51316-7494-`Embedded Monitoring System for Determination of Aluminum Alloy Sensitization

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Product Number: 51316-7494-`SG

ISBN: 7496 2016 CP

Author: Kevin Farinholt

Publication Date: 2016

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Non Member Price: $20.00

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New Navy combatant and non-combatant vessels need to be faster carry bigger payloads travel longer distances and have reduced acquisition manning and life cycle costs. These goals are being achieved in part by incorporating light weight alloys and composite materials in advanced ship designs. The excellent intrinsic properties of the 5XXX series aluminum alloys such as a high strength-to-weight-ratio good as-welded properties and corrosion resistance make them desirable for use in these marine structures. However incidents with the aluminum alloys used in commercial ferries and patrol boats as well as in Navy ships have shown that the 5XXX series is prone to elemental migration and phase transformations at only slightly elevated temperatures (i.e. sensitization) leading to localized intergranular corrosion and stress corrosion cracking. In order to maximize structural performance through improved damage state awareness and maintenance scheduling Luna is developing in collaboration with our team members General Dynamics Bath Iron Works and the University of Virginia (UVa) a compact robust monitoring system for in situ measurement of degree of sensitization (DoS) of 5XXX series aluminum. This monitoring system uses eddy current measurements to measure local conductivity properties of the aluminum alloy and correlates the degree of sensitization to changes in the material’s electrical properties with time. Temperature compensation and normalization techniques are used to limit the influence of environmental parameters on measurements improving the technique’s robustness for application in the field. An overview of the technique will be presented along with results from laboratory testing of 5083 and 5456 aluminum alloy coupon samples that have been exposed to different thermal loading conditions.