On the relationship between statistical distributions of defect size and fatigue life in 7050-T7451 thick plate and A356-T6 castings

Tiryakioğlu, Murat

doi:10.1016/j.msea.2009.05.005

Cited by 32 publications

(15 citation statements)

References 47 publications

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“…3 Statistical techniques were † † As shown later, the log-normal was considered the best distribution for these EPS samples. ‡ ‡ Other studies of discontinuity distributions or probability of failure were not considered relevant here as either long-crack growth derived EIFS were used or total life and/or growth from a machined slot (many millimetres long) had been considered, for example, Refs [28][29][30][31][32]. The unknown initiating source sample possibly contained EPS with mixed initiating flaw types or just undefined because of damage.…”

Section: I S T R I B U T I O N a N A L Y S I S O F E Q U I V A L E mentioning

confidence: 99%

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A review of equivalent pre‐crack sizes in aluminium alloy 7050‐T7451

Molent

2014

Fatigue Fract Eng Mat Struct

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This paper reviews some analyses of quantitative fractography measurements of the fatigue fracture surfaces of 7050 aluminium alloy specimens along with relevant fatigue crack information including crack initiating discontinuity size and type. These data were used to assess whether surface finish or applied stress level has any effect on the estimated effective crack initiating discontinuity size, namely the equivalent pre‐crack size (EPS). The statistical distributions for the EPSs of the following initiating discontinuity types were examined: chemically etched pits, glass bead peening damage, mechanical damage, inclusions and porosity. The EPSs at various percentile levels for these types were determined on the basis of the samples considered. Finally, the correlation between measured initiating discontinuity depth and EPS was investigated, and good correlation was found in the case of mechanical damage. The purpose of conducting these analyses was to gain a better understanding of the parameters governing the fatigue crack‐like effect of discontinuities to facilitate the better prediction of fatigue lives.

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Section: I S T R I B U T I O N a N A L Y S I S O F E Q U I V A L E mentioning

confidence: 99%

“…‡‡ ‡‡ Other studies of discontinuity distributions or probability of failure were not considered relevant here as either long‐crack growth derived EIFS were used or total life and/or growth from a machined slot (many millimetres long) had been considered, for example, Refs .…”

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confidence: 99%

A review of equivalent pre‐crack sizes in aluminium alloy 7050‐T7451

Molent

2014

Fatigue Fract Eng Mat Struct

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“…This suggests that a wider temperature range between T solidus and T switch increases crack growth susceptibility, which is an important point to consider during industrial production. It is well known that pores and micro-cracks have strong effect on mechanical properties of materials, in particular toughness and fatigue properties [41][42][43][44][45]. This ultimately may influence the service lifetime and the safety factor of the product.…”

Section: Deformation Mechanisms and Fracture Behaviormentioning

confidence: 99%

Tensile mechanical properties, constitutive parameters and fracture characteristics of an as-cast AA7050 alloy in the near-solidus temperature regime

Subroto

Miroux

Eskin

et al. 2017

Materials Science and Engineering: A

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The knowledge on constitutive mechanical behavior at the temperatures close to the solidus is essential for predicting high-temperature deformation and fracture, e.g. cold and hot cracking of aluminum alloys. In this work we studied the tensile mechanical properties of an as-cast AA7050 alloy in a near-solidus temperature regime. Tensile tests were carried out using Gleeble-3800 TM system at temperatures from 400 to 465 °C and at strain rates from 0.0005 to 0.05 s -1 . The resultsshow that the strength decreases with increasing temperature and decreasing strain rate.Meanwhile, ductility decreases with the increase of temperature and strain rate. The constitutive parameters were extracted by fitting the test data to the extended-Ludwik and creep-law equations. The parameters for the extended-Ludwik equation are continuous with the values from a lower temperature regime obtained earlier, while the parameters for the creep-law equation are comparable with those obtained on other 7XXX aluminum alloys. We observed a change in fracture mode at 450 °C; from ductile transgranular to intergranular. This temperature coincides with the discontinuity point of the temperature-ductility slope. On the fracture surface of a sample that was deformed at 465 °C with a strain rate of 0.0005 s -1 , we observed features characteristic of micro-superplasticity. Considering the test conditions, viscous flows of incipient melt or liquid-like substances are suggested to be responsible for the formation of this feature.2 Keywords: AA7050, near-solidus temperature, tensile mechanical behavior, constitutive parameters, fracture surface analysis.

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“…If minimal values have to be taken into account, the inverse formulation can be applied:f(x)=1δexp()−x−μδexp[]−exp−x−μδ, with f(x) being the probability density function, its course is defined by the distribution parameters μ and δ, also called location and scale parameters. Tiryakioglu proposed a methodology to link the finite fatigue life with the cumulative distribution function of crack-initiating defect sizes [16,17]. By invoking the Paris–Erdoǵan law for stable crack growth, a proper relationship between the probability of failure Pf and micropore size distribution can be established—see Equation (2) [18]:Pf=1−exp{}−expμδ−2δπNf−NiB·σa−m22−m.…”

Section: Introductionmentioning

confidence: 99%

Modification of a Defect-Based Fatigue Assessment Model for Al-Si-Cu Cast Alloys

et al. 2018

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Cast parts usually inherit internal defects such as micro shrinkage pores due to the manufacturing process. In order to assess the fatigue behaviour in both finite-life and long-life fatigue regions, this paper scientifically contributes towards a defect-based fatigue design model. Extensive fatigue and fracture mechanical tests were conducted whereby the crack initiating defect size population was fractographically evaluated. Complementary in situ X-ray computed tomography scans before and during fatigue testing enabled an experimental estimation of the lifetime until crack initiation, acting as a significant input for the fatigue model. A commonly applied fatigue assessment approach introduced by Tiryakioglu was modified by incorporating the long crack threshold value, which additionally enabled the assessment of the fatigue strength in the long-life fatigue regime. The presented design concept was validated utilising the fatigue test results, which revealed a sound agreement between the experiments and the model. Only a minor deviation of up to about five percent in case of long-life fatigue strength and up to about 9% in case of finite-lifetime were determined. Thus, the provided extension of Tiryakioglu’s approach supports a unified fatigue strength assessment of cast aluminium alloys in both the finite- and long-life regimes.

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On the relationship between statistical distributions of defect size and fatigue life in 7050-T7451 thick plate and A356-T6 castings

Cited by 32 publications

References 47 publications

A review of equivalent pre‐crack sizes in aluminium alloy 7050‐T7451

A review of equivalent pre‐crack sizes in aluminium alloy 7050‐T7451

Tensile mechanical properties, constitutive parameters and fracture characteristics of an as-cast AA7050 alloy in the near-solidus temperature regime

Modification of a Defect-Based Fatigue Assessment Model for Al-Si-Cu Cast Alloys

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