Abstract
In the fracture toughness tests of welds, it is often found that fracture toughness values measured with reference to cleavage fracture initiation show a great amount of scatter even if testing conditions are much the same. Such scattering characteristics are also recognized in tests of macroscopically homogeneous steel, and in this case, the scatter is assumed to be caused by a statistical nature due to microstructures of the material.
In the tests of weld specimens with macroscopic heterogeneity along the crack front, for example cross-bond-type notched specimens, however, the scatter in cleavage resistances may be affected not only by heterogeneity in microstructures but also by macroscopic heterogeneity in toughness.
In the present paper, using a few types of bending COD specimens with macroscopic heterogeneity along the crack front, the effect of macroscopic heterogeneity on the scatter in fracture toughness values have been investigated. Moreover, a probabilistic model of the scatter of fracture toughness of welds is proposed, based on the following assumptions;
(1) the lowest toughness along the crack front controls the cleavage fracture toughness, that is, the weakest link model is available, and
(2) the size of the embrittled region along the crack front controls the scatter in fracture toughness values.
Comparing the distribution of fracture toughness values calculated by the present probabilistic model with that obtained from the tests, applicability of the model proposed in the present study is clarified.
