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Fracture Mechanics Forum

Plotting Crack Propagation using XFEM

Hi,

I am trying to understand Abaqus Benchmark example 1.19.2 - Crack proagation in a plate with a hole simulated using XFEM.

 

I ran the python script provided "crackprop_hole_lefm_xfem_cpe4.py" from the site: http://dsk.ippt.pan.pl/docs/abaqus/v6.13/books/bmk/default.htm?startat=c...

I want to try and output figure 1.19.2 - 4.

 

Would you suggest a textbook or a paper help for building such a model

 

Hi

I need to build a model to predict the fatigue life of notched metal. No pre-existing fatigue crack, as the specimens is not based on the ASTM standards.

The crack initiation from a notch, and then propagation till failure needed to be accounted for. 

The plasticity at the notch due to the cyclic loading & the crack closure effect needed to be considered. 

Mike Ciavarella's picture

Certification for Damage Tolerance

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I wonder if anyone in Imechanica follows or deals with Damage Tolerance of Aircraft Structures.  Not having to deal with everyday certification nor having direct experience, I know only what is reported in academic books, but I am confused about what is the standard in industry and certification, assuming there is one!

 

SUMMARIES OF AIRCRAFT LIFING CONCEPTS

 

Safe-Life design

Jabar's picture

Fracture mechanism in notched metal

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G'day all

Having a metal element with a notch like crack (assume sharp one, exhibits plasticity),  what are the actual fracture mechanism (the phases the crack goes through) in the total fatigue-life. 

please comment on these scenarios:

1- crack initiation life calculated from the (S-N, e-N), then using LEFM/EPFM to determine the cycles for the crack propagation to failure...

Q/ how to find the crack length between the two phases, I mean from which stresses and at which crack length we start the crack propagation life estimation.

Jabar's picture

Crack-initiation from notch

Hi All

The fracture mechanics of multiaxial fatigue loading In steel plates have been studied comprehensively since the late 70s.

simplified the case with an inclined crack in uniaxial load has been investigated in metal by many researchers, as well.

in this forum, few researchers present their work that focuses on crack initiation from notched in metals.

Jabar's picture

Identify load proportionality at a notch

Hi 

I want to check the stress biaxiality at critical location in FE model. the load applied is  proportional cyclic but the at stress concentrator lacation and due to the complex load states (multi-axial) I am not sure if the stresses proportional or not as that will effect the critrerion suits this case.

Is the check to be for the principle stress ratio (S2/S1) only.

should the check be conducted on one line of nodes (along the maximum stress location), or all node/or element in the area surround the stress concentrator.

cohesive model of Needleman was input into abaqus, but wrong???

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 I have written  vumat codes of a cohesive model of Needleman (whose paper entilted "Numerical simulations of fast crack growth in brittle solids"), and I have implemented it into ABAQUS/Explicit, but the predicted result is wrong. I don't know why. The corresponding fortran file is as follows:

      subroutine vumat(

C Read only (unmodifiable)variables -

     1  nblock, ndir, nshr, nstatev, nfieldv, nprops, lanneal,

     2  stepTime, totalTime, dt, cmname, coordMp, charLength,

     3  props, density, strainInc, relSpinInc,

Jabar's picture

simplified procedure to calcualte Fracture parameter SIF

Hi All

 

the stress intensity factor SIF of crack in the fIG. A attached has two components: for tension and shear

the SIF formula of this specimens derived in the literature and tabulated for different angles and crack length.

 

Is there a way to define the SIF of this specimen in term that one of crack perpendicular on the load (straight horizontal crack) in Fig. B

your comments will be helpful

Why Positive and Negative J-integral values by ANSYS?

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I did evaluation of J-integral distribution along a 3D semi-elliptical internal surface crack in a thick-walled pressure vessel using ANSYS APDL. The results I got included positive and negative values. Sometimes the values were all positive or negative and in other cases, negative and positive values were combined. What could be the interpretation of negative and positive values in ANSYS. I seriously seek assistance from someone.

 

High Artificial Energy (ALLAE) in Abaqus Explicit analysis

Hello everybody,

I am doing such a kind of FE simulation using ABAQUS Explicit for composite delamination analysis. In this case, I have used once Cohesive Zone Element (CZM) and then with Cohesive Surface for deboning analysis

The simulation is itself quite dynamic process, somehow the deformation time is only around 3[ms] and the deformation speed is around 5[m/s].

