iMechanica - ES 247 - Comments

J-integral for the ENF specimen

Andras Szekrenyes — Sat, 15 Oct 2011 07:59:33 -0400

Dear Colleagues,

My problem is that if I define a zero-area path around the crack tip of the mode-II ENF specimen and
calculate the traction vectors, there is a negative sign (2nd page)
that I do not understand and this is what leads to the wrong result. Can
You take a look at my note and tell me what is wrong?

page 1

page 2

Thanks

Andras

if you can just read this

DukeKim — Wed, 14 Sep 2011 14:01:01 -0400

if you can just read this part of the article and help with this?

Re: stress intensity factor

Zhigang Suo — Thu, 17 Feb 2011 21:07:12 -0500

Your question was answered in the next lecture of the course: toughness.

stress intensity factor

kirthanlj — Thu, 17 Feb 2011 14:13:54 -0500

hello sir,

This is kirthan from bangalore. I am getting confused with SIF. How exactly SIF comes handy in analysing crack growth. According to the westergaard equation as θ and r tends to zero stress goes to infinity. And if we substitute any value of stress and crack length with r=0 and θ=0 the value gives infinity.

Books express SIF as the one which charaterises the crack growth in a material. I am not able understand the book meaning for SIF. Can u please help me regarding this.

Re: J-Integral application in interaction of two cracks

Zhigang Suo — Wed, 12 Jan 2011 18:33:57 -0500

Dear Reza: You will get any useful result by using the J-integral around the point where two cracks intersect. For example, here is a paper on a crack impinging upon an interface. The J-integral is not useful here. There are many examples like this.

R. Huang, J.H. Prévost, Z.Y. Huang, and Z. Suo, "Channel-cracking of thin films with the extended finite element method". Engineering Fracture Mechanics,70, 2513-2526 (2003).

J-Integral application in interaction of two cracks

r.k — Wed, 12 Jan 2011 07:35:39 -0500

Dear Zhigang

You know, These days I'm working on the interaction of cracks but I've got a problem in applying J-Integral in the point where two cracks intersect.

Would you please let me know how can I possibly use J-Integral in intersection of two cracks.

Best,

Reza

To be precise the

jonesr — Thu, 06 Jan 2011 07:55:52 -0500

To be precise the J-integral is only path independent for isothermal, non-linear elastic problems where there are no body forces. For monotonic loading where there is plasticity then it is path independent only under deformation plasticity. For in-elastic problems where there you hasve cyclic loading the J-integral is not path dependent. In such situations the crack tip can be described by a related path integral called T*, that was first formulated by Satya Atluri. When J is path independent then J=T*. The importance of the J integral is related to its ability to characterise the near tip stresses and strains for a non-linear elastic material. The so called HRR solution. The experimental work of Professor Albert Kobayashi has shown that this is not true for cyclic loading.

As an aside many people mistakenly think that the J-Integral was developed by Jim Rice. This is not true. It was first proposed in the early 50's by Professor Eshelby at the University of Sheffield. Prof Rice popularised it many years later. The 3D variant was first developed in a joint paper by Professors George Sih and George Irwin, both at Lehigh, shortly thereafter. You can chase down the relevant references with a simple Google search. The reference to the original Sih-Irwin paper is in one of Professor Sih's papers in his Journal, viz: Theoretical and Applied Fracture Mechanics.

Hope this helps

Rhys Jones

J-integral validity

ahmadmani — Wed, 05 Jan 2011 18:31:55 -0500

Hi All,

I have a question in mind for a while and unfortunately
have not yet found a clear answer to it. I would highly appreciate if you
provide me with your idea about this question:

Is J-integral valid inside the process zone ahead of a
sharp crack? and if is valid, Is it equal to the value obtained from a contour
outside the process zone?

Thanks

Ahmad Khayer D.

J-integral validity

ahmadmani — Wed, 05 Jan 2011 18:31:29 -0500

Dear Professor Suo, I

AS — Thu, 30 Dec 2010 02:38:48 -0500

Dear Professor Suo,

I recently considered the issue under debate in a publication:

Salvadori, A., “Crack kinking in brittle materials”, Journal of the Mechanics and Physics of Solids, 58 (2010) 1835–1846

The conclusions seem to be interesting. In particular it seems that the local symmetry as well as any other criterion is not compatible with Griffith theory in the presence of kink. Furthermore, the onset of crack propagation seems to be always related to a prediction of the kinking angle in the eventuality of a crack elongation. In other words, the safety of a stationary crack, regardless of how far away it is from the critical state, depends on the angle the crack is going to kink at the time it grows.Therefore, SIFs or T seem to be unsufficient to fully characterize the safety of a stationary crack.

looking forward to your remarks,

very best
Alberto

Hi Li, you may find a

AS — Thu, 30 Dec 2010 02:30:09 -0500

Hi Li,

you may find a recent paper:

Salvadori, A., “Crack kinking in brittle materials”, Journal of the Mechanics and Physics of Solids, 58 (2010) 1835–1846

of interest for your question. I'm glad to send it if you are interested. Best!

Alberto

J-integral

SAURABH KUMAR YADAV — Sat, 20 Nov 2010 12:36:13 -0500

Dears

I found in XFEM J-integral is little bit path dependent for three dimensionalcracks. its value changes up to 8%for penny crack with path.

How to plot J-integral path

Suthama — Fri, 19 Nov 2010 22:13:53 -0500

Dear all,

I am a new Abaqus user. My work involve with fracture modelling by using Abaqus.

For 2D Edge Crack problem, I have requested 5 values of J contour integral in abaqus, but i can not plot the J-integral path (J - integral versus Radius). I know abaqus will choose the path of each contour integral automatically. But How to show the path of each contour integral?

Thank you so much,

Sutham A.

Re: fatigue

Zhigang Suo — Thu, 21 Oct 2010 06:38:06 -0400

I'm sorry. I have no expertise with ansys

fatigue

wajdi62 — Wed, 20 Oct 2010 14:51:47 -0400

could you please tell me how can apply cyclic loading to 2D model steel joint.And how can i connect them by welded type element.That should be in ansys commands.

regards