Determination of stress intensity factors for surface cracks using fatigue crack growth data

1986 ◽  
Vol 31 (1) ◽  
pp. 67-79 ◽  
Author(s):  
A. A. Aboutorabi ◽  
M. J. Cowling
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Surface Cracks ◽  
Growth Data ◽  
Intensity Factors

On the Characterization of Fatigue Crack Growth in a Plate With a Single-Sided Repair

2004 ◽  
Vol 126 (2) ◽  
pp. 192-198 ◽  
Author(s):  
C. N. Duong ◽  
C. H. Wang
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Load Path ◽  
Intensity Factors ◽  
Analytical Work ◽  
Out Of Plane ◽  
Plane Bending

An unsupported cracked plate repaired with a reinforcement bonded on one side may experience considerable out-of-plane bending due to the load-path eccentricity. This out-of-plane bending causes the stress intensity factor at the crack tip to vary significantly through the plate’s thickness with a maximum value attained at the un-patched side of the crack. Even though significant analytical work has been done in the past to evaluate these thickness-varying stress intensity factors, however, to the authors’ knowledge, little work has been done to characterize the fatigue crack growth in a plate with a single-sided repair. The purposes of the present work are to (i) assess the accuracy of the available analytical methods for predicting the stress intensity factors of the panels with a single-sided repair and more importantly, and (ii) characterize the fatigue crack growth in these panels, using test results generated recently under the Composite Repair of Aircraft Structures (CRAS) program.

Effect fracture resistance on retardation of crack growth

2015 ◽  
Vol 6 (4) ◽  
pp. 510-521
Author(s):  
Jirí Behal ◽  
Petr Homola ◽  
Roman Ružek
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Aluminium Alloy ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
High Stress ◽  
Intensity Factors ◽  
Content Type

Purpose – The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation model. This model is implemented in the AFGROW code, which allows different retardation models to be compared. The primary advantage of the model is that all input parameters, including those for an initial plane-strain state and its transition to a plane-stress-state, are objectively measured using standard middle-crack-tension M(T) specimens. The purpose of this paper is to evaluate the ability of the FASTRAN model to predict correct retardation effects due to high loading peaks that occur during variable amplitude loading in sequences representative of an aircraft service. Design/methodology/approach – This paper addresses pre-setting of the fracture toughness K R (based on J-integral J Q according to ASTM1820) in the FASTRAN retardation model. A set of experiments were performed using specimens made from a 7475-T7351 aluminium alloy plate. Loading sequences with peaks ordered in ascending-descending blocks were used. The effect of truncating and clipping selected load levels on crack propagation behaviour was evaluated using both experimental data and numerical analyses. The findings were supported by the results of a fractographic analysis. Findings – Fatigue crack propagation data defined using M(T) specimens made from Al 7475-T7351 alloy indicate the difficulty of evaluating the following two events simultaneously: fatigue crack increments after application of loads with maximum amplitudes that exceeded J Q and subcritical crack increments caused by loads at high stress intensity factors. An effect of overloading peaks with a maximum that exceeds J Q should be assessed using a special analysis beyond the scope of the FASTRAN retardation model. Originality/value – Measurements of fatigue crack growth on specimens made from 7475 T7351 aluminium alloy were carried out. The results indicated that simultaneously evaluating fatigue crack increments after application of the load amplitude above J Q and subcritical increments caused by the loads at high stress intensity factors is difficult. Experiments demonstrated that if the fatigue crack reaches a specific length, the maximal amplitude load induces considerable crack growth retardation.

Experimental Study and Numerical Simulation on Fatigue Crack Growth Behavior of GH4133B Superalloy

2012 ◽  
Vol 512-515 ◽  
pp. 980-988
Author(s):  
Rong Guo Zhao ◽  
Xiu Juan Li ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Jun Fei Li ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Threshold Stress ◽  
Threshold Stress Intensity ◽  
Intensity Factors

The fatigue crack growth tests for nickel-based GH4133B superalloy used in turbine disk of a type of aero-engine are carried out at room temperature. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding threshold stress intensity factor ranges are determined. Using the Paris formula, the experiment data of fatigue crack growth are analyzed. It is shown that the fatigue crack growth rate increasing with increasing stress intensity factor range and stress ratio, and a modified Paris formula considering threshold stress intensity factor range can describe the fatigue crack growth behavior precisely. The fracture surface morphologies are investigated using a scanning electron microscope. It is shown that in the crack initiation region, steady growth region and rapid growth region, the fracture surface exhibits a cleavage fracture mode, fatigue striations and an intergranular fracture mode, respectively. Finally, the von Mises stresses and stress intensity factors at the crack tip of specimen of GH4133B superalloy at various external loads and crack lengths are simulated using the finite element method, and the threshold stress intensity factors under different maximal external loads at a certain crack length are calculated. The comparison between test and simulation indicates that the stress intensity factors at the crack tip calculated by the finite element method agree well with experimental data.

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