TWI Industrial Member Report Summary 184/1982
By I J Smith, I F C Smith and S J Hurworth
A 3-D stress analysis of the longitudinal non-load-carrying fillet welded fatigue specimen is reported. A specimen used at Cambridge University for fatigue crack growth studies was strain gauged and also modelled by finite elements. The agreement between the experimental data and the stress analysis was good. The effects of changes in attachment height and length were examined briefly. It is shown that, due to the high degree of triaxiality just below the weld toe yielding should be resisted by about 33% more than specimens not developing this level of triaxiality. This implies that LEFM can still be valid for.defects in this specimen at higher stress than thought previously.
Using a similar number of elements as the stress analysis mesh, a 3-D semi-elliptical defect was modelled. Accuracies in stress intensity factors of 5-10% as compared with previous work were achieved. As it would be preferable to obtain accuracies of 1-2% for fatigue studies it is suggested that further development of the crack region modelling is made before incorporating cracks into the specimen model.