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Research Papers

Application of Viscous and Iwan Modal Damping Models to Experimental Measurements From Bolted Structures

[+] Author and Article Information
Brandon J. Deaner

Mercury Marine,
W6250 Pioneer Road,
P.O. Box 1939,
Fond du Lac, WI 54936-1939
e-mail: brandon.deaner@mercmarine.com

Matthew S. Allen

Associate Professor
Department of Engineering Physics,
University of Wisconsin-Madison,
535 Engineering Research Building,
1500 Engineering Drive,
Madison, WI 53706
e-mail: msallen@engr.wisc.edu

Michael J. Starr

Sandia National Laboratories,
P.O. Box 5800,
Albuquerque, NM 87185
e-mail: mjstarr@sandia.gov

Daniel J. Segalman

Department of Engineering Physics,
University of Wisconsin-Madison,
538 Engineering Research Building,
1500 Engineering Drive,
Madison, WI 53706
e-mail: segalman@wisc.edu

Hartono Sumali

Science, Technology and
Engineering Integration,
Sandia National Laboratories,
P.O. Box 5800,
Albuquerque, NM 87185
e-mail: hsumali@sandia.gov

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received June 1, 2013; final manuscript received November 8, 2014; published online January 20, 2015. Assoc. Editor: Weidong Zhu.

J. Vib. Acoust 137(2), 021012 (Apr 01, 2015) (12 pages) Paper No: VIB-13-1188; doi: 10.1115/1.4029074 History: Received June 01, 2013; Revised November 08, 2014; Online January 20, 2015

Measurements are presented from a two-beam structure with several bolted interfaces in order to characterize the nonlinear damping introduced by the joints. The measurements (all at force levels below macroslip) reveal that each underlying mode of the structure is well approximated by a single degree-of-freedom (SDOF) system with a nonlinear mechanical joint. At low enough force levels, the measurements show dissipation that scales as the second power of the applied force, agreeing with theory for a linear viscously damped system. This is attributed to linear viscous behavior of the material and/or damping provided by the support structure. At larger force levels, the damping is observed to behave nonlinearly, suggesting that damping from the mechanical joints is dominant. A model is presented that captures these effects, consisting of a spring and viscous damping element in parallel with a four-parameter Iwan model. The parameters of this model are identified for each mode of the structure and comparisons suggest that the model captures the stiffness and damping accurately over a range of forcing levels.

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References

Figures

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Fig. 1

Schematic of the model for each modal DOF. Each mode has a unique set of Iwan parameters that characterize its nonlinear damping and a viscous damper that captures the linear component of the damping.

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Fig. 2

Photograph of the two-beam test structure

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Fig. 3

Photograph of the suspension setup for the two-beam test structure

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Fig. 4

Two-beam mass normalized mode shapes at 3.39 N m torque

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Fig. 7

Slope of energy dissipation versus modal force for modal Iwan models and a polynomial fit to the experimental measurements

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Fig. 5

Comparison between measured natural frequency versus force and two models

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Fig. 6

Energy dissipation comparison of two optimized modal models to experimental data over a range of forces

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Fig. 8

ZEFFTs for the midpoint of the structure for both the experimental measurement (solid lines) and the model (dashed lines)

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Fig. 9

Zoomed in view of the first resonant peak with ZEFFTs for the both the experimental measurement (solid lines) and the model (dashed lines)

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Fig. 10

Time response comparison of the filtered experimental measurement (solid lines) and the model (dashed lines)

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