The validity of the equivalent energy definition depends partly on the relation between J1mm
upper shelf correlation (Figure 5). As a validity check, tear- ing resistance data for EN-GJS-400-15U12
the average general relation between J1mm definition appears to be appropriate. and JIC average value of 9%. and Cv
11 shows large scale specimen fracture toughness data from Reference 7 plotted in a normal probability diagram. It can be seen that the variation in fracture toughness for nodular cast iron is well described by a normal distribution with the standard deviation being approximately 9% of the average. This is fully in line with the data from Reference 12 where the standard deviation for three different heats at different temperatures, varies in the range of 6 - 17% of KJIC
One issue having an impact on the reliability of the correla- tion between Cv
and KJIC is the scatter in KJIC values. Figure , with an
As a final quality assurance check of the relation between KJIC
for nodular cast iron, the scatter in the rela- tion was compared to an assumed 10% deviation of indi- vidual fracture toughness values (Figure 12). Nearly all the data points fall within the ±2·σ scatter bounds. This indicates that the relation has the same confidence as a single fracture toughness value and the valid- ity of the average relation (Eqn. 4) is verified.
Table 1. Equivalent Charpy-V impact
Toughness for Nodular Cast Iron
Summary and Conclusions
Nodular cast iron has different transition behaviour than steel and they experience notches dif- ferently. By accounting for these differences, the relevance of the Charpy-V test for nodular cast iron has been re-examined. As a result, a new definition of an equivalent energy criterion for nodular cast iron is proposed. The results can be used to define case specific Charpy-V require- ments for nodular cast iron. For example, if the Charpy-V re- quirement for steel would be 28 J, the corresponding requirement for nodular cast iron should be 13 J (See Table 1).
It should be pointed out that the present work is not focusing on
International Journal of Metalcasting/Volume 8, Issue 2, 2014
Figure 10. Validation of relation between J1mm nodular cast iron. Data taken from Reference 12.
and m for and m (Figure 10).
The validity of the general relation with respect to nodular cast iron is well confirmed by the data. Thus, the transfor- mation between J1mm
used for the equivalent energy
and m used in the general was compared to
Figure 9. Equivalent Charpy-V impact toughness for nodular cast iron.
Figure 11. Observed scatter of fracture toughness for nodular cast iron. Based on data from Reference 7.
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