Quantitative NDE (QNDE) of a Circumferential Weld Mismatch Zone Using Digital Image Correlation (DIC)

Circumferential weld mismatch is often observed during the welding of two cylindrical shells. The effect of such a weld anomaly becomes more detrimental, and the structural integrity is compromised when the ovalities of the welded shells are large. This paper presents a unique NDE usage of DIC wherein a theoretically unacceptable weld mismatch zone on a rocket propellant tank is assessed during its acceptance testing. The critical strain and displacement behavior on the tank was monitored in situ and online. Furthermore, the stress magnitudes at these critical locations were estimated to understand the design margins. It was found that the margins were satisfactory for the operation of the tank. The same was flown in the launch vehicle mission successfully.