Cumulative damage model for structural analysis of filed polymeric materials
AssigneeThe United States of America, Secretary of the Navy
InventorsGary L. Biggs, John J. Nestor, III
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Abstract
A method of predicting fatigue failure in a filled polymeric material is provided. The method involves the calculation of stress at the region of highest stress using an equation which includes as parameters, regression coefficients of the stress vs. modulus obtained from a finite element analysis. Once the regression coefficients are obtained, there is no further need to perform a finite element analysis. The calculated stresses are numerically integrated in a damage equation using a Monte Carlo method, using a cumulative model to estimate when failure will occur. The method has been tested in the case of temperature stress loading of a solid propellant rocket motor.
Claims21
A method for estimating damage to a filled polymeric material, comprising the steps of:
- building a finite element model of the polymeric material structure;
- identifying a high stress area of the polymeric material structure;
- determining an expected range of a relaxation modulus of the polymeric material expected for a load history for the structure;
- exercising the finite element model over discrete intervals for the expected relaxation modulus range;
- determining regression coefficients for a fit of stress versus relaxation modulus for the high stress area;
- determining the relaxation modulus history from the load history;
- determining a stress history from the load history using the determined regression coefficients and the relaxation modulus history;
- and
- numerically integrating a damage function using the determined stress history.
Dependencies are inferred from the claim text.