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Updated: 31 min 6 sec ago

Re: Oops.. 30 years old.

Mon, 2018-01-29 10:55

In reply to Oops.. 30 years old.

I am certain I typed "My" and not "By".

--Ajit

 

Oops.. 30 years old.

Mon, 2018-01-29 10:53

In reply to Why ultrasonics?

By NDT is 30 years old, not 20.

Best,

--Ajit

Why ultrasonics?

Mon, 2018-01-29 10:52

In reply to update: some workers were found to be running NDT on the line

Dear Mikey,

[Nice to connect with you after a long while :)]

But why ultrasound?

As might be expected, the suspected species of the cracks is the fatigue cracks, right? I mean, the surface-breaking cracks, the finer ones. And those precisely are the ones that would get lost in "boundary layer"/"edge effect" of the UT. [Sorry, but my NDE is some 20 years old, i.e., when it used to be NDT.]

If you were to say ET (I esp. mean eddy current), or MPI (magnetic particle inspections), and it would be OK by me [going by my good old knowlege]. But UT?

Guess what they showed (if they at all did) is a more good-natured reaction to help things out, even, to figure out things for themselves, rather than knowledge as such. Appreciated. Curiosity, when not interfering with a proper set of reactions in sad/bad situations like these, is perfectly OK, at least by me. ... Well... At least they weren't found busy taking selfies with the tracks and their equipment, I say! (The way it often happens... err... elsewhere and with others!)

...Anyway, I appreciate your trying to connect the knowledge with the practice.

Best wishes and regards,

--Ajit

[PS: BTW, as you can see, I've by now dropped my famous "E&OE" signature. I have resigned myself to whatever English that I do possess!]

 

Re: Applicability of Eshelby's Equivalent Inclusion Method

Mon, 2018-01-29 04:51

In reply to Re: Applicability of Eshelby's Equivalent Inclusion Method

Dear Arash,

It is surprising to find you replied me 3.5 years ago, and it is more embarrassing that I wasn't aware of that! Apologies.

If the English translation is still of interest to you, please email the paper in Chinese to me (entropie@live.cn), and I will tranlate it for you.

Best regards,

liebealt

petition doubles the number of signatures in 2 days!

Sun, 2018-01-28 17:12

In reply to Corriere della Sera: recruitment in Italian Academia

The number of signatures has doubled to 1200.  This was frankly unexpected, and most likely this will attract serious attention.

If you want to sign, I remind you

http://chn.ge/2DZH5it

update: some workers were found to be running NDT on the line

Sun, 2018-01-28 17:09

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

An update from italian newspapers is that some workers were found secretely into the closed area, running some NDT inspections (ultrasounds).  They were kept by police, and the mistery is large on what they were doing and for whom.

The impression is that the rail management is worried that there may be more cracks on the rail, nobody says the truth.

By the way, there is an interesting other parallel with another accident in UK, that which caused most of the UK rails to be replaced from jointed rails to welded ones.  Apparently on this italian line, we were still using bolted joints, since this is not the high speed train lines, but the "poor" line, which is quite neglected.

While for high speed trains, we spent 35 billions euros, for the poor lines, we were using techology similar to the third world.

Any comment?

Biswajit, a more scientific paper example

Sat, 2018-01-27 15:36

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

Biswajit

a more scientific paper is for example this  https://uic.org/cdrom/2008/11_wcrr2008/pdf/I.1.1.1.2.pdf

you can see that trains can run even at 285kmh, while performing the diagnostics.  But these are mostly significant geometrical irregularities able to lead to significant accelerations.

Now, it is too early to say what happened in Milano (the newspapers say that a problem had been identified if a rudimental reparation had been introduced in the form of a wooden pad, but the authorities say that such wooden pads are NOT permitted by their standards).  

On the other hand, the diagnostic train had been used, and if there was a significant problem in the rail, it would have been noticed.

So obviously someone is lying here.  But if the problem were a crack (most likely, horizontal and deep under the rail, not a surface one, from the images), then it would not have been noticed most likely by diagnostic trains, nor by visual inspection.  It is all very confused and, maybe this is different from what would happen in UK or US, no academic is speaking to the press.  Only some anoninous, and the infrastructure administration managers.  So journalists are using very rudimental ways to launch articles.

What do you think?

