The assessment of residual stress effects on ductile tearing using continuum damage mechanics

This paper presents the results of a numerical study undertaken to assess the influence of residual stresses on the ductile tearing behaviour of a high strength, low toughness aluminium alloy. The Gurson-Tvergaard model [1, 2] was calibrated against conventional fracture toughness data using parameters relating to void nucleation, growth and coalescence. The calibrated model was used to predict the load versus ductile tearing behaviour of a series of full-scale and quarterscale wide-plate tests. These centre-cracked tension tests included specimens that contained a self-balancing residual stress field that was tensile in the region of the through-wall crack. Analyses of the full-scale wide-plate tests indicated that the model provides a good prediction of the load versus ductile tearing behaviour up to approximately 3 mm of stable tearing. The influence of residual stress on the load versus crack growth behaviour was accurately simulated. Predictions of the load versus crack growth behaviour of full-scale wide-plate tests for crack extensions greater than 3 mm, and of the quarter-scale tests, were low in terms of predicted load at a given amount of tearing. This was considered to result from: (i) the 'valid' calibration range in terms of specimen thickness and crack extension, (ii) the development of shear lips and (iii) differences in the micro-mechanism of ductile void formation under plane strain and under plane stress conditions. Copyright © 2005 by ASME.