Dynamic J-integral fracture-toughness test results were obtained for several different ductile irons over a range of temperatures. The ductile irons were all of a chemistry and microstructure in nominal compliance with ASTM Specification for Ferritic Ductile Iron Suitable for Low Temperature Service (A 874).
Among the materials investigated were ductile irons from actual nuclear spent-fuel storage casks and from a cask to be used in a drop-test program at a national laboratory. These ductile irons were of a mainly ferritic matrix with highly spherical graphite nodules. The tests were performed over a range of temperatures in an attempt to define the dynamic fracture-toughness transition temperature regime, important because the service temperature for transport casks for “normal” conditions can be as low as −40°C.
The technique employed for measuring the dynamic J-integral value was based on the multiplespecimen technique described in ASTM Test for JIc, a Measure of Fracture Toughness (E 813). Details of the test technique are discussed.
The upper-shelf dynamic fracture-toughness values for the three ductile irons investigated were similar, ranging from 61 to 77 MPa∙m½ at room temperature.
The transition between upper-shelf and lower-shelf dynamic fracture toughness occurred over the range of approximately -35 to -50°C for one ductile iron and the range of -50 to -68°C for another. These transition temperature regimes were higher than the quasi-static transition temperature noted for similar ductile iron material.
The influence of microstructure on the fracture toughness of ductile iron is discussed.