Identification of Equivalent Damage Growth Parameters for General Crack Geometry

Alexandra Coppe, Matthew J. Pais, Nam-Ho Kim, and Raphael T. Haftka
Submission Type: 
Full Paper
Supporting Agencies (optional): 
NASA and Air Force
AttachmentSizeTimestamp
phmc_10_061.pdf353.73 KBOctober 3, 2010 - 6:16am

Analytical damage growth equations, such as Paris law, need the stress intensity factor for predicting damage growth. Analytical expressions for the stress intensity factor are limited to simplified crack location, geometries and loading conditions. Therefore, actual damage growth requires numerical solution, such as by finite elements. However, for estimating the uncertainty in remaining useful life (RUL), thousands of simulations of crack growth must be undertaken, which is computationally expensive. Here, we estimate the error associated with RUL estimation based on an analytical stress intensity factor that does not consider the effects caused by boundary, crack location, geometry, or loading conditions. Effective damage parameters are then identified which, although different from the true values, result in the correct damage growth prediction. Damage growth is simulated using the extended finite element method (XFEM) to consider the effects of crack location and geometries. The XFEM data are then contaminated with noise to simulate measurements. The damage growth parameter are then identified using least square filtered Bayesian method (LSFB). The identified parameter can then be used with the model to estimate the (RUL at a given inspection. Examples considered include a center and edge cracks in a plate which experiences both horizontal and vertical finite effects and crack growth in the presence of a plate with holes.

Publication Control Number: 
061
Submission Keywords: 
prognosis
Fracture Mechanics
extended finite element method
parameter identification
Bayesian inference
least square
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