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ventional method. Tis explains why no castings failed on the test stand.


Durability Prediction of Gray Iron Bearing Support


A durability strength value of 190


MPa was measured for a gray iron bearing support. Conventional methods, which are based on established stan- dards, showed only a value of 140 MPa for this material. Results of fatigue tests for the bearing support are shown in Figure 8 for two different melts. Besides showing these quantitative


differences in values, it clearly defines potentially weak areas. Figure 9 com- pares the conventional (microstructure independent) and improved prediction of crack initiation areas in the bear- ing support. Only the microstructure distribution-based durability calcula- tion predicts the correct location of weak spots in the casting.


Outlook Te results of this research project


are the first steps toward integrating process and application simulation to predict correct and robust fatigue/life- time values. One essential goal of the work presented here was to realize a new methodology and show its poten- tial. Te local material behavior of many cast alloys is not only defined by


Fig. 10. The predicted locally varying durability values are compared to measured values in a windmill base frame.


their microstructure distribution, but also by local defects. Tis is especially important for ductile iron materials. Teir performance can be significantly reduced by inclusions and dross. Te calculation of these effects, so they can be considered in predictive tools, is currently being worked on. The proposed concept of local


durability values offers great poten- tial in the design of safety critical


components, like wind energy parts. Figure 10 shows the local durability values for a ductile iron (GJS-400) windmill base frame. Te red dots in Figure 11 on


the left side show the local fatigue strengths (351–455 MPa) based on conventional standards. Tat approach leads to a very conservative design compared to when locally predicted durability values would be used. Te conventional approach puts ductile iron to a disadvantage. Casting buyers and designers have


learned over the years that early infor- mation regarding expected property distributions in castings is contributing to quality assurance and risk minimiza- tion. Tey are also increasingly utilizing this information as a chance to reduce weight and optimize the performance of castings. A casting design where the application load and weight are opti- mized is only achievable if the designer can fully unlock the potential of the material. Te integration of process and application simulation offers the development of more realistic design rules for castings.


Fig. 11. Calculated (blue) tension-compression durability for ductile iron is compared to predicted standard values (red) in the same locations.


Tis research presented in this article was originally published online in the Interna- tional Journal of Metalcasting in 2016. It can be found in the Volume 11 April 2017 Issue 2. https://link.springer.com/journal/


volumesAndIssues/40962 April 2017 MODERN CASTING | 39


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