ULTRASONIC BAND-GAPS IN AGGREGATES OF SINTERED ALUMINUM BEADS

Periodic structures have complicated dispersion curves that contain st op bands and pass bands. Initial experimental work is reported in whic h the transmission power spectrum of a three- dimensional block of sin tered aluminum beads is examined. The power transmission spectrum of t he agglomeration of sintered beads is strikingly different than that o f a solid aluminum block. In particular, pass bands and stop bands wer e observed in the sintered blocks although the beads were not periodic ally arranged. The positions of the observed pass bands are found to a gree with theoretical predictions. The width of the bands is shown to be directly related to the sintering level and the corresponding coupl ing between beads.