THE I.F. IN METALS AS A FUNCTION OF PHASE VELOCITY OF ELASTIC WAVES

Abstract
A great number of results of experiments carried out on some metals at vanishing amplitude and room temperature, reveal that it is possible to plot univocally I.F. versus the phase velocity of elastic waves. Measures obtained with longitudinal, flexural and torsional waves find their correct place in the diagram, when error sources have been localized and eliminated. Particular attention is to be paid to the effects of the interaction between specimen motion and suspensions : to this end reference has been made to the concept of oscillators showing nodes characterized by no displacements and rotations (binull nodes). When supported at these points, they guarantee that a minimum of energy may espace from specimens. Bars up to six meters in length, rings disks up to one meter in diameter have been tested, making it possible to judge the reliability of testing methods and to establish the limits of testing with each type of oscillator. Therefore, plotted against phase velocity, the I.F. gives rise to a trilateral diagram that shows no peaks revealing an experimental behaviour different in shape and absolute values from that predicted from Zener's thermo-elastic relaxation theory. Torsion tests on rectangular cross section bars, whose velocities are lower than that of distorsional waves, exhibit the same I.F. values measured in flexure in the same velocity field.