ESTIMATION OF THE ELASTIC-CONSTANTS OF A CYLINDER WITH A LENGTH EQUALTO ITS DIAMETER

A simple and noncomputational intensive method is proposed for elastic ally characterizing an isotropic material. The Poisson's ratio and the shear modulus are determined from the axisymmetric vibrations of a cy linder with a length equal to its diameter. These vibrations are excit ed by means of a wide spectrum impact. The optical system used allows the simultaneous detection of several vibration modes. The out-of-plan e displacement is detected by speckle interferometry. From the resulti ng vibration displacement spectrum, the two lowest frequencies are obt ained, both corresponding to axisymmetric modes-specifically, the firs t symmetric mode and the first antisymmetric mode. The values of both dynamic elastic constants are obtained by comparing previously compute d nondimensional natural frequencies and the measured frequencies. The method requires only one experiment and needs no electronic computati on, The results obtained for an aluminum cylinder are coherent and con firm the appropriateness of the method. The relative difference betwee n the Young's modulus values calculated by the proposed method and app lying the elementary theory to a long rod of the same material is 0.27 %. Comparing the shear modulus value obtained by this method and the c alculated one from the lower frequency in torsion, a relative differen ce of 4.6% is found. (C) 1998 Acoustical Society of America. [S0001-49 66(98)01007-8].