FRACTURE TOUGHNESS CHARACTERIZATION OF 316L STAINLESS STEEL WELDED PLATES AT LIQUID NITROGEN (77 K) AND LIQUID HELIUM (4 K) TEMPERATURES
Enrico LuconDogwood A
In the framework of a collaborative project between ASME, NASA, and NIST, quasi-static fracture toughness tests were performed at liquid nitrogen temperature (77 K, or 196 °C) and liquid helium temperature (4 K, or -269 °C) on precracked SEN(B) specimens extracted from the centers of four separate lots of welded 316L stainless steel plates. Although the plates were produced in accordance with the same specifications from the same material (316L), large differences in fracture toughness have been observed, with the toughest weld exhibiting almost twice the critical toughness of the least tough at 77 K (219 kJ/m2 vs. 113 kJ/m2), and about seven times the critical toughness of the least tough at 4 K (146 kJ/m2 as compared to 21 kJ/m2). Charpy absorbed energies previously obtained at 77 K for three of the four welds were found to be strongly linearly correlated with fracture toughness at both test temperatures, with an exception represented by the fourth weld, which provided the highest impact toughness and the second lowest quasi-static fracture toughness. Dynamic toughness measurements at impact loading rates were also performed on precracked SEN(B) specimens, in order to deconvolute the roles of strain rate and notch sensitivity on the fracture properties.