IN-SITU DETERMINATION OF THE COMPLEX MODULUS FROM STRAIN-MEASUREMENTS ON AN IMPACTED STRUCTURE

A method is proposed for in situ determination of the complex modulus of a member of an impact-loaded structure. The modulus was obtained in terms of strains measured at three different cross-sections of a uniform part of the member, by using one-dimensional theory. The potential of the method was examined for a cylindrical polypropylene bar mounted as a member in each of two simple frame structures, and the modulus was obtained in the frequency range of 500 Hz to 3 kHz. For comparison, the modulus was also determined from tests on the same member, dismounted from the structures, by using a different method based on measurement of end-point accelerations. The results obtained from the in situ tests on the two frame structures and from the tests on the dismounted member are in fair agreement. The larger scatter in the results of the in situ tests is probably explained by a lower signal-to-noise ratio due to the use of strain gauges rather than accelerometers and to differences in excitation. © 1993 Academic Press Limited.