SOME ASPECTS OF FATIGUE CRACK GROWTH IN WELDMENTS IN THE NEAR-THRESHOLD REGIME.

By changing the geometry and the pattern of weld metal deposition, 'composite' steel specimens were prepared in which the relative importance of the weld metal, heat-affected zone and parent metal was different. Fatigue crack growth behaviour in the near-threshold region was investigated. The results have been explained in terms of the residual stress present in the welds, the microstructure, the position of the heat-affected zone in relation to the fatigue crack-tip.