The objective of this study was to investigate the low velocity impact behavior of both monolithic and laminated aluminum alloy plates. For this purpose, a drop-weight test unit was used. The test unit included the free fall and impact of an 8 kg hammer with an 8 mm punching rod from 0.5 m to 4 m. The
relationship between the change in static mechanical properties (hardness,
ultimate tensile strength, yield strength, strain hardening rate) and low velocity
impact behavior of monolithic aluminum plates were investigated. Tested
material was AA 2024, heat treatable aluminum alloy, which was artificially
aged to obtain a wide range of mechanical properties. In the second stage of the study, the relationship between the low velocity impact behavior of laminated plates was compared with that of monolithic aluminum plates at
identical areal densities. For this purpose, a series of AA 2024 thin plates were combined with different types of adhesives (epoxy, polyurethane or tape).
Finally, fracture surface of the samples and microstructure at the deformation
zone were examined with both scanning electron microscope and optical
microscope.
It is found that the ballistic limit velocities of AA 2024 plates increase with
increase in hardness, yield strength and ultimate tensile strength. It is also
found that a linear relation exists between the ballistic limit velocity and strain hardening rate or hardness. When the low velocity impact behaviors of
laminated and monolithic targets were compared, it was seen that monolithic
targets have a higher ballistic limit velocity values for from the 2.5 to 10 mm
thick targets. It was also observed that adhesives are not so effective to
strengthen the low velocity impact performance. On the other hand, with
increasing Charpy impact energy, penetration and perforation behaviors are
getting worse in 10 to 30 joules energy range.
Different types of failure mechanisms involving, plugging, dishing, stretching
and bending were determined. For high strength and thick plates plugging type
deformation was leaded. In contrast, for thinner and weaker targets bending,
stretching and dishing type failures were dominating. For laminated targets
also dishing type failure was determined.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1096726/index.pdf |
| Date | 01 January 2003 |
| Creators | Kalay, Yunus Emre |
| Contributors | Ogel, Bilgehan |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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