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Fatigue Crack Propagation Analysis by means of ANSYS

Fri, 2008-10-24 02:26 - Sanam Saebi
research

HI Every Body

 I am postgraduate student of NavalArchitecture, My thesis is Fatigue Crack Propagation in ship Industry, I want to use Ansys Software for this purpose, at first I generated a plate with a central Crack and did fine mesh around crack and saw the results, for next step I should propagate the crack, my questions are as below:

1. How we can predict the Crack path?

2. how should I growth the crack? shall I clear mesh and extend the crack or.....???? I don't know?

3. How Can I use from Interface Elements?

 Thanks in advance

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Comments

Fred Sansoz's picture

Submitted by Fred Sansoz on Fri, 2008-10-24 14:30.

Dear Sanam,

simulating the propagation of fatigue cracks using FEA can be done simply by using a node-release scheme, where nodes in the mesh are released one by one as a function of the number of applied fatigue cycles.  The mesh size and release rate can be adapted based on actual fatigue crack growth rates that are measured experimentally.  I have applied this technique a while ago to the problem of growth of short fatigue cracks in flat and notched samples.  I am attaching below the corresponding paper.  There should also be some more sophisticated techniques in the literature using cohesive elements. I hope this helps a little bit.

Regards,

Fred

Propagation of Short Fatigue Cracks from Notches in a Ni base Superalloy: Experiments and Modelling, F. Sansoz, B. Brethes and A. Pineau, FATIGUE FRACT. ENGNG. MATER. STRUCT. 25, issue 1, 41-53 (2002).

 

 

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Submitted by Sanam Saebi on Fri, 2008-10-24 23:49.

Dear Fred

 Many thanks for your Advise, I will proceed with your comments and attached paper, let me back to you if I have any other problem regarding to fatigue propagation.

 Kind regards

Sanam

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Submitted by mohsenkh on Sat, 2009-08-08 02:42.

i am a naval architecture too,i have a project to find stress function in a cracked disck due to torsion,but i cant model the crack,can u help me? the disk has a central crack,but i dont know how to model it,do u have any model?

thanks

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Submitted by Sanam Saebi on Tue, 2008-10-28 23:11.

Hi

As I already mentioned I am modeling Crack Propagation in Ansys Software, I want to use Interface Elements around the crack, could you please let me know if you have any refrences or sample regarding to using Interface elements in Ansys Software for Crack propagation modeling?

Regards

Sanam

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Submitted by Nieslony on Wed, 2008-10-29 04:46.

Hi Sanam,

Please, try to get in contact with J. Martinsson from Sweden, Royal Institute of Technology, who model crac propagation using Ansys some years ago. Look also to this conference paper.

Regards,

Adam

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aamirmub's picture

Submitted by aamirmub on Wed, 2008-10-29 09:38.

Hi

I am using interface or cohesive zone elements for damage and failure modelling in joints. But I am using MSC.Marc and Abaqus for my work and have no idea about Ansys. Generally, the interface elements represent the crack in the mesh and may be introduced at the suspected crack growth path in the mesh. The elements themselves are controlled by a traction-seperation law. One of the common forms of the law is a bilinear law, where, after reaching a maximum traction, the stiffness of the interface element starts to degrade and element fails after a predefined displacement i.e has no stiffness. I have just tried to explain it very generally as there are many forms of cohesive zone laws and a lot of published work is available as reference.

 Hope it helped.

 Regards

Aamir

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Submitted by David Gonzalez on Mon, 2009-06-08 12:16.

Hi  Aamir,

It looks like we are doing something similar. Let me introduce briefly my work. I am also using Abaqus using cohesive elements trying to model Inter-granular damage. I am using 3D truncated octohedrons to simulate the crystals. I have implemented Huang's Soubroutine (1991). I have also done succesful validation of the model.

 My intention is to study the local stress concentrations around the boundaries originated by neighbouring crystals acting as constraints. I am aware that:

1- certain neighbouring orientations act as a "soft matter" creating an heterogeneous stress field (I even checked that myself for a bycristal case).[Simonovski et al. 2006]

2- In Stress Corrosion Cracking SCC it is also known that certain combination of orientations (missorientation between adjacent lattices, CSL (sigma) and grain boundary angle) are more susceptible to SCC damage. [marrow et al. 2006]

3- grain boundary angle plays also a decisive role in the stress concentration around the boundaries.

4- Different grain sizes also generate over stresses around the boundary.

 Here is my question; are you aware of any references in features: 1, 3 and 4? - Any other paper worth browsing regarding overstresses generated on Grain boundaries due to this/other geometrical features? (shapes, size, orientations of crystals...)

Cheers,

David

 

PhD student

University of Manchester

david.gonzalez@postgrad.manchester.ac.uk

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Submitted by bubilu on Thu, 2008-11-13 11:08.

hello Sanam,
I am postgraduate student at the Mecanica a university in South America, I want to install the ANSYS I am 11 and I can not crack version, you can help me please.
You are very pretty I would like us to be friends.

bye

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Submitted by bin_tarek on Tue, 2010-03-16 14:11.

bin_tarek@yahoo.com

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Arshad's picture

Submitted by Arshad on Fri, 2009-07-10 16:02.

Hi Sanam 

I have seen your research topic Fatigue Crack Propagation Analysis by means of ANSYS, it is quite intersting to me because I want to see the crack propagation under static loading, I am also using ANSYS, I am trying to use the cohesive zone modelling technique for crack propagation.  The major problem that I am facing is that, the cohesive zone approach including some element types which will be used in this analysis are not available in Graphical user interface of ANSYS hence command line interface will be used instead.  I am still studying my research area.  Finally I need some help in crack propagation in ANSYS if you have some example like problem kindly share it on line so that many users could take some help, and this help will propagate to every user who need.  Thanks and regards.

Arshad Ali 

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Submitted by maaah on Fri, 2010-02-05 17:32.

Hi,

 I would to use code ansys. I have many problem to define the contact  between master and slave because i want to create a crack in the surface of contact . i want to simulate the fatigue crack in the surface source  of contact.

can you help me please

maaah

thank you

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Submitted by maaah on Thu, 2010-03-04 14:40.

Hi,

i have a problem to use the crack propagation about a problem of contact using ansys classic. can you help tank you

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