 

Re: High-speed diagnostic trains

Sat, 2018-01-27 14:36

In reply to Biswajit, here is what I can say in public

Mike,

I had a quick read through the articles and advertisement and couldn't find any claims of being able to find cracks using the trains (though they say something about being able to find defects but don't specify what that means).  I agree with you that at the operating speeds of the trains it will be next to impossible to separate signal from noise if one wants to detect cracks.

-- Biswajit

Biswajit, here is what I can say in public

Sat, 2018-01-27 05:21

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

Biswajit, your comment about airplanes is very pertinent.

What I can say is that in airplanes, things are done very properly in general (although human error is always possible), and "damage tolerance" is a very refined technique. I have described elsewhere how it works.

In Train, there is nothing remotely so sophisticated, and the Hatfield accident in 2001 showed that it was all based on a mass of people who admitted candidly they were "ignorant" on safety issues!

In the Italian accident, it is early to say what happened, clearly I have some ideas, not all of them I can share in public.  Do you believe in these "diagnostic trains" which run fast on tracks and pretend to diagnostic?  I do beleive they can approximately, measure rail corrugation, but defects?  What I can find in scientific literature is very scarse, I only find commercial presentations of systems that in fact are even Italian, and sold all over the world, so reported as a success story: here and here.   They also say that an inspection with the diagnostic train DIAMANTE had been done, and nothing had emerged. 

However, in July on a very close line, a derailment did occur.  What do you think? What is your impression?

Re: Trains, rails, and maintenance strategies

Fri, 2018-01-26 23:37

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

Mike,

The "preventive maintenance" conjecture is interesting, partly because a lot of AI and machine learning companies (cough)IBM(cough) say that they can predict when a component is going to fail.  If inspections did not see anything but machine learning did, that's a massive advance!

Regarding vibrations and crack location, I don't have aa clear idea about the latest state-of-the-art but don't they do that sort of inspection on airplanes routinely?

Keep up posted on what is found if you find out more.

-- Biswajit

petition on 1300 jobs as Researchers RTD-B reaches 600 signature

Fri, 2018-01-26 09:48

In reply to Corriere della Sera: recruitment in Italian Academia

In only 3 days we obtained over 600 signatures for the petition to give priority to the ASN "abilitati" (italian habilitation) for the new 1300 jobs in Italian Academia!

This is way beyond any expectation

We need to keep going as in February the Ministry will give the final rules

http://chn.ge/2DZH5it

 

maintenance strategies

Fri, 2018-01-26 00:45

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

Biswaijt

particularly in this case, there was a fishplate joint which clearly failed, but was set to be replaced within few hours?  Why? The authorities do not say there was any sign of a problem, even just 2 weeks before inspections were done. So replacement was based on some preventive maintenance?   But these strategies are very empirical, and  perhaps arrived too late.

 

On the other hand, inspections are based on specialized perssonel + some "diagnostic trains" ------ the former could be lazy, and not do their job.  On the second, I have many things to say, do you really beleive these diagnostic trains, which sell for millions, can really diagnostic failures of small cracks by means of vibrations?   They can perhaps, if we are lucky, measure some wear and geometrical status of the rails, but not really cracks.

But my golden rule is to see things first person to make a really final assessment.  I am not officially in charge of the investigation nor in the technical commettee -- as for yet.

Very interested in the position

Thu, 2018-01-25 20:10

In reply to Summer Internship (US Ph.D. candidate of Mechanical / Materials Science and Engineering)

Hi Soud,

My PhD thesis topic is on the operation and damage of low volume solder interconnections for 3DIC packaging systems, and I am in my third year of PhD studies, here at Texas A&M University. Could you please let me know how can I apply?

email: attari.v@tamu.edu

Vahid

 

 

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Re: Train accident

Thu, 2018-01-25 18:38

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

Mike,

Thank you for highlighting these problems with rail (fretting?) fatigue.  Sometimes I wonder if there can be technological solution to such problems that is cost effective.  Perhaps what's needed is an attitude fix?

