Variable amplitude fatigue crack growth, experimental results and modeling

Hamam, Rami; Pommier, Sylvie; Bumbieler, F.

doi:10.1016/j.ijfatigue.2007.02.005

Cited by 34 publications

(29 citation statements)

References 14 publications

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“…Since the material available was limited at that time, C(T) specimens were the first choice. However, conservative data than possible on C(T) specimens [8][9][10][11][12][13] were required and were to be acquired on M(T) specimens and at a low load ratio (R = 0.1). The topics turned up were possibility of the size effect (specifically, specimen width) and the method to be used for the indirect crack length measurement.…”

Section: (2010) 11-12mentioning

confidence: 99%

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Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Vaidya¹,

Horstmann²,

Angamuthu³

et al. 2010

Materials Testing

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Accuracy of indirect fatigue crack length measurement by potential drop method or by compliance technique may be affected at low load ratio due to fracture surface contact, crack closure or mixed mode fracture. As an alternative, the maximum value of crack opening displacement, CODmax, from a clip gauge was utilized. Middle crack tension M(T) specimens were used to obtain conservative data at a low load ratio (R = 0.1). Thin sheet specimens (B = 3.2 mm) with different widths (100 mm ≤ W ≤ 400 mm) of AA6056-T4 were investigated in the mid-regime (Paris regime), which is of interest for damage tolerance analysis. The use of CODmax is found to provide crack lengths equivalent to those measured optically. Hence, the method is very suitable for indirect crack length measurement. Furthermore, small width specimens provided data equivalent to large width specimens. Insofar, the size effect is found to be absent, and fatigue crack propagation data can be acquired on small width specimens when material availability is limited.

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Section: (2010) 11-12mentioning

confidence: 99%

“…This would limit the accuracy of data acquired. Moreover, specimen geometry can affect a fatigue crack propagation curve such that compared to C(T) specimens, M(T) specimens provide more conservative data [8][9][10][11][12][13].…”

mentioning

confidence: 99%

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Vaidya¹,

Horstmann²,

Angamuthu³

et al. 2010

Materials Testing

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“…Previously, a model was developed and validated for mode I fatigue crack growth under variable amplitude loadings conditions [25,26]. It was able to model fatigue crack growth including plasticity induced history effects.…”

Section: Modellingmentioning

confidence: 99%

“…The local FE results are then brought to the global scale using a multiscale approach tailored for crack problems [25][26][27]. The global data generated by the post [25][26][27].…”

Section: The Multiscale Approachmentioning

confidence: 99%

“…In order to model service conditions in engineering applications, the computations become even more expensive, because real components often have fatigue lives of millions cycles, and cracks do not generally remain planar. The objective of the proposed methodology is to combine the precision of local finite element computations with the rapidity of a global approach [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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History effect in fatigue crack growth under mixed-mode loading conditions

Decreuse¹,

Pommier²,

Gentot³

et al. 2009

International Journal of Fatigue

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Plastic deformation within the crack tip region introduces internal stresses that modify subsequent behaviour of the crack and are at the origin of history effects in fatigue crack growth.Consequently, fatigue crack growth models should include plasticity induced history effects. A model was developed and validated for mode I fatigue crack growth under variable amplitude loading conditions. The purpose of this study was to extend this model to mixed mode loading conditions. Finite element analyses are commonly employed to model crack tip plasticity and were shown to give very satisfactory results. However, if millions of cycles need to be modelled to predict the fatigue behaviour of an industrial component, the finite element method becomes computationally too expensive. By employing a multiscale approach, the local results of FE computations can be brought to the global scale. This approach consists of partitioning the velocity field at the crack tip into plastic and elastic parts. Each part is partitioned into mode I and mode II components, and finally each component is the product of a reference spatial field and an intensity factor. The intensity factor of the mode I and mode II plastic parts of the velocity fields, denoted by dρ I /dt and dρ II /dt, allow measuring mixed-mode plasticity in the crack tip region at the global scale.Evolutions of dρ I /dt and dρ II /dt, generated using the FE method for various loading histories, enable the identification of an empirical cyclic elastic-plastic constitutive model for the crack tip region at the global scale. Once identified, this empirical model can be employed, with no need of additional FE computations, resulting in faster computations. With the additional hypothesis that the fatigue crack growth rate and direction can be determined from mixed mode crack tip plasticity (dρ I /dt and dρ II /dt), it becomes possible to predict fatigue crack growth under I/II mixed mode and variable amplitude loading conditions. To compare the predictions of this model with experiments, an asymmetric four point bend test system was set-up. It allows applying any mixed mode loading case from a pure mode I condition to a pure mode II. Initial experimental results showed an increase of the mode I fatigue crack growth rate after the application of a set of mode II overload cycles.

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Extended Finite Element Method for Crack Propagation

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Variable amplitude fatigue crack growth, experimental results and modeling

Cited by 34 publications

References 14 publications

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

History effect in fatigue crack growth under mixed-mode loading conditions

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Variable amplitude fatigue crack growth, experimental results and modeling

Cited by 34 publications

References 14 publications

Utilising CODmax as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Utilising CODmax as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

History effect in fatigue crack growth under mixed-mode loading conditions

Bibliography

Contact Info

Product

Resources

About

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056

Utilising COD_max as an Indirect Fatigue Crack Length Measurement Parameter for M(T) Specimens of an Airframe Aluminium Alloy AA6056