NDLI: Stress Intensity Factors for Unusual Semi-Elliptical Surface Cracks With Ratio a/l Greater Than 0.5

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Malekian, Christian Wyart, Eric Savelsberg, Michael Lacroix, David Teughels, Anne Minjauw, Nicolas Wendling, Audrey
Copyright Year	2009
Abstract	Most of the literature about fracture mechanics treats cracks with a flaw aspect ratio a/l lower or equal to 0.5 where a is the crack depth and l the total length of the crack. The limitation to 0.5 corresponds to a semi-circular shape for surface cracks and to circular cracks for subsurface cracks. This limitation does not seem to be inspired by a theoretical limitation nor by a computational limit. Moreover, limiting the aspect ratio a/l to 0.5 may generate some unnecessary conservatism in flaw analysis. The present article deals with surface cracks in plates with more unusual aspect ratios a/l>0.5 (narrow cracks). A series of Finite-Elements calculations is made to compute the stress intensity factor KI for a large range of crack depths having an aspect ratio greater than 0.5. The KI values can be used with the same formalism as the ASME XI Appendix A, such that this approach can provide an extension above the inherent limitation to 0.5. Some of the results obtained are checked by using two different Finite-Elements softwares (Systus and Ansys), each one with a different cracked mesh. In addition, a comparison is made for some cases with results obtained by a XFEM approach (eXtended Finite-Element Method), where the crack does not need to be meshed in the same way as in classical Finite-Elements. The results show a reduction of stress intensity factor, sometimes significant, when considering a flaw aspect ratio above 0.5 instead of the conventional semi-circular flaw. They also show that it is not always possible to reduce the analysis of KI to only 2 points, namely the crack surface point and the crack deepest point. The growth by fatigue or by corrosion of a crack with such unusual shape should still be investigated.
Sponsorship	Nuclear Engineering Division
Starting Page	131
Ending Page	141
Page Count	11
File Format	PDF
ISBN	9780791843529
DOI	10.1115/ICONE17-75441
e-ISBN	9780791838525
Volume Number	Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications
Conference Proceedings	17th International Conference on Nuclear Engineering
Language	English
Publisher Date	2009-07-12
Publisher Place	Brussels, Belgium
Access Restriction	Subscribed
Subject Keyword	Fracture mechanics Corrosion Plates (structures) Fatigue Fracture (materials) Finite element analysis Shapes Finite element methods Surface cracks Stress
Content Type	Text
Resource Type	Article

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