Developments in Local Approach methodology with application to the analysis/re-analysis of the NESC-1 PTS benchmark experiment

Local Approach methods have received considerable attention in recent years as a complementary approach to structural integrity assessment. These appr oaches are based on the application of micro-mechanistic models of failure in which the stress, strain and 'damage' local to the crack-tip are related to the critical conditions required to initiate/propagate fracture. The mo dels are calibrated in terms of material parameters that are deemed fully t ransferable and derived using a combination of reference test data and supp orting stress analysis. Once calibrated, using small-scale test data, the m odels are assumed independent on geometry and loading configuration. For a given failure mechanism, the model parameters may be used in the assessment of a structure fabricated from the same material (for appropriate temperat ures, loading rates, etc). The paper describes the work initially undertaken in relation to the NESC-1 (Network for Evaluating Steel Components) spinning cylinder test, in order to validate the application of Local Approach methods for the case of PTS loading. The predicted amount of pre-cleavage ductile tearing and the timin g of the subsequent cleavage event are compared with the observed fracture behaviour of the defect. The paper then highlights several areas in which Local Approach methodology has been developed since the initial work on PTS. These include: . Calibration of the cleavage model across a range of temperatures and cons traint states. . Treatment of 3D defects. . Reference to hydrostatic stress in cleavage fracture predictions. . Simplification and standardisation of analytical techniques for more rout ine use in integrity assessments. The paper concludes that results from large-scale structural experiments, s uch as the NESC-1 spinning cylinder test, will be of lasting value in valid ating developments in Local Approach methodology and other advanced methods of fracture assessment. This is particularly true in the authors' current work that seeks to achieve an overall simplification in methodology, withou t sacrificing predictive accuracy. (C) 2001 Elsevier Science Ltd. All right s reserved.