From NASGRO to fractals: Representing crack growth in metals

Jones, Rhys; Chen, Faxiang; Pitt, Susan; Paggi, Marco; Carpinteri, A.

doi:10.1016/j.ijfatigue.2015.09.009

Cited by 25 publications

(21 citation statements)

References 45 publications

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“…This loglinear formulation together with the cubic stress dependency forms part of the certification basis for RAAF F/A-18 (Hornet), P3C (Orion) aircraft and PC9 trainer aircraft [1,41,47,48]. The physical reason for this 7 formulation is that, as explained in [49,50], the growth of cracks that initiate from small naturally occurring material discontinuities behave, as explained by 4 Nevertheless limited crack growth was observed in operational aircraft. 5 Here it should be noted that it is now know that for a range of materials tested under a range of operational load spectra the growth of cracks that initiate and grow from small naturally occurring material discontinuities can be accurately computed using the R ratio independent da/dN versus ΔK small crack relationship and setting closure effects to zero [27,28,[34][35][36][37].…”

Section: Exponential Crack Growthmentioning

confidence: 99%

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Composite repairs to bridge steels demystified

Ali

Raman

Zhao

et al. 2017

Composite Structures

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Section: Exponential Crack Growthmentioning

confidence: 99%

“…8 An interview with Professor Mandlebrot where he gives an explanation of fractals and roughness is available on line at: https://www.youtube.com/watch?v=Xm-2ouPGrlY 52]. The fact that this value of the fractal box dimension D (= 1.2) holds for a large crossection of materials is documented in [49,53].…”

Section: Exponential Crack Growthmentioning

confidence: 99%

Composite repairs to bridge steels demystified

Ali

Raman

Zhao

et al. 2017

Composite Structures

Self Cite

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“…It is also shown that for lead cracks the crack growth rate at one stress level can be predicted accurately with knowledge of the second stress level and the effective initiating crack size. The fundamental physics underpinning this exponential crack growth and the cubic rule [24] is also discussed.…”

Section: Introductionmentioning

confidence: 99%

Crack Growth From Naturally Occurring Material Discontinuities

Jones

Peng

McMillan

2018

Aircraft Sustainment and Repair

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All repairs to airframes now need to be assessed as to their effect on the damage tolerance the aircraft. To this end this Chapter first discusses difference between the analysis tools needed for ab initio design and aircraft sustainment. It is shown that using small or physically short crack da/dN versus ∆K data results in reduced through life costs and increased aircraft availability. The tests procedures needed to validate composite, or supersonic particle deposition (SPD), repairs to operational aircraft are also discussed as is their relationship to the ASTM fatigue test standard E647-13a. This leads to an examination of the problem of crack growth from small naturally occurring material discontinuities under operational load spectra. A range of tools are available to account for crack growth in operational aircraft and several such tools are discussed, 2 Reference [2] also provides an historical perspective as to how the military, the Federal Aviation Administration (FAA) and industry have dealt with these threats. 3 Widespread fatigue damage (WFD) is defined [11] as the simultaneous presence of cracks at multiple structural locations that are of sufficient size and density such that the structure will no longer meet the residual strength requirements of FAR section §25.571(b). 4 Damage tolerance requirements were not adopted by the FAA until 1978, see [12]. 5 Limit of validity-The period of time (in flight cycles, flight hours, or both) up to which widespread fatigue damage will not occur in the airplane structure.

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“…In addition, it is interesting to note that the fractal Paris' law in Equation and the NASGRO crack growth equation can capture equally well the anomalous small crack behaviour. In fact, as stated in Jones et al, the NASGRO crack growth equation can be used to represent the small crack propagation if closure effects are neglected and the fatigue threshold is set to a very small value. Furthermore, notice that the scaling law proposed for Paris parameter C can be applied only to a limited crack‐size range in order to consider a constant value of the dimensional increment

d_{G}

.…”

Section: Fractal and Multi‐fractal Approach To Paris Regimementioning

confidence: 99%

Scaling and fractality in subcritical fatigue crack growth: Crack‐size effects on Paris' law and fatigue threshold

Carpinteri

Montagnoli

2020

Fatigue Fract Eng Mat Struct

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The present contribution investigates the crack‐size effects on Paris' law in accordance with dimensional analysis and intermediate asymptotics theory, which makes it possible to obtain a generalised equation able to provide an interpretation to the various empirical power‐laws available in the Literature. Subsequently, within the framework of fractal geometry, scaling laws are determined for the coordinates of the limit‐points of Paris' curve so that a theoretical explanation is provided to the so‐called short cracks problem. Eventually, the proposed models are compared with experimental data available in the literature which seem to confirm the advantage of applying a fractal model to the fatigue problem.

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From NASGRO to fractals: Representing crack growth in metals

Cited by 25 publications

References 45 publications

Composite repairs to bridge steels demystified

Composite repairs to bridge steels demystified

Crack Growth From Naturally Occurring Material Discontinuities

Scaling and fractality in subcritical fatigue crack growth: Crack‐size effects on Paris' law and fatigue threshold

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