Measurement of the flexural damping capacity and dynamic Young's modulus of metals and reinforced plastics

An apparatus is described which is suitable for measuring the flexural damping and dynamic Young's modulus of beam specimens at stress levels up to 200 MN m⁻². Symmetric free-free flexural modes of vibration are excited by a coil/magnet pair, the coil being attached to the midpoint of the beam. Extraneous sources of damping have been reduced to a low level despite the difficulties of producing high-amplitude vibration. Low-damping specimens must be tested in vacuo (0·5 Torr was usually sufficient) if the effects of air damping are not to be significant. Specific damping capacities from 0·1 to 50% can be accurately measured over a frequency range of 100 to 800 Hz and a temperature range -50 to +200°C.