Experimental Determination of J for a HSLA Steel Welded Joint

Most serious weldment failures have catastrophic consequences in terms of damage to other equipment, loss of production, and risks to worker health and safety. For the above reasons, there is a tendency to find the line between safety and disaster, and this requires a guarantee of the integrity of the welded structure even if a crack is present. The structural and mechanical heterogeneity of a welded joint affects its resistance to cracking in both the elastic and plastic regions. Therefore, it is important to define the test method and the position of the fatigue crack. The behavior of an elasto-plastic material, during stable crack growth can be described by the J-Δa diagram. As the crack propagates, a point on the curve is defined, which represents the critical value of the J-integral. The aim of this experiment is to determine JIC value and the procedure is reflected in the determination of the R-curve, i.e., the J‒Δa curve, which consists of the value of the J-integral for uniform crack increments Δa. In this paper, precracked SEN(B) specimens with the fatigue crack positioned in the weld metal (WM) were tested according to standard ASTM E1820 at room temperature (RT), -20 °C and -30 °C.