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Effects of flaw shape (idealization) on the interaction of co-planar surface flaws

Kaveh Samadian (UGent) , Stijn Hertelé (UGent) and Wim De Waele (UGent)
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Abstract
Engineering Critical Assessment (ECA) guidelines contain amongst others, rules to assess flaw interaction. Major flaw dimensions (depth or height and length) are typically characterized assuming the flaws to be contained entirely within a bounding rectangle through a procedure known as flaw idealization. In (computational) fracture mechanics based calculations, flaws are often assumed to be (semi-) elliptical. This paper investigates the interaction between identical co-planar surface breaking flaws. Two flaw shapes are considered and compared: “canoe-shaped” (quarter-circular ends and constant depth elsewhere) and semi-elliptical. Especially for long shallow flaws, the canoe-shaped approximates the bounding rectangle, whereas the semi-elliptical shape only touches the bounding rectangle at three points (deepest point and two points at the surface). Several flaw dimensions and spacing distances are studied through an extensive parametric study comprising elastic and elastic-plastic finite element simulations. The results, based on Stress Intensity Factor (SIF) and J-integral analysis, show how the flaw shape can affect the degree of interaction. Notably, the inconsistency is less in linear-elastic analysis, but becomes more pronounced at higher (elastic-plastic) loading levels. This work highlights a challenge of comparing analytical and numerical based evaluations of interaction with ECA guidelines.

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Chicago
Samadian, Kaveh, Stijn Hertelé, and Wim De Waele. 2019. “Effects of  Flaw Shape (idealization) on the Interaction of Co-planar Surface Flaws.” In PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, VOL 5. American Society of Mechanical Engineer (ASME).
APA
Samadian, K., Hertelé, S., & De Waele, W. (2019). Effects of  flaw shape (idealization) on the interaction of co-planar surface flaws. PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, VOL 5. Presented at the ASME Pressure Vessels and Piping Conference (PVP 2018) , American Society of Mechanical Engineer (ASME).
Vancouver
1.
Samadian K, Hertelé S, De Waele W. Effects of  flaw shape (idealization) on the interaction of co-planar surface flaws. PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, VOL 5. American Society of Mechanical Engineer (ASME); 2019.
MLA
Samadian, Kaveh, Stijn Hertelé, and Wim De Waele. “Effects of  Flaw Shape (idealization) on the Interaction of Co-planar Surface Flaws.” PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, VOL 5. American Society of Mechanical Engineer (ASME), 2019. Print.
@inproceedings{8583030,
  abstract     = {Engineering  Critical Assessment  (ECA)  guidelines contain amongst  others, rules  to  assess  flaw interaction. Major  flaw dimensions    (depth    or    height    and    length)    are    typically characterized assuming the flaws to be contained entirely within a   bounding   rectangle   through   a   procedure   known   as  flaw idealization. In (computational)   fracture   mechanics   based calculations,  flaws  are  often  assumed  to  be (semi-) elliptical. This  paper  investigates  the  interaction  between identical co-planar  surface  breaking  flaws. Two flaw  shapes are  considered and compared:  {\textquotedblleft}canoe-shaped{\textquotedblright}  (quarter-circular   ends   and constant  depth  elsewhere)  and  semi-elliptical.  Especially  for long    shallow    flaws,    the    canoe-shaped approximates the bounding   rectangle,   whereas   the   semi-elliptical   shape only touches  the  bounding  rectangle  at  three  points  (deepest  point and  two  points  at  the  surface).  Several  flaw  dimensions  and spacing  distances  are  studied  through  an  extensive  parametric study   comprising   elastic   and   elastic-plastic   finite   element simulations. The  results,  based  on  Stress  Intensity  Factor  (SIF) and J-integral  analysis, show how the flaw shape can affect the degree  of  interaction.  Notably,  the  inconsistency  is  less  in linear-elastic analysis, but  becomes more pronounced at  higher (elastic-plastic) loading levels. This work highlights a challenge of  comparing  analytical  and  numerical  based  evaluations  of interaction with ECA guidelines.},
  articleno    = {V005T10A011 },
  author       = {Samadian, Kaveh and Hertel{\'e}, Stijn and De Waele, Wim},
  booktitle    = {PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, VOL 5},
  isbn         = {9780791851661},
  language     = {eng},
  location     = {Prague, Czech Republic},
  publisher    = {American Society of Mechanical Engineer (ASME)},
  title        = {Effects of  flaw shape (idealization) on the interaction of co-planar surface flaws},
  url          = {http://dx.doi.org/10.1115/PVP2018-84506},
  year         = {2019},
}

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