The work was divided into four technical work packages. WP1 focuses on materials characterisation of ferritic and austenitic pipes, and dissimilar metal welds (DMW). The tearing resistance curves (J-R curves) were determined with compact tension (C(T)) and single-edge notched tension (SE(T)) specimens. The tensile properties were characterised with smooth round bar specimens and notched tension specimens. The pipes were tested in four-point bending with elliptical cracks on the outside of the pipe, and through wall cracks. The testing was mostly done in room temperature, but for one case the testing was carried out in 100 °C. The data was applied in WP3 for development of numerical models.
WP2 primarily focuses on modelling and measuring residual stresses. Thick and thin-walled (manufactured with low and high heat-input) narrow-gap gas tungsten arc-welds (GTAW) (AISI 316L), fully circumferential and 120° patch overlay welds, and thick walled thermally aged NG-GTAW were manufactured, and the residual stress profiles were measured with different techniques vital to minimize uncertainty. The FEM 2D and 3D residual stress predictions agreed with the experimental results. The austenitic pipe girth welds are important new benchmarks for RS simulation of engineering weldments. The austenitic pipe girth welds provide valuable new data for improving the RS profiles used in engineering structural integrity assessments. WP2 focused also on improving the assessment of residual stress profiles, assessing residual stresses in operation conditions and investigating the effect of residual stresses on fracture.
The objective of sub-WP 3.2 is to benchmark selected Local Approach (LA) models on WP 1 experimental data dealing with the transferability of ductile fracture toughness properties from a specimen to a component. Most of the participating organizations were able to develop a reasonable approach for prediction of ductile fracture in large and mid-scale mock-ups that are representative of real nuclear components. The achieved results have potential to improve the qualification of key mechanical components relevant for safety of nuclear power plants. Based on the results of LA analyses the following recommendations are given: 1) develop appropriate optimization tools for material parameter selection. 2) The results indicate that, if possible, it is beneficial to calibrate the material parameters with both low and high constrained fracture mechanical specimens.
In WP4, the results have made it possible to better understand how different assumptions and parameters influence a probabilistic assessment. When evaluating results from probabilistic analyses using a specific tool, it is important to have a good knowledge of how this tool define different limit states, how the deterministic fracture assessment methodology is defined and how the re-characterization of surface breaking defects at “Snap-Through” is defined.
The results have been used for developing the standards/Codes, e.g. the tools developed and results for residual stresses are implemented to the UK codes. Similar thoughts have been presented for the validated and developed ductile tearing models. The results have been disseminated at many public events e.g. NUGENIA, SNETP, FISA, FSI, EC, PVP, SMiRT and national conferences. All together 27 publications were written
