The Relation Between Charpy-V Fracture Toughness for Nodular Cast Iron
Fracture toughness with accompanying Charpy-V data is somewhat scarce for nodular cast iron. However, there are a few good sources, where the fracture toughness has been estimated using a valid elastic-plastic procedure.5-7
6 contains a compilation of ductile KJIC of nodular cast iron, plotted against Cv a clear relation between KJIC
can be expressed in the form of Eqn. 4. and Cv
estimate corresponding to the general relation given by Figures 4 and 5 and Eqn. 3. As for the general rela- tion, the KJIC
Included in Figure 6 is the KJIC and the KJIC
estimate corresponding to ETOT
estimate than predicted based on the general relation. This difference highlights the higher notch sensitiv- ity of nodular cast iron compared to bulk metals.
Figure 7 contains a compilation of partly brittle KIC values for a range of nodular cast iron. The ETOT based on Kinst cause Kinst than KJIC
4). Thus, one single equation seems sufficient to describe the fracture toughness - Charpy-V relation of nodular cast iron.
Discussion
The relation between Charpy-V impact energy and fracture toughness is different for structural steel and nodular cast iron. Since the important parameter describing the material’s resistance to cracks is the fracture toughness, it means that the Charpy-V requirements for nodular cast iron should be different from steel. With the help of the general relation and the nodular cast iron specific relation, it is possible to estimate an equivalent impact energy that gives for steel the same fracture toughness as for nodular cast iron. The pro- cedure to estimate the equivalent impact energy is shown schematically in Figure 8. This allows for one to transform a nodular cast iron impact toughness value to a corresponding impact toughness for bulk metals. The resulting equivalent impact energies are given in Table 1 and Figure 9.
Table 1 can be used to define case specific Charpy-V require- ments for nodular cast iron. If, for example, the Charpy-V requirement for steel would be 28 J, the corresponding re- quirement for nodular cast iron should be 13 J.
84
these materials, the partly brittle fracture toughness can be described with the same relation as found for KJIC
. Probably due to the flat tearing resistance curve for (Equation
and KIC
Figure 7. Relation between Charpy-V energy and fracture toughness for nodular cast iron. Data taken from References 7-11.
and Kinst estimate
is even lower than the estimate for KJIC can correspond to a larger crack extension
, be-
an absolute lower bound to the data, but the data is clearly closer to the ETOT
estimate corresponding to ETOT forms basically
iron grade. The proportional scatter in the relation is similar as the scatter in the general relation shown in Figure 4. The average relation between KJIC
and Cv for nodular cast iron Eqn. 4
Figure 6. Relation between Charpy-V energy and ductile fracture toughness for nodular cast iron. Data taken from References 5-7.
, that is independent of
Figure
values for a range . The data indicate
Figure 8. Principle of determining an equivalent impact energy for nodular cast iron.
International Journal of Metalcasting/Volume 8, Issue 2, 2014
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97