Experimental study of low velocity impact effect on fracture energy of API X65 steel using drop weight tear test

The purpose of this research is to investigate low velocity impact effect on fracture energy of DWTT specimen made of API X65 steel. As in some cases due to sudden impact (pre Loading) and permanent deformation, fracture energy of steel may be changed, the investigation of this study is important. Test specimen is API X65 steel of single edge notch type with Chevron notch with a depth of 5.1 mm which is cut from a spiral seam welded steel pipe with an outside diameter of 1219mm and wall thickness of 14.3mm. This steel is widely used in oil and gas industery in the world. The experiments were performed on 21 specimens. In the first stage, the drop height of the hammer was low so that the specimens did not fail and only the area adjacent to the crack tip entered the plastic zone. Subsequently, the samples were fractured by applying a second impact from a standard height of 2 meters. By analyzing experimental data, the fracture energy for each sample was calculated and compared with each other. By plotting the fracture energy in terms of the initial impact energy, it was observed that by increasing the initial impact energy in the sample, its fracture energy decreased. Finally, a linear relationship with acceptable accuracy for this energy drop was proposed, which showed a direct relationship between the fracture energy and the initial impact energy.