SEDL / STP / STP1372-EB / STP13439S

Use of Small Fatigue Crack Growth Analysis in Predicting the S-N Response of Cast Aluminum Alloys

Caton, MJ
Graduate Student and Professor, University of Michigan, Ann Arbor, MI

Jones, JW
Graduate Student and Professor, University of Michigan, Ann Arbor, MI

Allison, JE
Senior Staff Technical Specialist, Ford Motor Company Scientific Research Laboratories, MD 3182 SRL, Dearborn, MI

Pages: 19    Published: Jan 2000

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Abstract

The development of a material model to estimate the S-N response of a cast aluminum alloy is described. An important requirement of such a model is sensitivity to processing effects such as solidification time and subsequent material characteristics such as secondary dendrite arm spacing (SDAS), strength, and porosity. It has been speculated that the fatigue properties of aluminum castings are dominated by the propagation of cracks which initiate from microshrinkage pores ranging in size from ∼ 10 to 1000 μm. A model was developed that calculates fatigue life based on small crack growth rates measured in cast 319 aluminum specimens with two different solidification times. Results from this small crack model are compared with predictions from a traditional LEFM model using long-crack data and measured thresholds.