AN IMPROVED TORSION PENDULUM FOR MEASURING INTERNAL DAMPING

A new torsion pendulum for measuring internal damping of metals and alloys is described. Improvements over earlier apparatus of this type include (1) a more convenient specimen shape, (2) an electromechanical transducer to measure angular deflections, (3) automatic compensation for eccentric vibrations when operated in the bearingfree mode, and (4) a continuous range of over 500:1 in strain amplitudes with a signal-to-noise ratio of better than 2:1 at a strain of less than 6×10-6. Specific damping capacities ranging from 80% (log decrement, 0.81) to 0.01% (log decrement, 5×10-5) have been measured, and stresses as high as 1970 kg·cm-2 have been used. © 1969 The American Institute of Physics.