Sameera Naib

Calibration of Hardness Transfer Functions Based on Micro Tensile and All Weld Metal Tensile Tests of Heterogeneous Welds

In order to assess the integrity of welded structures, it is important to accurately know the material characteristics of the weld regions. A weldment is heterogeneous i.e. strength properties vary at different locations within the weld. This influences the behavior of the structure when it is subjected to loading. Hence, the evaluation of material properties within the weld region plays a pivotal role in structural integrity assessment. Traditionally, tensile tests provide constitutive properties like tensile strength and yield strength along with stress (σ) – strain (e) curves. Alternatively, hardness indentations are also used to procure strength properties of a material. Several transfer functions have been formulated to convert hardness values to strength properties. The validity of these transfer functions with the presence of strength variations is questionable, as these relations do not consider the aspect of heterogeneity. Accordingly, in this research, a heterogeneous weld was considered to assess the relation between Vickers hardness (HV5) and strength properties. Two tensile test configurations were considered – All Weld Metal Tensile Tests (AWMTT) and Micro Tensile Tests (MTT). While AWMTT provides average weld stress-strain properties, MTT provide local properties. These results help to validate the hardness transfer functions and thus calibrate them appropriately. Hardness maps were obtained on polished weld macrographs. The material properties obtained from three methods were compared and significant variations were observed. Based on these differences, an experimentally calibrated transfer function is implemented. With this relation, it is possible to predict weld behavior more accurately and appropriately using hardness maps and tensile tests.