iMechanica - Crack Propagation - Comments

fortran code XFEM

amirhasibi — Sun, 30 Nov 2008 05:42:31 -0500

Im a student of kntu aerospace in iran(master)

My thesis is about crack propagation with using xfem code in fortran

I need a help for that code.

thanks

cracks in geotechnical engineering

Rocket Qin — Wed, 17 Sep 2008 10:29:42 -0400

freedom teaching and research

Can you please contact me

Stephane Bordas — Sun, 14 Sep 2008 17:30:40 -0400

Can you please contact me by email? Thanks,

Dr Stephane Bordas

http://people.civil.gla.ac.uk/~bordas

Stephane, can you email me a copy of your computer code?

Charlie.liang — Fri, 12 Sep 2008 02:22:44 -0400

Stephane,

May you email me a copy of your XFEM code?

I want to see if I can use it to do simulations of some fluid shock wave problem.

Thank you!

Charlie

Reply to Peter: A world of cracks...

Ajit R. Jadhav — Wed, 10 Sep 2008 04:18:42 -0400

Dear Peter,

Welcome!

1. Roughly speaking, cracks form in the regions of stress concentration. Even after they are formed, they would propagate in the region of high local stresses or strain energy. Some of the expert discussions are about deciding which measures of local stresses/energy could best characterize the aforementioned "concentrations," in different contexts. (At other times, the crack-tip may be taken to be infinitely sharp in which case the stress field is singular, and so, the criteria of crack-growth to be applied have to be global in nature.)

2. The wall-cracks seen radiating from the corner of a window or a door are not necessarily deep. They may exist only in the outer plaster coating. If so, they pose no threat to structural integrity.

And, BTW, these cracks begin radiating from the corners because corners are the places of stress concentrations. In fact, any sudden change of geometry would act as a stress concentrator.

This form of cracking (in outer thin layers), is actually used as a means of experimental measurement of stresses. The technique is called "brittle coatings." Browse through the books on experimental stress analysis, or do a search on the Internet. For example, see the following URLs:
http://www.springerlink.com/content/dm161v0241j1x703/ (It gives a nice photograph)
http://courses.washington.edu/me354a/chap6.pdf (These class notes explain the thing a bit.)

3. As to the cracks you see on tunnels, I am guessing that they too must have formed in the outer plaster coating only. However, one would need to have a look at a few photographs or so before one could tell.... But I am sure in Japan there are concerned engineers anyway.

4. Overall, please note. Stress fields, being tensor fields, are mathematically more complicated than many vector fields such as, e.g., EM fields, or velocity fields in the laminar flow (as traced out by, say, ink streaks in clear water) are.

A world of cracks in Japan

Peter Matthews — Mon, 08 Sep 2008 08:10:56 -0400

Hi,

I am no engineer, but live in Japan and see many kinds of cracks every day, and sometimes new ones after an earthquake. I am intrigued by how cracks appear to radiate out from the corners of squares of concrete on the ground, or from the corners of window and door frames. I guess predicting where cracks go could largely depend on being able to predict where they start.

It gets more scary when we see news reports on the abundance of cracks in road tunnels, train tunnels, and the like. It is not clear what keeps all the infrastructure together, apart from hope.

Peter

Website:
The Research Cooperative
(NPO)http://cooperative.ning.com - an online meeting place for researchers,science writers, editors, translators, publishers and others

TO LEARN ABAQUS, come this web:

Nguyen Chau Linh — Wed, 27 Aug 2008 05:30:38 -0400

TO LEARN ABAQUS, come this web:

http://cobweb.ecn.purdue.edu/~ahvarma/

Re: Dilational vs longitudinal wave speed

Biswajit Banerjee — Tue, 26 Aug 2008 23:21:00 -0400

If you think of the crack tip as a point dislocation source, then there are essentially two types of elastic waves that propagate. These are the P-wave (pressure wave or primary wave) that shows up first in an accelerometer trace and the S-wave (shear wave or secondary wave) which shows up later.

The P-wave is also called the "longitudinal wave" because the direction of the particle motion is the same as the direction of propagation. The velocity of this wave is c_p = sqrt{(lambda+2 mu)/rho}. This wave is also called the "dilational" wave. See for example "Waves and Imaging Through Complex Media ".

A good book for the basics is "Wave Propagation in Elastic Solids" by Jan D. Achenbach. Another that is good for applied wave propagation is "Quantitative Seismology - Vol 1" by Keiti Aki and Paul Richards.

-- Biswajit

Effect of reflected stress wave on the local crack-tip fileds

Nguyen Chau Linh — Tue, 26 Aug 2008 22:23:40 -0400

Dear alls,

I have some points which i not yet understood, can you give me some comments:

1. Maybe you know the Book of Anderson (Fracture Mechanics), 3rd edition. In the chapter 4, page 183, example 4.1, i want to know why he use the longitudinal wave speed Cl, because you know, the dilatational wave speed Cd bigger longitudinal wave speed Cl, right?

So dilatational wave in the material body will come to crack tip sooner Cl.

2. Did you know the paper or the other source say about the sinificant effect of reflected stress wave on the local crack-tip fileds?

Please help me!!

Thanks and Regards,,

Chau

HELP

chinivasa — Thu, 21 Aug 2008 03:03:18 -0400

HELLO FRIEND MY NAME IS SRINI.. I AM STARTED DOING PROJECT WORK IN ABAQUS

I NEED SOME TUTORIALS TO LEARN ABAQUS

PLEASE SEND ME TO MY MAIL ID chinivasan2000@gmail.com

Maybe of interest

AS — Sat, 16 Aug 2008 10:12:43 -0400

Maybe this reference can be of interest: A. Salvadori: “A plasticity framework for (linear elastic) fracture mechanics” - Journal of the Mechanics and Physics of Solids, 56 (2008) 2092–2116. Hope it helps, Alberto

documentation for those criteria

Steve Labbe — Fri, 25 Jul 2008 09:20:26 -0400

Dear ALAAELSISI,

Do you have some doc regarding those criteria ?

Tks !

Steve

Are you trying to say that

WANG Yan — Fri, 18 Jul 2008 08:16:56 -0400

Are you trying to say that the J is a vector?

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from Mohammad Eqbal

eqbal734 — Thu, 17 Jul 2008 12:04:42 -0400

My thesis is about crack propagation in rock slope (brittle materials) with mathematica 6Before use G ore S ore sikma critration I need a failoure critration for start of Crack appearance and this is a problem.I need a sample of mathematica based on crack propagation.

thanks

solving with mathematica

eqbal734 — Thu, 17 Jul 2008 11:47:50 -0400

Im a student of rock mechanic engineer(master)

Crack Propagation

atmaca — Sun, 18 Feb 2007 06:36:28 -0500

I have an investigation on Crack Propagation.

How can i predict the path of a crack.

Please help me!