METHODOLOGY FOR EXAMINING SYSTEM AGING DUE TO INTERACTIONS BETWEEN CHEMICALLY INCOMPATIBLE MATERIALS Page: 2 of 7
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A Methodology for Examining System Aging
Due to Interactions Between Chemically Incompatible Materials
J. P. Deininger and J.A. Tanski
Los Alamos National Laboratory, Engineering Sciences and Applications Division, Los Alamos, NM 87545
ABSTRACT
We start with a stored and unused population of fielded engineered units that are composed of chemically
incompatible materials. The units age primarily through heterogeneous chemical reactions between the materials
resulting in possible degradation in performance. The engineered units are unused in storage, but may be called
into actual service at any time. We sample several units from the population per year and perform a number of
non-destructive evaluation (NDE) techniques, such as radiography, low-frequency vibration analysis, and
ultrasonic imaging on the selected units. From those units, some are selected for destructive testing (D-test)
involving disassembly and testing of internal parts and components. Chemical analyses, mechanical properties
measurements and other tests are performed. All of the above steps provide information that is used in the
system simulation mathematical model. The system simulation model incorporates chemical reactions and gas-
solid transport processes, along with changes in both the surface and bulk properties of the solids. Model
results are used to suggest improvements in NDE analyses of the units and improvements in component and
material analyses. Model results give trending indications of individual component and overall system changes
over time, plus some understanding of the mechanisms involved which allow science-based predictions of the
aged state of the units in future times. The NDE, D-test, and model results can also be used to assess statistically
the reliability and performance of the overall aging population of units.
INTRODUCTION
There are thousands of devices and products made and distributed around the world by
industrial society. It is an empirical observation that the vast majority of these products
begin to change from the day that they are released from manufacture, that many retain their
design functionality for a very long time measured in years or centuries, that many lose their
design functionality in a very short time measured in a few hours or days, and that many
simply degrade in functionality at rates anywhere between these extremes. There are many
mechanisms by which these degradations occur. A particular subset exists, however, in which
changes in the devices and products occur primarily due to chemical reactions which take
place between the various "chemically incompatible" materials which are in close proximity
to each other within the device or system. Other effects such as mechanical damage due to
stress or internal material changes in phase or structure will occur, of course, but in these
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DENINGER, J. & TANSKI, J. METHODOLOGY FOR EXAMINING SYSTEM AGING DUE TO INTERACTIONS BETWEEN CHEMICALLY INCOMPATIBLE MATERIALS, article, April 1, 1999; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc720187/m1/2/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.