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STRUCTURAL & MULTIDISCIPLINARY OPTIMIZATION GROUP
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Dr. Haftka Dr. Kim Mechanical
& Aerospace Engineering University
of Florida |
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Protecting Aircraft Against Unexpected Structural
Problems The growing complexity of engineering systems, such as airplanes, forces designers to face uncertainties. For example, complexity increases unforeseen interactions among components and parts, leading to imperfect prediction models. Complexity also introduces a chance of missing even well-known failure modes. This in turn may lead to fatal accidents and schedule delays in system development. For example, Boeing experienced costly program delays for its 787 Dreamliner, which reportedly cost hundreds of millions of dollars, due to an error in load prediction that caused an unexpected failure in a certification test of the entire wing. To tackle unexpected failure modes, aircraft builders and operators have been relying on several approaches. Aircraft builders conduct a series of structural tests intended to discover unexpected failure modes. In service, Operators deploy inspection and maintenance to deal with the aging of a structure, such as fatigue and wear. Finally, elaborate accident investigations identify failure causes to ensure that they will not occur again. These processes, however, are very costly and have been customarily conducted without quantifying the cost effectiveness. The Structural and Multidisciplinary Optimization Group addresses this issue from both engineering and economic points of view. The research involves the following objectives: I. Explore the effectiveness of a series of tests A hierarchical test
procedure called the building block
test (Fig 1) is commonly applied to the development of complex systems.
The effectiveness of these multi-stage tests, such as pre-design element
tests, post-design element tests and component tests, is examined with
probabilistic models in order to shed light on effective resource allocation
for preventing the unexpected.
Figure 1. Building block test approach for a wing of an airplane. It starts with lower structural complexity such as material levels and ends up with a system certification test. II. To investigate the effectiveness of accident investigations Effectiveness of accident investigation is studied by considering society’s “willingness to pay” for a reduced risk of fatality. Accident investigations for commercial airplanes and the Space Shuttles are contrasted. III. To develop a framework of simultaneous optimization of design, test and redesign Redesign is a costly corrective when tests reveal the design is unexpectedly unsafe. A conservative initial design will reduce the chance of redesign but will suffer performance loss (e.g., increased structural weight). We develop a design framework that captures the tradeoff between performance and redesign cost. This framework allows manufacturers to reasonably pursue performance depending on budget and schedule constraints.
doi:
Doi 10.2514/1.J051150 |