The welding process induces residual stresses because of the non-uniform heating and cooling of the material. Residual stresses are known to influence fatigue crack growth. However, studies addressing both the formation of residual stress – giving a realistic multi-directional stress and strain field – and redistribution of residual stresses due to crack growth in the case of a surface crack have not been found. The extended finite element method was employed in this study to evaluate the stress intensity factors of a planar, growing crack in a welded T-joint with and without welding induced residual stresses. The initial residual stress field was taken from a welding simulation using the finite element method. The redistribution of the residual stress field due to crack growth was studied in addition to the shape and growth rate of the planar crack. The study shows that, in agreement with experimental evidence, the external stress ratio has a significant influence in the absence of residual stress but it does not have a significant influence in the presence of residual stress. The current study gives insight into the cause of this observation.

To monitor the growth of fatigue cracks in steel specimens, several methods exists. In this paper, the magnetic stray field, which is generated by the magnetisation of the specimen, was measured during loading to investigate how to utilise this data to reliably monitor fatigue crack initiation and growth. Data was collected in a series of fatigue tests on Compact Tension specimens with different force ratios. The evolution of the mean value of the dominant stray field component displayed a sensitivity to stress, plastic deformation and displacement of the specimen. By analysing the stress field induced by the loading, these three causes were distinguished from another. Crack initiation was marked by a large change of the mean magnetic stray field. Moreover, the amplitude of the magnetic stray field components showed a clear peak, at which moment 20% of the life time of the specimen is remaining, indicating that the magnetic stray field might provide a useful method to monitor the evolution of fatigue cracks.

Orthotropic bridge decks are susceptible to fatigue cracks which are influenced by the thickness of their components, welding procedure, type of the weld, the position of the considered detail in relation to the local loading condition and by residual stresses due to welding. The above-mentioned parameters determine the detail category for fatigue resistance. This research focuses on an experimental investigation of the temperature distribution and distortions due to the welding of a connection between the deck plate, longitudinal stiffener and crossbeam. Three specimens were welded with dimensions of: 900x400 mm deck plate, 350mm deep trapezoidal longitudinal stiffener and 600mm long crossbeam in a workshop of a bridge fabricator. The crossbeams were manufactured with Haibach cope holes. The thickness of the deck plate and crossbeam was 15 mm, and the thickness of the longitudinal stiffener was 8mm. During the welding, the temperature was measured using a FLIR