Growth of Corner Cracks at a Hole

1982 ◽  
Vol 104 (2) ◽  
pp. 107-114 ◽  
Author(s):  
A. F. Liu ◽  
H. P. Kan
Keyword(s):  
Growth Rate ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Crack Size ◽  
Crack Growth Behavior ◽  
Intensity Factors ◽  
Open Hole ◽  
Corner Cracks

The two-dimensional growth characteristics of corner cracks emanating from an open hole were demonstrated by conducting constant amplitude cyclic crack growth tests on a set of 51 specimens. The specimens were machined from 2024-T851 aluminum alloy in three thicknesses (6.35, 12.7, and 19.30 mm) and three hole diameters (6.35, 12.7, and 19.05 mm). The precrack sizes are very small (typically 0.5 to 1.0 mm in either length or depth dimensions) having many arbitrary initiated length-to-depth ratios. Empirical stress intensity factors for various crack size, crack shape, and specimen geometry combinations were calibrated by back-tracking of the crack growth rate behavior in these specimens and the material baseline crack growth rate data (also in three thicknesses of the same heat) developed from compact specimens. Superposition principles were applied to separate the lumped stress intensity factors into a parametric functional form. It has been demonstrated that these empirically derived stress intensity expressions are capable of predicting the crack growth behavior in both the length (on specimen surface) and depth (on the hole wall) directions.

Study on Fatigue Crack Growth Behavior of Zr702/TA2/Q345R Composite Plate With a Through-Wall Crack and a Crack Normal to Interface for SENT Specimen

2019 ◽  
Author(s):  
Binbin Zhou ◽  
Changyu Zhou ◽  
Xiaohua He
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Composite Plate ◽  
Homogeneous Material ◽  
Crack Growth Behavior ◽  
Strength Material

Abstract In this paper, the fatigue crack growth behavior of Zr702/TA2/Q345R composite plate with a through-wall crack and a crack normal to interface for SENT specimen are studied. For the through-wall crack, the mutual interference in fatigue crack growth rate is found. The crack growth rate of the through-wall crack on both sides in Zr702/TA2/Q345R composite plate depends on the difference of stress intensity factors amplitude caused by the different positions of crack tips on both sides and the crack growth rate in corresponding homogeneous material. For the crack normal to interface, two crack propagation directions are taken into account. When crack initiates from the lower strength material side, the crack growth rate decreases to the minimum before crack penetrates the interface. After crack penetrates the interface, crack growth rate accelerates continuously. When crack initiates from the higher strength material side, the fatigue crack growth rate generally increases with the crack length. For both crack forms, all experiment results demonstrate that the crack growth rate is dependent on the competition of the stress intensity factor amplitude, the crack growth rate in corresponding homogeneous material and the interface strength. Besides, finite element results show that elastic mismatch results in a significantly change in the distribution of stress intensity factor amplitude.

scholarly journals Creep crack growth assessment in terms of continuum damage mechanics

2018 ◽  
Vol 165 ◽  
pp. 19003
Author(s):  
Valery Shlyannikov ◽  
Andrey Tumanov
Keyword(s):  
Growth Rate ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Process Zone ◽  
Creep Crack Growth ◽  
Intensity Factors ◽  
Stress Strain ◽  
Creep Crack ◽  
Creep Stress

The stress, strain rate, and process zone with respect to the creep-crack growth in compacttension C(T) specimen is analyzed by employing damage-evolution equations. The damage model for the fracture of the process zone is represented using a stress based formulation. Both damage free and defective creeping solids have been studied. The variations in the creep stress/strain and crack-tip governing parameter in terms of the creep stress intensity factors with respect to time and the evolution of creep damage are analyzed using an FE model for C(T) specimen. The creep-fatigue crack growth rate tests were performed on special designed program test-cycle. The interpretation of the experimental creep crack growth rate data was given in terms of introduced creep stress intensity factors based on undamaged and damaged stress/strain fields.

A Parametric Study of Fatigue Crack Growth Behavior in Adhesively Bonded Metallic Structures

1978 ◽  
Vol 100 (1) ◽  
pp. 46-51 ◽  
Author(s):  
M. M. Ratwani
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Intensity Factors ◽  
Adhesively Bonded

Problems of adherend cracks inadhesively bonded structures are considered in this paper. Two different methods of analysis, namely the finite element method and the integral equation approach, are used to obtain the stress intensity factors, which are compared with those obtained experimentally. The results of fatigue crack growth tests on two-ply, adhesively bonded panels with a width of 300 mm and 150 mm, a crack at a hole, and a cracked plate with a bonded stiffener are discussed. Fatigue crack growth behavior predictions based on the analytical stress intensity factors are correlated with those obtained from experiments for a variety of test geometries. The influence of adhesive type, adhesive thickness, and stiffener thickness on crack growth behavior are discussed for the case of a cracked plate with a bonded stiffener.

Stress intensity factors for corner cracks at a hole under remote tension

1991 ◽  
Vol 7 (1) ◽  
pp. 76-81 ◽  
Author(s):  
Zhao Wei ◽  
Wu Xueren ◽  
Yan Minggao
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Corner Cracks

Fatigue Crack Growth of Alloy 7050-T7451 Plate in L-S Orientation

2012 ◽  
Vol 525-526 ◽  
pp. 221-224
Author(s):  
Rui Bao ◽  
Xiao Chen Zhao ◽  
Ting Zhang ◽  
Jian Yu Zhang
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Characteristics ◽  
Stress Intensity Factor Range ◽  
Constant Amplitude ◽  
Stress Ratios

Experiments have been conducted to investigate the crack growth characteristics of 7050-T7451 aluminium plate in L-S orientation. Two loading conditions are selected, i.e. constant amplitude and constant stress intensity factor range (ΔK). The effects of ΔK-levels and stress ratios (R) on crack splitting are studied. Test data shows that crack splitting could result in the reverse of crack growth rate trend with the increasing R ratio at high ΔK-level. The appearance of crack splitting depends on both ΔK and R.

scholarly journals In-situ SEM and optical microscopy testing for investigation of fatigue crack growth mechanism under overload

2018 ◽  
Vol 165 ◽  
pp. 13013
Author(s):  
Wei Zhang ◽  
Liang Cai
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Optical Microscopy ◽  
Crack Growth ◽  
Load Condition ◽  
Crack Tip ◽  
Initial Crack ◽  
Crack Growth Behavior ◽  
Single Overload

In this paper, the in-situ scanning electron microscope (SEM) and optical microscopy experiments are performed to investigate the crack growth behavior under the single tensile overload. The objectives are to (i) examine the overload-induced crack growth micromechanisms, including the initial crack growth acceleration and the subsequent retardation period; (ii) investigate the effective region of single overload on crack growth rate. The specimen is a small thin Al2024-T3 plate with an edge-crack, which is loaded and observed in the SEM chamber. The very high resolution images of the crack tip are taken under the simple variable amplitude loading. Imaging analysis is performed to quantify the crack tip deformation at any time instant. Moreover, an identical specimen subjected to the same load condition is observed under optical microscope. In this testing, fine speckling is performed to promote the accuracy of digital imaging correlation (DIC). The images around the crack tip are taken at the peak loads before, during and after the single overload. After that, the evolution of local strain distribution is obtained through DIC technique. The results show that the rapid connection between the main crack and microcracks accounts for the initial crack growth acceleration. The crack closure level can be responsible for the crack growth rate during the steady growth period. Besides that, the size of retardation area is larger than the classical solution.

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

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