Effects of Cleavage Triggers and Constraint on Brittle Fracture in Steel Weld Heat Affected Zone

Abstract

Cleavage fracture in steel is usually evaluated by using the stress criterion. However, some researchers indicated the necessity of strain in the stress criterion according to the cleavage fracture test results of steel base metal. If so, the cleavage fracture criterion should be also applicable to steel welded joints. In this study, cleavage fracture tests, SEM fracture surface observations and FEA were conducted using the smooth and notched round bar tensile specimens of the simulated HAZ microstructure of JIS SM490A. Cleavage trigger types did not influence the cleavage fracture properties of the specimens obviously. FEA results suggested that the critical condition of cleavage fracture initiation was associated not only with stress but also with strain.