Helium as good as vaccum: the poor man's approach for accurate material damping measurements

摘要

In this paper a relatively simple method s presented which allows the performance of accurate material damping experiments in a frequency range where usually the internal losses are masked by sound radiation. Damping measurements performed on beam specimen vibrating in bending are renown to suffer from such problems, in particular whn they regard lightweight materials with small internal losses such as for instance aluminium allys. Instead of turning to complex measurements in vacuo, it is shown that a plastic bag filled with helium is most cases provides a satisfactory reduction of the sound emissions.