Experimental Mechanics

, Volume 25, Issue 3, pp 308–311 | Cite as

Dispersive bending waves in uniform bars

  • A. K. Roy
  • R. Plunkett


The traveling bending waves in a long beam of rectangular cross section were measured and calculated. The bending waves were induced by impacting with a steel sphere and measured with strain gages at several distances from the point of impact. The impact force was calculated as a function of time by integrating the dynamic equations of the sphere and the beam. The force spectrum was then found using a fast-Fourier-transform (FFT) calculation and multiplied by the moment-frequency response of the beam to determine the moment spectrum. The moment-time function was calculated by an inverse FFT. The traveling wave is dispersive; its spectrum was found from that at the point of impact by phase shifting each component by an angle proportional to the distance and to the square root of the frequency. Again the time curve was determined by an inverse FFT. The indentation stiffness of the beam was found to be very much less than that of the elastic half space because of transverse bending. After the impact force was recalculated with this correction, the calculated moment-time traces agreed very well with the measured ones.


Mechanical Engineer Fluid Dynamics Dynamic Equation Strain Gage Time Curve 
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Copyright information

© Society for Experimental Mechanics, Inc. 1985

Authors and Affiliations

  • A. K. Roy
    • 1
  • R. Plunkett
    • 1
  1. 1.Department of Aerospace Engineering and MechanicsUniversity of MinnesotaMinneapolis

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