Experimental Study of Fracture Surface Thickness Variations of Inhomogeneous Drop Weight Tear Test Specimen (with Horizontal Weld Seam) Made from API X65 Steel

In this study for the first time, changes in the thickness of the fracture cross-section of the inhomogeneous sample (with horizontal weld seam) of the API X65 steel, using drop weight tear test specimen have been investigated experimentally. The fracture surface of the test specimen consisted of three zones of base metal, heat affected zone and weld metal with different microstructure and mechanical properties. The most thickness reduction was in the cleavage fracture area of the notch root. In the base metal zone, thickness changes were constant which indicated the stable crack growth in this area. In both heat affected zones before and after the weld zone, the thickness changed with a constant slope. Due to the high hardness and low fracture energy of the weld zone, the lowest percentage of thickness changes was in this zone. Thickness in the weld zone increased with a constant slope due to the stretching of the weld zone to the end of the crack growth path by the force caused by the change of fracture mode from tensile to shear. Also in the reverse fracture zone, due to the increased in compressive strain caused by impact of the hammer on the sample, the thickness increases with a significant slope and reached the maximum value.