iMechanica - crack propagation - Comments

thanks mani for giving

sasivamsi — Fri, 26 Dec 2008 09:23:00 -0500

thanks mani for giving reply to my probem. if u dnt min can u tell me abt that fortran
sub routine. i dnt know much about that. what it exactly means?

do i hav to write a program for that?

thank you mani

sasivamsi — Fri, 26 Dec 2008 06:43:00 -0500

thanks mani for giving reply to my probem. if u dnt min can u tell me abt that fortran sub routine. i dnt know much about that. what it exactly means?

do i hav to write a program for that?

DEAR sasi, for that ou

iitd.mani — Fri, 05 Dec 2008 14:16:48 -0500

DEAR sasi,

for that ou need to write fortran subroutine.

because i am also tried but , then i came to know about this..

Bye

Mani

IIT Delhi

xfem for beginners

vinh phu nguyen — Fri, 05 Sep 2008 19:12:59 -0400

Hi Mike,

In below, I am trying to answer your questions.

1. The asymptotic functions are only used for cases where exact solutions are known such as in linear elastic fracture mechanics (all we know the Westeergaard solution.). In other cases, only enriched by Heaviside function is enough as done in cohesive cracks modelling.

2. You were talking about crack propagation simulation with xfem. So, starting with an existing crack, the nodal unknowns are computed, including the displacement dofs (u) and enrichment dofs (b). Then, you then use some criteria to compute the crack propagation angle, and provided a crack advance length, you update the crack geometry, then the process is repeated again.

There are many criteria for this depending on LEFM or cohesive cracks. Noting that xfem can be used for crack initiation too.

There is a simple xfem Matlab code, available for free for which you can get by writing to Dr. Stephane Bordas at stephane.bordas@gmail.com.

You can also write to me at nvinhphu@gmail.com for discussion concerning xfem, if you like.

Good luck.

Dofs in X-FEM

N. Sukumar — Mon, 28 Apr 2008 16:22:08 -0400

You have not indicated if quasi-static or dynamic fracture is the crack
propagation problem of interest. I will assume it is the former; I
am not sure if there is a consensus in terms of best enrichment in time
in regard to dynamic fracture. For quasi-static fracture, a static
problem is solved at each step, so once you advance the crack and know
the new location of the crack surface and front, it becomes a new
static problem. So, the enriched dofs are determined afresh at each
step, and therefore, the dofs of the enriched nodes from the
previous step do not enter the solution process.

Hi Mai Lan, It is very

vinh phu nguyen — Sat, 05 Jan 2008 19:19:00 -0500

Hi Mai Lan,

It is very nice to know one more Vietnamese from the mechanics field.

You have posted your question quite long ago so I assume that it has been solved.

Concerning your question, in my opinion, just plot the load displacement curve of the loading node. Then the area of this curve = the fracture energy since the work of external load must be equal to the dissipated energy. I think the vertical displacement of the loading node is appropriate for this. But I am not sure.

BTW, I guess that you are working in France now? Could you email to me at V.P.Nguyen@tudelft.nl for more discussing on mechanics and the like?

Displacement or Deflection for Gf determination in a 4 points?

Mai Lan NGUYEN — Mon, 08 Oct 2007 07:03:35 -0400

Hi Hamanh, thank you very much for your help. I've read this document. However, there is no work on four point bending beam (only three points bending). In fact, in a three points bending fracture test, these two types of displacement (displacement mesured at the upper support and deflection of the beam) is the same. Whereas, in a four point bending fracture test, these two displacements are different. So anyone can help me to show which displacement that's needed to determination of fracture energy in a four points bending fracture test?

Best regards

try this

hamanh — Sat, 06 Oct 2007 07:53:36 -0400

Hi Mai Lan,

Try to look at these link if you can find any interesting points inside.

http://www.lrrb.org/PDF/200615.pdf

or: http://www.lrrb.org/pdf/200423.pdf

Hope it help

Hamanh

I found that there is a

Mai Lan NGUYEN — Fri, 05 Oct 2007 05:31:24 -0400

I found that there is a document : RILEM TC-50 FMC, "Dtermination of the fracture energy of mortar and concrete by means of three-point bend tests on notched beams", Mat. Struct. 18 (1985) 285-290.

Anyone can show me this document, please?