Fatigue of 8630 cast steel in the presence of porosity

Sigl, K.M.; Hardin, Richard A.; Stephens, Robert J.; Beckermann, C.

doi:10.1179/136404604225020588

Cited by 42 publications

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References 8 publications

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“…[3,14] Because the largest possible nonpropagating crack can be predicted for a given material and an alternating stress field using fracture mechanics, it can be used in damage-tolerant design life prediction in castings. [15][16][17] The effects of porosity on the fatigue behavior of cast metals have been measured in steels, [18][19][20][21][22][23][24] in cast irons, [16,17,25,26] and in aluminum alloys. [27][28][29][30][31][32][33][34][35][36] Also, Murakami [37] gives a good overview of the effects of small defects and inclusions on metal fatigue.…”

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confidence: 99%

“…[18][19][20][21][22][23][24]26,[31][32][33] Applying a strain-life model alone assumes that crack nucleation encompasses the majority of the life of the component and that the time for fatigue crack propagation to fracture is insignificant relative to crack initiation. The use of strain-life models requires that pore geometry information, primarily the minimum notch radius and the major axes of the ellipsoidal notch, be known or be determined from fracture surfaces, to determine a stress concentration factor.…”

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confidence: 99%

“…[33] For the second stage of component life, fatigue life estimation of cast metals by fracture mechanics approaches are used: for nodular cast iron, [16,17,25,26] cast aluminum alloys, [27,[32][33][34][35][36]38] and steel alloys. [15,19,20,23] One difficulty in applying fracture mechanics concepts to cast parts is determining the final, or failure, crack length. For example, failure of components has been assumed when the remaining net section area stress is at or is greater than the yield strength [19] and when the crack depth propagates to the section wall thickness at the defect location.…”

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confidence: 99%

“…[15,19,20,23] One difficulty in applying fracture mechanics concepts to cast parts is determining the final, or failure, crack length. For example, failure of components has been assumed when the remaining net section area stress is at or is greater than the yield strength [19] and when the crack depth propagates to the section wall thickness at the defect location. [15] A comparison between the measured fatigue life of cast steel test specimens containing porosity and inclusions and the fatigue life obtained by modeling the specimen using crack initiation (local stain-life concepts) and LEFM approaches has been presented.…”

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confidence: 99%

“…The current authors have found that local strain-life modeling of porosity as a notch gave better agreement with measurements than did LEFM in cast 8630 steel. [19] In the present study, a simulation method is developed to predict the measured fatigue lives of 25 cast steel specimens containing up to 21 pct shrinkage porosity over the gage length. This is a challenging task, not only because the measured fatigue lives of the specimens are much below the values corresponding to sound steel, but also because the measured lives vary by more than four orders of magnitude at the same applied stress amplitude.…”

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Prediction of the Fatigue Life of Cast Steel Containing Shrinkage Porosity

Hardin

Beckermann

2009

Metall Mater Trans A

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A simulation methodology for predicting the fatigue life of cast steel components with shrinkage porosity is developed and validated through comparison with previously performed measurements. A X-ray tomography technique is used to reconstruct the porosity distribution in 25 test specimens with average porosities ranging from 8 to 21 pct. The porosity field is imported into finite element analysis (FEA) software to determine the complex stress field resulting from the porosity. In the stress simulation, the elastic mechanical properties are made a function of the local porosity volume fraction. A multiaxial strain-life simulation is then performed to determine the fatigue life. An adaptive subgrid model is developed to reduce the dependence of the fatigue life predictions on the numerical mesh chosen and to account for the effects of porosity that is too small to be resolved in the simulations. The subgrid model employs a spatially variable fatigue notch factor that is dependent on the local pore radius relative to the finite element node spacing. A probabilistic pore size distribution model is used to estimate the radius of the largest pore as a function of the local pore volume fraction. It is found that, with the adaptive subgrid model and the addition of a uniform background microporosity field with a maximum pore radius of 100 lm, the measured and predicted fatigue lives for nearly all 25 test specimens fall within one decade. Because the fatigue lives of the specimens vary by more than four orders of magnitude for the same nominal stress amplitude and for similar average porosity fractions, the results demonstrate the importance of taking into account in the simulations the distribution of the porosity in the specimens.

