A SWT Fatigue Mean Stress Model for A356-T6 Cast Aluminum Alloy

Cordes, Thomas S.; Berns, Hans; Lingenfelser, D. J.; Mahoney, Brandon; Testin, R. A.

doi:10.4271/881703

Cited by 3 publications

(7 citation statements)

References 5 publications

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“…Here, f is a multiplier on b to represent eutectic strain intensification in the LCF regime. We note that the threshold for b shifts downward with an increase of the R-ratio, evidently in a manner very similar to that described by the Smith-Watson-Topper (SWT) parameter [3]. An increase of the applied peak stress due to an overload drops the threshold level for local microplasticity associated with preexisting debonds.…”

Section: Multiple Regimes Of Fatigue Crack Development and Growthmentioning

confidence: 61%

“…The predictions are very similar to the correlation offered by the SWT parameter (product of the maximum stress and cyclic strain range) applied in strain-life relations. [3] found that the SWT parameter appeared to correlate mean stress effects within the context of a strain-life algorithm relatively well for A356-T6; the SWT parameter is known to describe normal stress-dominated early growth of fatigue cracks in alloys (cf. [22,30]).…”

Section: Stress-strain Behaviormentioning

confidence: 99%

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Microstructure-based fatigue modeling of cast A356-T6 alloy

McDowell

Gall

Horstemeyer

et al. 2003

Engineering Fracture Mechanics

328

207

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High cycle fatigue (HCF) life in cast Al-Mg-Si alloys is particularly sensitive to the combination of microstructural inclusions and stress concentrations. Inclusions can range from large-scale shrinkage porosity with a tortuous surface profile to entrapped oxides introduced during the pour. When shrinkage porosity is controlled, the relevant microstructural initiation sites are often the larger Si particles within eutectic regions. In this paper, a HCF model is introduced which recognizes multiple inclusion severity scales for crack formation. The model addresses the role of constrained microplasticity around debonded particles or shrinkage pores in forming and growing microstructurally small fatigue cracks and is based on the cyclic crack tip displacement rather than linear elastic fracture mechanics stress intensity factor. Conditions for transitioning to long crack fatigue crack growth behavior are introduced. The model is applied to a cast A356-T6 Al alloy over a range of inclusion severities.

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Section: Multiple Regimes Of Fatigue Crack Development and Growthmentioning

confidence: 61%

Section: Stress-strain Behaviormentioning

confidence: 99%

Microstructure-based fatigue modeling of cast A356-T6 alloy

McDowell

Gall

Horstemeyer

et al. 2003

Engineering Fracture Mechanics

328

207

View full text Add to dashboard Cite

show abstract

“…These tests were conducted under uniaxial tension-compression without torsion included. Cordes et al (1988) provided some data for a cast A356 aluminum alloy and showed that the Smith-WatsonTopper (1970) approximates the results fairly well. In the long life regime, the Cordes et al (1988) model gives unconservative estimations of the fatigue life.…”

Section: Mean Stress Effectsmentioning

confidence: 99%

“…Cordes et al (1988) provided some data for a cast A356 aluminum alloy and showed that the Smith-WatsonTopper (1970) approximates the results fairly well. In the long life regime, the Cordes et al (1988) model gives unconservative estimations of the fatigue life. The data in the study as well as that from Cordes et al (1988) was used for the development of the microstructure-property fatigue model discussed in Chapter 2 of this report.…”

Section: Mean Stress Effectsmentioning

confidence: 99%

“…The application of LEFM is also appealing, especially in the HCF regime, because the behavior of the cast material appears to be that of a brittle material, with propagation nominally mode-I dominated. Cordes et al (1988) found that the Smith-WatsonTopper (SWT) parameter (product of the maximum stress and cyclic strain range) appeared to correlate mean stress effects within the context of a strain-life algorithm relatively well for A356-T6; the SWT parameter is well-known to describe normal stress-dominated early growth of fatigue cracks in alloys (cf. Socie, 1993;McDowell, 1996a).…”

Section: Mechanisms Of Fatigue Of Casting Alloysmentioning

confidence: 99%

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Microstructure-Property Relations in Fatigue of a Cast A356-T6 Aluminum Alloy

Horstemeyer¹

2001

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The work in this report was a five year effort to foster fundamental advances in microstructureproperty fatigue relations of a cast A356-T6 aluminum alloy. We identified and quantified microstructure-property relations and then developed a mathematical tool for fatigue analysis of a cast A356-T6 aluminum alloy that is used in automotive structural components. We focused on three main areas of research: a wide variety of cyclic experiments in which specimens were examined with scanning electron microscopic imaging, finite element micromechanical modeling, and the development of a macroscale microstructure-property model for fatigue. Collaborations with Lawrence Livermore National Laboratory (LLNL) and Oak Ridge National Laboratory (ORNL) were important to this work. LLNL provided quantitative data for casting pore size, distribution, volume fraction, and nearest neighbor distance using nondestructive methods. ORNL performed solidification modeling of the casting process and provided insight into the silicon particle size, distribution, and volume fraction; the pore size, distribution, volume fraction, and nearest neighbor distance; and the dendrite cell size. EXECUTIVE SUMMARYThe work in this report, performed by Sandia National Laboratories (SNL) in collaboration with Georgia Institute of Technology, was a five year effort to foster fundamental advances in microstructure-property fatigue relations of a cast A356-T6 aluminum alloy. The goal was to identify and quantify microstructure-property relations and then develop mathematical tools for fatigue analysis of a cast A356-T6 aluminum alloy that is used in automotive structural components. This comprehensive experimental-computational fatigue study was conducted in parallel with developing microstructure-property relations for monotonic loading conditions, covered in a companion report (Microstructure-Property Relations for a Cast A356 Aluminum Alloy). We focused on three main areas of research: a wide variety of cyclic experiments in which specimens were examined with scanning electron microscopic imaging, finite element micromechanical modeling, and the development of a macroscale microstructure-property model for fatigue. Collaborations with Lawrence Livermore National Laboratory (LLNL) and Oak Ridge National Laboratory (ORNL) were important to this work. LLNL provided quantitative data for casting pore size, distribution, volume fraction, and nearest neighbor distance using nondestructive methods. ORNL performed solidification modeling of the casting process and provided insight into the silicon particle size, distribution, and volume fraction; the pore size, distribution, volume fraction, and nearest neighbor distance; and the dendrite cell size.The mechanical, physical, and casting properties of this A356 aluminum alloy make it attractive for use in cheaper and lighter engineering components. However, to successfully use cast A356 in long life components, it is necessary to understand its resistance to fatigue. The standard method in determining fa...

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Case Study: A Microstructure–Property Multistage Fatigue (MSF) Analysis of a Cadillac Control Arm

Horstemeyer¹

2012

Integrated Computational Materials Engineering (ICME) for Metals

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A SWT Fatigue Mean Stress Model for A356-T6 Cast Aluminum Alloy

Cited by 3 publications

References 5 publications

Microstructure-based fatigue modeling of cast A356-T6 alloy

Microstructure-based fatigue modeling of cast A356-T6 alloy

Microstructure-Property Relations in Fatigue of a Cast A356-T6 Aluminum Alloy

Case Study: A Microstructure–Property Multistage Fatigue (MSF) Analysis of a Cadillac Control Arm

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