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Research Papers

A Structural Dynamic Model Inversion-Based Technique to Characterize Impacts to a Full-Scale and Operational Helicopter Rotor Blade

[+] Author and Article Information
Blake Hylton

Assistant Professor
Mem. ASME
Mechanical Engineering,
Ohio Northern University,
525 S. Main Street,
Ada, OH 45810
e-mail: j-hylton@onu.edu

Andrew Crandall

Texas A&M Turbomachinery Laboratory,
1485 George Bush Drive West,
College Station, TX 77840
e-mail: arcranda@tamu.edu

Dave Koester

Research Engineer
Vanderbilt University Laboratory for
Systems Integrity and Reliability,
566 Mainstream Drive #600,
Nashville, TN 37228
e-mail: david.koester@vanderbilt.edu

Brian Bouquillon

Rotor System Engineering IPT Lead,
Sikorsky Aircraft Corporation,
4800 Overton Plaza #440,
Fort Worth, TX 76109
e-mail: Brian.Bouquillon@sikorsky.com

Peter Meckl

Assistant Head
Professor
Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: meckl@purdue.edu

Douglas Adams

Professor
Fellow ASME
Civil and Environmental Engineering,
Vanderbilt University,
267A Jacobs Hall,
Nashville, TN 37235
e-mail: douglas.adams@vanderbilt.edu

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received March 8, 2016; final manuscript received September 12, 2016; published online September 27, 2016. Assoc. Editor: Alexander F. Vakakis.

J. Appl. Mech 83(12), 121007 (Sep 27, 2016) (10 pages) Paper No: JAM-16-1127; doi: 10.1115/1.4034704 History: Received March 08, 2016; Revised September 12, 2016

The incorporation of real-time structural health monitoring has the potential to substantially reduce the inspection burden of advanced composite rotor blades, particularly if impacts can be detected and characterized using operational data. Data-driven impact identification techniques, such as those applied in this work, require that a structural dynamic model of blade frequency response functions (FRFs) be developed for the operational environment. However, the operational characteristics of the rotor system are not accurately described by a model developed and validated in a nonrotating environment. The discrepancies are predominately due to two sources: the change in the blade root boundary condition and the presence of a centrifugal force. This research demonstrates an analytical methodology to compensate for the first of these effects. Derivations of this method are included, as well as analytical and experimental results. Additionally, the theory and experimental results are presented for an approach by which planar impact area and impactor stiffness may be estimated. Applying these techniques, impact location estimation accuracy was improved from 51.6% to 94.2%. Impacts produced by objects of 2–in. diameter were demonstrated to be distinguishable from those of 1 in. or less diameter. Finally, it was demonstrated that the impacts by objects of metallic material were distinguishable from those of rubber material, and that such differentiation was robust to impactor size and impact force magnitude.

Copyright © 2016 by ASME
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References

Figures

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Fig. 5

Blade in two testing conditions

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Fig. 6

Location error (inches)

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Fig. 4

Top-down view of the testing grid

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Fig. 3

Illustrative rotor blade

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Fig. 2

A pinned cantilevered beam

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Fig. 1

A cantilevered beam

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Fig. 7

Force error (decimal form percentage)

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Fig. 11

Estimated force impulsiveness for impacts of 0.25 in. (top left), 1 in. (top right), and 2 in. (bottom). All plots use the colormap shown with a scale of 0–100% probability of being an impulsive force.

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Fig. 12

Set of custom strikers

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Fig. 13

Impact area results for pocket region

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Fig. 14

Impact area results for spar region

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Fig. 8

Signed percent force error for calculated ratio case

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Fig. 9

Absolute value of unbiased percentage force error for calculated ratio case

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Fig. 10

PCB 086C03, 086D05, and 086D20 impact hammers

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Fig. 15

Stiffness estimation results for a preliminary spar region test region

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Fig. 16

Stiffness estimation results for the spar region

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Fig. 17

Stiffness estimation results for the pocket

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