Dynamic Rolling Process FE Simulation

Dear All,

I hope all feel so fine with your simulations.

Recently, I am simulation a rolling process with a very high dynamic speed (around 5 m/s). Hence, the model is quite dynamic and not Quasi-static.

I use Abaqus Explicit for this simulation. The structure is composite material including several layers with different material properties. In this case, I am using ''Cohesive Surface'' definition as the surface interaction between different layers. 

shreeram111's picture

Harmonic analysis with a crack?

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Hello everybody,

                          I am trying to perform a harmonic analysis of a material sample (say a simple 2D plate) with an edge crack in it using 'Ansys R16'. I see that under sinusoidal loading condition, the two crack faces open or close and interpenetrate (after closing which is not possible practically).

          1.  I believe, stiffnesses of the crack faces change during interpenetration and so the results are not credible anymore.

Jabar's picture

delt

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Fatigue analysi to get crack initiation life using ABAQUS/CAE

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Dear All,

for LCF analysis to get crack initation life for simple plate with central hole specimen.

I used direct cyclic approach but getting error as o/p "CYCLEINI" is not available for your element type.

with fe-safe fatigue tool i got the crack initiation life but I want to get with Abaqus/CAE only

kindly help me out.

how to obtain the crack initation life using abaqus only.

Thanks in adavance

 

Call for Papers // Fatigue Durability India 2016 // Publishing Partner Springer

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FatigueDurability India 2016 invites technical papers from all Academicians/ individuals/companies associated with engineering design, analysis, testing, instrumentation, research on Fatigue Durability & Fracture Mechanics or related technologies .

The Authors are encouraged to submit paper on the following themes, but not limited to

mathematical and statistical fatigue life estimation models

How the mathematical and statistical fatigue life estimation models, based on microplastic strain energy accumulation, correlate between static test results and the cyclic loading condition?

numerical modeling using abaqus 6.14

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<p>What is static riks solver?? Please explain in details.. As I am a learner of abaqus I get problem understanding some things, like arc length, &nbsp;increment in static riks etc.. I find that it is very useful for simulating collaps behaiour.. I wish to do a thrust experiment regarding geological setup... Please help and guide me..&nbsp;</p>
<p>&nbsp;</p>
<p>Thank you&nbsp;</p>

crack propagation in Abaqus (VCCT) with remeshing

I started using VCCT with quarter tip elements in Abaqus (not XFEM). I can solve the problem and get the SIFs.
How can I let the crack grow? Has someone a script for crack growth and remeshing that I can implement?

Modeling with line spring elements to find failure pressure of steam generator tube

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Hello, All
I am trying to model steam generator tube of length 110 , radius 11mm, thickness 1.27mm. It has 2 axial cracks of length 6.35mm. length between 2 cracks is 0.254mm. 

SIF for an edge crack in mode III

Hi everyone,

 

I am working on the propagation of an edge crack in semi-infinite plate under antiplane loading.

I need to estimate the stress intensity factor KIII at the front of the crack but I can't find a theoretical formula for this purpose. For an embedded crack of length l in an infinite plate under shear stress sigma_23 I can use KIII = sigma23*sqrt(pi*l). But I don't know what I must use in the case of an edge crack.

 

Orthogonality and closure relations in Stroh formalism

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Orthogonality reationDear iMechanica members,

I deal with exteded Stroh formalism for piezoelectric media. I have problems with orthogonalization of Stroh´s matrices A, B, respectively how to fulfil the ortogonality relations (see attachments). I tried to "rape" it and made the left matrix inverse of the right matrix (then the product is an unit matrix) and I became very similar singularity expomemt as in the paper

How to model hybrid composite in ABAQUS?

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Hello everyone,

Bending simulation using WARP3D code

Hi,

I want to know how to perform bending simulation of a surface cracked-model using WARP3D code?

Thanks.

XFEM ABAQUS- Different "K" for different mesh sizes

I'm trying to model semi elliptical part through circumferential crack on a pipe. I'm getting different values of stress intensity (max. energy release criterion) for different mesh densities/configurations. What could be the possible reason?

Asking for help regarding the failure modelling of polymers in Abaqus

Hi guys,

I have a porous structure (bio-scaffold) made of photopolymer. After doing experimental compression test for this model, I found out that the stress/strain curve has a non-linear section (non-elastic behaviour) before it gets fractured.

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