13th International Conference on Fracture June 16–21, 2013, Beijing, China -14- Rice-Tracey failure criteria ( )= 1 2 + 3 Hydrostatic Stress failure criteria ( )= 4 Power function ( )= 5 Initial values of 0, 1 and 2 were determined from acquired four points in Fig. 36. The final values of 0, 1 and 2 were determined by minimizing residue defined by Eq. (8). =( −1) 2 +( −1) 2 +( −1) 2 (8) Where , , respectively stand for damage indicator in shear, notch tension and punch. Table 3 summarizes initial values and final values of coefficients 0, 1 and 2. Table 4 gives values of each coefficient after optimization. Fig. 37 plots the two failure locus respectively from average stress triaxiality and from damage evolution rule. From these two comparative curves, failure strains under shear and uniaxial tension are increased after modification with optimization method. Table 3. Initial values and final values of coefficients 0, 1 and 2 0 1 2 initial values 1.12 -1.97 3.04 final values 1.22 -2.05 2.96 Table 4. Coefficients after optimization 0.0019 1.0192 1.0083 0.9614 Figure 37. Failure locus from average stress triaxiality and from damage evolution rule 8.2. Failure locus under dynamic loading 0.0 0.2 0.4 0.6 0.8 0.6 0.8 1.0 1.2 1.4 1.6 average stress triaxiality optimized result based on damage evolution Equivalent plastic failure strain Stress triaxiality
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