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Prediction of the Fatigue Life of Cast Steel Containing Shrinkage Porosity

Hardin

Beckermann

2009

Metall Mater Trans A

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Effect of Porosity on Deformation, Damage, and Fracture of Cast Steel

Hardin¹,

Beckermann²

2012

Supplemental Proceedings

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A combined experimental and computational study is performed to investigate the effect of internal shrinkage porosity on the mechanical behavior of cast steel under static loading. Steel plates containing various levels of porosity are cast in a sand mold, machined, and tensile tested until fracture. A significant loss of ductility is observed. Radiographic imaging is used to reconstruct the porosity field in the test specimens. The measured porosity field is then used in a finite-element stress analysis of the tensile tests. The local elastic properties are reduced according to the porosity fraction present and porous metal plasticity theory is used to model the damage due to porosity. Good agreement between measured and predicted stress-strain curves is obtained. The computational model proposed in this study allows for a detailed evaluation of the effect of porosity, including its size, shape and location, on the mechanical performance of a steel casting.

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Study of Pd–Ag dental alloys: examination of effect of casting porosity on fatigue behavior and microstructural analysis

Baba

Brantley

et al. 2010

J Mater Sci: Mater Med

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The goals of this study were to investigate the fatigue limits of two Pd-Ag alloys (Ivoclar Vivadent) with differing mechanical properties and varying proportions of secondary alloying elements, examine the effect of casting porosity on fatigue behavior, and determine the effect of casting size on microstructures and Vickers hardness. The alloys selected were: IPS d.SIGN 59 (59.2Pd-27.9Ag-8.2Sn-2.7In-1.3Zn); and IS 64 (59.9Pd-26.0Ag-7.0Sn-2.8Au-1.8 Ga-1.5In-1.0Pt). Tension test bars, heat-treated to simulate dental porcelain application, were subjected to cyclic loading at 10 Hz, with R-ratio of -1 for amplitudes of compressive and tensile stress. Two replicate specimens were tested at each stress amplitude. Fracture surfaces were examined with a scanning electron microscope (SEM). Sectioned fatigue specimens and additional cast specimens simulating copings for a maxillary central incisor restoration were also examined with the SEM, and Vickers hardness was measured using 1 kg load. Casting porosity was evaluated in sectioned fatigue fracture specimens, using an image analysis program. The fatigue limit (2 × 10(6) loading cycles) of IS 64 was approximately 0.20 of its 0.2% yield strength, while the fatigue limit of d.SIGN 59 was approximately 0.25 of its 0.2% yield strength. These relatively low ratios of fatigue limit to 0.2% yield strength are similar to those found previously for high-palladium dental alloys, and are attributed to their complex microstructures and casting porosity. Complex fatigue fracture surfaces with striations were observed for both alloys. Substantial further decrease in the number of cycles for fatigue failure only occurred when the pore size and volume percentage became excessive. While the heat-treated alloys had equiaxed grains with precipitates, the microstructural homogenization resulting from simulated porcelain firing differed considerably for the coping and fatigue test specimens; the latter specimens had significantly higher values of Vickers hardness.

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Fatigue of 8630 cast steel in the presence of porosity

Cited by 42 publications

References 8 publications

Prediction of the Fatigue Life of Cast Steel Containing Shrinkage Porosity

Prediction of the Fatigue Life of Cast Steel Containing Shrinkage Porosity

Effect of Porosity on Deformation, Damage, and Fracture of Cast Steel

Study of Pd–Ag dental alloys: examination of effect of casting porosity on fatigue behavior and microstructural analysis

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