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STRUCTURAL & MULTIDISCIPLINARY OPTIMIZATION GROUP

Dr. Haftka       Dr. Kim       Mechanical & Aerospace Engineering        University of Florida

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Research

SBDO

Probabilistic SHM

Multiscale Modeling

ITPS

Evolution

Resource Allocation

Unexpected Structural Problems

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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. 
(Related papers: [1],[2])

 

BBtest

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.
(Related papers: [3], [4]) 

 

                      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.    
(Related papers: [5],[6],[7],[8])

 



[1]           Matsumura, T., Haftka, R.T., and Kim, N.H., "The contribution of Building-Block Test to Discover Unexpected Failure Modes," 52th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Denver, April 4-7, 2011.

 

[2]           Matsumura, T., Haftka, R.T., and Kim, N.H., "Effective Tests for Discovering Unexpected Structural failure Modes," 53th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Honolulu, Hawaii, April 23-26, 2012.

 

[3]           Matsumura, T., Park, C., Doyon, D., Haftka, R.T., and Kim, N.H., "Modeling the Contribution of Accident Investigation to Airplane Safety," 10th AIAA Aviation Technology, Integration, and Operations Conference, Fort Worth, Texas, September 13-15, 2010.

 

[4]           Matsumura, T., Haftka, R.T., Kim, N.H., "Effectiveness of Accident Investigations of the Space Shuttle for Safety Improvement," 12th AIAA Aviation Technology, Integration, and Operations Conference, Indianapolis, Indiana, 17-19 September, 2012.

 

[5]           Villanueva, D., Haftka, R. T., and Sankar, B. V., "Including the Effect of a Future Test and Redesign in Reliability Calculations," AIAA Journal, Vol. 49, No. 12, 2011, pp. 2760-2769.

                doi: Doi 10.2514/1.J051150

 

[6]           Matsumura, T., Haftka, R.T., and Sankar, B.V., "Reliability Estimation Including Redesign Following Future Test for an Integrated Thermal Protection System," 9th World Congress on Structural and Multidisciplinary Optimization, Shizuoka, Japan, June 14-17, 2011.

 

[7]           Villanueva, D., Haftka, R.T. , Sankar, B.V., "Accounting for Future Redesign in the Optimization of an Integrated Thermal Protection System," 14th AIAA Non-Deterministic Approaches Conference, Honolulu, Hawaii, 2012.

 

[8]           Matsumura, T., Haftka, R.T., and Sankar, B. V., "Reliability Based Design Optimization Considering Future Redesign with Different Epistemic Uncertainty Treatments," ASME 2012 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, Chicago, IL, August 12-15, 2012.