Measuring the toughness of weld joints on a tensile test machine

Abstract

In the tensile strength of weld joints, the sample breaks at the point of least strength or at the point of the defect. If there is a fracture of the basic material, we do not get an overview of the strength of the individual parts of the weld joint. For that reason, a shear test has been developed. This process implies that it would be possible to measure shear strength and toughness in butt welds of base materials, in different places of the heat affected zone and the weld metal. Mechanical properties of the welded joint can be characterized by determination of strength and from the force-displacement dependence by the toughness. The fracture in the shape of the S curve subsequently causes a reduction in the gradient of the decrease in force by mutual friction with the created surface, which increases the value of the measured fracture energy. Therefore, it is possible to exactly determine the energy only up to the maximum value of the force. In the shear test a special device with universal testing machine was used. For accurate force measurement, the strain gauge force sensor of the universal testing machine was calibrated using an externally calibrated strain gauge pressure sensor.