PREDICTION OF THE FIRST SPINNING CYLINDER TEST USING CONTINUUM DAMAGEMECHANICS

For many years large-scale experiments have been performed world-wide to validate aspects of fracture mechanics methodology. Special emphasi s has been given to correlations between small- and large-scale specim en behaviour in quantifying the structural behaviour of pressure vesse ls, piping and closures. Within this context, the first three spinning cylinder tests, performed by AEA Technology at its Risley Laboratory, addressed the phenomenon of stable crack growth by ductile tearing in contained yield and conditions simulating pressurized thermal shock l oading in a PWR reactor pressure vessel. A notable feature of the test data was that the effective resistance to crack growth, as measured i n terms of the J R-curve, was appreciably greater than that anticipate d from small-scale testing, both at initiation and after small amounts (a few millimetres) of tearing. In the present paper, two independent finite element analyses of the first-spinning cylinder test (SC 1) ar e presented and compared. Both involved application of the Rousselier ductile damage theory in an attempt to understand better the transfera bility of test data from small specimens to structural validation test s. In each instance, the parameters associated with the theory's const itutive equation were calibrated in terms of data from notched-tensile and (or) fracture mechanics tests, metallographic observations and (o r) chemical composition. The evolution of ductile damage local to the crack tip during SC 1 was thereby calculated and, together with a crac k growth criterion based on the maximisation of opening-mode stress, u sed as the basis for predicting cylinder R-curves (angular velocity vs . Delta a, J integral vs. Delta a). Except in the initiation region, t he results show the Rousselier model to be capable of predicting corre ctly the enhancement of tearing toughness of the cylinder relative to that of conventional test specimens, given an appropriate choice of fi nite element cell size in the region representing the crack tip. As su ch, they represent a positive step towards achieving the goal to estab lish continuum damage mechanics as a reliable predictive engineering t ool.