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Fracture Mechanics Forum

Does the J-integral method for energy release rate require a small displacement assumption?

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As I understand it, there are many geometries for which the j-integral has been found to give useful simplifications when evaluating the energy release rate. Many of these geometries seem to require small displacements. I would like to know if the small displacement requirement is necessary for the contour integral before any simplifications are made or if small displacements are only necessary because the large deformation geometry of some specimens conflicts with those simplifications.

David J Unger's picture

J-Integral Elliptical Hole (Plane Stress) Perfectly Plastic Material

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The fracture mechanics community may be interested in a new evaluation of a J-Integral for a fundamental geometry:  an elliptical hole in a perfectly plastic material under the Tresca yield condition for plane stress loading conditions. The analysis is exact and involves only elementary functions.  This makes the problem suitable as a classroom example or as a homework problem for a graduate level course in fracture mechanics.  See J. Elasticity (2008) 92:217-226. http://www.springerlink.com/content/102932/

How should one compare material fatigue strength in thin film area?

For several common electroplated materials: Ni, Cu, Au and Al, which one has strongest fatigue strength? We know the mechanical properties of thin films are different with their bulk counterparts due to the so called "size effect", and material properties depends largely on the microstructure and processing technique. But is there some mateiral laws or guidelines for designers to choose the "best material" as for fatigue resistant? Yield limit? ultimate tensile strength? or elongation? How could one compare material candidates without doing time-consuming test?

Miniature disk bend testing and its fixture design

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hii

I  need a bit help in preparing my seminar topic on the subject "Miniature disk bend testing".If anyone can help me out from this problem i will be indebted for life time.

    You can post me the link, sites, any information on my email  id- bapu285@gmail.com.

waiting for a reply.

please help me out from this problem

                                   Durgamadhaba Tripathy

about analytical solution of S.I.F

Sir,

I am doing my PG in Design Engg. & project is going on. Please tell me where I will get the analytical solution of S.I.F. for a plate with central crack & under tensile loading. please tell me the names & authors of the books.Also if possible derivation of Tada Fedderrson & Irwin formulae.

Thanking you

Journal paper

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Hi every one,

    Iam searching for the paper 

    "  charalambides P.G. ,J. Lund, A.G. Evans and R.M. McMeeking(1989),  A test Specimen for determing fracture resistance of     bimaterial interfaces . Journal of Applied mechanics, volume :56, pages 77-82. "

     Iam unable to find this paper. I need this paper for my thesis work. Is there any one find this copy please attach the copy.

XFEM

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Hello,

As far as I understand from the previous blogs: we can now embed XFEM in ABAQUS. Is this approach restricted to linear elastic behavior? Can we simulate fracture propagation in an elasto-plastic material ("XFEM coupled with ABAQUS" type analysis) or is this approach only limited to fracture propagation in elastic materials.

 Thanks,

 Uno.

The question about the mesh of crack tip

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I am working for the FE model of cracked pipes. I use Hypermesh to mesh the model, but the element can not be set to the C3D20R type. I donnot kwon why it is. So I can use the C3D15. Then I can th following error message:
***NOTE: THE COORDINATES OF NODES WITHIN THE SAME CLUSTER ARE NOT IDENTICAL.  THIS IS THE CASE FOR NODES 22 1224

***ERROR: TRIANGLES, TETRAHEDRA, AND WEDGES MAY NOT BE USED IN A CONTOUR INTEGRAL REGION. ELEMENT 960 IS WITHIN A CONTOUR REGION

a question about chebyshev polynomials in a crack problem

I use the chebyshev polynomials to solve the singular integral equation of a crack problem. I encountered a problem that when Chebyshev polynomials are truncated  at the even order, the results are convergent. However, if the polynomials are truncated at the odd order, the results are not convergent. Does anybody have any idea about this?  Thanks a lot.

Central crack loaded with stress

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1. Central crack loaded with stress.

(A) The stress intensity factor for a central line crack in an infinite plate is found to be  

 K=p(πa)^.5

 

where p is the pressure exerted along the crack line. (A) Does this formula imply a stable or an unstable crack propagation when p reaches the critical stress level? (B)  Present an experiment to support your answer in (A). Specify your experiment in details.

Jintegral and Umat subroutine

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Hello,

Stress concentration at a corner of varying angles, mode I and mode II

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I was looking at the stress concentration at a corner for both a mode I and mode II loading situation.

For reference, see: Carpenter, 1984. Mode I and mode II stress intensities for plates with cracks of finite opening. International Journal of Fracture. V. 26. 201-214. 1984.

