Fatigue crack growth of a corner crack in a square prismatic bar under combined cyclic torsion–tension loading

Abstract Fatigue crack growth laws are typically dependent on the ratio between minimum and maximum Stress Intensity Factor (SIF), referred to as the load ratio (R). When part of the SIF range is compressive (and hence R is negative) the amount of growth for a given SIF range is reduced due to crack closure effects. Methods for capturing the effect of crack closure were presented in a previous PVP paper [1]. These methods are based around defining a scaling factor (q0) which is dependent on R and applied to the SIF range before calculated growth. Equations were provided for both best fit and bounding q0 factors. This paper presents a comparison between these methods and results of testing. The specimens used were square cross-section bars and were made from Type 304L stainless steel with an initial corner crack. A range of load ranges and R ratios (including some positive R values) were used and the testing was undertaken at 250°C in both air and a simulated PWR environment. The growth rate observed in the tests was used to derive the effective q0 factor observed in each stage of the testing. These values were then compared with the q0 methods that are used in actual defect tolerance calculations. The results agreed very closely with the derived best estimate q0 curves, with no discernible difference between the air and water results.

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Fatigue crack growth in a Ti–15–3 matrix/SCS–6 fibre metal matrix composite under tension–tension loading

Materials Science and Technology ◽

10.1179/mst.1996.12.6.523 ◽

1996 ◽

Vol 12 (6) ◽

pp. 523-530 ◽

Cited By ~ 10

Author(s):

P. J. Cotterill ◽

P. Bowen

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Metal Matrix Composite ◽

Crack Growth ◽

Matrix Composite ◽

Metal Matrix ◽

Fibre Metal ◽

Tension Loading

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Composite Repair of Curved Stiffened Aluminum Panels under Combined Tension and Shear Cyclic Loadings

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.225.219 ◽

2012 ◽

Vol 225 ◽

pp. 219-224

Author(s):

Hossein Hosseini-Toudeshky ◽

Mir Ali Ghaffari ◽

Bijan Mohammadi

Keyword(s):

Finite Element ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Initial Crack ◽

Stiffened Panels ◽

Crack Trajectory ◽

Aluminum Panels ◽

Crack Growth Modeling ◽

Tension Loading

In this study, finite element method is used to investigate the fracture analyses, crack growth trajectory and fatigue life of curved stiffened panels repaired with composite patches subjected to combined tension and shear cyclic loadings. For this purpose, 3-D finite element modeling are performed for consideration of real 3-D crack-front in general mixed-mode conditions. Contact elements are used between the crack surfaces on two crack sides to prevent interferences of crack surfaces and a complementary program was developed to handle the automatic fatigue crack growth modeling. The effects of various patch layups and shear-tension loading ratios on fracture parameters of the aluminum panel are investigated. It is shown that in low shear to tension ratios like 0.4, the patch layup of [90]4 (perpendicular to the initial crack) is more efficient than the patch with layups angle along the tension loading. As the shear to tension ratio increases, effect of patch layups with orientations of almost perpendicular to the crack trajectory on fatigue crack growth life is increased comparing with the patch layups parallel to the tension orientation like [90]4.

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