IAEA Coordinated Research Project on Master Curve Approach to Monitor Fracture Toughness of Reactor Pressure Vessel Steels: Effect of Loading Rate

In the final evaluation for the application of the Master Curve in the IAEA Coordinated Research Project Phase 5 (CRP-5), one of the areas which was identified as needing further work concerning the effects of loading rate on the reference temperature To up to impact loading conditions. This subject represents one of the three topic areas within the current CRP-8.
The effect of loading rate can be broken down into two distinct aspects: 1) the effect of loading rate on the determined Master Curve To values for loading rates within the loading rate range specified in ASTM E1921-05 for quasi-static loading, and; 2) the effect of loading rate on determined Master Curve To values for higher loading rates including impact conditions using instrumented precracked Charpy (PCC) specimens. The new CRP includes both aspects, but primarily focuses on the second element of loading rate effects, i.e. loading rate ranges beyond the upper limit of the E1921-05 standard (2 MPam/s). These issues are investigated within the topic area#2 Loading Rate Effects – Impact Loading.
The mandatory portion of this topic area required participation in a round-robin exercise to validate the application of the Master Curve approach to PCC specimens tested in the ductile-to-brittle transition region using an instrumented pendulum (10 tests per participant on the JRQ material). The current status of the round-robin is presented in the paper PVP2007-26087.
The non-mandatory portion of the topic area consists in providing Master Curve data obtained at different loading rates on various RPV steels, in order to assess the loading rate dependence of To and compare it with an empirical model proposed by Wallin. Moreover, additional topics will be addressed, such as:

• comparison of results from unloading compliance and monotonic loading in the quasi-static range;
• estimation of fracture toughness from Charpy V-notch data;
• assessment of crack arrest properties from instrumented Charpy results;
• effect of irradiation on the relationship between static and dynamic fracture toughness.