The influence of cold work on the J resistance curve behaviour of a BS1500 steel

The irradiation of reactor pressure vessel (RPV) materials is known to produce a reduction in ductility, upper shelf Charpy energy and fracture toughness together with an increase in tensile yield and ultimate tensile strength. These changes in properties are believed to arise primarily from material hardening due to the formation of lattice defects which impede dislocation movement but may also be associated with copper precipitation. During plant operation important mechanical properties are monitored, primarily, by testing surveillance specimens placed in the RPV during commissioning. However, only a limited amount of surveillance material is usually available, mostly in the form of Charpy specimens. Once the specimens have been tested the fractured halves are available for further investigations. A good deal of work has been performed on extracting further useful data from fractured Charpy specimens including, for example, tests on sub-sized Charpy specimens, reconstituted specimens and punch test specimens. In addition to these direct measurements, modelling irradiation behaviour also plays an important role in establishing material properties. This may take the form of numerical modelling, for example, by finite element analysis methods or by simulation of irradiation effects. Cold work is one candidate method for simulation of these effects since it is known to increase the strength of ferrous materials, and reduce the ductility and fracture toughness in an analogous way to the influence of radiation behaviour. The programme of work reported here, funded by NSD, has examined the influence of cold work on the J integral resistance curve behaviour of a plate material of similar composition to that used in Magnox reactor pressure vessels. The long term aim of the work is to establish whether cold work could be used as a surrogate for irradiation in materials characterisationSIGLEAvailable from British Library Document Supply Centre-DSC:4274.85355(01/08) / BLDSC - British Library Document Supply CentreGBUnited Kingdo