METHODOLOGIES FOR PREDICTING J-INTEGRALS UNDER LARGE PLASTIC-DEFORMATION .1. FURTHER DEVELOPMENTS FOR TENSION LOADING

Based on the results of a parametric finite element study on single ed ge notch specimens with shallow crack geometries (0.05 less than or eq ual to a/W less than or equal to 0.01) under large plastic deformation , a revised J-estimation method is presented. The revised scheme focus ed on material laws which can be approximated by a power law represent ation. the scheme uses the format of an existing method which adopts T urner's EnJ tripartite approach of J-estimation: Linear Elastic Fractu re Mechanics, Net Section Yield and Gross Section Yield. The for of th e J vs strain relationship in the gross section yield region was deriv ed from a consideration of the HRR strain field equation, the EPRI pla stic J equation and the definition of J in terms of the energy release rate. Comparison with finite element results shows that the revised s cheme generally provides safe predictions of the crack driving paramet er. For low to medium work hardening materials (power law exponent n g reater than or equal to 5), the accuracy of prediction is within about 5%. The scheme has also been shown to be equally applicable to centre cracked panels with short cracks.