New developments in fracture toughness evaluation

Micromechanical material models are applied to analyse ductile failure processes during tensile tests and Charpy-V tests. The parameters are used to predict J-resistance curves for neutronembrittled weld material of nuclear pressure vessels. To validate the approach, dynamic tensile tests and instrumented impact tests with notched and precracked Charpy specimens are performed and simulated. 'Re results suggest that the critical void volume fraction f(ind c) and the characteristic length l(ind c) are practically independent of strain-rate and specimen geometry. The tunnelling of the crack in the interior of the Charpy specimen is predicted in a satisfactory way by a three-dimensional analysis with a strainrate dependent Gurson model.