Fatigue and fracture behaviour of structural Al-alloys up to very long life regimes

An energy based fatigue life prediction framework has been developed for calculation of remaining fatigue life of in service gas turbine materials. The purpose of the life prediction framework is to account aging effect caused by cyclic loadings on fatigue strength of gas turbine engines structural components which are usually designed for very long life. Previous studies indicate the total strain energy dissipated during a monotonic fracture process and a cyclic process is a material property that can be determined by measuring the area underneath the monotonic true stress-strain curve and the sum of the area within each hysteresis loop in the cyclic process, respectively. The energy-based fatigue life prediction framework consists of the following entities: (1) development of a testing procedure to achieve plastic energy dissipation per life cycle and (2) incorporation of an energy-based fatigue life calculation scheme to determine the remaining fatigue life of in-service gas turbine materials. The accuracy of the remaining fatigue life prediction method was verified by comparison between model approximation and experimental results of Aluminum 6061-T6. The comparison shows promising agreement, thus validating the capability of the framework to produce accurate fatigue life prediction.

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“…12(k), fully developed cracks on subsurface facets, and combined micro-voids, cleavage fracture mode in Fig. 12(l) were observed [18][19][20].…”

Section: Failure Energy Of In-service Partsmentioning

confidence: 88%

An Energy Based Fatigue Life Prediction Framework for In-Service Structural Components

et al. 2010

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“…Possibly, the coalescence of these point defects increases with increasing number of cycles. It is also assumed, according to [40], that so pores with a critical size are generated, where a crack can initiate. At the smooth specimens of EN AW 6056 failure started several millimetre below the surface at N > 8Á10 5 in the maximum precipitation hardened condition and at N > 3Á10 6 for the marginal overaged condition, Figure 11, 12.…”

Section: Fatigue Behaviour Of Type II Materialsmentioning

confidence: 99%

Beyond HCF – Is there a fatigue limit?

Berger

Pyttel²,

Schwerdt

2008

Materialwissenschaft Werkst

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The paper gives an overview to the present state of research on fatigue strength and failure mechanisms at very high number of cycles (N>10 7 ). Testing facilities are listed. A classification of materials with typical S-N curves and influencing factors like notches, residual stresses and environment are given. Different failure mechanisms, which occur especially in the VHCF-region like subsurface failure, are explained. There microstructural inhomogeneities and statistical conditions play an important role. Investigated materials are different metals with body-centred cubic lattice like lowor high-strength steels and quenched and tempered steels but also materials with a face-centred cubic lattice like aluminium alloys and copper.

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“…There have been growing interests in light metals, such as aluminium, magnesium and titanium-aluminium alloys, which have been widely applied to aeronautic and automotive industries because of their high strength-toweight ratios, [1][2][3] but improvements are needed in their fatigue properties, [4][5][6][7][8] very high-cycle fatigue behaviour of aluminium alloys [9][10][11] and some factors of high humidity on fatigue properties of aluminium alloys. 12 As one of the important materials in aeronautic and automotive structures, the aluminium alloy is usually directly exposed to the corrosive environment with stress/strain, 13 in which the corrosive fatigue cracking mechanism is rather a complex process and needs to be deeply understood.…”

Section: Introductionmentioning

confidence: 99%

Synergistic effect of environmental media and stress on the fatigue fracture behaviour of aluminium alloys

Yang

Wang

et al. 2016

Fatigue Fract Eng Mat Struct

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A B S T R A C T The present study aims at explaining the synergistic effect of environmental media and stress/strain on fatigue lives of aluminium alloys. Rotating bending fatigue tests were carried out using four different aluminium alloys LY12-CZ, 2024-T4, 7475-T7351 and 7075-T651, at air state, 3.5% and 5.0% NaCl aqueous solutions. These results indicated that synergistic actions of the environmental media and cyclic loading accelerated the fatigue crack propagation of aluminium alloys. Furthermore, various influence factors (such as solution concentration, cyclic numbers, high (low) strength aluminium alloys etc.) of the fatigue life at synergistic actions of the environmental media and stress were quantificationally discussed in this paper.Keywords aluminium alloy; corrosion environment; fatigue life; fracture behaviour; synergistic effect. N O M E N C L A T U R Eα = the stress concentration factor (1.08) B, C = the distance between adjacent striations, respectively d, L = the geometry size, respectively g = the acceleration of gravity (9.8 m/s 2 ) N f = number of cycles to failure σ = stress amplitude (MPa) R = stress ratio I N T R O D U C T I O NThere have been growing interests in light metals, such as aluminium, magnesium and titanium-aluminium alloys, which have been widely applied to aeronautic and automotive industries because of their high strength-toweight ratios, 1-3 but improvements are needed in their fatigue properties, 4-8 very high-cycle fatigue behaviour of aluminium alloys 9-11 and some factors of high humidity on fatigue properties of aluminium alloys. 12As one of the important materials in aeronautic and automotive structures, the aluminium alloy is usually directly exposed to the corrosive environment with stress/strain, 13 in which the corrosive fatigue cracking mechanism is rather a complex process and needs to be deeply understood. More data, especially fatigue properties in such an environment, are crucial for safety. In recent years, many studies have focused on the fatigue behaviour of Al alloys in the corrosive environment.14 Li et al. 15estimated the effect of pre-corrosion states on the fatigue microcrack initiation and early stage propagation behaviour of 6151-T6 aluminium alloy based on scanning electron microscopy (SEM) in situ observation. Hui et al. 16 and Qian et al.14 conducted fatigue life tests in the laboratory air and salt water environment by using several pre-corrosion 7XXX aluminium alloys and a structural steel 40Cr and reported that the salt water environment significantly reduced the fatigue performance, especially under low stress amplitude and the fatigue life is about 2.2% of that at air state. These results indicated that the effect of different pre-corrosion states on the fatigue damage of aluminium alloys is mainly producing more stress concentration sites (or pits) and inducing more fatigue cracks. Zhang et al. 17proposed a novel model to predict the residual fatigue life of 2A12 aluminium alloy subjected to alternating corrosion and fatigue based on the ...

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Fatigue and fracture behaviour of structural Al-alloys up to very long life regimes

Cited by 77 publications

References 17 publications

An Energy Based Fatigue Life Prediction Framework for In-Service Structural Components

An Energy Based Fatigue Life Prediction Framework for In-Service Structural Components

Beyond HCF – Is there a fatigue limit?

Synergistic effect of environmental media and stress on the fatigue fracture behaviour of aluminium alloys

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