iMechanica - cracks - Comments

Google Group

Martin J. Gross — Fri, 06 Jun 2008 03:50:47 -0400

Dear Stephane,

could you please give a link to the mentioned google group. I can't find it. Thank you.

By the way, I tried to download the openXFEM++ from your homepage, but it doesn't work.

Best regards from Munich/Germany

Martin J. Gross

shock capturing

Charlie.liang — Thu, 05 Jun 2008 03:41:36 -0400

Any application of XFEM to capture compressible flow shocks?

Any suggestions will be appreciated.

XFEM Codes Matlab and C++

Stephane Bordas — Fri, 23 May 2008 06:51:07 -0400

Thanks for your interest in these codes, I am happy that we finally got communicating through regular email and that you found these codes useful.

Do not hesitate to get back to me, I strongly believe in sharing codes to facilitate work, and will be happy to help you, you can also visit computational_mechanics_discussion on google group,

Dr Stephane Bordas

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

XFEM Matlab code

AdyDesh — Tue, 20 May 2008 14:03:47 -0400

Hello,

I am doing MS in Civil Engineering Dept. in the Indian Institute of Science, Bangalore.

My problem involves crack propagation under fatigue loading, for which I am going to implement the XFEM method.

For that I was trying to download the Extended FEM Matlab code from http://people.civil.gla.ac.uk/~bordas/phu.html, but was unable to download.

I am studying all the XFEM related papers, to start coding the method, I thought it would be easier if I go through a code for a basic XFEM problem.

If anybody has the code, please send it to me at aditya[at]civil[dot]iisc[dot]ernet[dot]in

Thank You.

XFEM- Matrix of extended shape functions derivatives

Marco A. Fdz — Fri, 02 May 2008 00:54:37 -0400

Hello, I am interesting on the implementation of XFEM for fracture problems, especially for quasi-static crack growth analysis. (Currently)I have been reading all around the X-FEM (papers published, programs, etc), also I am exploring the XFEM matlab code developed by Nguyen Vinh Phu and Dr. Stephane Bordas (http://people.civil.gla.ac.uk/~bordas). However some basic queries regarding the evaluation of enriched shape functions and how to form the associated matrix of extended shape functions derivatives [B], launch me to consult your help. I noticed that in some earlier publications, the evaluation of each enrichment function is performed only at simple sample points (i.e. gauss points) w.r.t the crack, and in others like in your job it is performed on two different points at the same time (i.e. gauss point and the node to enrich) also w.r.t. the crack.

For the last, Why did you do a subtraction of both evaluations? Are there specific reasons?, and what can you recommend me? I know that my question could be very obviously, but as soon as I noticed, the doubt arise.

To be more explicit for example in the former, the following about the build of matrix [B] is reported as: for a H(x) enrichment type Bia =[(Ni*H),x 0

0 (Ni*H),y

(Ni*H),y (Ni*H),x]

for a B(x) enrichment type Bibalpha=[(Ni*PHIa),x 0

0 (Ni*PHIa),y

(Ni*PHIa),y (Ni*PHIa),x]

And in your code a subtraction between the evaluation of two different points are done,

for a H(x) enrichment type Bia = [(Ni*(H-H(xi))),x 0

0 (Ni*(H-H(xi))),y

(Ni*(H-H(xi))),y (Ni*(H-H(xi))),x]

for a B(x) enrichment type Bbalpha= [(Ni*(PHIa-PHIa(xk))),x 0 0 (Ni*(PHIa-PHIa(xk))),y (Ni*(PHIa-PHIa(xk))),y (Ni*(PHIa-PHIa(xk))),x] ___________________________________________________________________

Thanks in advance for your support. Marco

re: XFEM

John E. Dolbow — Wed, 28 Mar 2007 11:12:44 -0400

Sofia,

We typically do not attempt to statically condense out the enriched degrees of freedom with the X-FEM. One simply solves for all of the degrees of freedom (classical plus enriched) at once.

XFEM

Sofia Costa — Wed, 28 Mar 2007 10:41:41 -0400

I am a PhD student in Department of Mechanical Engineering of University of Aveiro, Portugal.

I studied papers on XFEM methods and I am trying to implement XFEM in my finite element code to enrich the asymptotic near tip crack field, but I am having a difficulty.

I constructed the strain-displacement matrix in the FEM method, then we have Kuu, Kua and Kaa stiffness matrices. My problem is that I want to invert Kaa to perform static condensation of the enriched degrees of freedom and I cannot invert Kaa because a lot of eigenvalues of this matrix are zero. I cannot find any bug in my implementation. Did you experienced similar problems with your implementation or did you perform enrichment in a different way?
If you could help me, I would appreciate it very much!Sofia.