Prediction of the first spinning cylinder test using continuum damage mechanics

• Published in: Nuclear engineering and design 1994-11, Vol.152 (1), p.1-10
• Main Authors: Lidbury, D.P.G., Sherry, A.H., Bilby, B.A., Howard, I.C., Li, Z.H., Eripret, C.
• Format: Article
• Language: English
• Subjects: Q1; Structural analysis
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/0029-5493(94)90069-8

For many years large-scale experiments have been performed world-wide to validate aspects of fracture mechanics methodology. Special emphasis has been given to correlations between small- and large-scale specimen behaviour in quantifying the structural behaviour of pressure vessels, 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 loading in a PWR reactor pressure vessel. A notable feature of the test data was that the effective resistance to crack growth, as measured in terms of the J R-curve, was appreciably greater than that anticipated 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) are presented and compared. Both involved application of the Rousselier ductile damage theory in an attempt to understand better the transferability of test data from small specimens to structural validation tests. In each instance, the parameters associated with the theory's constitutive equation were calibrated in terms of data from notched-tensile and (or) fracture mechanics tests, metallographic observations and (or) chemical composition. The evolution of ductile damage local to the crack tip during SC 1 was thereby calculated and, together with a crack growth criterion based on the maximisation of opening-mode stress, used as the basis for predicting cylinder R-curves (angular velocity vs. Δa, J integral vs. Δa). Except in the initiation region, the results show the Rousselier model to be capable of predicting correctly the enhancement of tearing toughness of the cylinder relative to that of conventional test specimens, given an appropriate choice of finite element cell size in the region representing the crack tip. As such, they represent a positive step towards achieving the goal to establish continuum damage mechanics as a reliable predictive engineering tool.