Influence of internal volumetric imperfections on the tearing resistance curve of welded single edge notched tension (SENT) specimens

The acceptance of volumetric weld imperfections is subjected to workmanship guidelines, which are subjective quality criteria loosely related to fitness for purpose assessments. However, the relative impact of such imperfections may be accentuated in fracture toughness tests, given the relatively small dimensions of the test specimens. This study analyses the impact of weld volumetric imperfections on the outcome of fracture toughness tests. Single Edge Notched Tensile (SENT) specimens were machined from steel plates joined by robotic Metal Inert Gas (MIG) welding. The specimens contained different levels of volumetric imperfections which were characterized by high-resolution X-ray Computed Tomography (mu CT) scans. Single specimen fracture toughness tests were conducted and crack growth was monitored by applying both the Unloading Compliance (UC) technique and the Direct Current Potential Drop (DCPD) technique. Tearing resistance curves (R-curves) were constructed based on UC and DCPD data. Results showed that specimens containing volumetric imperfections acceptable by workmanship guidelines may yield significantly inferior fracture initiation toughness values compared to imperfection-free specimens