IDENTIFICATION OF GURSON MATERIAL CONSTANTS BY USING KALMAN FILTER

A new approach based on the inverse analysis is proposed for estimatin g material parameters of nonlinear constitutive equations. Using the m easurable response of experimental specimens, an inverse analysis is c arried out to predict most suitable values of unknown material constan ts. In general, the accuracy of prediction depends on geometries of sp ecimens and types of measurements. In order to identify optimal experi mental procedure, the Kalman filter technique is employed. We have cho sen the Gurson model for porous elastic-plastic materials as the mater ial model and its two parameters as the unknown constants. Gurson's co nstitutive model has been widely used for studying ductile fracture as well as shear localization of various metals. Detailed finite element simulations are performed to demonstrate the effectiveness of the pro posed method in determination of the two parameters relating to void n ucleation. In the Kalman filter procedure, it is found that the rate o f convergence to the correct solutions depends on shapes of test speci mens, initial estimates of the unknown parameters, and accuracy of mea sured data as well as computed reference data. Our analysis predicts t hat when two differently shaped specimens under tension are used (i.e. , a plate with a center hole and another with double side notches), a significant improvement occurs in the rate of convergence.