Confocal microscopy-fracture reconstruction and finite element modeling characterization of local cleavage toughness in a ferritic/martensitic steel in subsized Charpy V-notch impact tests

The confocal microscopy (CM)-fracture reconstruction (FR) method, coupled w ith scanning: electron microscopy (SEM) fractography, was used to measure t he critical notch deformation conditions at cleavage initiation for two sub sized Charpy V-notch (CVN) specimen geometries of Japan ferritic/martensiti c steel (JFMS). A new method was developed to permit FR of notched specimen s. Three-dimensional finite element analysis (FEB) simulations of the notch and specimen deformation were used to estimate values of critical micro-cl eavage fracture stress, sigma*, and critical stressed area, A*. Since sigma *-A* is independent of size and geometry, it provides a fundamental local m easure of cleavage toughness. (C) 2000 Elsevier Science B.V. All rights res erved.