Methodologies for predicting [formula omitted] under large plastic deformation—I. further developments for tension loading

Abstract

Based on the results of a parametric finite element study on single edge notch specimens with shallow crack geometries ( 0.05 ⩽ a/W ⩽ 0.1) under large plastic deformation, a revised J- estimation method is presented. The revised scheme focused on material laws which can be approximated by a power law representation. The scheme uses the format of an existing method which adopts Turner's En J tripartite approach of J- estimation : Linear Elastic Fracture Mechanics, Net Section Yield and Gross Section Yield. The form of the J vs strain relationship in the gross section yield region was derived from a consideration of the HRR strain field equation, the EPRI plastic J equation and the definition of J in terms of the energy release rate. Comparison with finite element results shows that the revised scheme generally provides safe predictions of the crack driving parameter. For low to medium work hardening materials (power law exponent n ⩾ 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.