Aviation is known to have some of the most stringent structural health monitoring standards in
the world. An example of this would be the fact that certain bolts in the aircraft assembly must
be periodically removed and inspected for fatigue damage. This can be a very costly endeavour:
a case in point being the Hercules C130 aircraft, which requires approximately 200 man hours
of down-time for the inspection of the bolts that attach the wings to the fuselage. The
substitution of TRIP (Transformation Induced Plasticity) steel bolts for the current HSLA steel
(AISI 4340) from which the bolts are manufactured, allows the bolt to act in the capacity of
load bearing member as well as damage detector. This unique feature is a consequence of the
transformation characteristic exhibited by TRIP steels when they are strained: an irreversible
change within their microstructure from paramagnetic austenite parent phase to permanent
ferromagnetic state occurs in direct proportion to the peak strain. This property allows us to
establish a relationship from which the service life of the component can be determined. A
prototype of a smart aircraft bolt and washer system has been developed, where the bolt acts as
damage detector and the washer effectively examines the health of the bolt by reading the
changing magnetic susceptibility of the bolt.
This study presents both material development and product development phases of the Smart
Aircraft Bolt prototype. A prediction of transformation characteristic due to deformation is
carried out using finite element analysis (mechanical model) and a constitutive model (strain induced
martensitic transformation kinetics) to predict the best situation for the smart washer. In
addition, experimental work is performed in the form of cyclic temperature testing (with and
without external loading) and tension-tension fatigue testing. For both sets of experimental
testing, two positions of washer placement are tested. A correlation between volume fraction of
martensite present and remaining life, is therefore possible. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9057 |
| Date | January 2008 |
| Creators | Mukosa, Namanyenu Sheleni. |
| Contributors | Bodger, Rob., Verijenko, Belinda-Lee. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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