reply to Can we predict when the Larsen-C ice shelf will fail?


Given the near impossibility of predicting everyday experiences using mechanics, let alone more difficult problems involing unknown geometries and materials, it's not surprising that mechanicians have moved to easier problems instead of harder problems over the past 30 years.

I've spent a considerable amount of time trying to solve some simple problems such as splintering wood, making flour dough, or even trying to model what happens when you press your foot into partially saturated sand on a beach - using Newton's laws and widely used material models.  I've failed to predict anything useful every time.  I wish other mechanicians tried to solve more problems of that nature.

-- Biswajit

Tall order!

Thu, 2017-07-13 12:43

In reply to Can we predict when the Larsen-C ice shelf will fail?

Read your analysis on your company blog. From your list of the issues to be resolved, is it point no. 3 (branching) which is the hardest to deal with? Just asking... On second thoughts, no. 2 (significant variation of crack growth rate) also might be a factor that makes predictions difficult. I mean, how do you know that factors other than pure fracturre mechanics (such as presence of meso- or larger-scale features, concentration variations, etc.) were not present and responsible for those variations?

All in all, a tall order, it is!

There are any number of problems that (i) look simple to simulate, (ii) but still lie hopelessly out of the reach of the current state of the art. This is one of them. (Even just the ``simple'' problem of predicting at precisely what time what exact shape is assumed by a melting snowman, is a tough one. I know, because I tried it.)

Anyway, an interesting bit, it was, though. A 10 km by 100 km piece of rock that is about to break away? The mind numbs. ... They had quite an opportunity to advance science though. For instance, how big a noise did it make when it finally broke away? (read: acoustic emission signatures)...

OK. Let me wind up.



Thanks for the advice

Tue, 2017-07-11 23:33

In reply to Seek your input on nano-indentation or basic mechanics of materials

Roy,  Thank you for pointing out that the stress/strain field may differ under dynamic test, for the moment we will keep it simple so we only obtain the force-displacement (or the stres-strain curves) of the micro-pillar under different strain rates. I will keep you posted if we find anything interesting.    -Kejie

No simple answers on the strain rates during nano-indentation te

Tue, 2017-07-11 13:13

In reply to Congratulations!


Thanks for your encouragement!  You know a nano-indentation problem is a two-body contact mechanics problem. If a same indenter tip hits two samples very quickly, the strain fields and strain rates of a soft sample and a hard sample would be very different, so I really cannot tell you a general rule. But you may run a finite element analysis on your micro-pillar compression test to find maximum strain and the rate, if you know the maximum tip speed of your nano-indentation system.  Look forward to knowing nice result from you.



Mon, 2017-07-10 22:09

In reply to No strain rate tests using nanoindentation

Dear Roy,

I am glad to hear that the proposal works out, brilliant ideas will enventually be funded, congratulations!  I understand that indentation would be in the quasi-static range, I was wondering how much we can play..  Look foward to discussing more next time.


No strain rate tests using nanoindentation

Mon, 2017-07-10 20:02

In reply to strain rate of nanoindentation


Glad to hear from you. I didn’t know any nano-indentation system is able to conduct a “strain rate” test--- because we often use gas guns to conduct high strain rate tests. Think about the test procedure: an indenter tip compresses a sample and can get the indentation depth. But in terms of the strain measurement, we need another length scale…..Moreover, the indenter tip must move as fast as a gas gun projectile (e.g., > 20 m/s) to get a high strain rate during the initial contact with the sample.  I think we cannot make such a fast nano-indentation system now.

Good news is after we submitted a rebuttal to the funding agency, our proposal would be funded. Here is an illustration of our major idea, and we’d discuss more details with you. Keep in touch!

 A Multi-Scale Approach of Combining Nano-indentation with Computational Mechanics to Predict Impact Behavior of Structural Composite Materials



strain rate of nanoindentation

Mon, 2017-07-10 14:59

In reply to low-speed impact is much faster than nanoindentation

Dear Roy,

We are using indentation (Keysight G200) to perform micro-pillar compression tests. We are interested in the strain rate performance of the micro-pillars. In your exerience, may I ask the range of strain-rate the indenter can apply? Many thanks,


I think Abaqus has .jnl or

Sat, 2017-07-08 23:21

In reply to Does anyone know how to keep a record of what you have done in a CAE session?

I think Abaqus has .jnl or maybe it is in the temp folder. - how to buy soundcloud likes


Sat, 2017-07-08 11:27

In reply to 2017 Stephen P. Timoshenko Medal - Professor Viggo Tvergaard

Congrats Dr. Tvergaard! ... Very happy here...

Had been reading his papers in the [very distant and by now unrelated] past.

[But, Pradeep, may be, if you still are on the job next year too, the, may be, just may be, you'd better begin lining up our own Zhigang here too, for this prize. ... And, soon enough!

Yes, the recommendation is shameless. But it also is very honest. ... So, there.]

But back to those early 90s... May be some other iMechanicians chip in here, and share about Prof. Tvergaard's contributions. ... I, by turns and turns of misfortune, left this area back behind me. ...

... But anyway, as to a simple guy like me, yes, Dr. Tvergaard did produce some very neat models by venturing into what back then was a very difficult territory, given the methods available back then. ... So, congrats, once again!



thanks for leading the discussion on the interesting topic

Sat, 2017-07-08 01:43

In reply to Geometrically nonlinear microstructured materials for mechanical wave tailoring

Nick, many thanks for leading the discussion on the interesting topic. 

As we know, the heat transport of a dielectric is mainly through phonon. According to my limited knowledge on both fields (thermal conduction of solids and elastodyanmic waves in lattice structures), there are lots of similarities  (at least mathematically) between the heat tranport in a dielectric solid and elastodynamic wave propagation in lattic structures as you discussed above. Do you know if there is any interaction between the two fields?  For example, using experiments on elastodynamic wave propagating in lattice structure to uncover something about heat transport in a dielectric solid. Or, designning a dieletric solid with interesting thermal transport properteis based on the new discoveries of the elastodynamic wave propagating in a lattice structure. 



For reaction-diffusion and

Thu, 2017-07-06 09:09

In reply to Reaction diffusion problems in mechanics

For reaction-diffusion and mechanics of cardiac myocytes, including also for the first time a computational model for contact interactions between myocytes and adhesion, see:


Thank you Prithiv.

Tue, 2017-07-04 08:05

In reply to A quick insight

This is the catchy and simple answer that I got till now about this question. It seems totally makes sense. I wish to make some more research into it. Thanks :) 


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