EFFECT OF EXPLOSIVE BONDS ON ACOUSTIC LOSS OF ALUMINUM-MAGNESIUM ALLOYS

The amplitude-independent mechanical quality factors of the commercial aluminium-magnesium alloys 5056 and 5456 were measured from 50 mK to 300 K in torsional mechanical resonators in which the rotation axis co incides with an essentially flat explosive-bond plane. The 1 kHz reson ators were configured to minimize extraneous internal friction effects . The results are compared with those obtained in similar experiments on a 5056 resonator in which there were no explosive bonds. Numerical estimates of the quality factor of the bond material are obtained. Fro m high-resolution resonant frequency measurements, the superconducting transition temperatures were determined and the effect of superconduc tivity on the torsion modulus was observed. The work was motivated by recent proposals to fabricate massive spherical resonant gravitational wave detectors from explosively bonded stacks of aluminium alloy plat es. (C) 1996 Elsevier Science Limited