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High energy welding technologies, such as electron beam, have a number of potential benefits including: faster process time, smaller heat affected zone and potentially favourable weld residual stresses. Therefore, they are good candidates for manufacturing complex components for the next generation of nuclear power plants. However, before electron beam can be deployed on a wide scale, further work is required in a number of areas, including how these welds are treated in structural integrity assessments. As an example, the full extent of the effects of complex residual stress (RS) fields, arising from high energy welding technology, on the fracture behaviour of components has not been fully investigated. This understanding is essential for defect tolerance calculations using integrity assessment procedures. In this study, the fracture toughness of austenitic stainless steel 316L plates with various thicknesses (6mm to 25mm), joined by electron beam welding, is evaluated. Residual stresses were measured using non-destructive diffraction and mechanical relief methods (contour method). This is to examine the effect of welding residual stresses on the resistance of the welded component to fracture.

Tensile residual stress can reduce the load carrying capability of a structure. However, residual stresses may be redistributed during the life of a component by, for example, permanent deformation. This paper explains an experiment carried out to understand how applied and residual stresses interact and to seek a method of measuring elastic follow-up during the interaction. A friction stir welded aluminium alloy plate was subjected to a series of incrementally increasing load and unload cycles, whilst simultaneously measuring residual stresses and deformation. In-situ loading of the specimen during the residual stress measurements allowed the relaxation of the residual stress to be quantified. The elastic follow-up has been estimated and measured by considering both the structural stiffnesses of the specimen and the relaxation of the residual stress. It was found that global yielding, which can result in no net change of incompatibility, has to be considered when calculating elastic follow-up. An estimation of the elastic follow-up factor based on the structural stiffnesses of the specimen was found to be non-conservative and an elastic follow-up factor of 2.9 was measured. That is three times as much plastic strain is required to relax the residual stress when compared to the fixed-displacement case.

Residual stresses resulting from welds are a key consideration in the design and assessment of piping and pressure vessels. As welding is a variable process, the resulting variability in weld residual stress should be accounted for in design and assessment. This paper investigates the variability in residual stress resulting from flux cored arc welds by performing residual stress measurements on a set of nominally identical welds between 25mm plates of grade DH36 steel. The welds were produced in two environments to assess the impact on residual stress variability: a well-controlled laboratory environment and a less controlled factory environment. The results showed significant variability in the residual stresses between the welds, with standard deviations up to 25% of the peak value in some locations near the weld center. The welds were two sided and higher variability was measured in the side performed second, with the variability in heat applied appearing to be a key driver of the residual stress variability. A difference was observed between the standard deviations of residual stress in the factory and laboratory samples, with the laboratory samples showing less residual stress variability. Whilst the small number of samples measured prevents firm quantitative conclusions being drawn about the potential differences in residual stress variability between production environments the results do suggest that there is value in further study.