Fatigue assessment using an integrated threshold curve method – applications

Chapetti, Mirco Daniel

doi:10.1016/j.engfracmech.2006.11.005

Cited by 23 publications

(15 citation statements)

References 24 publications

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“…The local FCG behaviour of microcracks with size a < gr is sensitive to microstructural features such as the grain orientation and cannot be properly modelled using macroscopic material properties. Such problems have academic interest, [4][5][6][7][8][9] but as the grains still cannot be mapped in practice, they cannot be properly used for structural engineering applications yet.…”

Section: Figmentioning

confidence: 99%

“…Microstructurally short cracks, those small compared with the grain size gr, are much affected by microstructural barriers such as grain boundaries; hence, cannot be well modelled for structural design purposes using macroscopic stress analysis techniques and isotropic properties. [4][5][6][7][8][9] Mechanically short cracks, on the other hand, with sizes a > gr, may be modelled by Linear Elastic Fracture Mechanics (LEFM) concepts if the stress field that surrounds them is predominantly Linear Elastic, and if the material can be treated as isotropic and homogeneous in such a scale. Because near-threshold FCG is always associated with small-scale yielding conditions, to check if short cracks really may be modelled in such a way, the idea is to follow Irwin's steps by first assuming that such concepts are valid and then verifying if their predictions are validated by proper tests.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of notch sensitivity effects in fatigue and in environmentally assisted cracking

Castro

Landim

Leite

et al. 2014

Fatigue Fract Eng Mat Struct

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Semi‐empirical notch sensitivity factors q have been used for a long time to quantify notch effects in fatigue design. Recently, this old concept has been mechanically modelled using sound stress analysis techniques, which properly consider the notch tip stress gradient influence on the fatigue behaviour of mechanically short cracks. This mechanical model properly calculates q values from the basic fatigue properties of the material, its fatigue limit and crack propagation threshold, considering all the characteristics of the notch geometry and of the loading, without the need for any adjustable parameter. This model's predictions have been validated by proper tests, and a criterion to accept tolerable short cracks has been proposed based on it. In this work, this criterion is extended to model notch sensitivity effects in environmentally assisted cracking conditions.

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Section: Figmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Prediction of notch sensitivity effects in fatigue and in environmentally assisted cracking

Castro

Landim

Leite

et al. 2014

Fatigue Fract Eng Mat Struct

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“…Newman [25][26][27][28] developed a crack closure model to calculate the short crack growth rate and fatigue lives for 2 aluminium alloys. Chapetti [29][30][31] proposed a method to predict FCG rates in the SC regime by introducing microthreshold and the long crack threshold. Gubeljaka et al 32 adopted the Chapetti's model and determined an allowable size of the inclusion in a spring steel.…”

Section: Introductionmentioning

confidence: 99%

“…Their results showed that the estimated FCG rates in the PSC region were higher than the ones in the LC regime. 30 Hussain 35 proposed a crack growth model to depict short crack growth behaviour by modifying the LC analytical model.…”

Section: Introductionmentioning

confidence: 99%

A modification of UniGrow 2‐parameter driving force model for short fatigue crack growth

Bang

Ince

Tang

2018

Fatigue Fract Eng Mat Struct

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In this paper, a modification of the UniGrow model is proposed to predict total fatigue life with the presence of a short fatigue crack by incorporating short crack propagation into the UniGrow crack growth model. The UniGrow model is modified by 2 different methods, namely the “short crack stress intensity correction method” and the “short crack data‐fitting method” to estimate the total fatigue life including both short and long fatigue crack propagations. Predicted fatigue lives obtained from these 2 methods were compared with experimental data sets of 2024‐T3, 7075‐T56 aluminium alloys, and Ti‐6Al‐4V titanium alloy. Two proposed methods have shown good fatigue life predictions at relatively high maximum stresses; however, they provide conservative fatigue life predictions at lower stresses corresponding high cycle fatigue lives where short crack behaviour dominates total fatigue life at lower stress levels.

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“…Chapetti [28] assumed that the strongest microstructure was the barrier for fatigue crack propagation at the critical nominal stress range needed for a continued crack growth (microstructural threshold). Fatigue crack is assumed to be hindered at the first basketweave under very high cycle fatigue limit stress; the FGA area can be treated as a circular area with a radius equal to basketweave.…”

Section: Effect Of Basketweave On Fatigue Fracture Mechanismmentioning

confidence: 99%

Effect of Basketweave Microstructure on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy

Nie

Zhang

Chen

et al. 2018

Metals

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This paper discusses the effect of basketweave microstructure on the very high cycle fatigue behavior of TC21 titanium alloy. Ultrasonic fatigue tests at 20 kHz are done on a very high cycle fatigue (VHCF) property of the alloys with 60 µm and 40 µm basketweave size, respectively. Results show that the alloys illustrate step-wise S-N characteristics over the 10 5 -10 9 cycle regimes and that fatigue fracture in both of the alloys occur beyond the conventional fatigue limit of 10 7 cycles. Subsurface crack initiation occurs at low stress amplitude. A fine granular area (FGA) is observed along the α lamella at the subsurface crack initiation site. The mechanism for the subsurface crack initiation is revealed using layer-by-layer-polishing, due to the micro-voids that are introduced at the granular α phase. The colony of α lamella is due to the local stress concentrated between them under the cyclic load. The stress intensity factor range at the FGA front is regarded as the threshold value controlling the internal crack propagation. Furthermore, the effect of the baseketweave size on the very high cycle fatigue limits of the TC21 titanium alloy is evaluated based on the Murakami model, which is consistent with the experimental results. The fatigue life of TC21 titanium alloy is well predicted using the energy-based crack nucleation life model.

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Fatigue assessment using an integrated threshold curve method – applications

Cited by 23 publications

References 24 publications

Prediction of notch sensitivity effects in fatigue and in environmentally assisted cracking

Prediction of notch sensitivity effects in fatigue and in environmentally assisted cracking

A modification of UniGrow 2‐parameter driving force model for short fatigue crack growth

Effect of Basketweave Microstructure on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy

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