iMechanica - Comments for "Stress intensity factors for a slanted crack under compression"
https://imechanica.org/node/5389
Comments for "Stress intensity factors for a slanted crack under compression"enHello,
https://imechanica.org/comment/28774#comment-28774
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<p><em>In reply to <a href="https://imechanica.org/node/5389">Stress intensity factors for a slanted crack under compression</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Hello,</p>
<p>It is not clear to me what you meant by "analytical solutions for tge Ks, based on polynomial distribution, which allows negative values". But, anyway, I agree with you that you can set Kinitial to zero in cases where they turn out to be negative. As a matter of fact, the crack faces would close even before the complete unloading, because of the plastic deformations at the crack tips left behind by the maximum loading -- a phenomenon discovered by Elber back in 1968. Therefore, the effective DK would be even less than the DK that you would get if you set Kinitial to zero when Kinitial is negative. You may want to read a little bit about the Elber crack closure concept.</p>
<p>Hope this is helpful!</p>
<p>Mujibur Rahman</p>
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</ul>Sun, 08 Jan 2017 01:41:47 +0000m_rahmancomment 28774 at https://imechanica.orgNegative stress intensity factors for crack growth
https://imechanica.org/comment/28773#comment-28773
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<p><em>In reply to <a href="https://imechanica.org/node/5389">Stress intensity factors for a slanted crack under compression</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Hello, I am using a simple Paris law for crack growth, and in calculating Delta K, one of the values I get is negative, should I set it to zero before calculating Deta K? For example. DK=Kfinal-KInitial, and say KFinal=20, and Kinitial=-5, is DK 20 or 25?</p>
<p>im using analytical solutions for tge Ks, based on polynomial distributions, which allow negative values as far as I can see. Physically it doesn't make sense to increase the range if there are compressive stresses at one point in the cycle. Thanks !</p>
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</ul>Sat, 07 Jan 2017 16:59:07 +0000jstellocomment 28773 at https://imechanica.orgNegative K2
https://imechanica.org/comment/19000#comment-19000
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<p><em>In reply to <a href="https://imechanica.org/comment/10713#comment-10713">Some comments</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>
Hi I am modelling a plate with two non aligned cracks
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I got negative value for K2 at one of the crack tips from ABAQUS
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If I derive K2 from the post processing of nodal forces and displacements from MVCCI technique
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Then K2 = (G2 x E) ^ 0.5
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If I get negative G2 how do I get K2from it
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thank you
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<p>
M.Surendran
</p>
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</ul>Tue, 08 May 2012 09:46:09 +0000Surendran Mcomment 19000 at https://imechanica.orgSlanted crack
https://imechanica.org/comment/10722#comment-10722
<a id="comment-10722"></a>
<p><em>In reply to <a href="https://imechanica.org/node/5389">Stress intensity factors for a slanted crack under compression</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>
Julien,
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<p>
The case where the body is under uniform tension at infinity was solved by V. V. Panasiuk and A. P. Datsyshin (see their paper, On the limiting equilibrium of a half-plane with an arbitrarily oriented crack at its boundary, Soviet Materials Science, vol. 7, No. 6, 1974). To my knowledge, there is no exact solution to this problem available in the literature. You can also look at the Handbook of Stress Intensity Factors by Murakami, to see if there is any exact soultion derived by any one. The Panasiuk-Datshyshin solution is based on a pair of singular integral equations derived by using Muskhelishvili's complex variable approach.
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Regarding the case where the solid is under compressive load, you can introduce some kind of contact condition of the crack faces, and then use the same approach as Panasiuk-Datshyshin. Of course, in this case the problem willl be lot more complicated, but from a purely conceptual standpoint, I do not see any signficant problem. You should also look at the works of Dundurs and Comninou, who did a considerable amount of work on crack problems involving contacting crack faces.
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Hope this helps!
</p>
<p>
Mujibur Rahman
</p>
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</ul>Tue, 05 May 2009 02:38:02 +0000m_rahmancomment 10722 at https://imechanica.orgRe: Some comments
https://imechanica.org/comment/10718#comment-10718
<a id="comment-10718"></a>
<p><em>In reply to <a href="https://imechanica.org/node/5389">Stress intensity factors for a slanted crack under compression</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>
Dear Chad,
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<p>
Thank you so much for your reply. I actually forgot to mention that my model does impose contact constraints on the crack faces so that they cannot overlap (use of penalty terms). However Abaqus still gives negative values for KI, which I was quite surprised about. The stress ahead of the crack should have shear terms (which is the case, as KII≠0 and the crack faces slip on one another), but as you mentioned, no square root compressive terms (which I apparently get). The J-integral maybe needs to be redefined another way in case of compressive loading, that is what I'm trying to figure out.
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Anyhow, I would be very interested in the analytic solutions for the problem of a center crack in an infinite medium, this would probably help me a lot. My email is <a href="mailto:jjonva2@uic.edu">jjonva2@uic.edu</a>.
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Thank you very much, again, I highly appreciate your help.
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<p>
Julien
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<p>
</p>
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</ul>Mon, 04 May 2009 15:19:47 +0000Julien Jonvauxcomment 10718 at https://imechanica.orgSome comments
https://imechanica.org/comment/10713#comment-10713
<a id="comment-10713"></a>
<p><em>In reply to <a href="https://imechanica.org/node/5389">Stress intensity factors for a slanted crack under compression</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Julien,</p>
<p>Some comments. If you are not actually imposing contact constraints then finite element simulations will allow the crack faces to interpenetrate. This is why you are not getting zero for KI. The answer to your question 2 is yes and no. As you have realized, if KI < 0 then this implies that the crack faces overlap. It also implies that the stresses ahead of the crack are compressive and square root singular. However, contact will prevent this from happening. The answer to your 3rd question is also yes. If you are interested in a centered through crack in an infinite medium then there is quite a bit that you can do. You should even be able to solve the contact case. Contact me if you are interested in the details.</p>
<p>Chad </p>
<p>P.S. I just re-read your post and noticed it's an edge crack, not a center crack. You still might want to look at the center crack if you are interested in analytic solutions. </p>
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</ul>Mon, 04 May 2009 00:35:53 +0000Chad Landiscomment 10713 at https://imechanica.org