Method of predicting crack initiation based fatigue life
AssigneeFord Global Technologies, LLC
InventorsChu Chin-Chan, Angela Hubner
Life of this patent
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Abstract
A method of predicting crack initiation based fatigue life includes the steps of plotting the elastic finite element stress states of a stress history for a given component at a predetermined critical location in the stress space and determining the least square fit ellipsoid of the stress states by a straight line through the center of gravity. An aspect ratio .lambda..sub.2 /.lambda..sub.1 is defined where .lambda..sub.1 and .lambda..sub.2 are the two largest eigen values of the eigen system of matrix M which defines the least square fit ellipsoid and where .lambda..sub.1 .gtoreq..lambda..sub.2. A multiaxial fatigue analysis is performed where the aspect ratio exceeds a predetermined value.
Claims14
A method of predicting crack initiation based fatigue life, said method including the steps of:
- plotting elastic finite element stress states of a stress history for a given component at a predetermined location in a stress space;
- determining a least square fit ellipsoid of the stress states by a straight line through a center of gravity;
- defining an aspect ratio .lambda..sub.2 /.lambda..sub.1, where .lambda..sub.1 and .lambda..sub.2 are the two largest eigen values of an eigen system of matrix M which defines the least square fit ellipsoid and where .lambda..sub.1 .gtoreq..lambda..sub.2 ;
- and
- performing a multiaxial fatigue analysis where the aspect ratio .lambda..sub.2 /.lambda..sub.1 exceeds a predetermined value.
A method of predicting crack initiation based fatigue life, said method including the steps of:
- plotting elastic finite element stress states of a stress history for a given component at a predetermined location in a stress space;
- determining a least square fit ellipsoid of the stress states by a straight line through a center of gravity;
- defining an aspect ratio .lambda..sub.2 /.lambda..sub.1, where .lambda..sub.1 and .lambda..sub.2 are the two largest eigen values of an eigen system of matrix M which defines the least square fit ellipsoid and where .lambda..sub.1 .gtoreq..lambda..sub.2 ;
- and
- performing a uniaxial fatigue analysis where the aspect ratio is less than a predetermined value.
Dependencies are inferred from the claim text.