Highly Loaded Airframe Fittings
BELL HELICOPTER TEXTRON INC FORT WORTH TX
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The analysis and design of airframe fittings subjected to large loads applied at high strain rates have been investigated with the goals of reducing analytical inaccuracy, reducing airframe structure weight and cost, and reducing airframe structure development time. Beginning with an assessment of the current state of the art in sizing highly loaded airframe fittings, analytical methodologies that account for rate-sensitive material behavior and internal stress wave propagation were evaluated. A comprehensive energy-based analytical approach is proposed in which the dynamic behavior of all the components in the system is accurately represented. High strain rate material characterization tests were performed on various aluminum alloys commonly used in airframe fitting design. Results indicated increases in both yield strength and elongation at high strain rates. The test results indicate that, in the absence of stress concentrations, structural aluminum alloys behave in an increasingly ductile manner as strain rate increases, with no apparent change in stiffness.
- Couplers, Fasteners and Joints