havelmay's blog
https://www.imechanica.org/blog/70612
enWhich theory Abaqus' Contour Integral for the determination of SIFs is based on?
https://www.imechanica.org/node/20633
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/289">ABAQUS</a></div><div class="field-item odd"><a href="/taxonomy/term/11446">Contour integral</a></div><div class="field-item even"><a href="/taxonomy/term/1545">J integral</a></div><div class="field-item odd"><a href="/taxonomy/term/32">fracture mechanics</a></div><div class="field-item even"><a href="/taxonomy/term/256">Fatigue</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>I am actually using Abaqus' Contour Integral for the determination of stress intensity factors. But I do not know, which theory it is based on. Is it the same like the path-independent determination of J integral? Or is there a difference?</p>
</div></div></div>Tue, 29 Nov 2016 12:30:54 +0000havelmay20633 at https://www.imechanica.orghttps://www.imechanica.org/node/20633#commentshttps://www.imechanica.org/crss/node/20633How can I get in Abaqus (XFEM) the Griffith' energy release rate G per time increment?
https://www.imechanica.org/node/17196
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/10086">ABAQUS XFEM crack propagation; Crack Growth; XFEM; screw</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>I want to visualize my results of the XFEM crack growth in form of a diagram with the time increments or the crack length on the horizontal axis and the Griffith' energy release rate G or the stress intensity factor K on the vertical axis. I am using the energy-based damage model.</p>
<p>I don't know, where to activate those values in the Output History. The best solution for me is, if the energy release rate G can be transformed into the stress intensity factor.</p>
<p>When I do it for my own, I can use the formula: G = KI² / E'. In my case, I have an axis-symmetric problem (crack propagation in a screw thread). Which E' can I use? That one of a plane strain problem type (E' = E/(1-v²) )?</p>
<p> </p>
<p>Thank you for help,</p>
<p> </p>
<p>Thomas</p>
</div></div></div>Thu, 18 Sep 2014 18:28:26 +0000havelmay17196 at https://www.imechanica.orghttps://www.imechanica.org/node/17196#commentshttps://www.imechanica.org/crss/node/17196Can somebody assist me with modelling the crack propagation with XFEM (Abaqus) in connection with contact problems?
https://www.imechanica.org/node/17195
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/7069">EXTENDED FINITE ELEMENTS METHOD</a></div><div class="field-item odd"><a href="/taxonomy/term/6893">Abaqus XFEM</a></div><div class="field-item even"><a href="/taxonomy/term/1914">screw</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Hello,</p>
<p>I want to arrange a crack propagation in a screw thread. Therefor I use two dimensional axissymmetric elements in Abaqus 6.12-3 (it is the first version, that allows XFEM in axissymmetric models). The boundaries of the screw thread are on the one hand the symmetry axis, on the other hand the contact to a nut thread that is hold in vertical direction. Thus, there are two nonlinear problems: 1.) the contact problem and 2.) the XFEM crack growth.</p>
<p>1.) Arranging the analysis of the contact problem without crack growth works thoroughly.</p>
<p>2.) The XFEM crack propagation itself also works, when there is no contact (the screw thread is hold at the bottom). But it just works with problems (after a few little propagation steps, the analysis stops with the error:"ERROR: TOO MANY ATTEMPTS MADE FOR THIS INCREMENT"). The problem is that the tolerance f is exceeded. I think, this problem can be solved by increasing the number of possible attempts. But I do not know, where to change it.</p>
<p>3.) The connection of the XFEM crack growth with the contact is not possible. The analysis stops with the warning:"WARNING: DISPLACEMENT INCREMENT FOR CONTACT IS TOO BIG.". There is of course a certain expansion of the first carrying pitch of screw thread, but this condition I cannot change.</p>
<p>Has someone an idea, what I can do? How can I increase the number of attempts of an not working increment in CAE?I read, that the standart number is 5, but that is much to less. The minimum increment size is less enough (1e-12).</p>
<p>Greets, </p>
<p>Thomas</p>
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</div></div></div>Thu, 18 Sep 2014 15:18:27 +0000havelmay17195 at https://www.imechanica.orghttps://www.imechanica.org/node/17195#commentshttps://www.imechanica.org/crss/node/17195