Application of √area-concept to assess fatigue strength of AlSi7Cu0.5Mg casted components

Garb, Christian; Leitner, Martin; Grün, Florian

doi:10.1016/j.engfracmech.2017.03.018

Cited by 25 publications

(12 citation statements)

References 9 publications

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“…To increase the applicable data a power-function like projection method for specimens failed in the finite life region is executed. This method is suitable to increase the data points in the run out region of N = 1×10 7 without significant falsification of the scatter band in the HCF region 1/T s , see [21].…”

Section: Fatigue Assessment Modelmentioning

confidence: 99%

“…Murakami proposed the exponent m of the defect size to possess a constant value of 3, which revealed sound results for preliminary studies [21]. Furthermore, Murakami estimated the material and defect location coefficient C 1 as 1.43 for surface and 1.56 for subsurface cracks and the material dependent parameter C 2 to possess a constant value of 120 by applying the least squares method [19].…”

Section: Introductionmentioning

confidence: 99%

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Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

Aigner

Garb

Leitner

et al. 2018

Metals

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This paper contributes to the effect of elevated temperature on the fatigue strength of common aluminum cast alloys EN AC-46200 and EN AC-45500. The examination covers both static as well as cyclic fatigue investigations to study the damage mechanism of the as-cast and post-heat-treated alloys. The investigated fracture surfaces suggest a change in crack origin at elevated temperature of 150 ∘ C. At room temperature, most fatigue tests reveal shrinkage-based micro pores as their crack initiation, whereas large slipping areas occur at elevated temperature. Finally, a modified a r e a -based fatigue strength model for elevated temperatures is proposed. The original a r e a model was developed by Murakami and uses the square root of the projected area of fatigue fracture-initiating defects to correlate with the fatigue strength at room temperature. The adopted concept reveals a proper fit for the fatigue assessment of cast Al-Si materials at elevated temperatures; in detail, the slope of the original model according to Murakami should be decreased at higher temperatures as the spatial extent of casting imperfections becomes less dominant at elevated temperatures. This goes along with the increased long crack threshold at higher operating temperature conditions.

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Section: Fatigue Assessment Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

Aigner

Garb

Leitner

et al. 2018

Metals

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“…The role of porosity in the fatigue properties has been assessed in traditional cast 21 and powder metallurgy 22 materials, which is based on specimen-level testing and fractography investigation post mortem. The sizes of pores that initiate fatigue cracks have been applied in a Murakami-type analysis, 23 where the defect strength is taken as the remote stress multiplied by a factor of the square root of the projected area of the pore onto the principal stress axis, 24,25 or a Kitagawa-Takahashi method, 26 which relates the fatigue crack growth threshold concept to the high-cycle fatigue (HCF) endurance limit. 25 These methods have been applied to AM materials, 15 although these approaches do not capture the complex interactions of the local microstructure surrounding the pore.…”

Section: Introductionmentioning

confidence: 99%

ICME Approach to Determining Critical Pore Size of IN718 Produced by Selective Laser Melting

Sangid

Ravi

Prithivirajan

et al. 2019

JOM

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A degree of porosity is expected in additively manufactured (AM) materials. To aid in the qualification of AM materials, the smallest pore size that results in a debit in the fatigue performance is quantified. In the work presented herein, crystal plasticity simulations are used to identify the stress concentration around pores of various sizes, revealing that a single 20-lm pore or two 10-lm pores (with centers spaced 15 lm apart) localize stress at the pore, as opposed to elsewhere in the microstructure. In situ microtomography and far-field high-energy x-ray diffraction microscopy were used to identify crack formation and the evolution of the grain-level micromechanical fields during cyclic loading. Eighteen cracks were observed (15 at pores, 3 at the surface) at highly stressed grains in a sample, although most did not propagate. The dominant crack was seen to originate from the free surface, which is rationalized by fracture mechanics.

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“…The defect size is evaluated as the projected flaw area perpendicular to the direction of the maximum principal normal stress [29]. On the one hand, preliminary studies [38] reveal a proper conformance with Murakami’s empirical approach, but the present model does not invoke the defect size distribution itself. As presented in preliminary studies [39,40,41,42], the statistical distribution of flaw sizes can be evaluated by non-destructive investigation of the defect population, such as X-ray computed tomography scanning.…”

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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Application of √area-concept to assess fatigue strength of AlSi7Cu0.5Mg casted components

Cited by 25 publications

References 9 publications

Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

ICME Approach to Determining Critical Pore Size of IN718 Produced by Selective Laser Melting

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

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