Zone wise local characterization of welds using digital image correlation technique

Author-Highlights
• Proposed zone wise local characterization of welds using digital image correlation.
• Weld zones are identified using a strain based method coupled with micrographs.
• Full range stress–strain curves are extracted for each local weld zones.
• Local elastic, plastic properties and microhardness across the weld are extracted.
• Local properties of welds produced using different current ratings are compared.

The process of welding is associated with high and varying thermal gradients across the weld, resulting in inhomogeneous material properties surrounding the weldment. A proper understanding of the varying mechanical properties of the weld and surrounding materials is important in designing and modelling of components with weld. In the present study the characterization of different zones such as fusion zone, heat affected zones and unaffected base material of a deposited weld is carried out using digital image correlation (DIC) technique. A methodology using the micrographic observation and image processing is proposed for accurate identification of various weld zones. The response of welded samples in the elastic and plastic region is compared with the virgin sample. Full range stress–strain curves are obtained for each zone using the whole field strain measurement involving DIC. The parameters investigated are Young׳s modulus, Poisson׳s ratio, yield stress, strain hardening exponent and strength coefficient. A study regarding the variation of properties with respect to varying weld currents of 100 A, 130 A and 150 A is carried out. The Vickers microhardness measurement is also conducted to obtain the variation in hardness across weldment. Fusion zone of all the welded samples have reported lower Young׳s modulus and higher yield strength compared to virgin samples. The Vickers hardness values obtained for fusion and heat affected zones are in line with the yield stress variation obtained zone wise.