Predicting reference temperature from instrumented Charpy V-notch impact tests using modified Schindler procedure for computing dynamic fracture toughness

Abstract

Reactor pressure vessel (RPV) steels are increasingly being characterised in terms of the reference temperature T 0 and the associated Master Curve (MC) Procedure, following the ASTM E-1921 standard. Though correlations have been proposed to predict the T 0 from Charpy transition temperature T 28J or instrumented impact test parameters like T 4kN, none can be taken as a universal correlation. Here we are proposing a new correlation of T 0 with T 0Sch dy, where T 0Sch dy is the reference temperature corresponding to a median K Id=100 MPa√m evaluated by the ASTM E1921 procedure applied to K Id vs T data, and K Id has been calculated from instrumented CVN impact test data using modified Schindler relations. This will provide a reliable method for determining T 0 from instrumented CVN tests alone. T 0Sch dy provides a conservative alternative to T 0 dy for application of the ASTM E 1921 MC procedure in dynamic situations. Since the above procedure depends only on instrumented CVN data, it will be less costly to apply (no precracking is necessary) and will also obviate the difficulties associated with determining T 0 dy from precracked CVN testing (because of severe size limitations, associated scatter and signal oscillations from the mechanics of the test, there needs to be precise control over test temperatures and test velocity for obtaining valid data from limited number of specimens). The RT NDT(est) from the suggested procedure (or its modifications based on future work) will provide an acceptable alternative to RT NDT for application of the ASME K IR curve based on instrumented CVN tests alone. For low-uppershelf steels, the new reference temperature estimate T 0.075 and its correlation to T 0Sch dy will provide a methodology for application of MCs to such steels. Further comprehensive work is needed to validate the procedures and correlations suggested in this paper.