Determination of CTOA in the molten material of spot welds using the Digital Image Correlation technique

In order to compare the strength of the molten material of different spot welds bonding steel sheets, a specific wedge test has been developed. It produces stable crack growth at the interface of sectioned spot welds. The deformation of the molten material at the progressing crack tip is observed in situ during wedge insertion. The Crack Tip Opening Angle and the extend of the strain localization ahead of the crack tip are measured by Digital Image Correlation. It is shown that the rather simple measurement of the Crack Tip Opening Angle provides a good indication of the extend of the strain localization, which is believed to be related to the toughness of the molten material.

► Novel experiment to study the strength of the molten material of spot welds.
► In situ observations of the stable crack growth through the weld.
► Digital Image Correlation to quantify the strain localization at the crack tip.
► The Crack Tip Opening Angle indicates well the extend of the strain localization.