APPLICATION OF THE LOCAL APPROACH TO CLEAVAGE FRACTURE TO FAILURE PREDICTIONS OF HEAT-AFFECTED ZONES

With the increased capabilities of elastic-plastic finite element anal yses and hence the possibilities to determine accurately the stress di stribution ahead of sharp cracks the use of fracture risk predictions based on a local fracture parameter has recently attracted much intere st. To date most investigations in this area concentrated on homogeneo us materials avoiding the complications related to the complex situati on of welded joints. In this paper results are presented where the Loc al Approach to cleavage fracture has been applied to the heat affected zone of two structural steel welds. Local cleavage fracture parameter s were determined from tests and finite element modelling of notched t ensile specimens. In all cases the properties of the weld metal, the p arent material and the heat affected zone (HAZ) were determined. A the rmal simulation technique was used to produce large enough areas of HA Z microstructures for tensile and notched tensile testing. Subsequent application of the Local Approach to the crack tip situation for the p rediction of the dependence of fracture toughness on temperature and t he scatter in fracture toughness only produced satisfactory results fo r a limited number of the situations modelled. Discrepancies between p redictions and actual results are thought to be due partly to the diff erences in FE mesh and stress distribution between notched tensile and pre-cracked bend specimens.