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Estimation of Static Stiffnesses from Free Boundary Dynamic (FRF) Measurements

Pasha, Hasan G

Abstract Details

2014, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Static structural stiffness is an important criterion in automobile structure design as it impacts vehicle handling, ride comfort, safety and durability. Traditionally, automobile manufacturers used special test rigs to estimate stiffness, which require precise setup and expensive instrumentation. In the past decade, dynamic frequency response function (FRF) measurements with modeling techniques were used to estimate static stiffness. Though test setup time and expense associated with the instrumentation are considerably reduced, heroic technical measures in terms of user experience and data processing are required to get reasonable stiffness estimates. The premise of this research is that static stiffness information contained in the measured free-free FRFs can be extracted by utilizing spatial/geometric filtering and averaging techniques. Two simple and efficient methods to estimate static stiffness from free-free FRFs are developed in this research. The enhanced Rotational and Bending Compliance Function (eRCF and eBCF) methods presented here utilize novel tools to enhance response functions and estimate static stiffness; such as mass perturbation during structural testing, spatial/geometric filtering and averaging techniques. The stiffness estimates obtained from these methods were comparable with the results from existing methods, while requiring significantly less resources. This dissertation presents the theoretical development of these methods and experimental validations on a rectangular plate (eRCF and eBCF) and an auto body (eRCF). Sensitivity studies on the effects of varying boundary conditions, dimensions and parameter estimation bandwidth on torsional and bending stiffness are presented. The effects of off-centered loading and overhang on stiffness are also discussed in detail. Finally, the conclusions and recommendations for future research are presented.
Randall Allemang, Ph.D. (Committee Chair)
David Brown, Ph.D. (Committee Member)
J. Kim, Ph.D. (Committee Member)
Allyn Phillips, Ph.D. (Committee Member)
230 p.

Recommended Citations

Citations

  • Pasha, H. G. (2014). Estimation of Static Stiffnesses from Free Boundary Dynamic (FRF) Measurements [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416569956

    APA Style (7th edition)

  • Pasha, Hasan. Estimation of Static Stiffnesses from Free Boundary Dynamic (FRF) Measurements. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416569956.

    MLA Style (8th edition)

  • Pasha, Hasan. "Estimation of Static Stiffnesses from Free Boundary Dynamic (FRF) Measurements." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416569956

    Chicago Manual of Style (17th edition)