Experimental study on dynamic nanoindentation on structural weld zone

In this study, dynamic spherical indentation and finite element analysis were used to assess the strain rate sensitivity behavior of the SS400 structural steel weld zone. The influences of the loading rate on both yield strength and hardness of the base metal, heat-affected zone, and weld metal are studied using dynamic spherical nanoindentation. The strain rate sensitivity (SRS) of three microstructural phases in the weld zone was also determined using the hardness model, as a result, the SRS behavior in the weld zone was investigated. The relationship of the SRS to the minimum yield stress of the investigated weld zone was constructed and compared with the general trend reported for several types of structural steel in the literature. To verify the SRS behavior in the weld zone, the tensile loading experiments on the weld specimen and finite element (FE) simulation of the tensile process considering the SRS behaviors of base metal, heat affected zone, and weld metal were conducted. The comparison of the engineering stress-engineering strain curves obtained from the tensile experiment and FE analysis is then constructed. Thus, the SRS behavior of the SS400 structural steel weld zone was validated through experimental verification. The present study provided a basic methodology to dynamic nanoindentation on the weld zone, and the experimental results of this study can be used in the practical designs and to understand the strain rate sensitivity behavior of microstructural phases in the weld zone.