Methods and systems to predict fatigue life in aluminum castings

Abstract

The invention relates to methods and systems to predict fatigue life in aluminum castings. Methods and systems of predicting fatigue life in aluminum castings that combines extreme values of both casting flaws and microstructures with multiscale life models. The multiscale life models account for differing fatigue crack initiation based on the size scale of the defect and microstructure features,including provisions for generally millimeter scale casting flaws, generally micrometer scale second phase particles by cracking or debonding, or submicrometer scale dislocation interactions with precipitates which form persistent slip bands. In the presence of casting flaws, the fatigue initiation life is negligible and the total fatigue life is spent in propagation of a fatigue crack from such flaws. In the absence of casting flaws, however, the total fatigue life is spent in both crack initiation and propagation, except for the case where fatigue cracks initiate from large second phase particles in a coarse microstructure. The extreme values of casting flaws, second phase particles, mean free path through an aluminum matrix or grain sizes are obtained from extreme value statistics whentwo or three dimensional sizes of casting flaws and microstructure features are provided by either direct measurement or analytical prediction. The upper bound flaw or microstructure feature size is calculated by extreme value statistics.

Description

technical field [0001] The present invention relates generally to methods and systems for predicting the fatigue life of aluminum castings, and more particularly to predicting cast aluminum products by combining extreme value statistics and multi-scale fatigue life models with compositional types, sizes and shapes of casting defects and microstructures fatigue life. Background technique [0002] Improving fuel efficiency is an important goal in automotive design. One way to help achieve this goal is to use lightweight materials in the construction of vehicle component parts, including in the powertrain and its associated components. In addition to making such components lighter, it is also desirable to keep production costs low by utilizing casting and related scalable processes. For example, aluminum-based materials and associated casting methods can be used where heavy materials (typically steel or other iron-based alloys) were previously used. [0003] However, care mu...

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Problems solved by technology

[0005] The inventors have recognized that the lack of computational tools capable of incorporating statistical methods to account for different classes or scales of defect size limits the ability to accurately predict fatigue performance of castings

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