Motivation. The low temperature fracture behaviour is one of the main concerns regarding steels and weldments for Arctic applications. In Arctic Materials I project, properties of steel and weldments at low temperature (mainly at -60°C) were investigated, and the first generation guideline was proposed. Deterministic design criteria for C-Mn steels were defined as well. However, there is a need to extend the criteria to include quantification of safety levels. Thus, development of knowledge-based quantitative models for brittle fracture will be of the highest importance with regards to laying down the basis for robust guideline requirements. This will include investigations on the impact of geometry constraint, materials mismatch and temperature on fracture toughness level and scatter. In addition to the general models for brittle fracture, there is a need to address specific topics, e.g., wider temperature range from -60°C to -15°C, quantification the effect of residual stresses, low-temperature fatigue behaviour, crack arrest and tensile properties. The way of treatment of residual stresses is extremely important to increase the utility of materials. It is believed that the current fracture assessment procedure is too conservative. Therefore, the investigation of the impact of residual stresses will have huge impact on materials utilization and required fracture toughness. Fatigue properties were not tested in AM I, and the temperature effect on crack growth rate and fatigue should be examined. Finally, as disclosed in AM I, the crack arrest properties seem to be important.
Work description. The following tasks are included:
2 PhDs are included.
Published January 8, 2010