A comparison of fatigue-crack propagation behavior in sheet and plate aluminum-lithium alloys

Rao, K. T. Venkateswara; Bucci, R. J.; Jata, Kumar V.; Ritchie, Robert O.

doi:10.1016/0921-5093(91)90705-r

Cited by 23 publications

(11 citation statements)

References 18 publications

(32 reference statements)

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“…Thus, the fracture path in A300 includes more surface irregularities than T3, which are expected however to have small contribution to the measured crack closure levels in the intermediate Δ Κ region. This effect has been shown to be significant in microstructures with variations in grain morphology characteristics, which is not the case in the present study.…”

Section: Resultscontrasting

confidence: 57%

Improvement of fatigue crack growth resistance by controlled overaging in 2024‐T3 aluminium alloy

Tzamtzis

Kermanidis

2014

Fatigue Fract Eng Mat Struct

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A B S T R A C T A controlled overaging process is proposed to increase region II fatigue crack propagation resistance of 2024-T3 aluminium alloy. Overaging was achieved by subjecting the material from the initial T3 state to heat treatment at specific aging temperatures resulting in substantial reduction in hardness. Fatigue crack growth tests were subsequently performed in the intermediate ΔΚ region to assess the influence of aging treatment on fatigue crack propagation rate. The experimental results showed that overaging at high temperatures enhances the fatigue crack growth resistance of the material with regard to initial T3 state. Fatigue crack growth rates were found to decrease with increasing overaging temperature. Cyclic stress strain tests were performed to assess the impact of the performed overaging on cyclic behaviour. The results revealed that cyclic strain hardening is enhanced in the overaged material, contributing to increased fatigue crack closure levels.A 25 = elongation at fracture b = fatigue strength exponent C = parameter of Paris equation c = fatigue ductility exponent E = Young's modulus h = cyclic hardening capacity as a percentage increase of yield strength H = strength coefficient H' = cyclic strength coefficient m = Paris equation exponent n = strain hardening exponent n' = cyclic strain hardening exponent N f = fatigue life p = cumulated plastic strain P max = maximum applied load P min = minimum applied load P op = crack opening load Q = maximum amount of hardening R = stress/strain ratio V = crack opening displacement at points A,B in C(T) specimen V max = crack opening displacement at points A,B in C(T) specimen corresponding at P max V min = crack opening displacement at points A,B in C(T) specimen corresponding at P min V op = crack opening displacement at points A,B in C(T) specimen when crack surfaces come into contact β = driving rate of hardening ΔV = crack opening displacement range at points A,B in C(T) specimen Δε = total strain range Δε p = plastic strain range ΔΚ = stress intensity factor range Correspondence: A. Tzamtzis.

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Section: Resultscontrasting

confidence: 57%

Improvement of fatigue crack growth resistance by controlled overaging in 2024‐T3 aluminium alloy

Tzamtzis

Kermanidis

2014

Fatigue Fract Eng Mat Struct

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“…Previous research describes the effects these divider delaminations, and delamination cracks in other configurations, have on fracture and fatigue behavior of the primary crack. Rao and Ritchie [7][8][9][10][11][12][13][14] conducted some of the earliest work on the effect of delamination cracks on primary crack growth in second-generation Al-Li alloys. For most experimental configurations, they concluded that delamination cracking increases the apparent fracture toughness of the material via deflection and shielding of the primary crack.…”

Section: Frobenius Norm αmentioning

confidence: 99%

An interface compatibility/equilibrium mechanism for delamination fracture in aluminum–lithium alloys

Messner

Beaudoin

Dodds

2015

Engineering Fracture Mechanics

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This work describes a mechanism for the initiation of delamination cracks in Al-Li alloys based on the soft/stiff character of adjacent grains. Small-scale-yielding, crystal plasticity simulations of divider grain configurations (L-T) reveal an elevated mean stress on grain boundaries. This mean stress increase drives a sharp localization of the Rice-Tracey parameter to the grain boundaries-elevation of the RT parameter indicates favorable conditions for void growth and triggering of delamination cracking, in agreement with the fractography of Ritchie and co-workers. Our simulation results and available experimental evidence indicate delamination initiates typically between soft/stiff grain pairs, often Bs (Bunge-convention Euler angles φ 1 = 131 • , Φ = 83 • , φ 2 = 307 •) or S (φ 1 = 233 • , Φ = 151 • , φ 2 = 105 •) orientations. The crystal plasticity results and a simple model of a soft/stiff material interface show that mean stress accumulation is a consequence of the mechanics of such an interface, and not necessarily tied to material inhomogeneities near the GBs (such as precipitate free zones).

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“…Al-Li alloys are lighter, stronger, and generally more fracture resistant than conventional aerospace aluminums, but the difficulty of predicting the development of delaminations hinders their application [51]. Fractography by Richie et al [58][59][60][61][62][63][64]67] indicates void-growth on grain boundaries triggers delamination failure. Experiments [6,11,55] suggest that delamination typically develops along certain favored grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

A grain boundary damage model for delamination

2015

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Intergranular failure in metallic materials represents a multiscale damage mechanism: some feature of the material microstructure triggers the separation of grain boundaries on the microscale, but the intergranular fractures develop into long cracks on the macroscale. This work develops a multiscale model of grain boundary damage for modeling intergranular delamination-a failure of one particular family of grain boundaries sharing a common normal direction. The key feature of the model is a physically-consistent and mesh independent, multiscale scheme that homogenizes damage at many grain boundaries on the microscale into a single damage parameter on the macroscale to characterize material failure across a plane. The specific application of the damage framework developed here considers delamination failure in modern Al-Li alloys. However, the framework may be readily applied to other metals or composites and to other non-delamination interface geometries-for example, multiple populations of material interfaces with different geometric characteristics.

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A comparison of fatigue-crack propagation behavior in sheet and plate aluminum-lithium alloys

Cited by 23 publications

References 18 publications

Improvement of fatigue crack growth resistance by controlled overaging in 2024‐T3 aluminium alloy

Improvement of fatigue crack growth resistance by controlled overaging in 2024‐T3 aluminium alloy

An interface compatibility/equilibrium mechanism for delamination fracture in aluminum–lithium alloys

A grain boundary damage model for delamination

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