Development of Sand Cast E357 Design Allowables for Incorporation Into MMPDS

Design engineers need properties not based upon typicals but ones representative the of population variation observed in manufacturing that would be encountered as a function of different processes section thickness (cooling rates) encountered in complex casting designs and also from multiple supply sources. The requirements for components that are considered flight critical are even more demanding as the Federal Aviation Administration (FAA) FAR 25.613 requires statistically validated properties for structural materials and FAR 25.621 compels the use of casting factors, which means that a more conservative design approach is used which adds section thickness and weight. Currently, most casting alloys have no statistical validation and cannot be considered for replacement or new design without developing this data on a component by component basis. This expensive process requires an extraordinary business case analysis to justify this added expense and time delay. Yet this is routinely done in the jet engine business and is documented in the Metallic Materials Properties Development and Standardization (MMPDS) Handbook. The approach taken in this project was to develop statistical basis A & B design allowables for sand cast E357 for six thicknesses from 1/8 to 2.5 inches to supplement statistically based allowables for investment cast E357 at five thicknesses (< 0.500, 0.501-1.000, 1.001-1.500, 1.501-2.00, 2.001-2.500-inches) available in the MMPDS-05 Handbook. A consortium of casting users, foundries, suppliers and organizations that support metalcasting assisted in design of the test castings, devising the gating and rigging practice and manufacturing the tooling and test parts, establishing the melt and metal treatment, heat treatment and evaluation practice for the plates produced to develop these properties. Also critical was to demonstrate the utilization of Computer Aided Engineering and Modeling tools to create the tooling design as an approach to design reliability and repeatability into the process, also collect valuable information on the repeatability of inspection validation systems. This project was also to consolidate weld knowledge to develop an AFS Recommend Practice for the in-process weld repair of aluminum-silicon hypo-eutectic alloys and develop mechanical properties to demonstrate the efficacy of the practice, and develop statistical data that facilitates acceptance of weld practice.