Weld investigations by 3D analyses of Charpy V-notch specimens

The Charpy impact test is a standard procedure for determining the ductile-brittle transition in welds. The predictions of such tests have been investigated by full three dimensional transient analyses of Charpy V-notch specimens. The material response is characterised by an elastic-viscoplastic constitutive relation for a porous plastic solid, accounting for adiabatic heating due to plastic dissipationfiand the resulting thermal softening.

The onset of cleavage is taken to occur when the average of the maximum principal stress over a speci¯ed volume attains a critical value. Typically, the material parameters in the weld material differ from those in the base material, and the heat a®ected zone (HAZ) tends to be more brittle than the other material regions.

The effect of weld strength undermatch or overmatch is an important issue. Some specimens, for which the notched surface is rotated relative to the surface of the test piece, have so complex geometry that only a full 3D analysis is able to account for the interaction of failure in the three different material regions, whereas ther specimens can be approximated in terms of a planar analysis.