-- Biswajit

but it looks very different from Hatfield

Thu, 2018-01-25 16:57

In reply to Tragic train accident in Milano for a broken rail: 3 killed and 46 injured

In Hatfield, it rapidly became apparent that the derailment was caused by a fractured rail on the outer line of the curve. Of particular concern was that beyond the first fracture, the next 35 metres of rail had broken into 300 pieces, and some 44 metres further on, another length of about 54 metres was similarly fragmented. It was clear that the original and subsequent fractures had largely been triggered from fatigue cracks existing in the rail: although the term “gauge corner cracking” was used as the first description, “head checking” and the more generic “rolling contact fatigue” (RCF) were used later. These events caused detailed inspections to be made of tracks throughout Britain in the days that followed. Many sites were located where cracks were visible on the surface of rails. Speed restrictions, some as low as 8 km/hour, were quickly introduced. Many trains were cancelled; schedules were revised to double or treble normal journey times and even then were unreliable. Motorways became choked as people switched their journey to roads and internal domestic flights became overbooked. When a journalist wrote, “no other railway accident in British history, or, I would guess, any other country’s history – has led to the degree of public anger, managerial panic, political confusion, blame and counterblame that came in the wake of the Hatfield crash. In fact, outside wars and nuclear accidents, it is hard to think of any technological failure which has had such lasting and widespread effects” [2], he was not exaggerating. 

 

 

Here, there is no report of many fragments, but just one.  However, I do see large signs of wear, meaning the rail may have been really quite old and overfatigued.   We will see what the investigation brings.

Veamy v2.0 (software for VEM) is out

Wed, 2018-01-24 10:45

In reply to Veamy: an extensible object-oriented C++ library for the virtual element method

Veamy v2.0 is out.

http://camlab.cl/research/software/veamy/

Veamy 2.0 (23-Jan-2018)

 From Veamy v1.1.1 to Veamy 2.0:

  • Add documentation to the source code.
  • Implement VEM for the two-dimensional Poisson problem.
  • Implement Feamy, a FEM module that uses three-node triangular finite elements for the solution of the two dimensional linear elastostatic problem.
  • Add methods to compute the L2-norm and H1-seminorm of the error.
  • Improve the in-built polygonal mesh generator.
  • Change to Eigen’s sparse solver for the solution of the system of linear equations.
  • Add additional test files.
  • New simplified methods to impose essential and Neumann boundary conditions.
  • Fix several bugs.

From Veamy 1.0 to Veamy v1.1.1:

  • Add documentation.
  • Add method to include custom precision for printing output data.
  • Add plane stress material formulation.
  • Update installation instructions.
  • Include more tests and mesh examples.
  • Fix several bugs

i 1300 posti da Ricercatore RTD-B ai migliori personalmente!

Tue, 2018-01-23 01:56

In reply to Corriere della Sera: recruitment in Italian Academia

Salve,

 

   i membri del gruppo ASN su facebook mi hanno chiesto di aiutarli a lanciare la petizione 

 

"MIUR: Che i 1300 posti da Ricercatore RTD-B siano assegnati ai migliori abilitati personalmente" 

 

e vorrei sapere se potete darmi una mano aggiungendo la tua firma. Puoi saperne di più e firmare la petizione qui:

 

http://chn.ge/2DZH5it

 

 

Grazie!

Mike

a summary of the follow-up debate on facebook

Mon, 2018-01-22 03:45

In reply to Corriere della Sera: recruitment in Italian Academia

carissimi

 

 a seguito della ns lettera a Corriere, che abbiamo tradotto e postato anche su un blog di Harvard, http://imechanica.org/node/22065, anche per gli aspetti internazionali della difficilissima entrata da parte di "esterni" o addirittura non "locali" nelle Università Italiane, c'è un certo dibattito sul gruppo ASN https://www.facebook.com/groups/166806536849115/ nel quale siete benvenuti a partecipare.  Ovviamente le proposte sono di vario tipo, molti temono che ASN per es. scomparirà dopo questa tornata in atto, perchè già troppi sono gli abilitati. Prevale un'idea di chiedere con forza un finanziamento apposito (ma non lo chiamerei "straordinario") per sbloccare la situazione di questi oltre 40 mila giovani meritevoli (e altri che non abbiano ancora fatto la ASN ma che possano partecipare a questo nuovo "concorso"), che però perchè non sia "OPE LEGIS" passi da una nuova strettoia concorsuale ---- che di fatto sostituirebbe il concorso "locale".   Si tratterebbe quindi di una forma rivista e molto moderata delle "Cattedre Natta" che erano una ottima idea in linea di principio di Tommaso Nannicini, ma che è naufragata per tante resistenze interne in parte giustificabili per la ingiustificabile idea del trattamento economico diverso, e per la contemporanea idea di usare quei fondi per calmare la peraltro quasi altrettanto giusta protesta dei docenti anziani come me, che chiedevano "scatti" di stipendio.

 

Saluti, MC

 

 

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