Experimental Determination of Vibration Characteristics of Structures

A method is described in this paper for experimentally determining vibration characteristics by observing the characteristic motion of a small test mass attached to the structure by a linear spring. The specific motions that are observed are those following the release of the test mass from rest in a displaced position and for a series of closely spaced frequencies of the test mass on its spring. A possible arrangement of the test mass is shown in Fig. 1. The outer frame to which the springs are attached is itself a ttached to the structure by the fitting provided at the top. Small adjustments in frequency are made by removing various parts of the segmented mass; larger variations can be attained by changing the springs. Since observations are restricted to vibration amplitudes they can be made visually on the wedge-shaped pointer attached to the mass as shown in Fig. 1.