The problem that is being addresses is the stress concentration found at a corner in an infine body as seen in the figure below. β=0...π.

Orthogonal Metal Cutting simulation using ABAQUS

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Hello,
I am pursuing masters and I have chosen the orthogonal cutting
simulation as my project.
We have done the experimentation work and now I am looking for the FEA
simulation of the same operation. (The parameters I am interested in
are Chip Morphology, Cutting Forces & Residual stresses in the
component)

I am just going to use explicit first time and I am looking for some
reference doc. & input file.

Any help in this regard would be highly appreciated.

Crack Kinking Out of an Interface - realization in a software

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Dear Collegues,

poissons ratio effect on Stress intensity factor

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Hi :

I am obtainning the Stress Intensity factors along the front of cracks in a 3D FE models (ANSYS). The loading mode is mixed and Ki, Kii and Kii should be estimated. I have noticed that the SIF  strongly depends on the poisson's ratio but i understand Ki does not depends on the elastic properties of material. I know ANSYS calculates the SIF from the displacements at the crack tip using E and mu, but i did not expect so huge differences in SIF values, In fact all analytical predictions for SIF does not depends on poisson's ratio....

The method for measuring the Kc value of 2024-T3 sheet?

Dear all,

I want to measure the Kc value of 2024-T3 sheet. But the sheet with 80x100x2.5 mm is so small that Kc value can not be measured out. Maybe the sheet for measuring the Kc value shall be 400x1000x2.5mm. And in experimental scale, that so large sheet of 400x1000x2.5 mm is difficult to processing.

And are there another value to substitute the Kc value to weigh the fracture toughness of the alloy sheet with 80x100x2.5 mm?  May I measure the Jc value of that material and then convert it to Kc value?

Thanks for your time.

Crack propagation in two regions in Franc3d

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Hello Everybody

I´ve got problem with propagating the crack in
two regions at the same time in Franc3d. I initialized the crack in one
region and propagated it, but the crack is propagating only in one
region, although the crack should be propagated also in second region.
Can anyone help me, pleease? Which steps do I need to take to obtain
the propagation in first and second region? It´s imposibble to
initialize crack in two regions? 

Thanx

Zoeb Kaizar Lakdawala's picture

help regarding plotting normalization curve

HI,

 

I am an M. Tech Student working on fracture mechanics. I just want to know how do i plot Normalization curve as describe in ASTM E-1180. It is of the form 

y = (ax^2 + bx + c)/(d + x)

 

any help in this regard will be appreciated

Zoeb Kaizar Lakdawala's picture

reducing SEPC ERROR of crack problem

hi

 

i have mapped meshed the compact tension specimen in ansys but every when i see sepc error using prerr it always shows above 20. i have change the mesh size to a very fine still it shows 18 i will be thankful to this forum people if you give me some useful tips

 

Regards

Zoeb Lakdawala

heqilin's picture

crack velocity and FGM

hi, everybody

i am going to simulate crack propagate by ABAQUS, but i haven't used ABAQUS before.
now i have two problems:
 1) can abaqus calculate the velocity of crack advancing?

 2)FGM(functionally graded materials ). material property varies at
 different position,such as density ,modulus, possion ration. can
 abaqus deal with this problem by umat .

thanks

Open source code for Embedded Strong Discontinuity (EFEM)

Hi all,

I am now learning strain localization in solids and geometerial by
using Embedded Strong Discontinuity theory (EFEM or elemental
enrichment).  I am looking for an open source code to learn how to
understand and how to reproduce some examples by using EFEM. Did anyone
know that?

Any advice will be appreciated.

Cheers.

Arash Karpour's picture

Using Acoustic Emission to Detect onset of Fracture

Hi Every one,

Dose any one know where I can get a good Manual/document on "detecting onset of fracture using acoustic emission"?

I heard some say this method of detecting onset of the fracture has
lots of error and is not accurate..is this true? if yes,why? Are there
other methods to find the onset of the fracture in an experiment?

question about interaction integral

 hi

I'm doing my master's in mechanical engineering.and my thesis is about fracture mechanics and meshless method (NEM).I got good results for two problems (single edge and single centered crack) using j- integral with NEM.I want to get stresss intensity factor with j-integral  for a mixed mode problem (single centered angled crack). I need your helps.I don't know how to get stress intensity factor for mode I and mode II using j-integral?

Best Regards.

applications of maths in the study of fractured surfaces

Hello everybody,

Please recommand me bibliography or the links on the WEB concerning the applications of different maths in the study of fractured surfaces. Thank you very much. In my country, Romania this domain is not know very well. Best regards from Romania!

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