Application of damage models to the ductile-brittle transition region of Reactor steels

摘要

Two German ferritic pressure vessel steels (JFL,JQR) are examined in the brittle to ductile transition regime as function of temperature and irradiation.The experiments are done by a miniaturized Small-Punch-Test (SPT) in hot cells within the temperature range of -185oC up to 70oC.From the load-displacement curve of the SPT,the yield curves and parameters of both a non-local GURSON-TVERGAARD-NEEDLEMAN ductile damage model and the BEREMIN-model are identified.The influence of temperature and irradiation on the determined model parameters is analyzed.All parameters are verified by comparison with results from standard test methods.The parameters,identified from SPT,are used to simulate the failure behaviour in standard fracture mechanics specimens.In the upper shelf,the non-local GTN-model is applied to simulate J-Δa-resistance curves,from where the fracture toughness data JIc could be successfully predicted.In the lower shelf,the WEIBULL-stress of the specimens was computed to find out the statistics of KIc - values.Finally,a modified BEREMIN-model and the non-local GTN-model were combined to evaluate the failure of fracture specimens in the brittle-ductile transition region.This way,an acceptable agreement with Master-curve data for non-irradiated steels could be achieved over the whole temperature range.