A micromechanical analysis of the ductile-brittle transition at a weld
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abstract
The competition between brittle and ductile modes of failure is analyzed in a weld specimen subject to dynamic transverse loading. Full transient analyses under plane strain conditions are carried out. The material response is characterized by an elastic-viscoplastic constitutive relation for a porous plastic solid, with adiabatic heating due to plastic dissipation and the resulting thermal softening accounted for. The onset of cleavage is assumed to occur when a critical value of the maximum principal stress is attained. Different levels of undermatched or overmatched welds are analyzed. It is found that high flow strength in the heat affected zone (HAZ) can have a strong influence on the transition temperature, but this can differ significantly between undermatched and overmatched welds. A comparison of a low strain hardening material with a high strain hardening material shows that strain hardening also strongly affects the transition behavior. In addition, the transition behavior is compared for a high yield strength material and a low yield strength material, with a proportional change in the critical stress for cleavage. 1998 Elsevier Science Ltd.
