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Discussion of fracture paper #18 - A crack tip energy release rate caused by T-stress

A T-stress is generally not expected to contribute to the stress intensity factor because its contribution to the free energy is the same before and after crack growth. Nothing lost, nothing gained. Some time ago I came across a situation when a T-stress, violates this statement. The scene is the atomic level. As the crack is producing new crack surfaces the elastic stiffness in the few atomic layers closest to the crack plane are modified. This changes the elastic energy which could provide, contribute to or at least modify the energy release rate.

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Discussion of fracture paper #16 - What is wrong with pure mode I and II? A lot it seems.

It is common practice when solving boundary value problems to split the solution into a symmetric and an antisymmetric part to temporarily reduce the number of variables and the mathematical administration. As soon as the symmetric problem is solved, the antisymmetric problem, or vice versa, is almost solving itself. Any problem can be split into a symmetric and an antisymmetric part which is a relief for anyone who analyses mixed cases.

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Discussion of fracture paper #12 - Crack paths and fracture process region autonomy

Cracks typically follow paths that locally give a mode I crack tip load. At mixed modes crack are extended via a kink in a direction that locally restores mode I. In isotropic materials this is known to more or less, true for static and dynamic loads. Exceptions are cracks that are subjected to high compressive load, e.g., at contact between train wheels and rails or at cracks caused by seismic movements. Other exceptions are cracks growing in anisotropic materials, at grain boundaries or other weak, or by deformation weakened, interfaces. 

The recently published 

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Discussion of fracture paper #11 - Fracture processes and phase field modelling

In the latest volume of Engineering Fracture Mechanics there is an interesting paper about the calculation of crack growth paths by use of a phase field model. The considered material is inhomogeneous and that causes the crack to follow a winding path through the material. The material structure is from a CT scanned micro-structure of a cement-based porous material. The paper is:

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Discussion of fracture paper #10 - Searching for the length scale of stress corrosion

According to the Swedish Plant Inspectorate the major part of all reported fracture related failures in Sweden are due to stress corrosion. I guess it is more or less a reality everywhere. The association with accidents is probably because it comes without warning and usually at surprisingly low loads. Just a mm sized spot of decomposing grease is enough to create a locally extremely acid environment. In an otherwise friendly environment this often not even considered as a possibility by the designer.

The paper for this discussion is:

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Discussion of fracture paper #9 - Crack tip modelling

Dear Reader, 

I recently took over as the ESIS blog editor. Being the second in this baton relay, I will do my best to live up to the good reader expectations that has been established by my precursor, who is also one of the instigators of the blog, Wolfgang Brock. 

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Discussion of fracture paper #8 - Elastic follow-up

P.M. James: Re-derivation of plasticity interaction for combined loading under significant levels of elastic follow-up. Engineering Fracture Mechanics, Vol. 126, 2014, pp. 12–26.

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Discussion of fracture paper #7 - Configurational force approach

K. Özenç, M. Kaliske, G. Lin, G. Bhashyam: Evaluation of energy contributions in elasto-plastic fracture: A review of the configurational force approach, Engineering Fracture Mechanics, 2014, Vol. 115, pp. 137-153.

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Discussion of fracture paper #6 - Stress intensity factor for steep yield distribution

T. Yasuoka, Y. Mizutani, A. Todoroki: Applicable limit of the stress intensity factor for steep yield strength distribution, Engineering Fracture Mechanics, 2013, Vol. 110, pp. 1-11.

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Discussion of fracture paper #5 - Yield ciriterion or failure criterion?

Henrik Danielsson and Per Johan Gustafsson: A three dimensional plasticity model for perpendicular to grain cohesive fracture in wood, Engineering Fracture Mechanics Vol. 98 2013, pp.137–152.

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Discussion of fracture paper #4 - Is paper ductile?

P. Mäkelä and S. Östlund: Cohesive crack modelling of thin sheet material exhibiting anisotropy, plasticity and large-scale damage evolution. Engineering Fracture Mechanics,Vol. 79, 2012 pp. 50-60.

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Discussion of fracture paper #3 - Length scales in fracture

H. Krull and H. Yuan: Suggestions to the cohesive traction–separation law from atomistic simulations. Engineering Fracture Mechanics, Vol. 78, 2011, pp. 525-533.

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Discussion of fracture paper #2 - The role of the T-stress

J.C. Sobotka, R.H. Dodds: Steady crack growth in a thin, ductile plate under small-scale yielding conditions: Three-dimensional modelling., Engineering Fracture Mechanics, Vol. 78, 2011, pp. 343-363; J.C. Sobotka, R.H. Dodds: T-stress effects on steady crack growth in a thin, ductile plate under small-scale yielding conditions: Three-dimensional modelling., Engineering Fracture Mechanics, Vol. 78, 2011, pp. 1182-1200. 

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Discussion of fracture paper #1 - A contol volume model

This is a premiere: my first contribution to the new ESIS' blog announced in January. Why comment on papers in a scientific journal after they have passed the review process already? Not to question their quality, of course, but animating a vital virtue of science again, namely discussion. The pressure to publish has increased so much that one may doubt whether there is enough time left to read scientific papers. This impression is substantiated by my experience as a referee.

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A blog for discussing fracture papers

The aim of ESIS is not only to develop and extend knowledge in all aspects of structural integrity, but also to disseminate this knowledge world-wide by means of scientific publications and to educate young engineers and scientists.

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