Stress intensity factors for three-dimensional surface cracks using enriched finite elements

2002 ◽  
Vol 54 (6) ◽  
pp. 899-921 ◽  
Author(s):  
A. O. Ayhan ◽  
H. F. Nied
Keyword(s):  
Stress Intensity ◽  
Finite Elements ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Enriched Finite Elements ◽  
Dimensional Surface

Stress Intensity Factors for Semi-Elliptical Surface Cracks With Flaw Aspect Ratio Beyond the ASME XI Limit

2009 ◽  
Author(s):  
Christian Malekian ◽  
Eric Wyart ◽  
Michael Savelsberg ◽  
Anne Teughels ◽  
Pierre-Eric Fouquet ◽  
...  
Keyword(s):  
Stress Intensity ◽  
Finite Elements ◽  
Aspect Ratio ◽  
Stress Intensity Factors ◽  
Large Range ◽  
Crack Depth ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Flat Plates ◽  
Circular Shape

Most of the literature about fracture mechanics considers cracks having an elliptical shape 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. This is also case in the ASME XI Appendix A where Stress Intensity Factors KI formulations are given for a large range of crack depths and for a flaw aspect ratio a/l between 0 and 0.5. The limitation to 0.5 corresponds to a semi-circular shape for surface cracks and to a circular shape for subsurface cracks. This limitation does not seem to be inspired by a theoretical limitation nor by a computational limit. Moreover, it appears that limiting the ratio a/l to 0.5 may generate in some cases some unnecessary conservatism in flaw analysis. The present article specifically deals with the more unusual narrow cracks having a/l >0.5, in the case of surface cracks in infinite flat plates. Several Finite-Elements calculations are performed to compute KI for a large range of crack depths and for 4 typical load cases (uniform, linear, quadratic and cubic). The results can be presented with the same formalism as in the ASME XI Appendix A, such that the work can provide an extension of the ASME coefficients in table A-3320-1&2. By doing the study, one had the opportunity to compare the results obtained by two different Finite-Elements softwares (Systus and Ansys), each one with a different cracked mesh. In addition, a comparison has been 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 indicate how the KI can be reduced when considering the real flaw aspect ratio instead of the conventional semi-circular flaw shape. They also show that, for specific theoretical stress distributions, 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 crack growth evaluation of such unusual crack shape should still be investigated to verify whether simple rules can be established to estimate the evolution of the crack front.

Stress Intensity Factors for High Aspect Ratio Semi-Elliptical External Surface Cracks in Cylindrical Vessels

2014 ◽  
Vol 986-987 ◽  
pp. 882-886
Author(s):  
Hong Yu Qi ◽  
Peng Chao Guo
Keyword(s):  
Stress Intensity ◽  
Aspect Ratio ◽  
Stress Intensity Factors ◽  
High Aspect Ratio ◽  
External Surface ◽  
Superposition Principle ◽  
Three Dimensional ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Aspect Ratios

External surface cracks can occur in cylindrical vessels due to damage and propagate in the manufacturing process and during service life. Most of research focuses on stress intensity factors for surface cracks with low aspect ratios, i.e., a/c ≤1.0. Situation may well arise where the aspect ratio of cracks is larger than one. An external longitudinal surface crack is assumed to be subjected to different types of hoop stress distributions acting perpendicular to the crack faces. The stress intensity factors (SIFs) along the crack front were determined through the three-dimensional finite element method. Then these results are used to compute approximate values of SIFs in the case of complex loadings by employing both the superposition principle and the power series expansions of the actual hoop stresses. It is found that the maximum stress intensity factor for external surface cracks with high aspect ratio occurs at different point to that with low aspect ratio.

scholarly journals Photoelastic research of threedimensional problems of fracture mechanics

2021 ◽  
Vol 1 (101) ◽  
pp. 5-14
Author(s):  
Yu. Rudyak ◽  
M. Pidgurskyi ◽  
I. Matvieieva ◽  
V. Groza ◽  
V. Sіchко ◽  
...  
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Thin Plates ◽  
Engineering Practice ◽  
Thin Shells ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Polarization Optical Method

A polarization-optical method for studying three-dimensional problems of fracture mechanics has been developed. The method was tested to determine the values of stress intensity factors (SIF) for surface cracks in thin plates and thin shells. The data of SIF values for surface cracks of different geometry, which are subjected to different loadings, are obtained. The experimentally obtained values of SIF were compared with those calculated analytically. The efficiency of the proposed technique for solving the corresponding problems of engineering practice is shown.

Stress intensity factors by enriched finite elements

1978 ◽  
Vol 10 (3) ◽  
pp. 485-496 ◽  
Author(s):  
L. Nash Gifford ◽  
Peter D. Hilton
Keyword(s):  
Stress Intensity ◽  
Finite Elements ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Enriched Finite Elements
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